Add the Web Authentication.

.drone.yaml

@@ -0,0 +1,52 @@
+kind: pipeline
+type: docker
+name: default
+
+environment:
+  DATABASE_NAME: link_shortener_dev
+  DATABASE_USERNAME: postgres
+  DATABASE_PASSWORD: postgres
+  DATABASE_HOST: postgres
+  DATABASE_PORT: 5432
+  SECRET_KEY_BASE: TestSecretKeycRZ1H45gfdAsdf8DIb45df4664mRCruzwVEF68wosddfg324ost
+
+steps:
+  - name: install dependencies
+    image: elixir:1.14.0-slim
+    volumes:
+      - name: mix
+        path: /root/.mix
+    commands:
+      - mix local.hex --force
+      - mix local.rebar --force
+      - mix deps.get
+      - mix compile
+
+  - name: run migrations
+    image: elixir:1.14.0-slim
+    volumes:
+      - name: mix
+        path: /root/.mix
+    commands:
+      - mix ecto.setup
+
+  - name: run tests
+    image: elixir:1.14.0-slim
+    volumes:
+      - name: mix
+        path: /root/.mix
+    commands:
+      - mix test
+
+volumes:
+- name: mix
+  temp: {}
+
+services:
+  - name: postgres
+    image: postgres:15-alpine
+    environment:
+      POSTGRES_DB: link_shortener_dev
+      POSTGRES_USER: postgres
+      POSTGRES_PASSWORD: postgres
+

CHANGELOG.org

@@ -32,4 +32,28 @@
     Fix Links.update_one/2.
 ** 0.4.5 <2023-08-01 Tue>
     Fix the route path in LinkController.create/2.
+** 0.4.6 <2023-08-01 Tue>
+    Add the API to update the Link model.
+** 0.4.7 <2023-08-01 Tue>
+    Add tests for the API.
+** 0.4.8 <2023-08-02 Wed>
+    Refactor the Links module.
+** 0.4.9 <2023-08-02 Wed>
+    Add tests for the Links module.
+** 0.4.10 <2023-08-03 Thu>
+    Add the CI/CD configuration.
+    Add the test config.
 
+** 0.5.1 <2023-08-04 Fri>
+    Add a generator for Link with random shorten.
+    Update Links.create_one to use a function.
+** 0.5.2 <2023-08-05 Sat>
+    Add dependencies for API Authentication.
+** 0.6.0 <2023-08-05 Sat>
+    Add User model.
+** 0.7.0 <2023-08-06 Sun>
+    Add the API Authentication.
+** 0.7.1 <2023-08-07 Mon>
+    Add tests for UserController, Accounts, Generators.
+** 0.8.0 <2023-08-08 Tue>
+    Add the Web Authentication.

config/config.exs

@@ -47,6 +47,10 @@ config :logger, :console,
 # Use Jason for JSON parsing in Phoenix
 config :phoenix, :json_library, Jason
 
+config :link_shortener, LinkShortenerWeb.Auth.Guardian,
+  issuer: "link_shortener",
+  secret_key: System.get_env("SECRET_KEY_BASE")
+
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
 import_config "#{config_env()}.exs"

config/test.exs

@@ -0,0 +1,33 @@
+import Config
+
+# Only in tests, remove the complexity from the password hashing algorithm
+config :bcrypt_elixir, :log_rounds, 1
+
+# Configure your database
+#
+# The MIX_TEST_PARTITION environment variable can be used
+# to provide built-in test partitioning in CI environment.
+# Run `mix help test` for more information.
+config :link_shortener, LinkShortener.Repo,
+  username: System.get_env("DATABASE_USERNAME"),
+  password: System.get_env("DATABASE_PASSWORD"),
+  hostname: System.get_env("DATABASE_HOST"),
+  database: "link_shortener_test#{System.get_env("MIX_TEST_PARTITION")}",
+  pool: Ecto.Adapters.SQL.Sandbox,
+  pool_size: 10
+
+# We don't run a server during test. If one is required,
+# you can enable the server option below.
+config :link_shortener, LinkShortenerWeb.Endpoint,
+  http: [ip: {127, 0, 0, 1}, port: 4002],
+  secret_key_base: System.get_env("SECRET_KEY_BASE"),
+  server: false
+
+# In test we don't send emails.
+config :link_shortener, LinkShortener.Mailer, adapter: Swoosh.Adapters.Test
+
+# Print only warnings and errors during test
+config :logger, level: :warn
+
+# Initialize plugs at runtime for faster test compilation
+config :phoenix, :plug_init_mode, :runtime

lib/link_shortener/accounts/accounts.ex

@@ -0,0 +1,353 @@
+defmodule LinkShortener.Accounts do
+  @moduledoc """
+  The Accounts context.
+  """
+
+  import Ecto.Query, warn: false
+  alias LinkShortener.Repo
+
+  alias LinkShortener.Accounts.{User, UserToken, UserNotifier}
+
+  ## Database getters
+
+  @doc """
+  Gets a user by email.
+
+  ## Examples
+
+      iex> get_user_by_email("foo@example.com")
+      %User{}
+
+      iex> get_user_by_email("unknown@example.com")
+      nil
+
+  """
+  def get_user_by_email(email) when is_binary(email) do
+    Repo.get_by(User, email: email)
+  end
+
+  @doc """
+  Gets a user by email and password.
+
+  ## Examples
+
+      iex> get_user_by_email_and_password("foo@example.com", "correct_password")
+      %User{}
+
+      iex> get_user_by_email_and_password("foo@example.com", "invalid_password")
+      nil
+
+  """
+  def get_user_by_email_and_password(email, password)
+      when is_binary(email) and is_binary(password) do
+    user = Repo.get_by(User, email: email)
+    if User.valid_password?(user, password), do: user
+  end
+
+  @doc """
+  Gets a single user.
+
+  Raises `Ecto.NoResultsError` if the User does not exist.
+
+  ## Examples
+
+      iex> get_user!(123)
+      %User{}
+
+      iex> get_user!(456)
+      ** (Ecto.NoResultsError)
+
+  """
+  def get_user!(id), do: Repo.get!(User, id)
+
+  ## User registration
+
+  @doc """
+  Registers a user.
+
+  ## Examples
+
+      iex> register_user(%{field: value})
+      {:ok, %User{}}
+
+      iex> register_user(%{field: bad_value})
+      {:error, %Ecto.Changeset{}}
+
+  """
+  def register_user(attrs) do
+    %User{}
+    |> User.registration_changeset(attrs)
+    |> Repo.insert()
+  end
+
+  @doc """
+  Returns an `%Ecto.Changeset{}` for tracking user changes.
+
+  ## Examples
+
+      iex> change_user_registration(user)
+      %Ecto.Changeset{data: %User{}}
+
+  """
+  def change_user_registration(%User{} = user, attrs \\ %{}) do
+    User.registration_changeset(user, attrs, hash_password: false)
+  end
+
+  ## Settings
+
+  @doc """
+  Returns an `%Ecto.Changeset{}` for changing the user email.
+
+  ## Examples
+
+      iex> change_user_email(user)
+      %Ecto.Changeset{data: %User{}}
+
+  """
+  def change_user_email(user, attrs \\ %{}) do
+    User.email_changeset(user, attrs)
+  end
+
+  @doc """
+  Emulates that the email will change without actually changing
+  it in the database.
+
+  ## Examples
+
+      iex> apply_user_email(user, "valid password", %{email: ...})
+      {:ok, %User{}}
+
+      iex> apply_user_email(user, "invalid password", %{email: ...})
+      {:error, %Ecto.Changeset{}}
+
+  """
+  def apply_user_email(user, password, attrs) do
+    user
+    |> User.email_changeset(attrs)
+    |> User.validate_current_password(password)
+    |> Ecto.Changeset.apply_action(:update)
+  end
+
+  @doc """
+  Updates the user email using the given token.
+
+  If the token matches, the user email is updated and the token is deleted.
+  The confirmed_at date is also updated to the current time.
+  """
+  def update_user_email(user, token) do
+    context = "change:#{user.email}"
+
+    with {:ok, query} <- UserToken.verify_change_email_token_query(token, context),
+         %UserToken{sent_to: email} <- Repo.one(query),
+         {:ok, _} <- Repo.transaction(user_email_multi(user, email, context)) do
+      :ok
+    else
+      _ -> :error
+    end
+  end
+
+  defp user_email_multi(user, email, context) do
+    changeset =
+      user
+      |> User.email_changeset(%{email: email})
+      |> User.confirm_changeset()
+
+    Ecto.Multi.new()
+    |> Ecto.Multi.update(:user, changeset)
+    |> Ecto.Multi.delete_all(:tokens, UserToken.user_and_contexts_query(user, [context]))
+  end
+
+  @doc """
+  Delivers the update email instructions to the given user.
+
+  ## Examples
+
+      iex> deliver_update_email_instructions(user, current_email, &Routes.user_update_email_url(conn, :edit, &1))
+      {:ok, %{to: ..., body: ...}}
+
+  """
+  def deliver_update_email_instructions(%User{} = user, current_email, update_email_url_fun)
+      when is_function(update_email_url_fun, 1) do
+    {encoded_token, user_token} = UserToken.build_email_token(user, "change:#{current_email}")
+
+    Repo.insert!(user_token)
+    UserNotifier.deliver_update_email_instructions(user, update_email_url_fun.(encoded_token))
+  end
+
+  @doc """
+  Returns an `%Ecto.Changeset{}` for changing the user password.
+
+  ## Examples
+
+      iex> change_user_password(user)
+      %Ecto.Changeset{data: %User{}}
+
+  """
+  def change_user_password(user, attrs \\ %{}) do
+    User.password_changeset(user, attrs, hash_password: false)
+  end
+
+  @doc """
+  Updates the user password.
+
+  ## Examples
+
+      iex> update_user_password(user, "valid password", %{password: ...})
+      {:ok, %User{}}
+
+      iex> update_user_password(user, "invalid password", %{password: ...})
+      {:error, %Ecto.Changeset{}}
+
+  """
+  def update_user_password(user, password, attrs) do
+    changeset =
+      user
+      |> User.password_changeset(attrs)
+      |> User.validate_current_password(password)
+
+    Ecto.Multi.new()
+    |> Ecto.Multi.update(:user, changeset)
+    |> Ecto.Multi.delete_all(:tokens, UserToken.user_and_contexts_query(user, :all))
+    |> Repo.transaction()
+    |> case do
+      {:ok, %{user: user}} -> {:ok, user}
+      {:error, :user, changeset, _} -> {:error, changeset}
+    end
+  end
+
+  ## Session
+
+  @doc """
+  Generates a session token.
+  """
+  def generate_user_session_token(user) do
+    {token, user_token} = UserToken.build_session_token(user)
+    Repo.insert!(user_token)
+    token
+  end
+
+  @doc """
+  Gets the user with the given signed token.
+  """
+  def get_user_by_session_token(token) do
+    {:ok, query} = UserToken.verify_session_token_query(token)
+    Repo.one(query)
+  end
+
+  @doc """
+  Deletes the signed token with the given context.
+  """
+  def delete_session_token(token) do
+    Repo.delete_all(UserToken.token_and_context_query(token, "session"))
+    :ok
+  end
+
+  ## Confirmation
+
+  @doc """
+  Delivers the confirmation email instructions to the given user.
+
+  ## Examples
+
+      iex> deliver_user_confirmation_instructions(user, &Routes.user_confirmation_url(conn, :edit, &1))
+      {:ok, %{to: ..., body: ...}}
+
+      iex> deliver_user_confirmation_instructions(confirmed_user, &Routes.user_confirmation_url(conn, :edit, &1))
+      {:error, :already_confirmed}
+
+  """
+  def deliver_user_confirmation_instructions(%User{} = user, confirmation_url_fun)
+      when is_function(confirmation_url_fun, 1) do
+    if user.confirmed_at do
+      {:error, :already_confirmed}
+    else
+      {encoded_token, user_token} = UserToken.build_email_token(user, "confirm")
+      Repo.insert!(user_token)
+      UserNotifier.deliver_confirmation_instructions(user, confirmation_url_fun.(encoded_token))
+    end
+  end
+
+  @doc """
+  Confirms a user by the given token.
+
+  If the token matches, the user account is marked as confirmed
+  and the token is deleted.
+  """
+  def confirm_user(token) do
+    with {:ok, query} <- UserToken.verify_email_token_query(token, "confirm"),
+         %User{} = user <- Repo.one(query),
+         {:ok, %{user: user}} <- Repo.transaction(confirm_user_multi(user)) do
+      {:ok, user}
+    else
+      _ -> :error
+    end
+  end
+
+  defp confirm_user_multi(user) do
+    Ecto.Multi.new()
+    |> Ecto.Multi.update(:user, User.confirm_changeset(user))
+    |> Ecto.Multi.delete_all(:tokens, UserToken.user_and_contexts_query(user, ["confirm"]))
+  end
+
+  ## Reset password
+
+  @doc """
+  Delivers the reset password email to the given user.
+
+  ## Examples
+
+      iex> deliver_user_reset_password_instructions(user, &Routes.user_reset_password_url(conn, :edit, &1))
+      {:ok, %{to: ..., body: ...}}
+
+  """
+  def deliver_user_reset_password_instructions(%User{} = user, reset_password_url_fun)
+      when is_function(reset_password_url_fun, 1) do
+    {encoded_token, user_token} = UserToken.build_email_token(user, "reset_password")
+    Repo.insert!(user_token)
+    UserNotifier.deliver_reset_password_instructions(user, reset_password_url_fun.(encoded_token))
+  end
+
+  @doc """
+  Gets the user by reset password token.
+
+  ## Examples
+
+      iex> get_user_by_reset_password_token("validtoken")
+      %User{}
+
+      iex> get_user_by_reset_password_token("invalidtoken")
+      nil
+
+  """
+  def get_user_by_reset_password_token(token) do
+    with {:ok, query} <- UserToken.verify_email_token_query(token, "reset_password"),
+         %User{} = user <- Repo.one(query) do
+      user
+    else
+      _ -> nil
+    end
+  end
+
+  @doc """
+  Resets the user password.
+
+  ## Examples
+
+      iex> reset_user_password(user, %{password: "new long password", password_confirmation: "new long password"})
+      {:ok, %User{}}
+
+      iex> reset_user_password(user, %{password: "valid", password_confirmation: "not the same"})
+      {:error, %Ecto.Changeset{}}
+
+  """
+  def reset_user_password(user, attrs) do
+    Ecto.Multi.new()
+    |> Ecto.Multi.update(:user, User.password_changeset(user, attrs))
+    |> Ecto.Multi.delete_all(:tokens, UserToken.user_and_contexts_query(user, :all))
+    |> Repo.transaction()
+    |> case do
+      {:ok, %{user: user}} -> {:ok, user}
+      {:error, :user, changeset, _} -> {:error, changeset}
+    end
+  end
+end

lib/link_shortener/accounts/user.ex

@@ -0,0 +1,140 @@
+defmodule LinkShortener.Accounts.User do
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  schema "users" do
+    field :email, :string
+    field :password, :string, virtual: true, redact: true
+    field :hashed_password, :string, redact: true
+    field :confirmed_at, :naive_datetime
+
+    timestamps()
+  end
+
+  @doc """
+  A user changeset for registration.
+
+  It is important to validate the length of both email and password.
+  Otherwise databases may truncate the email without warnings, which
+  could lead to unpredictable or insecure behaviour. Long passwords may
+  also be very expensive to hash for certain algorithms.
+
+  ## Options
+
+    * `:hash_password` - Hashes the password so it can be stored securely
+      in the database and ensures the password field is cleared to prevent
+      leaks in the logs. If password hashing is not needed and clearing the
+      password field is not desired (like when using this changeset for
+      validations on a LiveView form), this option can be set to `false`.
+      Defaults to `true`.
+  """
+  def registration_changeset(user, attrs, opts \\ []) do
+    user
+    |> cast(attrs, [:email, :password])
+    |> validate_email()
+    |> validate_password(opts)
+  end
+
+  defp validate_email(changeset) do
+    changeset
+    |> validate_required([:email])
+    |> validate_format(:email, ~r/^[^\s]+@[^\s]+$/, message: "must have the @ sign and no spaces")
+    |> validate_length(:email, max: 160)
+    |> unsafe_validate_unique(:email, LinkShortener.Repo)
+    |> unique_constraint(:email)
+  end
+
+  defp validate_password(changeset, opts) do
+    changeset
+    |> validate_required([:password])
+    |> validate_length(:password, min: 12, max: 72)
+    # |> validate_format(:password, ~r/[a-z]/, message: "at least one lower case character")
+    # |> validate_format(:password, ~r/[A-Z]/, message: "at least one upper case character")
+    # |> validate_format(:password, ~r/[!?@#$%^&*_0-9]/, message: "at least one digit or punctuation character")
+    |> maybe_hash_password(opts)
+  end
+
+  defp maybe_hash_password(changeset, opts) do
+    hash_password? = Keyword.get(opts, :hash_password, true)
+    password = get_change(changeset, :password)
+
+    if hash_password? && password && changeset.valid? do
+      changeset
+      # If using Bcrypt, then further validate it is at most 72 bytes long
+      |> validate_length(:password, max: 72, count: :bytes)
+      |> put_change(:hashed_password, Bcrypt.hash_pwd_salt(password))
+      |> delete_change(:password)
+    else
+      changeset
+    end
+  end
+
+  @doc """
+  A user changeset for changing the email.
+
+  It requires the email to change otherwise an error is added.
+  """
+  def email_changeset(user, attrs) do
+    user
+    |> cast(attrs, [:email])
+    |> validate_email()
+    |> case do
+      %{changes: %{email: _}} = changeset -> changeset
+      %{} = changeset -> add_error(changeset, :email, "did not change")
+    end
+  end
+
+  @doc """
+  A user changeset for changing the password.
+
+  ## Options
+
+    * `:hash_password` - Hashes the password so it can be stored securely
+      in the database and ensures the password field is cleared to prevent
+      leaks in the logs. If password hashing is not needed and clearing the
+      password field is not desired (like when using this changeset for
+      validations on a LiveView form), this option can be set to `false`.
+      Defaults to `true`.
+  """
+  def password_changeset(user, attrs, opts \\ []) do
+    user
+    |> cast(attrs, [:password])
+    |> validate_confirmation(:password, message: "does not match password")
+    |> validate_password(opts)
+  end
+
+  @doc """
+  Confirms the account by setting `confirmed_at`.
+  """
+  def confirm_changeset(user) do
+    now = NaiveDateTime.utc_now() |> NaiveDateTime.truncate(:second)
+    change(user, confirmed_at: now)
+  end
+
+  @doc """
+  Verifies the password.
+
+  If there is no user or the user doesn't have a password, we call
+  `Bcrypt.no_user_verify/0` to avoid timing attacks.
+  """
+  def valid_password?(%LinkShortener.Accounts.User{hashed_password: hashed_password}, password)
+      when is_binary(hashed_password) and byte_size(password) > 0 do
+    Bcrypt.verify_pass(password, hashed_password)
+  end
+
+  def valid_password?(_, _) do
+    Bcrypt.no_user_verify()
+    false
+  end
+
+  @doc """
+  Validates the current password otherwise adds an error to the changeset.
+  """
+  def validate_current_password(changeset, password) do
+    if valid_password?(changeset.data, password) do
+      changeset
+    else
+      add_error(changeset, :current_password, "is not valid")
+    end
+  end
+end

lib/link_shortener/accounts/user_notifier.ex

@@ -0,0 +1,79 @@
+defmodule LinkShortener.Accounts.UserNotifier do
+  import Swoosh.Email
+
+  alias LinkShortener.Mailer
+
+  # Delivers the email using the application mailer.
+  defp deliver(recipient, subject, body) do
+    email =
+      new()
+      |> to(recipient)
+      |> from({"LinkShortener", "contact@example.com"})
+      |> subject(subject)
+      |> text_body(body)
+
+    with {:ok, _metadata} <- Mailer.deliver(email) do
+      {:ok, email}
+    end
+  end
+
+  @doc """
+  Deliver instructions to confirm account.
+  """
+  def deliver_confirmation_instructions(user, url) do
+    deliver(user.email, "Confirmation instructions", """
+
+    ==============================
+
+    Hi #{user.email},
+
+    You can confirm your account by visiting the URL below:
+
+    #{url}
+
+    If you didn't create an account with us, please ignore this.
+
+    ==============================
+    """)
+  end
+
+  @doc """
+  Deliver instructions to reset a user password.
+  """
+  def deliver_reset_password_instructions(user, url) do
+    deliver(user.email, "Reset password instructions", """
+
+    ==============================
+
+    Hi #{user.email},
+
+    You can reset your password by visiting the URL below:
+
+    #{url}
+
+    If you didn't request this change, please ignore this.
+
+    ==============================
+    """)
+  end
+
+  @doc """
+  Deliver instructions to update a user email.
+  """
+  def deliver_update_email_instructions(user, url) do
+    deliver(user.email, "Update email instructions", """
+
+    ==============================
+
+    Hi #{user.email},
+
+    You can change your email by visiting the URL below:
+
+    #{url}
+
+    If you didn't request this change, please ignore this.
+
+    ==============================
+    """)
+  end
+end

lib/link_shortener/accounts/user_token.ex

@@ -0,0 +1,179 @@
+defmodule LinkShortener.Accounts.UserToken do
+  use Ecto.Schema
+  import Ecto.Query
+  alias LinkShortener.Accounts.UserToken
+
+  @hash_algorithm :sha256
+  @rand_size 32
+
+  # It is very important to keep the reset password token expiry short,
+  # since someone with access to the email may take over the account.
+  @reset_password_validity_in_days 1
+  @confirm_validity_in_days 7
+  @change_email_validity_in_days 7
+  @session_validity_in_days 60
+
+  schema "users_tokens" do
+    field :token, :binary
+    field :context, :string
+    field :sent_to, :string
+    belongs_to :user, LinkShortener.Accounts.User
+
+    timestamps(updated_at: false)
+  end
+
+  @doc """
+  Generates a token that will be stored in a signed place,
+  such as session or cookie. As they are signed, those
+  tokens do not need to be hashed.
+
+  The reason why we store session tokens in the database, even
+  though Phoenix already provides a session cookie, is because
+  Phoenix' default session cookies are not persisted, they are
+  simply signed and potentially encrypted. This means they are
+  valid indefinitely, unless you change the signing/encryption
+  salt.
+
+  Therefore, storing them allows individual user
+  sessions to be expired. The token system can also be extended
+  to store additional data, such as the device used for logging in.
+  You could then use this information to display all valid sessions
+  and devices in the UI and allow users to explicitly expire any
+  session they deem invalid.
+  """
+  def build_session_token(user) do
+    token = :crypto.strong_rand_bytes(@rand_size)
+    {token, %UserToken{token: token, context: "session", user_id: user.id}}
+  end
+
+  @doc """
+  Checks if the token is valid and returns its underlying lookup query.
+
+  The query returns the user found by the token, if any.
+
+  The token is valid if it matches the value in the database and it has
+  not expired (after @session_validity_in_days).
+  """
+  def verify_session_token_query(token) do
+    query =
+      from token in token_and_context_query(token, "session"),
+        join: user in assoc(token, :user),
+        where: token.inserted_at > ago(@session_validity_in_days, "day"),
+        select: user
+
+    {:ok, query}
+  end
+
+  @doc """
+  Builds a token and its hash to be delivered to the user's email.
+
+  The non-hashed token is sent to the user email while the
+  hashed part is stored in the database. The original token cannot be reconstructed,
+  which means anyone with read-only access to the database cannot directly use
+  the token in the application to gain access. Furthermore, if the user changes
+  their email in the system, the tokens sent to the previous email are no longer
+  valid.
+
+  Users can easily adapt the existing code to provide other types of delivery methods,
+  for example, by phone numbers.
+  """
+  def build_email_token(user, context) do
+    build_hashed_token(user, context, user.email)
+  end
+
+  defp build_hashed_token(user, context, sent_to) do
+    token = :crypto.strong_rand_bytes(@rand_size)
+    hashed_token = :crypto.hash(@hash_algorithm, token)
+
+    {Base.url_encode64(token, padding: false),
+     %UserToken{
+       token: hashed_token,
+       context: context,
+       sent_to: sent_to,
+       user_id: user.id
+     }}
+  end
+
+  @doc """
+  Checks if the token is valid and returns its underlying lookup query.
+
+  The query returns the user found by the token, if any.
+
+  The given token is valid if it matches its hashed counterpart in the
+  database and the user email has not changed. This function also checks
+  if the token is being used within a certain period, depending on the
+  context. The default contexts supported by this function are either
+  "confirm", for account confirmation emails, and "reset_password",
+  for resetting the password. For verifying requests to change the email,
+  see `verify_change_email_token_query/2`.
+  """
+  def verify_email_token_query(token, context) do
+    case Base.url_decode64(token, padding: false) do
+      {:ok, decoded_token} ->
+        hashed_token = :crypto.hash(@hash_algorithm, decoded_token)
+        days = days_for_context(context)
+
+        query =
+          from token in token_and_context_query(hashed_token, context),
+            join: user in assoc(token, :user),
+            where: token.inserted_at > ago(^days, "day") and token.sent_to == user.email,
+            select: user
+
+        {:ok, query}
+
+      :error ->
+        :error
+    end
+  end
+
+  defp days_for_context("confirm"), do: @confirm_validity_in_days
+  defp days_for_context("reset_password"), do: @reset_password_validity_in_days
+
+  @doc """
+  Checks if the token is valid and returns its underlying lookup query.
+
+  The query returns the user found by the token, if any.
+
+  This is used to validate requests to change the user
+  email. It is different from `verify_email_token_query/2` precisely because
+  `verify_email_token_query/2` validates the email has not changed, which is
+  the starting point by this function.
+
+  The given token is valid if it matches its hashed counterpart in the
+  database and if it has not expired (after @change_email_validity_in_days).
+  The context must always start with "change:".
+  """
+  def verify_change_email_token_query(token, "change:" <> _ = context) do
+    case Base.url_decode64(token, padding: false) do
+      {:ok, decoded_token} ->
+        hashed_token = :crypto.hash(@hash_algorithm, decoded_token)
+
+        query =
+          from token in token_and_context_query(hashed_token, context),
+            where: token.inserted_at > ago(@change_email_validity_in_days, "day")
+
+        {:ok, query}
+
+      :error ->
+        :error
+    end
+  end
+
+  @doc """
+  Returns the token struct for the given token value and context.
+  """
+  def token_and_context_query(token, context) do
+    from UserToken, where: [token: ^token, context: ^context]
+  end
+
+  @doc """
+  Gets all tokens for the given user for the given contexts.
+  """
+  def user_and_contexts_query(user, :all) do
+    from t in UserToken, where: t.user_id == ^user.id
+  end
+
+  def user_and_contexts_query(user, [_ | _] = contexts) do
+    from t in UserToken, where: t.user_id == ^user.id and t.context in ^contexts
+  end
+end

lib/link_shortener/generators/link_with_random_shorten.ex

@@ -0,0 +1,14 @@
+defmodule LinkShortener.Generators.LinkWithRandomShorten do
+  @moduledoc """
+  This module provides a generator for Link.
+  """
+
+  alias LinkShortener.Generators.SafeString
+
+  @doc """
+  Generate a Link with random shorten with the length.
+  """
+  def generate_one(attrs, length \\ 10, generator \\ &SafeString.generate/1) do
+    Map.put(attrs, :shorten, generator.(length))
+  end
+end

lib/link_shortener/links/links.ex

@@ -1,16 +1,16 @@
-defmodule LinkShortener.Links.Links do
+defmodule LinkShortener.Links do
   use Ecto.Schema
   import Ecto.Changeset
   import Ecto.Query
   alias LinkShortener.Repo
   alias LinkShortener.Links.Link
-  alias LinkShortener.Generators.SafeString
+  alias LinkShortener.Generators.LinkWithRandomShorten, as: LinkGenerator
 
-  def new_one(), do: Link.changeset(%Link{})
+  def new_one(), do: Link.changeset(%Link{}, %{})
 
-  def create_one(attrs, length \\ 10, generator \\ SafeString) do
+  def create_one(attrs, length \\ 10, generator \\ &LinkGenerator.generate_one/2) do
-    shorten = generator.generate(length)
+    generator.(attrs, length)
-    insert_one(Map.put(attrs, :shorten, shorten))
+    |> insert_one()
   end
 
   def insert_one(attrs) do
@@ -19,25 +19,10 @@ defmodule LinkShortener.Links.Links do
     |> Repo.insert()
   end
 
-  def edit_one(id) do
+  def get_one!(id) do
-    get_one(id)
+    Repo.get!(Link, id)
-    |> Link.changeset()
   end
 
-  def update_one(%Link{} = link, changes) do
-    link
-    |> Link.changeset(changes)
-    |> Repo.update()
-  end
-
-  def insert_one(attrs) do
-    %Link{}
-    |> Link.changeset(attrs)
-    |> Repo.insert()
-  end
-
-  def delete_one(%Link{} = link), do: Repo.delete(link)
-
   def get_one_by(attrs) do
     Repo.get_by(Link, attrs)
   end
@@ -46,12 +31,26 @@ defmodule LinkShortener.Links.Links do
     get_one_by(%{shorten: shorten})
   end
 
-  def get_one(id) do
+  def get_all() do
-    Repo.get!(Link, id)
+    from(Link)
+    |> Repo.all()
   end
 
   def get_all(opts) do
     from(Link)
     |> Repo.all()
   end
+
+  def edit_one(%Link{} = link) do
+    link
+    |> Link.changeset(%{})
+  end
+
+  def update_one(%Link{} = link, changes) do
+    link
+    |> Link.changeset(changes)
+    |> Repo.update()
+  end
+
+  def delete_one(%Link{} = link), do: Repo.delete(link)
 end

lib/link_shortener_web/auth/guardian.ex

@@ -0,0 +1,16 @@
+defmodule LinkShortenerWeb.Auth.Guardian do
+  use Guardian, otp_app: :link_shortener
+
+  alias LinkShortener.Accounts
+
+  def subject_for_token(user, _claims) do
+    sub = to_string(user.id)
+    {:ok, sub}
+  end
+
+  def resource_from_claims(claims) do
+    id = claims["sub"]
+    resource = Accounts.get_user!(id)
+    {:ok,  resource}
+  end
+end

lib/link_shortener_web/controllers/api/v1/link_controller.ex

@@ -1,13 +1,13 @@
 defmodule LinkShortenerWeb.Api.V1.LinkController do
   use LinkShortenerWeb, :controller
 
-  alias LinkShortener.Links.Links
+  alias LinkShortener.Links
   alias LinkShortener.Links.Link
 
   action_fallback LinkShortenerWeb.FallbackController
 
   def index(conn, _params) do
-    links = Links.get_all({})
+    links = Links.get_all()
     render(conn, "index.json", links: links)
   end
 
@@ -21,13 +21,20 @@ defmodule LinkShortenerWeb.Api.V1.LinkController do
   end
 
   def show(conn, %{"id" => id}) do
-    link = Links.get_one(id)
+    link = Links.get_one!(id)
+    render(conn, "show.json", link: link)
+  end
+
+  def update(conn, %{"id" => id, "link" => link_params}) do
+    link = Links.get_one!(id)
+
+    with {:ok, %Link{} = link} <- Links.update_one(link, link_params) do
       render(conn, "show.json", link: link)
     end
   end
 
   def delete(conn, %{"id" => id}) do
-    link = Links.get_one(id)
+    link = Links.get_one!(id)
 
     with {:ok, %Link{}} <- Links.delete_one(link) do
       send_resp(conn, :no_content, "")

lib/link_shortener_web/controllers/api/v1/user_controller.ex

@@ -0,0 +1,26 @@
+defmodule LinkShortenerWeb.Api.V1.UserController do
+  use LinkShortenerWeb, :controller
+
+  alias LinkShortener.Accounts
+  alias LinkShortener.Accounts.User
+  alias LinkShortenerWeb.Auth.Guardian
+
+  action_fallback LinkShortenerWeb.FallbackController
+
+  def create(conn, %{"user" => user_params}) do
+    with {:ok, %User{} = user} <- Accounts.register_user(user_params),
+	 {:ok, token, _claims} <- Guardian.encode_and_sign(user) do
+      conn
+      |> put_status(:created)
+      |> render("user.json", %{user: user, token: token})
+    end
+  end
+
+  def signin(conn, %{"email" => email, "password" => password}) do
+    with {:ok, user, token} <- Guardian.authenticate(email, password) do
+      conn
+      |> put_status(:created)
+      |> render("user.json", %{user: user, token: token})
+    end
+  end
+end

lib/link_shortener_web/controllers/user_auth.ex

@@ -0,0 +1,149 @@
+defmodule LinkShortenerWeb.UserAuth do
+  import Plug.Conn
+  import Phoenix.Controller
+
+  alias LinkShortener.Accounts
+  alias LinkShortenerWeb.Router.Helpers, as: Routes
+
+  # Make the remember me cookie valid for 60 days.
+  # If you want bump or reduce this value, also change
+  # the token expiry itself in UserToken.
+  @max_age 60 * 60 * 24 * 60
+  @remember_me_cookie "_link_shortener_web_user_remember_me"
+  @remember_me_options [sign: true, max_age: @max_age, same_site: "Lax"]
+
+  @doc """
+  Logs the user in.
+
+  It renews the session ID and clears the whole session
+  to avoid fixation attacks. See the renew_session
+  function to customize this behaviour.
+
+  It also sets a `:live_socket_id` key in the session,
+  so LiveView sessions are identified and automatically
+  disconnected on log out. The line can be safely removed
+  if you are not using LiveView.
+  """
+  def log_in_user(conn, user, params \\ %{}) do
+    token = Accounts.generate_user_session_token(user)
+    user_return_to = get_session(conn, :user_return_to)
+
+    conn
+    |> renew_session()
+    |> put_session(:user_token, token)
+    |> put_session(:live_socket_id, "users_sessions:#{Base.url_encode64(token)}")
+    |> maybe_write_remember_me_cookie(token, params)
+    |> redirect(to: user_return_to || signed_in_path(conn))
+  end
+
+  defp maybe_write_remember_me_cookie(conn, token, %{"remember_me" => "true"}) do
+    put_resp_cookie(conn, @remember_me_cookie, token, @remember_me_options)
+  end
+
+  defp maybe_write_remember_me_cookie(conn, _token, _params) do
+    conn
+  end
+
+  # This function renews the session ID and erases the whole
+  # session to avoid fixation attacks. If there is any data
+  # in the session you may want to preserve after log in/log out,
+  # you must explicitly fetch the session data before clearing
+  # and then immediately set it after clearing, for example:
+  #
+  #     defp renew_session(conn) do
+  #       preferred_locale = get_session(conn, :preferred_locale)
+  #
+  #       conn
+  #       |> configure_session(renew: true)
+  #       |> clear_session()
+  #       |> put_session(:preferred_locale, preferred_locale)
+  #     end
+  #
+  defp renew_session(conn) do
+    conn
+    |> configure_session(renew: true)
+    |> clear_session()
+  end
+
+  @doc """
+  Logs the user out.
+
+  It clears all session data for safety. See renew_session.
+  """
+  def log_out_user(conn) do
+    user_token = get_session(conn, :user_token)
+    user_token && Accounts.delete_session_token(user_token)
+
+    if live_socket_id = get_session(conn, :live_socket_id) do
+      LinkShortenerWeb.Endpoint.broadcast(live_socket_id, "disconnect", %{})
+    end
+
+    conn
+    |> renew_session()
+    |> delete_resp_cookie(@remember_me_cookie)
+    |> redirect(to: "/")
+  end
+
+  @doc """
+  Authenticates the user by looking into the session
+  and remember me token.
+  """
+  def fetch_current_user(conn, _opts) do
+    {user_token, conn} = ensure_user_token(conn)
+    user = user_token && Accounts.get_user_by_session_token(user_token)
+    assign(conn, :current_user, user)
+  end
+
+  defp ensure_user_token(conn) do
+    if user_token = get_session(conn, :user_token) do
+      {user_token, conn}
+    else
+      conn = fetch_cookies(conn, signed: [@remember_me_cookie])
+
+      if user_token = conn.cookies[@remember_me_cookie] do
+        {user_token, put_session(conn, :user_token, user_token)}
+      else
+        {nil, conn}
+      end
+    end
+  end
+
+  @doc """
+  Used for routes that require the user to not be authenticated.
+  """
+  def redirect_if_user_is_authenticated(conn, _opts) do
+    if conn.assigns[:current_user] do
+      conn
+      |> redirect(to: signed_in_path(conn))
+      |> halt()
+    else
+      conn
+    end
+  end
+
+  @doc """
+  Used for routes that require the user to be authenticated.
+
+  If you want to enforce the user email is confirmed before
+  they use the application at all, here would be a good place.
+  """
+  def require_authenticated_user(conn, _opts) do
+    if conn.assigns[:current_user] do
+      conn
+    else
+      conn
+      |> put_flash(:error, "You must log in to access this page.")
+      |> maybe_store_return_to()
+      |> redirect(to: Routes.user_session_path(conn, :new))
+      |> halt()
+    end
+  end
+
+  defp maybe_store_return_to(%{method: "GET"} = conn) do
+    put_session(conn, :user_return_to, current_path(conn))
+  end
+
+  defp maybe_store_return_to(conn), do: conn
+
+  defp signed_in_path(_conn), do: "/"
+end

lib/link_shortener_web/controllers/user_confirmation_controller.ex

@@ -0,0 +1,56 @@
+defmodule LinkShortenerWeb.UserConfirmationController do
+  use LinkShortenerWeb, :controller
+
+  alias LinkShortener.Accounts
+
+  def new(conn, _params) do
+    render(conn, "new.html")
+  end
+
+  def create(conn, %{"user" => %{"email" => email}}) do
+    if user = Accounts.get_user_by_email(email) do
+      Accounts.deliver_user_confirmation_instructions(
+        user,
+        &Routes.user_confirmation_url(conn, :edit, &1)
+      )
+    end
+
+    conn
+    |> put_flash(
+      :info,
+      "If your email is in our system and it has not been confirmed yet, " <>
+        "you will receive an email with instructions shortly."
+    )
+    |> redirect(to: "/")
+  end
+
+  def edit(conn, %{"token" => token}) do
+    render(conn, "edit.html", token: token)
+  end
+
+  # Do not log in the user after confirmation to avoid a
+  # leaked token giving the user access to the account.
+  def update(conn, %{"token" => token}) do
+    case Accounts.confirm_user(token) do
+      {:ok, _} ->
+        conn
+        |> put_flash(:info, "User confirmed successfully.")
+        |> redirect(to: "/")
+
+      :error ->
+        # If there is a current user and the account was already confirmed,
+        # then odds are that the confirmation link was already visited, either
+        # by some automation or by the user themselves, so we redirect without
+        # a warning message.
+        case conn.assigns do
+          %{current_user: %{confirmed_at: confirmed_at}} when not is_nil(confirmed_at) ->
+            redirect(conn, to: "/")
+
+          %{} ->
+            conn
+            |> put_flash(:error, "User confirmation link is invalid or it has expired.")
+            |> redirect(to: "/")
+        end
+    end
+  end
+end

lib/link_shortener_web/controllers/user_registration_controller.ex

@@ -0,0 +1,30 @@
+defmodule LinkShortenerWeb.UserRegistrationController do
+  use LinkShortenerWeb, :controller
+
+  alias LinkShortener.Accounts
+  alias LinkShortener.Accounts.User
+  alias LinkShortenerWeb.UserAuth
+
+  def new(conn, _params) do
+    changeset = Accounts.change_user_registration(%User{})
+    render(conn, "new.html", changeset: changeset)
+  end
+
+  def create(conn, %{"user" => user_params}) do
+    case Accounts.register_user(user_params) do
+      {:ok, user} ->
+        {:ok, _} =
+          Accounts.deliver_user_confirmation_instructions(
+            user,
+            &Routes.user_confirmation_url(conn, :edit, &1)
+          )
+
+        conn
+        |> put_flash(:info, "User created successfully.")
+        |> UserAuth.log_in_user(user)
+
+      {:error, %Ecto.Changeset{} = changeset} ->
+        render(conn, "new.html", changeset: changeset)
+    end
+  end
+end

lib/link_shortener_web/controllers/user_reset_password_controller.ex

@@ -0,0 +1,58 @@
+defmodule LinkShortenerWeb.UserResetPasswordController do
+  use LinkShortenerWeb, :controller
+
+  alias LinkShortener.Accounts
+
+  plug :get_user_by_reset_password_token when action in [:edit, :update]
+
+  def new(conn, _params) do
+    render(conn, "new.html")
+  end
+
+  def create(conn, %{"user" => %{"email" => email}}) do
+    if user = Accounts.get_user_by_email(email) do
+      Accounts.deliver_user_reset_password_instructions(
+        user,
+        &Routes.user_reset_password_url(conn, :edit, &1)
+      )
+    end
+
+    conn
+    |> put_flash(
+      :info,
+      "If your email is in our system, you will receive instructions to reset your password shortly."
+    )
+    |> redirect(to: "/")
+  end
+
+  def edit(conn, _params) do
+    render(conn, "edit.html", changeset: Accounts.change_user_password(conn.assigns.user))
+  end
+
+  # Do not log in the user after reset password to avoid a
+  # leaked token giving the user access to the account.
+  def update(conn, %{"user" => user_params}) do
+    case Accounts.reset_user_password(conn.assigns.user, user_params) do
+      {:ok, _} ->
+        conn
+        |> put_flash(:info, "Password reset successfully.")
+        |> redirect(to: Routes.user_session_path(conn, :new))
+
+      {:error, changeset} ->
+        render(conn, "edit.html", changeset: changeset)
+    end
+  end
+
+  defp get_user_by_reset_password_token(conn, _opts) do
+    %{"token" => token} = conn.params
+
+    if user = Accounts.get_user_by_reset_password_token(token) do
+      conn |> assign(:user, user) |> assign(:token, token)
+    else
+      conn
+      |> put_flash(:error, "Reset password link is invalid or it has expired.")
+      |> redirect(to: "/")
+      |> halt()
+    end
+  end
+end

lib/link_shortener_web/controllers/user_session_controller.ex

@@ -0,0 +1,27 @@
+defmodule LinkShortenerWeb.UserSessionController do
+  use LinkShortenerWeb, :controller
+
+  alias LinkShortener.Accounts
+  alias LinkShortenerWeb.UserAuth
+
+  def new(conn, _params) do
+    render(conn, "new.html", error_message: nil)
+  end
+
+  def create(conn, %{"user" => user_params}) do
+    %{"email" => email, "password" => password} = user_params
+
+    if user = Accounts.get_user_by_email_and_password(email, password) do
+      UserAuth.log_in_user(conn, user, user_params)
+    else
+      # In order to prevent user enumeration attacks, don't disclose whether the email is registered.
+      render(conn, "new.html", error_message: "Invalid email or password")
+    end
+  end
+
+  def delete(conn, _params) do
+    conn
+    |> put_flash(:info, "Logged out successfully.")
+    |> UserAuth.log_out_user()
+  end
+end

lib/link_shortener_web/controllers/user_settings_controller.ex

@@ -0,0 +1,74 @@
+defmodule LinkShortenerWeb.UserSettingsController do
+  use LinkShortenerWeb, :controller
+
+  alias LinkShortener.Accounts
+  alias LinkShortenerWeb.UserAuth
+
+  plug :assign_email_and_password_changesets
+
+  def edit(conn, _params) do
+    render(conn, "edit.html")
+  end
+
+  def update(conn, %{"action" => "update_email"} = params) do
+    %{"current_password" => password, "user" => user_params} = params
+    user = conn.assigns.current_user
+
+    case Accounts.apply_user_email(user, password, user_params) do
+      {:ok, applied_user} ->
+        Accounts.deliver_update_email_instructions(
+          applied_user,
+          user.email,
+          &Routes.user_settings_url(conn, :confirm_email, &1)
+        )
+
+        conn
+        |> put_flash(
+          :info,
+          "A link to confirm your email change has been sent to the new address."
+        )
+        |> redirect(to: Routes.user_settings_path(conn, :edit))
+
+      {:error, changeset} ->
+        render(conn, "edit.html", email_changeset: changeset)
+    end
+  end
+
+  def update(conn, %{"action" => "update_password"} = params) do
+    %{"current_password" => password, "user" => user_params} = params
+    user = conn.assigns.current_user
+
+    case Accounts.update_user_password(user, password, user_params) do
+      {:ok, user} ->
+        conn
+        |> put_flash(:info, "Password updated successfully.")
+        |> put_session(:user_return_to, Routes.user_settings_path(conn, :edit))
+        |> UserAuth.log_in_user(user)
+
+      {:error, changeset} ->
+        render(conn, "edit.html", password_changeset: changeset)
+    end
+  end
+
+  def confirm_email(conn, %{"token" => token}) do
+    case Accounts.update_user_email(conn.assigns.current_user, token) do
+      :ok ->
+        conn
+        |> put_flash(:info, "Email changed successfully.")
+        |> redirect(to: Routes.user_settings_path(conn, :edit))
+
+      :error ->
+        conn
+        |> put_flash(:error, "Email change link is invalid or it has expired.")
+        |> redirect(to: Routes.user_settings_path(conn, :edit))
+    end
+  end
+
+  defp assign_email_and_password_changesets(conn, _opts) do
+    user = conn.assigns.current_user
+
+    conn
+    |> assign(:email_changeset, Accounts.change_user_email(user))
+    |> assign(:password_changeset, Accounts.change_user_password(user))
+  end
+end

lib/link_shortener_web/router.ex

@@ -1,6 +1,8 @@
 defmodule LinkShortenerWeb.Router do
   use LinkShortenerWeb, :router
 
+  import LinkShortenerWeb.UserAuth
+
   pipeline :browser do
     plug :accepts, ["html"]
     plug :fetch_session
@@ -8,6 +10,7 @@ defmodule LinkShortenerWeb.Router do
     plug :put_root_layout, {LinkShortenerWeb.LayoutView, :root}
     plug :protect_from_forgery
     plug :put_secure_browser_headers
+    plug :fetch_current_user
   end
 
   pipeline :api do
@@ -27,6 +30,8 @@ defmodule LinkShortenerWeb.Router do
 
     scope "/v1", Api.V1, as: :v1 do
       resources "/links", LinkController
+      post "/users/signup", UserController, :create
+      post "/users/signin", UserController, :signin
     end
   end
 
@@ -58,4 +63,37 @@ defmodule LinkShortenerWeb.Router do
       forward "/mailbox", Plug.Swoosh.MailboxPreview
     end
   end
+
+  ## Authentication routes
+
+  scope "/", LinkShortenerWeb do
+    pipe_through [:browser, :redirect_if_user_is_authenticated]
+
+    get "/users/register", UserRegistrationController, :new
+    post "/users/register", UserRegistrationController, :create
+    get "/users/log_in", UserSessionController, :new
+    post "/users/log_in", UserSessionController, :create
+    get "/users/reset_password", UserResetPasswordController, :new
+    post "/users/reset_password", UserResetPasswordController, :create
+    get "/users/reset_password/:token", UserResetPasswordController, :edit
+    put "/users/reset_password/:token", UserResetPasswordController, :update
+  end
+
+  scope "/", LinkShortenerWeb do
+    pipe_through [:browser, :require_authenticated_user]
+
+    get "/users/settings", UserSettingsController, :edit
+    put "/users/settings", UserSettingsController, :update
+    get "/users/settings/confirm_email/:token", UserSettingsController, :confirm_email
+  end
+
+  scope "/", LinkShortenerWeb do
+    pipe_through [:browser]
+
+    delete "/users/log_out", UserSessionController, :delete
+    get "/users/confirm", UserConfirmationController, :new
+    post "/users/confirm", UserConfirmationController, :create
+    get "/users/confirm/:token", UserConfirmationController, :edit
+    post "/users/confirm/:token", UserConfirmationController, :update
+  end
 end

lib/link_shortener_web/templates/layout/_user_menu.html.heex

@@ -0,0 +1,10 @@
+<ul>
+<%= if @current_user do %>
+  <li><%= @current_user.email %></li>
+  <li><%= link "Settings", to: Routes.user_settings_path(@conn, :edit) %></li>
+  <li><%= link "Log out", to: Routes.user_session_path(@conn, :delete), method: :delete %></li>
+<% else %>
+  <li><%= link "Register", to: Routes.user_registration_path(@conn, :new) %></li>
+  <li><%= link "Log in", to: Routes.user_session_path(@conn, :new) %></li>
+<% end %>
+</ul>

lib/link_shortener_web/templates/layout/root.html.heex

@@ -18,6 +18,7 @@
               <li><%= link "LiveDashboard", to: Routes.live_dashboard_path(@conn, :home) %></li>
             <% end %>
           </ul>
+          <%= render "_user_menu.html", assigns %>
         </nav>
         <a href={Routes.page_path(@conn, :index)} class="phx-logo">
           Link Shortener

lib/link_shortener_web/templates/user_confirmation/edit.html.heex

@@ -0,0 +1,12 @@
+<h1>Confirm account</h1>
+
+<.form let={_f} for={:user} action={Routes.user_confirmation_path(@conn, :update, @token)}>
+  <div>
+    <%= submit "Confirm my account" %>
+  </div>
+</.form>
+
+<p>
+  <%= link "Register", to: Routes.user_registration_path(@conn, :new) %> |
+  <%= link "Log in", to: Routes.user_session_path(@conn, :new) %>
+</p>

lib/link_shortener_web/templates/user_confirmation/new.html.heex

@@ -0,0 +1,15 @@
+<h1>Resend confirmation instructions</h1>
+
+<.form let={f} for={:user} action={Routes.user_confirmation_path(@conn, :create)}>
+  <%= label f, :email %>
+  <%= email_input f, :email, required: true %>
+
+  <div>
+    <%= submit "Resend confirmation instructions" %>
+  </div>
+</.form>
+
+<p>
+  <%= link "Register", to: Routes.user_registration_path(@conn, :new) %> |
+  <%= link "Log in", to: Routes.user_session_path(@conn, :new) %>
+</p>

lib/link_shortener_web/templates/user_registration/new.html.heex

@@ -0,0 +1,26 @@
+<h1>Register</h1>
+
+<.form let={f} for={@changeset} action={Routes.user_registration_path(@conn, :create)}>
+  <%= if @changeset.action do %>
+    <div class="alert alert-danger">
+      <p>Oops, something went wrong! Please check the errors below.</p>
+    </div>
+  <% end %>
+
+  <%= label f, :email %>
+  <%= email_input f, :email, required: true %>
+  <%= error_tag f, :email %>
+
+  <%= label f, :password %>
+  <%= password_input f, :password, required: true %>
+  <%= error_tag f, :password %>
+
+  <div>
+    <%= submit "Register" %>
+  </div>
+</.form>
+
+<p>
+  <%= link "Log in", to: Routes.user_session_path(@conn, :new) %> |
+  <%= link "Forgot your password?", to: Routes.user_reset_password_path(@conn, :new) %>
+</p>

lib/link_shortener_web/templates/user_reset_password/edit.html.heex

@@ -0,0 +1,26 @@
+<h1>Reset password</h1>
+
+<.form let={f} for={@changeset} action={Routes.user_reset_password_path(@conn, :update, @token)}>
+  <%= if @changeset.action do %>
+    <div class="alert alert-danger">
+      <p>Oops, something went wrong! Please check the errors below.</p>
+    </div>
+  <% end %>
+
+  <%= label f, :password, "New password" %>
+  <%= password_input f, :password, required: true %>
+  <%= error_tag f, :password %>
+
+  <%= label f, :password_confirmation, "Confirm new password" %>
+  <%= password_input f, :password_confirmation, required: true %>
+  <%= error_tag f, :password_confirmation %>
+
+  <div>
+    <%= submit "Reset password" %>
+  </div>
+</.form>
+
+<p>
+  <%= link "Register", to: Routes.user_registration_path(@conn, :new) %> |
+  <%= link "Log in", to: Routes.user_session_path(@conn, :new) %>
+</p>

lib/link_shortener_web/templates/user_reset_password/new.html.heex

@@ -0,0 +1,15 @@
+<h1>Forgot your password?</h1>
+
+<.form let={f} for={:user} action={Routes.user_reset_password_path(@conn, :create)}>
+  <%= label f, :email %>
+  <%= email_input f, :email, required: true %>
+
+  <div>
+    <%= submit "Send instructions to reset password" %>
+  </div>
+</.form>
+
+<p>
+  <%= link "Register", to: Routes.user_registration_path(@conn, :new) %> |
+  <%= link "Log in", to: Routes.user_session_path(@conn, :new) %>
+</p>

lib/link_shortener_web/templates/user_session/new.html.heex

@@ -0,0 +1,27 @@
+<h1>Log in</h1>
+
+<.form let={f} for={@conn} action={Routes.user_session_path(@conn, :create)} as={:user}>
+  <%= if @error_message do %>
+    <div class="alert alert-danger">
+      <p><%= @error_message %></p>
+    </div>
+  <% end %>
+
+  <%= label f, :email %>
+  <%= email_input f, :email, required: true %>
+
+  <%= label f, :password %>
+  <%= password_input f, :password, required: true %>
+
+  <%= label f, :remember_me, "Keep me logged in for 60 days" %>
+  <%= checkbox f, :remember_me %>
+
+  <div>
+    <%= submit "Log in" %>
+  </div>
+</.form>
+
+<p>
+  <%= link "Register", to: Routes.user_registration_path(@conn, :new) %> |
+  <%= link "Forgot your password?", to: Routes.user_reset_password_path(@conn, :new) %>
+</p>

lib/link_shortener_web/templates/user_settings/edit.html.heex

@@ -0,0 +1,53 @@
+<h1>Settings</h1>
+
+<h3>Change email</h3>
+
+<.form let={f} for={@email_changeset} action={Routes.user_settings_path(@conn, :update)} id="update_email">
+  <%= if @email_changeset.action do %>
+    <div class="alert alert-danger">
+      <p>Oops, something went wrong! Please check the errors below.</p>
+    </div>
+  <% end %>
+
+  <%= hidden_input f, :action, name: "action", value: "update_email" %>
+
+  <%= label f, :email %>
+  <%= email_input f, :email, required: true %>
+  <%= error_tag f, :email %>
+
+  <%= label f, :current_password, for: "current_password_for_email" %>
+  <%= password_input f, :current_password, required: true, name: "current_password", id: "current_password_for_email" %>
+  <%= error_tag f, :current_password %>
+
+  <div>
+    <%= submit "Change email" %>
+  </div>
+</.form>
+
+<h3>Change password</h3>
+
+<.form let={f} for={@password_changeset} action={Routes.user_settings_path(@conn, :update)} id="update_password">
+  <%= if @password_changeset.action do %>
+    <div class="alert alert-danger">
+      <p>Oops, something went wrong! Please check the errors below.</p>
+    </div>
+  <% end %>
+
+  <%= hidden_input f, :action, name: "action", value: "update_password" %>
+
+  <%= label f, :password, "New password" %>
+  <%= password_input f, :password, required: true %>
+  <%= error_tag f, :password %>
+
+  <%= label f, :password_confirmation, "Confirm new password" %>
+  <%= password_input f, :password_confirmation, required: true %>
+  <%= error_tag f, :password_confirmation %>
+
+  <%= label f, :current_password, for: "current_password_for_password" %>
+  <%= password_input f, :current_password, required: true, name: "current_password", id: "current_password_for_password" %>
+  <%= error_tag f, :current_password %>
+
+  <div>
+    <%= submit "Change password" %>
+  </div>
+</.form>

lib/link_shortener_web/views/api/v1/user_view.ex

@@ -0,0 +1,12 @@
+defmodule LinkShortenerWeb.Api.V1.UserView do
+  use LinkShortenerWeb, :view
+
+  alias LinkShortenerWeb.Api.V1.UserView
+
+  def render("user.json", %{user: user, token: token}) do
+    %{
+      email: user.email,
+      token: token
+    }
+  end
+end

lib/link_shortener_web/views/user_confirmation_view.ex

@@ -0,0 +1,3 @@
+defmodule LinkShortenerWeb.UserConfirmationView do
+  use LinkShortenerWeb, :view
+end

lib/link_shortener_web/views/user_registration_view.ex

@@ -0,0 +1,3 @@
+defmodule LinkShortenerWeb.UserRegistrationView do
+  use LinkShortenerWeb, :view
+end

lib/link_shortener_web/views/user_reset_password_view.ex

@@ -0,0 +1,3 @@
+defmodule LinkShortenerWeb.UserResetPasswordView do
+  use LinkShortenerWeb, :view
+end

lib/link_shortener_web/views/user_session_view.ex

@@ -0,0 +1,3 @@
+defmodule LinkShortenerWeb.UserSessionView do
+  use LinkShortenerWeb, :view
+end

lib/link_shortener_web/views/user_settings_view.ex

@@ -0,0 +1,3 @@
+defmodule LinkShortenerWeb.UserSettingsView do
+  use LinkShortenerWeb, :view
+end

mix.exs

@@ -33,6 +33,7 @@ defmodule LinkShortener.MixProject do
   # Type `mix help deps` for examples and options.
   defp deps do
     [
+      {:bcrypt_elixir, "~> 3.0"},
       {:phoenix, "~> 1.6.15"},
       {:phoenix_ecto, "~> 4.4"},
       {:ecto_sql, "~> 3.6"},
@@ -48,7 +49,9 @@ defmodule LinkShortener.MixProject do
       {:telemetry_poller, "~> 1.0"},
       {:gettext, "~> 0.18"},
       {:jason, "~> 1.2"},
-      {:plug_cowboy, "~> 2.5"}
+      {:plug_cowboy, "~> 2.5"},
+      {:guardian, "~> 1.0"},
+      {:comeonin, "~> 5.3"},
     ]
   end
 

mix.lock

@@ -1,5 +1,7 @@
 %{
+  "bcrypt_elixir": {:hex, :bcrypt_elixir, "3.0.1", "9be815469e6bfefec40fa74658ecbbe6897acfb57614df1416eeccd4903f602c", [:make, :mix], [{:comeonin, "~> 5.3", [hex: :comeonin, repo: "hexpm", optional: false]}, {:elixir_make, "~> 0.6", [hex: :elixir_make, repo: "hexpm", optional: false]}], "hexpm", "486bb95efb645d1efc6794c1ddd776a186a9a713abf06f45708a6ce324fb96cf"},
   "castore": {:hex, :castore, "1.0.3", "7130ba6d24c8424014194676d608cb989f62ef8039efd50ff4b3f33286d06db8", [:mix], [], "hexpm", "680ab01ef5d15b161ed6a95449fac5c6b8f60055677a8e79acf01b27baa4390b"},
+  "comeonin": {:hex, :comeonin, "5.3.3", "2c564dac95a35650e9b6acfe6d2952083d8a08e4a89b93a481acb552b325892e", [:mix], [], "hexpm", "3e38c9c2cb080828116597ca8807bb482618a315bfafd98c90bc22a821cc84df"},
   "cowboy": {:hex, :cowboy, "2.10.0", "ff9ffeff91dae4ae270dd975642997afe2a1179d94b1887863e43f681a203e26", [:make, :rebar3], [{:cowlib, "2.12.1", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, "1.8.0", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm", "3afdccb7183cc6f143cb14d3cf51fa00e53db9ec80cdcd525482f5e99bc41d6b"},
   "cowboy_telemetry": {:hex, :cowboy_telemetry, "0.4.0", "f239f68b588efa7707abce16a84d0d2acf3a0f50571f8bb7f56a15865aae820c", [:rebar3], [{:cowboy, "~> 2.7", [hex: :cowboy, repo: "hexpm", optional: false]}, {:telemetry, "~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "7d98bac1ee4565d31b62d59f8823dfd8356a169e7fcbb83831b8a5397404c9de"},
   "cowlib": {:hex, :cowlib, "2.12.1", "a9fa9a625f1d2025fe6b462cb865881329b5caff8f1854d1cbc9f9533f00e1e1", [:make, :rebar3], [], "hexpm", "163b73f6367a7341b33c794c4e88e7dbfe6498ac42dcd69ef44c5bc5507c8db0"},
@@ -7,12 +9,15 @@
   "decimal": {:hex, :decimal, "2.1.1", "5611dca5d4b2c3dd497dec8f68751f1f1a54755e8ed2a966c2633cf885973ad6", [:mix], [], "hexpm", "53cfe5f497ed0e7771ae1a475575603d77425099ba5faef9394932b35020ffcc"},
   "ecto": {:hex, :ecto, "3.10.2", "6b887160281a61aa16843e47735b8a266caa437f80588c3ab80a8a960e6abe37", [:mix], [{:decimal, "~> 1.6 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "6a895778f0d7648a4b34b486af59a1c8009041fbdf2b17f1ac215eb829c60235"},
   "ecto_sql": {:hex, :ecto_sql, "3.10.1", "6ea6b3036a0b0ca94c2a02613fd9f742614b5cfe494c41af2e6571bb034dd94c", [:mix], [{:db_connection, "~> 2.5 or ~> 2.4.1", [hex: :db_connection, repo: "hexpm", optional: false]}, {:ecto, "~> 3.10.0", [hex: :ecto, repo: "hexpm", optional: false]}, {:myxql, "~> 0.6.0", [hex: :myxql, repo: "hexpm", optional: true]}, {:postgrex, "~> 0.16.0 or ~> 0.17.0 or ~> 1.0", [hex: :postgrex, repo: "hexpm", optional: true]}, {:tds, "~> 2.1.1 or ~> 2.2", [hex: :tds, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4.0 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "f6a25bdbbd695f12c8171eaff0851fa4c8e72eec1e98c7364402dda9ce11c56b"},
+  "elixir_make": {:hex, :elixir_make, "0.7.7", "7128c60c2476019ed978210c245badf08b03dbec4f24d05790ef791da11aa17c", [:mix], [{:castore, "~> 0.1 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}], "hexpm", "5bc19fff950fad52bbe5f211b12db9ec82c6b34a9647da0c2224b8b8464c7e6c"},
   "esbuild": {:hex, :esbuild, "0.7.1", "fa0947e8c3c3c2f86c9bf7e791a0a385007ccd42b86885e8e893bdb6631f5169", [:mix], [{:castore, ">= 0.0.0", [hex: :castore, repo: "hexpm", optional: false]}], "hexpm", "66661cdf70b1378ee4dc16573fcee67750b59761b2605a0207c267ab9d19f13c"},
   "expo": {:hex, :expo, "0.4.1", "1c61d18a5df197dfda38861673d392e642649a9cef7694d2f97a587b2cfb319b", [:mix], [], "hexpm", "2ff7ba7a798c8c543c12550fa0e2cbc81b95d4974c65855d8d15ba7b37a1ce47"},
   "file_system": {:hex, :file_system, "0.2.10", "fb082005a9cd1711c05b5248710f8826b02d7d1784e7c3451f9c1231d4fc162d", [:mix], [], "hexpm", "41195edbfb562a593726eda3b3e8b103a309b733ad25f3d642ba49696bf715dc"},
   "floki": {:hex, :floki, "0.34.3", "5e2dcaec5d7c228ce5b1d3501502e308b2d79eb655e4191751a1fe491c37feac", [:mix], [], "hexpm", "9577440eea5b97924b4bf3c7ea55f7b8b6dce589f9b28b096cc294a8dc342341"},
   "gettext": {:hex, :gettext, "0.22.3", "c8273e78db4a0bb6fba7e9f0fd881112f349a3117f7f7c598fa18c66c888e524", [:mix], [{:expo, "~> 0.4.0", [hex: :expo, repo: "hexpm", optional: false]}], "hexpm", "935f23447713954a6866f1bb28c3a878c4c011e802bcd68a726f5e558e4b64bd"},
+  "guardian": {:hex, :guardian, "1.2.1", "bdc8dd3dbf0fb7216cb6f91c11831faa1a64d39cdaed9a611e37f2413e584983", [:mix], [{:jose, "~> 1.8", [hex: :jose, repo: "hexpm", optional: false]}, {:phoenix, "~> 1.3", [hex: :phoenix, repo: "hexpm", optional: true]}, {:plug, "~> 1.3.3 or ~> 1.4", [hex: :plug, repo: "hexpm", optional: true]}], "hexpm", "723fc404edfb7bd5cba4cd83329b352037f102aa97468f44e58ac7f47c136a98"},
   "jason": {:hex, :jason, "1.4.0", "e855647bc964a44e2f67df589ccf49105ae039d4179db7f6271dfd3843dc27e6", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "79a3791085b2a0f743ca04cec0f7be26443738779d09302e01318f97bdb82121"},
+  "jose": {:hex, :jose, "1.11.6", "613fda82552128aa6fb804682e3a616f4bc15565a048dabd05b1ebd5827ed965", [:mix, :rebar3], [], "hexpm", "6275cb75504f9c1e60eeacb771adfeee4905a9e182103aa59b53fed651ff9738"},
   "mime": {:hex, :mime, "2.0.5", "dc34c8efd439abe6ae0343edbb8556f4d63f178594894720607772a041b04b02", [:mix], [], "hexpm", "da0d64a365c45bc9935cc5c8a7fc5e49a0e0f9932a761c55d6c52b142780a05c"},
   "phoenix": {:hex, :phoenix, "1.6.16", "e5bdd18c7a06da5852a25c7befb72246de4ddc289182285f8685a40b7b5f5451", [:mix], [{:castore, ">= 0.0.0", [hex: :castore, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:phoenix_pubsub, "~> 2.0", [hex: :phoenix_pubsub, repo: "hexpm", optional: false]}, {:phoenix_view, "~> 1.0 or ~> 2.0", [hex: :phoenix_view, repo: "hexpm", optional: false]}, {:plug, "~> 1.10", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 2.2", [hex: :plug_cowboy, repo: "hexpm", optional: true]}, {:plug_crypto, "~> 1.2", [hex: :plug_crypto, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "e15989ff34f670a96b95ef6d1d25bad0d9c50df5df40b671d8f4a669e050ac39"},
   "phoenix_ecto": {:hex, :phoenix_ecto, "4.4.2", "b21bd01fdeffcfe2fab49e4942aa938b6d3e89e93a480d4aee58085560a0bc0d", [:mix], [{:ecto, "~> 3.5", [hex: :ecto, repo: "hexpm", optional: false]}, {:phoenix_html, "~> 2.14.2 or ~> 3.0", [hex: :phoenix_html, repo: "hexpm", optional: true]}, {:plug, "~> 1.9", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm", "70242edd4601d50b69273b057ecf7b684644c19ee750989fd555625ae4ce8f5d"},

priv/repo/migrations/20230808170900_create_users_auth_tables.exs

@@ -0,0 +1,27 @@
+defmodule LinkShortener.Repo.Migrations.CreateUsersAuthTables do
+  use Ecto.Migration
+
+  def change do
+    execute "CREATE EXTENSION IF NOT EXISTS citext", ""
+
+    create table(:users) do
+      add :email, :citext, null: false
+      add :hashed_password, :string, null: false
+      add :confirmed_at, :naive_datetime
+      timestamps()
+    end
+
+    create unique_index(:users, [:email])
+
+    create table(:users_tokens) do
+      add :user_id, references(:users, on_delete: :delete_all), null: false
+      add :token, :binary, null: false
+      add :context, :string, null: false
+      add :sent_to, :string
+      timestamps(updated_at: false)
+    end
+
+    create index(:users_tokens, [:user_id])
+    create unique_index(:users_tokens, [:context, :token])
+  end
+end

test/link_shortener/accounts/accounts_test.exs

@@ -0,0 +1,508 @@
+defmodule LinkShortener.AccountsTest do
+  use LinkShortener.DataCase
+
+  alias LinkShortener.Accounts
+
+  import LinkShortener.AccountsFixtures
+  alias LinkShortener.Accounts.{User, UserToken}
+
+  describe "get_user_by_email/1" do
+    test "does not return the user if the email does not exist" do
+      refute Accounts.get_user_by_email("unknown@example.com")
+    end
+
+    test "returns the user if the email exists" do
+      %{id: id} = user = user_fixture()
+      assert %User{id: ^id} = Accounts.get_user_by_email(user.email)
+    end
+  end
+
+  describe "get_user_by_email_and_password/2" do
+    test "does not return the user if the email does not exist" do
+      refute Accounts.get_user_by_email_and_password("unknown@example.com", "hello world!")
+    end
+
+    test "does not return the user if the password is not valid" do
+      user = user_fixture()
+      refute Accounts.get_user_by_email_and_password(user.email, "invalid")
+    end
+
+    test "returns the user if the email and password are valid" do
+      %{id: id} = user = user_fixture()
+
+      assert %User{id: ^id} =
+               Accounts.get_user_by_email_and_password(user.email, valid_user_password())
+    end
+  end
+
+  describe "get_user!/1" do
+    test "raises if id is invalid" do
+      assert_raise Ecto.NoResultsError, fn ->
+        Accounts.get_user!(-1)
+      end
+    end
+
+    test "returns the user with the given id" do
+      %{id: id} = user = user_fixture()
+      assert %User{id: ^id} = Accounts.get_user!(user.id)
+    end
+  end
+
+  describe "register_user/1" do
+    test "requires email and password to be set" do
+      {:error, changeset} = Accounts.register_user(%{})
+
+      assert %{
+               password: ["can't be blank"],
+               email: ["can't be blank"]
+             } = errors_on(changeset)
+    end
+
+    test "validates email and password when given" do
+      {:error, changeset} = Accounts.register_user(%{email: "not valid", password: "not valid"})
+
+      assert %{
+               email: ["must have the @ sign and no spaces"],
+               password: ["should be at least 12 character(s)"]
+             } = errors_on(changeset)
+    end
+
+    test "validates maximum values for email and password for security" do
+      too_long = String.duplicate("db", 100)
+      {:error, changeset} = Accounts.register_user(%{email: too_long, password: too_long})
+      assert "should be at most 160 character(s)" in errors_on(changeset).email
+      assert "should be at most 72 character(s)" in errors_on(changeset).password
+    end
+
+    test "validates email uniqueness" do
+      %{email: email} = user_fixture()
+      {:error, changeset} = Accounts.register_user(%{email: email})
+      assert "has already been taken" in errors_on(changeset).email
+
+      # Now try with the upper cased email too, to check that email case is ignored.
+      {:error, changeset} = Accounts.register_user(%{email: String.upcase(email)})
+      assert "has already been taken" in errors_on(changeset).email
+    end
+
+    test "registers users with a hashed password" do
+      email = unique_user_email()
+      {:ok, user} = Accounts.register_user(valid_user_attributes(email: email))
+      assert user.email == email
+      assert is_binary(user.hashed_password)
+      assert is_nil(user.confirmed_at)
+      assert is_nil(user.password)
+    end
+  end
+
+  describe "change_user_registration/2" do
+    test "returns a changeset" do
+      assert %Ecto.Changeset{} = changeset = Accounts.change_user_registration(%User{})
+      assert changeset.required == [:password, :email]
+    end
+
+    test "allows fields to be set" do
+      email = unique_user_email()
+      password = valid_user_password()
+
+      changeset =
+        Accounts.change_user_registration(
+          %User{},
+          valid_user_attributes(email: email, password: password)
+        )
+
+      assert changeset.valid?
+      assert get_change(changeset, :email) == email
+      assert get_change(changeset, :password) == password
+      assert is_nil(get_change(changeset, :hashed_password))
+    end
+  end
+
+  describe "change_user_email/2" do
+    test "returns a user changeset" do
+      assert %Ecto.Changeset{} = changeset = Accounts.change_user_email(%User{})
+      assert changeset.required == [:email]
+    end
+  end
+
+  describe "apply_user_email/3" do
+    setup do
+      %{user: user_fixture()}
+    end
+
+    test "requires email to change", %{user: user} do
+      {:error, changeset} = Accounts.apply_user_email(user, valid_user_password(), %{})
+      assert %{email: ["did not change"]} = errors_on(changeset)
+    end
+
+    test "validates email", %{user: user} do
+      {:error, changeset} =
+        Accounts.apply_user_email(user, valid_user_password(), %{email: "not valid"})
+
+      assert %{email: ["must have the @ sign and no spaces"]} = errors_on(changeset)
+    end
+
+    test "validates maximum value for email for security", %{user: user} do
+      too_long = String.duplicate("db", 100)
+
+      {:error, changeset} =
+        Accounts.apply_user_email(user, valid_user_password(), %{email: too_long})
+
+      assert "should be at most 160 character(s)" in errors_on(changeset).email
+    end
+
+    test "validates email uniqueness", %{user: user} do
+      %{email: email} = user_fixture()
+
+      {:error, changeset} =
+        Accounts.apply_user_email(user, valid_user_password(), %{email: email})
+
+      assert "has already been taken" in errors_on(changeset).email
+    end
+
+    test "validates current password", %{user: user} do
+      {:error, changeset} =
+        Accounts.apply_user_email(user, "invalid", %{email: unique_user_email()})
+
+      assert %{current_password: ["is not valid"]} = errors_on(changeset)
+    end
+
+    test "applies the email without persisting it", %{user: user} do
+      email = unique_user_email()
+      {:ok, user} = Accounts.apply_user_email(user, valid_user_password(), %{email: email})
+      assert user.email == email
+      assert Accounts.get_user!(user.id).email != email
+    end
+  end
+
+  describe "deliver_update_email_instructions/3" do
+    setup do
+      %{user: user_fixture()}
+    end
+
+    test "sends token through notification", %{user: user} do
+      token =
+        extract_user_token(fn url ->
+          Accounts.deliver_update_email_instructions(user, "current@example.com", url)
+        end)
+
+      {:ok, token} = Base.url_decode64(token, padding: false)
+      assert user_token = Repo.get_by(UserToken, token: :crypto.hash(:sha256, token))
+      assert user_token.user_id == user.id
+      assert user_token.sent_to == user.email
+      assert user_token.context == "change:current@example.com"
+    end
+  end
+
+  describe "update_user_email/2" do
+    setup do
+      user = user_fixture()
+      email = unique_user_email()
+
+      token =
+        extract_user_token(fn url ->
+          Accounts.deliver_update_email_instructions(%{user | email: email}, user.email, url)
+        end)
+
+      %{user: user, token: token, email: email}
+    end
+
+    test "updates the email with a valid token", %{user: user, token: token, email: email} do
+      assert Accounts.update_user_email(user, token) == :ok
+      changed_user = Repo.get!(User, user.id)
+      assert changed_user.email != user.email
+      assert changed_user.email == email
+      assert changed_user.confirmed_at
+      assert changed_user.confirmed_at != user.confirmed_at
+      refute Repo.get_by(UserToken, user_id: user.id)
+    end
+
+    test "does not update email with invalid token", %{user: user} do
+      assert Accounts.update_user_email(user, "oops") == :error
+      assert Repo.get!(User, user.id).email == user.email
+      assert Repo.get_by(UserToken, user_id: user.id)
+    end
+
+    test "does not update email if user email changed", %{user: user, token: token} do
+      assert Accounts.update_user_email(%{user | email: "current@example.com"}, token) == :error
+      assert Repo.get!(User, user.id).email == user.email
+      assert Repo.get_by(UserToken, user_id: user.id)
+    end
+
+    test "does not update email if token expired", %{user: user, token: token} do
+      {1, nil} = Repo.update_all(UserToken, set: [inserted_at: ~N[2020-01-01 00:00:00]])
+      assert Accounts.update_user_email(user, token) == :error
+      assert Repo.get!(User, user.id).email == user.email
+      assert Repo.get_by(UserToken, user_id: user.id)
+    end
+  end
+
+  describe "change_user_password/2" do
+    test "returns a user changeset" do
+      assert %Ecto.Changeset{} = changeset = Accounts.change_user_password(%User{})
+      assert changeset.required == [:password]
+    end
+
+    test "allows fields to be set" do
+      changeset =
+        Accounts.change_user_password(%User{}, %{
+          "password" => "new valid password"
+        })
+
+      assert changeset.valid?
+      assert get_change(changeset, :password) == "new valid password"
+      assert is_nil(get_change(changeset, :hashed_password))
+    end
+  end
+
+  describe "update_user_password/3" do
+    setup do
+      %{user: user_fixture()}
+    end
+
+    test "validates password", %{user: user} do
+      {:error, changeset} =
+        Accounts.update_user_password(user, valid_user_password(), %{
+          password: "not valid",
+          password_confirmation: "another"
+        })
+
+      assert %{
+               password: ["should be at least 12 character(s)"],
+               password_confirmation: ["does not match password"]
+             } = errors_on(changeset)
+    end
+
+    test "validates maximum values for password for security", %{user: user} do
+      too_long = String.duplicate("db", 100)
+
+      {:error, changeset} =
+        Accounts.update_user_password(user, valid_user_password(), %{password: too_long})
+
+      assert "should be at most 72 character(s)" in errors_on(changeset).password
+    end
+
+    test "validates current password", %{user: user} do
+      {:error, changeset} =
+        Accounts.update_user_password(user, "invalid", %{password: valid_user_password()})
+
+      assert %{current_password: ["is not valid"]} = errors_on(changeset)
+    end
+
+    test "updates the password", %{user: user} do
+      {:ok, user} =
+        Accounts.update_user_password(user, valid_user_password(), %{
+          password: "new valid password"
+        })
+
+      assert is_nil(user.password)
+      assert Accounts.get_user_by_email_and_password(user.email, "new valid password")
+    end
+
+    test "deletes all tokens for the given user", %{user: user} do
+      _ = Accounts.generate_user_session_token(user)
+
+      {:ok, _} =
+        Accounts.update_user_password(user, valid_user_password(), %{
+          password: "new valid password"
+        })
+
+      refute Repo.get_by(UserToken, user_id: user.id)
+    end
+  end
+
+  describe "generate_user_session_token/1" do
+    setup do
+      %{user: user_fixture()}
+    end
+
+    test "generates a token", %{user: user} do
+      token = Accounts.generate_user_session_token(user)
+      assert user_token = Repo.get_by(UserToken, token: token)
+      assert user_token.context == "session"
+
+      # Creating the same token for another user should fail
+      assert_raise Ecto.ConstraintError, fn ->
+        Repo.insert!(%UserToken{
+          token: user_token.token,
+          user_id: user_fixture().id,
+          context: "session"
+        })
+      end
+    end
+  end
+
+  describe "get_user_by_session_token/1" do
+    setup do
+      user = user_fixture()
+      token = Accounts.generate_user_session_token(user)
+      %{user: user, token: token}
+    end
+
+    test "returns user by token", %{user: user, token: token} do
+      assert session_user = Accounts.get_user_by_session_token(token)
+      assert session_user.id == user.id
+    end
+
+    test "does not return user for invalid token" do
+      refute Accounts.get_user_by_session_token("oops")
+    end
+
+    test "does not return user for expired token", %{token: token} do
+      {1, nil} = Repo.update_all(UserToken, set: [inserted_at: ~N[2020-01-01 00:00:00]])
+      refute Accounts.get_user_by_session_token(token)
+    end
+  end
+
+  describe "delete_session_token/1" do
+    test "deletes the token" do
+      user = user_fixture()
+      token = Accounts.generate_user_session_token(user)
+      assert Accounts.delete_session_token(token) == :ok
+      refute Accounts.get_user_by_session_token(token)
+    end
+  end
+
+  describe "deliver_user_confirmation_instructions/2" do
+    setup do
+      %{user: user_fixture()}
+    end
+
+    test "sends token through notification", %{user: user} do
+      token =
+        extract_user_token(fn url ->
+          Accounts.deliver_user_confirmation_instructions(user, url)
+        end)
+
+      {:ok, token} = Base.url_decode64(token, padding: false)
+      assert user_token = Repo.get_by(UserToken, token: :crypto.hash(:sha256, token))
+      assert user_token.user_id == user.id
+      assert user_token.sent_to == user.email
+      assert user_token.context == "confirm"
+    end
+  end
+
+  describe "confirm_user/1" do
+    setup do
+      user = user_fixture()
+
+      token =
+        extract_user_token(fn url ->
+          Accounts.deliver_user_confirmation_instructions(user, url)
+        end)
+
+      %{user: user, token: token}
+    end
+
+    test "confirms the email with a valid token", %{user: user, token: token} do
+      assert {:ok, confirmed_user} = Accounts.confirm_user(token)
+      assert confirmed_user.confirmed_at
+      assert confirmed_user.confirmed_at != user.confirmed_at
+      assert Repo.get!(User, user.id).confirmed_at
+      refute Repo.get_by(UserToken, user_id: user.id)
+    end
+
+    test "does not confirm with invalid token", %{user: user} do
+      assert Accounts.confirm_user("oops") == :error
+      refute Repo.get!(User, user.id).confirmed_at
+      assert Repo.get_by(UserToken, user_id: user.id)
+    end
+
+    test "does not confirm email if token expired", %{user: user, token: token} do
+      {1, nil} = Repo.update_all(UserToken, set: [inserted_at: ~N[2020-01-01 00:00:00]])
+      assert Accounts.confirm_user(token) == :error
+      refute Repo.get!(User, user.id).confirmed_at
+      assert Repo.get_by(UserToken, user_id: user.id)
+    end
+  end
+
+  describe "deliver_user_reset_password_instructions/2" do
+    setup do
+      %{user: user_fixture()}
+    end
+
+    test "sends token through notification", %{user: user} do
+      token =
+        extract_user_token(fn url ->
+          Accounts.deliver_user_reset_password_instructions(user, url)
+        end)
+
+      {:ok, token} = Base.url_decode64(token, padding: false)
+      assert user_token = Repo.get_by(UserToken, token: :crypto.hash(:sha256, token))
+      assert user_token.user_id == user.id
+      assert user_token.sent_to == user.email
+      assert user_token.context == "reset_password"
+    end
+  end
+
+  describe "get_user_by_reset_password_token/1" do
+    setup do
+      user = user_fixture()
+
+      token =
+        extract_user_token(fn url ->
+          Accounts.deliver_user_reset_password_instructions(user, url)
+        end)
+
+      %{user: user, token: token}
+    end
+
+    test "returns the user with valid token", %{user: %{id: id}, token: token} do
+      assert %User{id: ^id} = Accounts.get_user_by_reset_password_token(token)
+      assert Repo.get_by(UserToken, user_id: id)
+    end
+
+    test "does not return the user with invalid token", %{user: user} do
+      refute Accounts.get_user_by_reset_password_token("oops")
+      assert Repo.get_by(UserToken, user_id: user.id)
+    end
+
+    test "does not return the user if token expired", %{user: user, token: token} do
+      {1, nil} = Repo.update_all(UserToken, set: [inserted_at: ~N[2020-01-01 00:00:00]])
+      refute Accounts.get_user_by_reset_password_token(token)
+      assert Repo.get_by(UserToken, user_id: user.id)
+    end
+  end
+
+  describe "reset_user_password/2" do
+    setup do
+      %{user: user_fixture()}
+    end
+
+    test "validates password", %{user: user} do
+      {:error, changeset} =
+        Accounts.reset_user_password(user, %{
+          password: "not valid",
+          password_confirmation: "another"
+        })
+
+      assert %{
+               password: ["should be at least 12 character(s)"],
+               password_confirmation: ["does not match password"]
+             } = errors_on(changeset)
+    end
+
+    test "validates maximum values for password for security", %{user: user} do
+      too_long = String.duplicate("db", 100)
+      {:error, changeset} = Accounts.reset_user_password(user, %{password: too_long})
+      assert "should be at most 72 character(s)" in errors_on(changeset).password
+    end
+
+    test "updates the password", %{user: user} do
+      {:ok, updated_user} = Accounts.reset_user_password(user, %{password: "new valid password"})
+      assert is_nil(updated_user.password)
+      assert Accounts.get_user_by_email_and_password(user.email, "new valid password")
+    end
+
+    test "deletes all tokens for the given user", %{user: user} do
+      _ = Accounts.generate_user_session_token(user)
+      {:ok, _} = Accounts.reset_user_password(user, %{password: "new valid password"})
+      refute Repo.get_by(UserToken, user_id: user.id)
+    end
+  end
+
+  describe "inspect/2" do
+    test "does not include password" do
+      refute inspect(%User{password: "123456"}) =~ "password: \"123456\""
+    end
+  end
+end

test/link_shortener/generators/link_with_random_shorten_test.exs

@@ -0,0 +1,44 @@
+defmodule LinkShortener.Generators.LinkWithRandomShortenTest do
+  use ExUnit.Case, async: true
+  
+  alias LinkShortener.Generators.LinkWithRandomShorten
+
+  @name "Some name"
+  @attrs %{
+    name: @name
+  }
+  
+  test "generate/1 returns random safe string with 10 as length" do
+    assert %{
+      name: @name,
+      shorten: shorten
+    } = LinkWithRandomShorten.generate_one(@attrs)
+
+    assert String.length(shorten) == 10
+  end
+
+  test "generate/2 returns random safe string with 5 as length" do
+    expected_length = 5
+
+    assert %{
+      name: @name,
+      shorten: shorten
+    } = LinkWithRandomShorten.generate_one(@attrs, expected_length)
+
+    assert String.length(shorten) == expected_length
+  end
+
+  test "generate/3 returns random safe string using a lambda function" do
+    random_generator = fn _ -> "random_shorten" end
+    expected_shorten = random_generator.(14) 
+    expected_length = expected_shorten |> String.length()
+
+    assert %{
+      name: @name,
+      shorten: shorten
+    } = LinkWithRandomShorten.generate_one(@attrs, expected_length, random_generator)
+
+    assert String.length(shorten) == expected_length
+    assert shorten == expected_shorten
+  end
+end

test/link_shortener/generators/safe_string_test.exs

@@ -0,0 +1,17 @@
+defmodule LinkShortener.Generators.SafeStringTest do
+  use ExUnit.Case, async: true
+
+  alias LinkShortener.Generators.SafeString
+
+  @lengths [1, 2, 5, 10]
+  
+  test "generate/1 returns random safe string with same length" do
+    for expected_length <- @lengths do
+      length = expected_length
+      |> SafeString.generate()
+      |> String.length()
+      
+      assert length = expected_length
+    end
+  end
+end

test/link_shortener/links_test.exs

@@ -0,0 +1,106 @@
+defmodule LinkShortener.LinksTest do
+  use LinkShortener.DataCase
+
+  alias LinkShortener.Links
+
+  @create_attrs %{
+    name: "some link name",
+    url: "https://gitlab.com/KKlochko/link_shortener",
+    shorten: "git_repo",
+  }
+  @create_generated_attrs %{
+    name: "some link name",
+    url: "https://gitlab.com/KKlochko/link_shortener",
+  }
+  @update_attrs %{
+    name: "some updated link name",
+    url: "https://gitlab.com/KKlochko/link_shortener2",
+    shorten: "new_git_repo",
+  }
+  @invalid_attrs %{
+    name: nil,
+    url: nil,
+    shorten: nil,
+  }
+
+  describe "links" do
+    alias LinkShortener.Links.Link
+
+    import LinkShortener.LinksFixtures
+
+    test "new_one/1 returns the changeset" do
+      assert %Ecto.Changeset{} = Links.new_one()
+    end
+
+    test "create_one/1 with valid data creates a link" do
+      assert {:ok, %Link{} = link} = Links.create_one(@create_generated_attrs)
+      assert link.name == "some link name"
+      assert link.url == "https://gitlab.com/KKlochko/link_shortener"
+      assert String.length(link.shorten) == 10
+    end
+
+    test "create_one/2 with valid data creates a link" do
+      assert {:ok, %Link{} = link} = Links.create_one(@create_generated_attrs, 5)
+      assert link.name == "some link name"
+      assert link.url == "https://gitlab.com/KKlochko/link_shortener"
+      assert String.length(link.shorten) == 5
+    end
+
+    test "insert_one/1 with valid data creates a link" do
+      assert {:ok, %Link{} = link} = Links.insert_one(@create_attrs)
+      assert link.name == "some link name"
+      assert link.url == "https://gitlab.com/KKlochko/link_shortener"
+      assert link.shorten == "git_repo"
+    end
+
+    test "insert_one/1 with invalid data returns error changeset" do
+      assert {:error, %Ecto.Changeset{}} = Links.insert_one(@invalid_attrs)
+    end
+
+    test "get_one!/1 returns the link with given id" do
+      link = link_fixture()
+      assert Links.get_one!(link.id) == link
+    end
+
+    test "get_one_by!/1 returns the link with given shorten" do
+      link = link_fixture()
+      assert Links.get_one_by(%{shorten: link.shorten}) == link
+    end
+
+    test "get_one_by_shorten!/1 returns the link with given shorten" do
+      link = link_fixture()
+      assert Links.get_one_by_shorten(link.shorten) == link
+    end
+
+    test "get_all/0 returns all links" do
+      link = link_fixture()
+      assert Links.get_all() == [link]
+    end
+
+    test "edit_one/1 with valid data returns the changeset" do
+      link = link_fixture()
+      assert %Ecto.Changeset{} = Links.edit_one(link)
+    end
+
+    test "update_one/2 with valid data updates the link" do
+      link = link_fixture()
+
+      assert {:ok, %Link{} = link} = Links.update_one(link, @update_attrs)
+      assert link.name == "some updated link name"
+      assert link.url == "https://gitlab.com/KKlochko/link_shortener2"
+      assert link.shorten == "new_git_repo"
+    end
+
+    test "update_link/2 with invalid data returns error changeset" do
+      link = link_fixture()
+      assert {:error, %Ecto.Changeset{}} = Links.update_one(link, @invalid_attrs)
+      assert link == Links.get_one!(link.id)
+    end
+
+    test "delete_one/1 deletes the link" do
+      link = link_fixture()
+      assert {:ok, %Link{}} = Links.delete_one(link)
+      assert_raise Ecto.NoResultsError, fn -> Links.get_one!(link.id) end
+    end
+  end
+end

test/link_shortener_web/controllers/api/v1/link_controller_test.exs

@@ -0,0 +1,97 @@
+defmodule LinkShortenerWeb.Api.V1.LinkControllerTest do
+  use LinkShortenerWeb.ConnCase
+
+  import LinkShortener.LinksFixtures
+
+  alias LinkShortener.Links.Link
+  alias LinkShortener.Links
+
+  @create_attrs %{
+    name: "some link name",
+    url: "https://gitlab.com/KKlochko/link_shortener",
+    shorten: "git_repo",
+  }
+  @update_attrs %{
+    name: "some updated link name",
+    url: "https://gitlab.com/KKlochko/link_shortener2",
+    shorten: "new_git_repo",
+  }
+  @invalid_attrs %{
+    name: nil,
+    url: nil,
+    shorten: nil,
+  }
+
+  setup %{conn: conn} do
+    {:ok, conn: put_req_header(conn, "accept", "application/json")}
+  end
+
+  describe "index" do
+    test "lists all links", %{conn: conn} do
+      conn = get(conn, Routes.v1_link_path(conn, :index))
+      assert json_response(conn, 200)["data"] == []
+    end
+  end
+
+  describe "create link" do
+    test "renders link when data is valid", %{conn: conn} do
+      conn = post(conn, Routes.v1_link_path(conn, :create), link: @create_attrs)
+      assert %{"id" => id} = json_response(conn, 201)["data"]
+
+      conn = get(conn, Routes.v1_link_path(conn, :show, id))
+
+      assert %{
+               "id" => ^id,
+	       "name" => "some link name",
+	       "url" => "https://gitlab.com/KKlochko/link_shortener",
+	       "shorten" => "git_repo",
+             } = json_response(conn, 200)["data"]
+    end
+
+    test "renders errors when data is invalid", %{conn: conn} do
+      conn = post(conn, Routes.v1_link_path(conn, :create), link: @invalid_attrs)
+      assert json_response(conn, 422)["errors"] != %{}
+    end
+  end
+
+  describe "update link" do
+    setup [:create_link]
+
+    test "renders link when data is valid", %{conn: conn, link: %Link{id: id} = link} do
+      conn = put(conn, Routes.v1_link_path(conn, :update, link), link: @update_attrs)
+      assert %{"id" => ^id} = json_response(conn, 200)["data"]
+
+      conn = get(conn, Routes.v1_link_path(conn, :show, id))
+
+      assert %{
+               "id" => ^id,
+	       "name" => "some updated link name",
+	       "url" => "https://gitlab.com/KKlochko/link_shortener2",
+	       "shorten" => "new_git_repo",
+             } = json_response(conn, 200)["data"]
+    end
+
+    test "renders errors when data is invalid", %{conn: conn, link: link} do
+      conn = put(conn, Routes.v1_link_path(conn, :update, link), link: @invalid_attrs)
+      assert json_response(conn, 422)["errors"] != %{}
+    end
+  end
+
+  describe "delete link" do
+    setup [:create_link]
+
+    test "deletes chosen link", %{conn: conn, link: link} do
+      conn = delete(conn, Routes.v1_link_path(conn, :delete, link))
+      assert response(conn, 204)
+
+      assert_error_sent 404, fn ->
+        get(conn, Routes.v1_link_path(conn, :show, link))
+      end
+    end
+  end
+
+  defp create_link(_) do
+    link = link_fixture()
+    %{link: link}
+  end
+end

test/link_shortener_web/controllers/api/v1/user_controller_test.exs

@@ -0,0 +1,46 @@
+defmodule LinkShortenerWeb.Api.V1.UserControllerTest do
+  use LinkShortenerWeb.ConnCase
+
+  import LinkShortener.AccountsFixtures
+
+  alias LinkShortener.Accounts.User
+
+  @create_attrs %{
+    email: "some_email@mail.com",
+    password: "some password"
+  }
+
+  @update_attrs %{
+    email: "some updated email",
+    password: "some updated password"
+  }
+
+  @invalid_attrs %{
+    email: nil,
+    encrypted_password: nil
+  }
+
+  setup %{conn: conn} do
+    {:ok, conn: put_req_header(conn, "accept", "application/json")}
+  end
+
+  describe "create user" do
+    test "renders user when data is valid", %{conn: conn} do
+      conn = post(conn, Routes.v1_user_path(conn, :create), user: @create_attrs)
+      assert %{
+	"email" => "some_email@mail.com",
+	"token" => token
+      } = json_response(conn, 201)
+    end
+
+    test "renders errors when data is invalid", %{conn: conn} do
+      conn = post(conn, Routes.v1_user_path(conn, :create), user: @invalid_attrs)
+      assert json_response(conn, 422)["errors"] != %{}
+    end
+  end
+
+  defp create_user(_) do
+    user = user_fixture()
+    %{user: user}
+  end
+end

test/link_shortener_web/controllers/page_controller_test.exs

@@ -0,0 +1,8 @@
+defmodule LinkShortenerWeb.PageControllerTest do
+  use LinkShortenerWeb.ConnCase
+
+  test "GET /", %{conn: conn} do
+    conn = get(conn, "/")
+    assert html_response(conn, 200) =~ "Usage"
+  end
+end

test/link_shortener_web/controllers/user_auth_test.exs

@@ -0,0 +1,170 @@
+defmodule LinkShortenerWeb.UserAuthTest do
+  use LinkShortenerWeb.ConnCase, async: true
+
+  alias LinkShortener.Accounts
+  alias LinkShortenerWeb.UserAuth
+  import LinkShortener.AccountsFixtures
+
+  @remember_me_cookie "_link_shortener_web_user_remember_me"
+
+  setup %{conn: conn} do
+    conn =
+      conn
+      |> Map.replace!(:secret_key_base, LinkShortenerWeb.Endpoint.config(:secret_key_base))
+      |> init_test_session(%{})
+
+    %{user: user_fixture(), conn: conn}
+  end
+
+  describe "log_in_user/3" do
+    test "stores the user token in the session", %{conn: conn, user: user} do
+      conn = UserAuth.log_in_user(conn, user)
+      assert token = get_session(conn, :user_token)
+      assert get_session(conn, :live_socket_id) == "users_sessions:#{Base.url_encode64(token)}"
+      assert redirected_to(conn) == "/"
+      assert Accounts.get_user_by_session_token(token)
+    end
+
+    test "clears everything previously stored in the session", %{conn: conn, user: user} do
+      conn = conn |> put_session(:to_be_removed, "value") |> UserAuth.log_in_user(user)
+      refute get_session(conn, :to_be_removed)
+    end
+
+    test "redirects to the configured path", %{conn: conn, user: user} do
+      conn = conn |> put_session(:user_return_to, "/hello") |> UserAuth.log_in_user(user)
+      assert redirected_to(conn) == "/hello"
+    end
+
+    test "writes a cookie if remember_me is configured", %{conn: conn, user: user} do
+      conn = conn |> fetch_cookies() |> UserAuth.log_in_user(user, %{"remember_me" => "true"})
+      assert get_session(conn, :user_token) == conn.cookies[@remember_me_cookie]
+
+      assert %{value: signed_token, max_age: max_age} = conn.resp_cookies[@remember_me_cookie]
+      assert signed_token != get_session(conn, :user_token)
+      assert max_age == 5_184_000
+    end
+  end
+
+  describe "logout_user/1" do
+    test "erases session and cookies", %{conn: conn, user: user} do
+      user_token = Accounts.generate_user_session_token(user)
+
+      conn =
+        conn
+        |> put_session(:user_token, user_token)
+        |> put_req_cookie(@remember_me_cookie, user_token)
+        |> fetch_cookies()
+        |> UserAuth.log_out_user()
+
+      refute get_session(conn, :user_token)
+      refute conn.cookies[@remember_me_cookie]
+      assert %{max_age: 0} = conn.resp_cookies[@remember_me_cookie]
+      assert redirected_to(conn) == "/"
+      refute Accounts.get_user_by_session_token(user_token)
+    end
+
+    test "broadcasts to the given live_socket_id", %{conn: conn} do
+      live_socket_id = "users_sessions:abcdef-token"
+      LinkShortenerWeb.Endpoint.subscribe(live_socket_id)
+
+      conn
+      |> put_session(:live_socket_id, live_socket_id)
+      |> UserAuth.log_out_user()
+
+      assert_receive %Phoenix.Socket.Broadcast{event: "disconnect", topic: ^live_socket_id}
+    end
+
+    test "works even if user is already logged out", %{conn: conn} do
+      conn = conn |> fetch_cookies() |> UserAuth.log_out_user()
+      refute get_session(conn, :user_token)
+      assert %{max_age: 0} = conn.resp_cookies[@remember_me_cookie]
+      assert redirected_to(conn) == "/"
+    end
+  end
+
+  describe "fetch_current_user/2" do
+    test "authenticates user from session", %{conn: conn, user: user} do
+      user_token = Accounts.generate_user_session_token(user)
+      conn = conn |> put_session(:user_token, user_token) |> UserAuth.fetch_current_user([])
+      assert conn.assigns.current_user.id == user.id
+    end
+
+    test "authenticates user from cookies", %{conn: conn, user: user} do
+      logged_in_conn =
+        conn |> fetch_cookies() |> UserAuth.log_in_user(user, %{"remember_me" => "true"})
+
+      user_token = logged_in_conn.cookies[@remember_me_cookie]
+      %{value: signed_token} = logged_in_conn.resp_cookies[@remember_me_cookie]
+
+      conn =
+        conn
+        |> put_req_cookie(@remember_me_cookie, signed_token)
+        |> UserAuth.fetch_current_user([])
+
+      assert get_session(conn, :user_token) == user_token
+      assert conn.assigns.current_user.id == user.id
+    end
+
+    test "does not authenticate if data is missing", %{conn: conn, user: user} do
+      _ = Accounts.generate_user_session_token(user)
+      conn = UserAuth.fetch_current_user(conn, [])
+      refute get_session(conn, :user_token)
+      refute conn.assigns.current_user
+    end
+  end
+
+  describe "redirect_if_user_is_authenticated/2" do
+    test "redirects if user is authenticated", %{conn: conn, user: user} do
+      conn = conn |> assign(:current_user, user) |> UserAuth.redirect_if_user_is_authenticated([])
+      assert conn.halted
+      assert redirected_to(conn) == "/"
+    end
+
+    test "does not redirect if user is not authenticated", %{conn: conn} do
+      conn = UserAuth.redirect_if_user_is_authenticated(conn, [])
+      refute conn.halted
+      refute conn.status
+    end
+  end
+
+  describe "require_authenticated_user/2" do
+    test "redirects if user is not authenticated", %{conn: conn} do
+      conn = conn |> fetch_flash() |> UserAuth.require_authenticated_user([])
+      assert conn.halted
+      assert redirected_to(conn) == Routes.user_session_path(conn, :new)
+      assert get_flash(conn, :error) == "You must log in to access this page."
+    end
+
+    test "stores the path to redirect to on GET", %{conn: conn} do
+      halted_conn =
+        %{conn | path_info: ["foo"], query_string: ""}
+        |> fetch_flash()
+        |> UserAuth.require_authenticated_user([])
+
+      assert halted_conn.halted
+      assert get_session(halted_conn, :user_return_to) == "/foo"
+
+      halted_conn =
+        %{conn | path_info: ["foo"], query_string: "bar=baz"}
+        |> fetch_flash()
+        |> UserAuth.require_authenticated_user([])
+
+      assert halted_conn.halted
+      assert get_session(halted_conn, :user_return_to) == "/foo?bar=baz"
+
+      halted_conn =
+        %{conn | path_info: ["foo"], query_string: "bar", method: "POST"}
+        |> fetch_flash()
+        |> UserAuth.require_authenticated_user([])
+
+      assert halted_conn.halted
+      refute get_session(halted_conn, :user_return_to)
+    end
+
+    test "does not redirect if user is authenticated", %{conn: conn, user: user} do
+      conn = conn |> assign(:current_user, user) |> UserAuth.require_authenticated_user([])
+      refute conn.halted
+      refute conn.status
+    end
+  end
+end

test/link_shortener_web/controllers/user_confirmation_controller_test.exs

@@ -0,0 +1,105 @@
+defmodule LinkShortenerWeb.UserConfirmationControllerTest do
+  use LinkShortenerWeb.ConnCase, async: true
+
+  alias LinkShortener.Accounts
+  alias LinkShortener.Repo
+  import LinkShortener.AccountsFixtures
+
+  setup do
+    %{user: user_fixture()}
+  end
+
+  describe "GET /users/confirm" do
+    test "renders the resend confirmation page", %{conn: conn} do
+      conn = get(conn, Routes.user_confirmation_path(conn, :new))
+      response = html_response(conn, 200)
+      assert response =~ "<h1>Resend confirmation instructions</h1>"
+    end
+  end
+
+  describe "POST /users/confirm" do
+    @tag :capture_log
+    test "sends a new confirmation token", %{conn: conn, user: user} do
+      conn =
+        post(conn, Routes.user_confirmation_path(conn, :create), %{
+          "user" => %{"email" => user.email}
+        })
+
+      assert redirected_to(conn) == "/"
+      assert get_flash(conn, :info) =~ "If your email is in our system"
+      assert Repo.get_by!(Accounts.UserToken, user_id: user.id).context == "confirm"
+    end
+
+    test "does not send confirmation token if User is confirmed", %{conn: conn, user: user} do
+      Repo.update!(Accounts.User.confirm_changeset(user))
+
+      conn =
+        post(conn, Routes.user_confirmation_path(conn, :create), %{
+          "user" => %{"email" => user.email}
+        })
+
+      assert redirected_to(conn) == "/"
+      assert get_flash(conn, :info) =~ "If your email is in our system"
+      refute Repo.get_by(Accounts.UserToken, user_id: user.id)
+    end
+
+    test "does not send confirmation token if email is invalid", %{conn: conn} do
+      conn =
+        post(conn, Routes.user_confirmation_path(conn, :create), %{
+          "user" => %{"email" => "unknown@example.com"}
+        })
+
+      assert redirected_to(conn) == "/"
+      assert get_flash(conn, :info) =~ "If your email is in our system"
+      assert Repo.all(Accounts.UserToken) == []
+    end
+  end
+
+  describe "GET /users/confirm/:token" do
+    test "renders the confirmation page", %{conn: conn} do
+      conn = get(conn, Routes.user_confirmation_path(conn, :edit, "some-token"))
+      response = html_response(conn, 200)
+      assert response =~ "<h1>Confirm account</h1>"
+
+      form_action = Routes.user_confirmation_path(conn, :update, "some-token")
+      assert response =~ "action=\"#{form_action}\""
+    end
+  end
+
+  describe "POST /users/confirm/:token" do
+    test "confirms the given token once", %{conn: conn, user: user} do
+      token =
+        extract_user_token(fn url ->
+          Accounts.deliver_user_confirmation_instructions(user, url)
+        end)
+
+      conn = post(conn, Routes.user_confirmation_path(conn, :update, token))
+      assert redirected_to(conn) == "/"
+      assert get_flash(conn, :info) =~ "User confirmed successfully"
+      assert Accounts.get_user!(user.id).confirmed_at
+      refute get_session(conn, :user_token)
+      assert Repo.all(Accounts.UserToken) == []
+
+      # When not logged in
+      conn = post(conn, Routes.user_confirmation_path(conn, :update, token))
+      assert redirected_to(conn) == "/"
+      assert get_flash(conn, :error) =~ "User confirmation link is invalid or it has expired"
+
+      # When logged in
+      conn =
+        build_conn()
+        |> log_in_user(user)
+        |> post(Routes.user_confirmation_path(conn, :update, token))
+
+      assert redirected_to(conn) == "/"
+      refute get_flash(conn, :error)
+    end
+
+    test "does not confirm email with invalid token", %{conn: conn, user: user} do
+      conn = post(conn, Routes.user_confirmation_path(conn, :update, "oops"))
+      assert redirected_to(conn) == "/"
+      assert get_flash(conn, :error) =~ "User confirmation link is invalid or it has expired"
+      refute Accounts.get_user!(user.id).confirmed_at
+    end
+  end
+end

test/link_shortener_web/controllers/user_registration_controller_test.exs

@@ -0,0 +1,54 @@
+defmodule LinkShortenerWeb.UserRegistrationControllerTest do
+  use LinkShortenerWeb.ConnCase, async: true
+
+  import LinkShortener.AccountsFixtures
+
+  describe "GET /users/register" do
+    test "renders registration page", %{conn: conn} do
+      conn = get(conn, Routes.user_registration_path(conn, :new))
+      response = html_response(conn, 200)
+      assert response =~ "<h1>Register</h1>"
+      assert response =~ "Log in</a>"
+      assert response =~ "Register</a>"
+    end
+
+    test "redirects if already logged in", %{conn: conn} do
+      conn = conn |> log_in_user(user_fixture()) |> get(Routes.user_registration_path(conn, :new))
+      assert redirected_to(conn) == "/"
+    end
+  end
+
+  describe "POST /users/register" do
+    @tag :capture_log
+    test "creates account and logs the user in", %{conn: conn} do
+      email = unique_user_email()
+
+      conn =
+        post(conn, Routes.user_registration_path(conn, :create), %{
+          "user" => valid_user_attributes(email: email)
+        })
+
+      assert get_session(conn, :user_token)
+      assert redirected_to(conn) == "/"
+
+      # Now do a logged in request and assert on the menu
+      conn = get(conn, "/")
+      response = html_response(conn, 200)
+      assert response =~ email
+      assert response =~ "Settings</a>"
+      assert response =~ "Log out</a>"
+    end
+
+    test "render errors for invalid data", %{conn: conn} do
+      conn =
+        post(conn, Routes.user_registration_path(conn, :create), %{
+          "user" => %{"email" => "with spaces", "password" => "too short"}
+        })
+
+      response = html_response(conn, 200)
+      assert response =~ "<h1>Register</h1>"
+      assert response =~ "must have the @ sign and no spaces"
+      assert response =~ "should be at least 12 character"
+    end
+  end
+end

test/link_shortener_web/controllers/user_reset_password_controller_test.exs

@@ -0,0 +1,113 @@
+defmodule LinkShortenerWeb.UserResetPasswordControllerTest do
+  use LinkShortenerWeb.ConnCase, async: true
+
+  alias LinkShortener.Accounts
+  alias LinkShortener.Repo
+  import LinkShortener.AccountsFixtures
+
+  setup do
+    %{user: user_fixture()}
+  end
+
+  describe "GET /users/reset_password" do
+    test "renders the reset password page", %{conn: conn} do
+      conn = get(conn, Routes.user_reset_password_path(conn, :new))
+      response = html_response(conn, 200)
+      assert response =~ "<h1>Forgot your password?</h1>"
+    end
+  end
+
+  describe "POST /users/reset_password" do
+    @tag :capture_log
+    test "sends a new reset password token", %{conn: conn, user: user} do
+      conn =
+        post(conn, Routes.user_reset_password_path(conn, :create), %{
+          "user" => %{"email" => user.email}
+        })
+
+      assert redirected_to(conn) == "/"
+      assert get_flash(conn, :info) =~ "If your email is in our system"
+      assert Repo.get_by!(Accounts.UserToken, user_id: user.id).context == "reset_password"
+    end
+
+    test "does not send reset password token if email is invalid", %{conn: conn} do
+      conn =
+        post(conn, Routes.user_reset_password_path(conn, :create), %{
+          "user" => %{"email" => "unknown@example.com"}
+        })
+
+      assert redirected_to(conn) == "/"
+      assert get_flash(conn, :info) =~ "If your email is in our system"
+      assert Repo.all(Accounts.UserToken) == []
+    end
+  end
+
+  describe "GET /users/reset_password/:token" do
+    setup %{user: user} do
+      token =
+        extract_user_token(fn url ->
+          Accounts.deliver_user_reset_password_instructions(user, url)
+        end)
+
+      %{token: token}
+    end
+
+    test "renders reset password", %{conn: conn, token: token} do
+      conn = get(conn, Routes.user_reset_password_path(conn, :edit, token))
+      assert html_response(conn, 200) =~ "<h1>Reset password</h1>"
+    end
+
+    test "does not render reset password with invalid token", %{conn: conn} do
+      conn = get(conn, Routes.user_reset_password_path(conn, :edit, "oops"))
+      assert redirected_to(conn) == "/"
+      assert get_flash(conn, :error) =~ "Reset password link is invalid or it has expired"
+    end
+  end
+
+  describe "PUT /users/reset_password/:token" do
+    setup %{user: user} do
+      token =
+        extract_user_token(fn url ->
+          Accounts.deliver_user_reset_password_instructions(user, url)
+        end)
+
+      %{token: token}
+    end
+
+    test "resets password once", %{conn: conn, user: user, token: token} do
+      conn =
+        put(conn, Routes.user_reset_password_path(conn, :update, token), %{
+          "user" => %{
+            "password" => "new valid password",
+            "password_confirmation" => "new valid password"
+          }
+        })
+
+      assert redirected_to(conn) == Routes.user_session_path(conn, :new)
+      refute get_session(conn, :user_token)
+      assert get_flash(conn, :info) =~ "Password reset successfully"
+      assert Accounts.get_user_by_email_and_password(user.email, "new valid password")
+    end
+
+    test "does not reset password on invalid data", %{conn: conn, token: token} do
+      conn =
+        put(conn, Routes.user_reset_password_path(conn, :update, token), %{
+          "user" => %{
+            "password" => "too short",
+            "password_confirmation" => "does not match"
+          }
+        })
+
+      response = html_response(conn, 200)
+      assert response =~ "<h1>Reset password</h1>"
+      assert response =~ "should be at least 12 character(s)"
+      assert response =~ "does not match password"
+    end
+
+    test "does not reset password with invalid token", %{conn: conn} do
+      conn = put(conn, Routes.user_reset_password_path(conn, :update, "oops"))
+      assert redirected_to(conn) == "/"
+      assert get_flash(conn, :error) =~ "Reset password link is invalid or it has expired"
+    end
+  end
+end

test/link_shortener_web/controllers/user_session_controller_test.exs

@@ -0,0 +1,98 @@
+defmodule LinkShortenerWeb.UserSessionControllerTest do
+  use LinkShortenerWeb.ConnCase, async: true
+
+  import LinkShortener.AccountsFixtures
+
+  setup do
+    %{user: user_fixture()}
+  end
+
+  describe "GET /users/log_in" do
+    test "renders log in page", %{conn: conn} do
+      conn = get(conn, Routes.user_session_path(conn, :new))
+      response = html_response(conn, 200)
+      assert response =~ "<h1>Log in</h1>"
+      assert response =~ "Register</a>"
+      assert response =~ "Forgot your password?</a>"
+    end
+
+    test "redirects if already logged in", %{conn: conn, user: user} do
+      conn = conn |> log_in_user(user) |> get(Routes.user_session_path(conn, :new))
+      assert redirected_to(conn) == "/"
+    end
+  end
+
+  describe "POST /users/log_in" do
+    test "logs the user in", %{conn: conn, user: user} do
+      conn =
+        post(conn, Routes.user_session_path(conn, :create), %{
+          "user" => %{"email" => user.email, "password" => valid_user_password()}
+        })
+
+      assert get_session(conn, :user_token)
+      assert redirected_to(conn) == "/"
+
+      # Now do a logged in request and assert on the menu
+      conn = get(conn, "/")
+      response = html_response(conn, 200)
+      assert response =~ user.email
+      assert response =~ "Settings</a>"
+      assert response =~ "Log out</a>"
+    end
+
+    test "logs the user in with remember me", %{conn: conn, user: user} do
+      conn =
+        post(conn, Routes.user_session_path(conn, :create), %{
+          "user" => %{
+            "email" => user.email,
+            "password" => valid_user_password(),
+            "remember_me" => "true"
+          }
+        })
+
+      assert conn.resp_cookies["_link_shortener_web_user_remember_me"]
+      assert redirected_to(conn) == "/"
+    end
+
+    test "logs the user in with return to", %{conn: conn, user: user} do
+      conn =
+        conn
+        |> init_test_session(user_return_to: "/foo/bar")
+        |> post(Routes.user_session_path(conn, :create), %{
+          "user" => %{
+            "email" => user.email,
+            "password" => valid_user_password()
+          }
+        })
+
+      assert redirected_to(conn) == "/foo/bar"
+    end
+
+    test "emits error message with invalid credentials", %{conn: conn, user: user} do
+      conn =
+        post(conn, Routes.user_session_path(conn, :create), %{
+          "user" => %{"email" => user.email, "password" => "invalid_password"}
+        })
+
+      response = html_response(conn, 200)
+      assert response =~ "<h1>Log in</h1>"
+      assert response =~ "Invalid email or password"
+    end
+  end
+
+  describe "DELETE /users/log_out" do
+    test "logs the user out", %{conn: conn, user: user} do
+      conn = conn |> log_in_user(user) |> delete(Routes.user_session_path(conn, :delete))
+      assert redirected_to(conn) == "/"
+      refute get_session(conn, :user_token)
+      assert get_flash(conn, :info) =~ "Logged out successfully"
+    end
+
+    test "succeeds even if the user is not logged in", %{conn: conn} do
+      conn = delete(conn, Routes.user_session_path(conn, :delete))
+      assert redirected_to(conn) == "/"
+      refute get_session(conn, :user_token)
+      assert get_flash(conn, :info) =~ "Logged out successfully"
+    end
+  end
+end

test/link_shortener_web/controllers/user_settings_controller_test.exs

@@ -0,0 +1,129 @@
+defmodule LinkShortenerWeb.UserSettingsControllerTest do
+  use LinkShortenerWeb.ConnCase, async: true
+
+  alias LinkShortener.Accounts
+  import LinkShortener.AccountsFixtures
+
+  setup :register_and_log_in_user
+
+  describe "GET /users/settings" do
+    test "renders settings page", %{conn: conn} do
+      conn = get(conn, Routes.user_settings_path(conn, :edit))
+      response = html_response(conn, 200)
+      assert response =~ "<h1>Settings</h1>"
+    end
+
+    test "redirects if user is not logged in" do
+      conn = build_conn()
+      conn = get(conn, Routes.user_settings_path(conn, :edit))
+      assert redirected_to(conn) == Routes.user_session_path(conn, :new)
+    end
+  end
+
+  describe "PUT /users/settings (change password form)" do
+    test "updates the user password and resets tokens", %{conn: conn, user: user} do
+      new_password_conn =
+        put(conn, Routes.user_settings_path(conn, :update), %{
+          "action" => "update_password",
+          "current_password" => valid_user_password(),
+          "user" => %{
+            "password" => "new valid password",
+            "password_confirmation" => "new valid password"
+          }
+        })
+
+      assert redirected_to(new_password_conn) == Routes.user_settings_path(conn, :edit)
+      assert get_session(new_password_conn, :user_token) != get_session(conn, :user_token)
+      assert get_flash(new_password_conn, :info) =~ "Password updated successfully"
+      assert Accounts.get_user_by_email_and_password(user.email, "new valid password")
+    end
+
+    test "does not update password on invalid data", %{conn: conn} do
+      old_password_conn =
+        put(conn, Routes.user_settings_path(conn, :update), %{
+          "action" => "update_password",
+          "current_password" => "invalid",
+          "user" => %{
+            "password" => "too short",
+            "password_confirmation" => "does not match"
+          }
+        })
+
+      response = html_response(old_password_conn, 200)
+      assert response =~ "<h1>Settings</h1>"
+      assert response =~ "should be at least 12 character(s)"
+      assert response =~ "does not match password"
+      assert response =~ "is not valid"
+
+      assert get_session(old_password_conn, :user_token) == get_session(conn, :user_token)
+    end
+  end
+
+  describe "PUT /users/settings (change email form)" do
+    @tag :capture_log
+    test "updates the user email", %{conn: conn, user: user} do
+      conn =
+        put(conn, Routes.user_settings_path(conn, :update), %{
+          "action" => "update_email",
+          "current_password" => valid_user_password(),
+          "user" => %{"email" => unique_user_email()}
+        })
+
+      assert redirected_to(conn) == Routes.user_settings_path(conn, :edit)
+      assert get_flash(conn, :info) =~ "A link to confirm your email"
+      assert Accounts.get_user_by_email(user.email)
+    end
+
+    test "does not update email on invalid data", %{conn: conn} do
+      conn =
+        put(conn, Routes.user_settings_path(conn, :update), %{
+          "action" => "update_email",
+          "current_password" => "invalid",
+          "user" => %{"email" => "with spaces"}
+        })
+
+      response = html_response(conn, 200)
+      assert response =~ "<h1>Settings</h1>"
+      assert response =~ "must have the @ sign and no spaces"
+      assert response =~ "is not valid"
+    end
+  end
+
+  describe "GET /users/settings/confirm_email/:token" do
+    setup %{user: user} do
+      email = unique_user_email()
+
+      token =
+        extract_user_token(fn url ->
+          Accounts.deliver_update_email_instructions(%{user | email: email}, user.email, url)
+        end)
+
+      %{token: token, email: email}
+    end
+
+    test "updates the user email once", %{conn: conn, user: user, token: token, email: email} do
+      conn = get(conn, Routes.user_settings_path(conn, :confirm_email, token))
+      assert redirected_to(conn) == Routes.user_settings_path(conn, :edit)
+      assert get_flash(conn, :info) =~ "Email changed successfully"
+      refute Accounts.get_user_by_email(user.email)
+      assert Accounts.get_user_by_email(email)
+
+      conn = get(conn, Routes.user_settings_path(conn, :confirm_email, token))
+      assert redirected_to(conn) == Routes.user_settings_path(conn, :edit)
+      assert get_flash(conn, :error) =~ "Email change link is invalid or it has expired"
+    end
+
+    test "does not update email with invalid token", %{conn: conn, user: user} do
+      conn = get(conn, Routes.user_settings_path(conn, :confirm_email, "oops"))
+      assert redirected_to(conn) == Routes.user_settings_path(conn, :edit)
+      assert get_flash(conn, :error) =~ "Email change link is invalid or it has expired"
+      assert Accounts.get_user_by_email(user.email)
+    end
+
+    test "redirects if user is not logged in", %{token: token} do
+      conn = build_conn()
+      conn = get(conn, Routes.user_settings_path(conn, :confirm_email, token))
+      assert redirected_to(conn) == Routes.user_session_path(conn, :new)
+    end
+  end
+end

test/link_shortener_web/views/error_view_test.exs

@@ -0,0 +1,14 @@
+defmodule LinkShortenerWeb.ErrorViewTest do
+  use LinkShortenerWeb.ConnCase, async: true
+
+  # Bring render/3 and render_to_string/3 for testing custom views
+  import Phoenix.View
+
+  test "renders 404.html" do
+    assert render_to_string(LinkShortenerWeb.ErrorView, "404.html", []) == "Not Found"
+  end
+
+  test "renders 500.html" do
+    assert render_to_string(LinkShortenerWeb.ErrorView, "500.html", []) == "Internal Server Error"
+  end
+end

test/link_shortener_web/views/layout_view_test.exs

@@ -0,0 +1,8 @@
+defmodule LinkShortenerWeb.LayoutViewTest do
+  use LinkShortenerWeb.ConnCase, async: true
+
+  # When testing helpers, you may want to import Phoenix.HTML and
+  # use functions such as safe_to_string() to convert the helper
+  # result into an HTML string.
+  # import Phoenix.HTML
+end

test/link_shortener_web/views/page_view_test.exs

@@ -0,0 +1,3 @@
+defmodule LinkShortenerWeb.PageViewTest do
+  use LinkShortenerWeb.ConnCase, async: true
+end

test/support/conn_case.ex

@@ -0,0 +1,64 @@
+defmodule LinkShortenerWeb.ConnCase do
+  @moduledoc """
+  This module defines the test case to be used by
+  tests that require setting up a connection.
+
+  Such tests rely on `Phoenix.ConnTest` and also
+  import other functionality to make it easier
+  to build common data structures and query the data layer.
+
+  Finally, if the test case interacts with the database,
+  we enable the SQL sandbox, so changes done to the database
+  are reverted at the end of every test. If you are using
+  PostgreSQL, you can even run database tests asynchronously
+  by setting `use LinkShortenerWeb.ConnCase, async: true`, although
+  this option is not recommended for other databases.
+  """
+
+  use ExUnit.CaseTemplate
+
+  using do
+    quote do
+      # Import conveniences for testing with connections
+      import Plug.Conn
+      import Phoenix.ConnTest
+      import LinkShortenerWeb.ConnCase
+
+      alias LinkShortenerWeb.Router.Helpers, as: Routes
+
+      # The default endpoint for testing
+      @endpoint LinkShortenerWeb.Endpoint
+    end
+  end
+
+  setup tags do
+    LinkShortener.DataCase.setup_sandbox(tags)
+    {:ok, conn: Phoenix.ConnTest.build_conn()}
+  end
+
+  @doc """
+  Setup helper that registers and logs in users.
+
+      setup :register_and_log_in_user
+
+  It stores an updated connection and a registered user in the
+  test context.
+  """
+  def register_and_log_in_user(%{conn: conn}) do
+    user = LinkShortener.AccountsFixtures.user_fixture()
+    %{conn: log_in_user(conn, user), user: user}
+  end
+
+  @doc """
+  Logs the given `user` into the `conn`.
+
+  It returns an updated `conn`.
+  """
+  def log_in_user(conn, user) do
+    token = LinkShortener.Accounts.generate_user_session_token(user)
+
+    conn
+    |> Phoenix.ConnTest.init_test_session(%{})
+    |> Plug.Conn.put_session(:user_token, token)
+  end
+end

test/support/data_case.ex

@@ -0,0 +1,58 @@
+defmodule LinkShortener.DataCase do
+  @moduledoc """
+  This module defines the setup for tests requiring
+  access to the application's data layer.
+
+  You may define functions here to be used as helpers in
+  your tests.
+
+  Finally, if the test case interacts with the database,
+  we enable the SQL sandbox, so changes done to the database
+  are reverted at the end of every test. If you are using
+  PostgreSQL, you can even run database tests asynchronously
+  by setting `use LinkShortener.DataCase, async: true`, although
+  this option is not recommended for other databases.
+  """
+
+  use ExUnit.CaseTemplate
+
+  using do
+    quote do
+      alias LinkShortener.Repo
+
+      import Ecto
+      import Ecto.Changeset
+      import Ecto.Query
+      import LinkShortener.DataCase
+    end
+  end
+
+  setup tags do
+    LinkShortener.DataCase.setup_sandbox(tags)
+    :ok
+  end
+
+  @doc """
+  Sets up the sandbox based on the test tags.
+  """
+  def setup_sandbox(tags) do
+    pid = Ecto.Adapters.SQL.Sandbox.start_owner!(LinkShortener.Repo, shared: not tags[:async])
+    on_exit(fn -> Ecto.Adapters.SQL.Sandbox.stop_owner(pid) end)
+  end
+
+  @doc """
+  A helper that transforms changeset errors into a map of messages.
+
+      assert {:error, changeset} = Accounts.create_user(%{password: "short"})
+      assert "password is too short" in errors_on(changeset).password
+      assert %{password: ["password is too short"]} = errors_on(changeset)
+
+  """
+  def errors_on(changeset) do
+    Ecto.Changeset.traverse_errors(changeset, fn {message, opts} ->
+      Regex.replace(~r"%{(\w+)}", message, fn _, key ->
+        opts |> Keyword.get(String.to_existing_atom(key), key) |> to_string()
+      end)
+    end)
+  end
+end

test/support/fixtures/accounts_fixtures.ex

@@ -0,0 +1,34 @@
+defmodule LinkShortener.AccountsFixtures do
+  @moduledoc """
+  This module defines test helpers for creating
+  entities via the `LinkShortener.Accounts` context.
+  """
+
+  @doc """
+  Generate a unique user email.
+  """
+  def unique_user_email, do: "user#{System.unique_integer()}@example.com"
+  def valid_user_password, do: "hello world!"
+
+  def valid_user_attributes(attrs \\ %{}) do
+    Enum.into(attrs, %{
+      email: unique_user_email(),
+      password: valid_user_password()
+    })
+  end
+
+  def user_fixture(attrs \\ %{}) do
+    {:ok, user} =
+      attrs
+      |> valid_user_attributes()
+      |> LinkShortener.Accounts.register_user()
+
+    user
+  end
+
+  def extract_user_token(fun) do
+    {:ok, captured_email} = fun.(&"[TOKEN]#{&1}[TOKEN]")
+    [_, token | _] = String.split(captured_email.text_body, "[TOKEN]")
+    token
+  end
+end

test/support/fixtures/links_fixtures.ex

@@ -0,0 +1,24 @@
+defmodule LinkShortener.LinksFixtures do
+  @moduledoc """
+  This module defines test helpers for creating
+  entities via the `LinkShortener.Links` context.
+  """
+
+  alias LinkShortener.Links
+
+  @doc """
+  Generate a link.
+  """
+  def link_fixture(attrs \\ %{}) do
+    {:ok, link} =
+      attrs
+      |> Enum.into(%{
+        name: "some name",
+	url: "https://gitlab.com/KKlochko/link_shortener",
+	shorten: "api-article",
+      })
+      |> Links.create_one()
+
+    link
+  end
+end

test/test_helper.exs

@@ -0,0 +1,2 @@
+ExUnit.start()
+Ecto.Adapters.SQL.Sandbox.mode(LinkShortener.Repo, :manual)