simple-cljs-blog/src/main/blog/db.cljs

(ns blog.db
  (:require ["pg" :refer [Client]]
            [cljs.core.async :refer [go, take!, put!, >!, chan]]
            [cljs.core.async.interop :refer-macros [<p!]]
            [cljs.core :refer [clj->js js->clj]]
            [blog.env :as env]))

(defn create-client
  "Create a new client for Postgres using enviroment variables."
  []
  (->> (env/get-database-credentials)
       (cljs.core/clj->js)
       (new Client)))

(defn connect-client
  "Connect a client to the database"
  [client]
  (. client connect))

(defn create-tables
  [client]
  (. client query "CREATE TABLE IF NOT EXISTS articles (id SERIAL PRIMARY KEY, title VARCHAR(255) NOT NULL, content TEXT NOT NULL, created TIMESTAMP DEFAULT CURRENT_TIMESTAMP);"))

(defn get-articles
  "Reads all articles and returns via channel. It gets and returns the same channel."
  [client channel]
  (go
    (try
      (let [res (<p! (. client query "select id, title, content, created from articles order by created desc"))]
        (>! channel (.-rows res)))
      (catch js/Error err (js/console.log (ex-cause err)))))
  channel)

(defn get-articles-briefly
  "Reads all articles and returns via channel. It gets and returns the same channel. The content will be brief (<=60 characters)."
  [client channel]
  (go
    (try
      (let [res (<p! (. client query
                        (str "select id, title, "
                             "substr(content, 0, 60) content, "
                             "length(content) content_length, "
                             "created from articles "
                             "order by created desc")))]
        (>! channel (.-rows res)))
      (catch js/Error err (js/console.log (ex-cause err)))))
  channel)

(defn search-articles-briefly
  "Search all articles by titles and contents and returns via channel. It gets and returns the same channel. The content will be brief (<=60 characters)."
  [client search channel]
  (go
    (try
      (let [res (<p! (.query client
                        (str "select id, title, "
                             "substr(content, 0, 60) content, "
                             "length(content) content_length, "
                             "created from articles "
                             "where title like $1 "
                             "or content like $1 "
                             "order by created desc")
                        (clj->js [(str "%" search "%")])))]
        (>! channel (.-rows res)))
      (catch js/Error err (js/console.log (ex-cause err)))))
  channel)

(defn get-article
  "Reads an article with the id and returns via channel. It gets and returns the same channel. Empty collection if not found."
  [client id channel]
  (go
    (try
      (let [res (<p! (.query client
                             "select id, title, content, created from articles where id=$1"
                             (clj->js [id])))]
        (>! channel (-> (.-rows res)
                        (js->clj :keywordize-keys true)
                        (first))))
      (catch js/Error err (js/console.log (ex-cause err)))))
  channel)

(defn get-article-briefly
  "Reads an article with the id and returns via channel. It gets and returns the same channel. Empty collection if not found. The content will be brief (<=60 characters)."
  [client id channel]
  (go
    (try
      (let [res (<p! (.query client
                        (str "select id, title,"
                             "substr(content, 0, 60) content,"
                             "length(content) content_length,"
                             "created from articles"
                             "where id=$1")
                        (clj->js [id])))]
        (>! channel (-> (.-rows res)
                        (js->clj :keywordize-keys true)
                        (first))))
      (catch js/Error err (js/console.log (ex-cause err)))))
  channel)

(defn insert-article
  "Insert an article and return the id via channel. It gets and returns the same channel."
  [client title content channel]
  (go
    (try
      (let [res (<p! (.query client
                             "insert into articles(title, content) values($1, $2) returning id;"
                             (clj->js [title content])))]
        (>! channel (-> (.-rows res)
                        (js->clj :keywordize-keys true)
                        (first)
                        (:id))))
      (catch js/Error err (js/console.log (ex-cause err)))))
  channel)

(defn update-article
  "Update an article and return the id via channel. The timestamp for created will be updated to current timestamp. It gets and returns the same channel."
  [client {:keys [id title content]} channel]
  (go
    (try
      (let [res (<p! (.query client
                             (str "update articles "
                                  "set title = $2,"
                                      "content = $3,"
                                      "created = CURRENT_TIMESTAMP "
                                  "where id = $1;")
                             (clj->js [id title content])))]
        (>! channel (-> id)))
      (catch js/Error err (js/console.log (ex-cause err)))))
  channel)

(defn delete-article
  "Delete an article and return the id via channel. It gets and returns the same channel."
  [client id channel]
  (go
    (try
      (let [res (<p! (.query client
                             "delete from articles where id = $1 returning id;"
                             (clj->js [id])))]
        (>! channel (-> (.-rows res)
                        (js->clj :keywordize-keys true)
                        (first)
                        (:id))))
      (catch js/Error err (js/console.log (ex-cause err)))))
  channel)