Add a function to decrypt a message with the gamma cipher.

src/cipher_analytical_machine/ciphers/gamma.clj

@@ -1,5 +1,8 @@
 (ns cipher-analytical-machine.ciphers.gamma
-  (:require [clojure.string :as cs])
+  (:require
+   [clojure.set :as set]
+   [clojure.string :as cs]
+   [cipher-analytical-machine.ciphers.simple-substitution :as ss])
   (:gen-class))
 
 (defn add-mod
@@ -40,6 +43,17 @@
          (map vector array)
          (map (fn [[a g]] (add-mod a g module))))))
 
+(defn encrypt-message
+  "Encrypt a message using the gamma cipher. The function is case-insensitive. The key is an array of three elements [a b c]. The array contains integer in range [0, module)."
+  [key symbols message]
+  (let [module (count symbols)
+        table (ss/generate-sorted-substitution-table symbols)]
+    (->> message
+         (ss/decrypt-by-table (set/map-invert table))
+         (encrypt-array key module)
+         (ss/decrypt-by-table table)
+         (cs/join))))
+
 (defn decrypt-array
   "Decrypt an array using the gamma cipher. The function is case-insensitive. The key is an array of three elements [a b c]. The array contains integer in range [0, module)."
   [key module array]
@@ -51,3 +65,14 @@
          (map vector array)
          (map (fn [[a g]] (add-mod a g module))))))
 
+(defn decrypt-message
+  "Decrypt a message using the gamma cipher. The function is case-insensitive. The key is an array of three elements [a b c]. The array contains integer in range [0, module)."
+  [key symbols message]
+  (let [module (count symbols)
+        table (ss/generate-sorted-substitution-table symbols)]
+    (->> message
+         (ss/decrypt-by-table (set/map-invert table))
+         (decrypt-array key module)
+         (ss/decrypt-by-table table)
+         (cs/join))))
+

src/cipher_analytical_machine/ciphers/simple_substitution.clj

@@ -29,11 +29,16 @@
   [char substitution-table]
   (get substitution-table char))
 
+(defn decrypt-by-table
+  "Decrypt a message by the substitution-table"
+  [substitution-table message]
+  (map (fn [char] (find-value-in-table char substitution-table)) message))
+
 (defn encrypt-message
   "Encrypt a message using the simple substitution cipher. The function is case-insensitive. If a symbol isn't in the symbols list, then it will be removed."
   [message substitution-table]
   (->> message
-       (map (fn [char] (find-value-in-table char substitution-table)))
+       (decrypt-by-table substitution-table)
        (remove nil?)
        (cs/join \,)))
 
@@ -44,11 +49,6 @@
       (caesar/encrypt-message key symbols)
       (encrypt-message substitution-table)))
 
-(defn decrypt-by-table
-  "Decrypt a message by the substitution-table"
-  [substitution-table message]
-  (map (fn [char] (find-value-in-table char substitution-table)) message))
-
 (defn decrypt-message-by-symbol-table
   "Decrypt a message using the simple substitution cipher. The function is case-insensitive. The substitution-table must be (symbols, symbols)."
   [substitution-table message]

test/cipher_analytical_machine/ciphers/gamma_test.clj

@@ -39,6 +39,13 @@
       [4 32 15] 33 [3 14 1 4 18 19 23 8 27 17] [6 28 2 8 3 5 13 16 21 1]
       [1 2  3 ] 3  [0 2 1 1 0 1 2 2 0]         [0 1 2 2 0 2 1 1 0])))
 
+(deftest encrypt-message-test
+  (testing "Checking that the message is encrypted as expected"
+    (are [key symbols message expected]
+        (= expected (encrypt-message key symbols message))
+      [4 32 15] "абвгґдеєжзиіїйклмнопрстуфхцчшщьюя" "гкбґопужчн" "ешвжгдймсб"
+      [1 2  3 ] "абв"  "авббабвва"  "абввавбба")))
+
 (deftest decrypt-array-test
   (testing "Checking that the message is decrypted as expected."
     (are [key module array expected]
@@ -46,3 +53,10 @@
       [4 32 15] 33 [6 28 2 8 3 5 13 16 21 1] [3 14 1 4 18 19 23 8 27 17]
       [1 2  3 ] 3  [0 1 2 2 0 2 1 1 0]       [0 2 1 1 0 1 2 2 0])))
 
+(deftest decrypt-message-test
+  (testing "Checking that the message is decrypted as expected"
+    (are [key symbols message expected]
+        (= expected (decrypt-message key symbols message))
+      [4 32 15] "абвгґдеєжзиіїйклмнопрстуфхцчшщьюя" "ешвжгдймсб" "гкбґопужчн"
+      [1 2  3 ] "абв" "абввавбба" "авббабвва")))
+