Update the simple substitution cipher to split the functions.

src/cipher_analytical_machine/ciphers/simple_substitution.clj

@@ -1,6 +1,5 @@
 (ns cipher-analytical-machine.ciphers.simple-substitution
   (:require [clojure.string :as cs]
-            [clojure.set :as set]
             [cipher-analytical-machine.ciphers.caesar :as caesar])
   (:gen-class))
 
@@ -20,28 +19,38 @@
 
 (defn find-value-in-table
   "It uses the substitution table to find the value of a char or a number."
-  [char substitution-table symbols]
+  [char substitution-table]
   (get substitution-table char))
 
 (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)))
+       (remove nil?)
+       (cs/join \,)))
+
+(defn encrypt-message-with-caesar
+  "Encrypt a message using the simple substitution cipher and the Caesar cipher. The function is case-insensitive. If a symbol isn't in the symbols list, then it will be removed."
   [message key substitution-table symbols]
-  (let [max-index (count symbols)]
-    (->> message
-         (cs/lower-case)
-         (caesar/encrypt-message key symbols)
-         (map (fn [char] (find-value-in-table char substitution-table symbols)))
-         (cs/join \,))))
+  (-> message
+      (caesar/encrypt-message key symbols)
+      (encrypt-message substitution-table)))
 
 (defn decrypt-message
-  "Decrypt a message using the simple substitution cipher. The function is case-insensitive."
+  "Decrypt a message using the simple substitution cipher. The function is case-insensitive. The substitution-table must be "
+  [message substitution-table]
+  (let [message (cs/split message #",")]
+    (->> message
+         (map #(Integer/parseInt %))
+         (map (fn [char] (find-value-in-table char substitution-table)))
+         (remove nil?)
+         (cs/join))))
+
+(defn decrypt-message-with-caesar
+  "Decrypt a message using the simple substitution cipher and the Caesar cipher. The function is case-insensitive."
   [message key substitution-table symbols]
-  (let [substitution-table (set/map-invert substitution-table)
-        max-index (count symbols)
-        message (cs/split message #",")]
-      (->> message
-           (map #(Integer/parseInt %))
-           (map (fn [char] (find-value-in-table char substitution-table symbols)))
-           (caesar/encrypt-message key symbols)
-           (cs/join))))
+  (-> message
+      (decrypt-message substitution-table)
+      (caesar/decrypt-message key symbols)))