Add decrypt to caesar cypher

Author: rjLelis

file-operations/caesar_cipher.py

@@ -1,38 +1,64 @@
 from file_utils import remove_accents
 
 
+ALPHABET = ('a', 'b', 'c', 'd', 'e', 'f',
+                'g', 'h', 'i', 'j', 'k', 'l', 'm',
+                'n', 'o', 'p', 'q', 'r', 's', 't',
+                'u', 'v', 'w', 'x', 'y', 'z')
+
+
 def encrypt(original_message, key):
     '''
         Encrypts a message using the caesar cypher
-
         :params original_message, key
         :returns encrypted_message
     '''
 
-    alphabet = ('a', 'b', 'c', 'd', 'e', 'f',
-                'g', 'h', 'i', 'j', 'k', 'l', 'm',
-                'n', 'o', 'p', 'q', 'r', 's', 't',
-                'u', 'v', 'w', 'x', 'y', 'z')
-
     encrypted_message = ''
 
     if type(key) == str:
-        key = alphabet.index(key) + 1
+        key = ALPHABET.index(key) + 1
 
     # Encrypts the original message then stores in the return variable
     for letter in remove_accents(original_message.lower()):
-        encrypted_letter = ''
-        if letter not in alphabet:
-            encrypted_letter = letter
+        if letter in ALPHABET:
+            index = ALPHABET.index(letter)
+            index += key
+
+            if index >= len(ALPHABET):
+                index -= len(ALPHABET)
+
+            encrypted_message += ALPHABET[index]
         else:
-            letter_index = alphabet.index(letter)
-            if letter not in alphabet:
-                encrypted_letter = letter
-            elif letter_index + key >= len(alphabet):
-                encrypted_letter = \
-                    alphabet[letter_index + key - len(alphabet)]
-            else:
-                encrypted_letter = alphabet[letter_index + key]
-        encrypted_message += encrypted_letter
+            encrypted_message += letter
 
     return encrypted_message
+
+
+def decrypt(encrypted_message, key):
+
+    '''
+        Decrypts a message using the caesar cypher
+        :params encrypted_message, key
+        :returns translated        
+    '''
+
+    translated = ''
+
+    if type(key) == str:
+        key = ALPHABET.index(key) + 1
+
+    for letter in remove_accents(encrypted_message.lower()):
+        if letter in ALPHABET:
+            index = ALPHABET.index(letter)
+            index -= key
+
+            if index < 0:
+                index += len(ALPHABET)
+
+            translated += ALPHABET[index]
+
+        else:
+            translated += letter
+    
+    return translated

file-operations/file_encrypt.py

@@ -1,16 +1,55 @@
 import argparse
-from caesar_cipher import encrypt
+import caesar_cipher
 from file_utils import get_file_content, store_file_content
 
-parser = argparse.ArgumentParser(description='Takes a file as argument and encrypts it')
+def main():
 
-parser.add_argument('file', metavar='file to be encrypted', type=str)
-parser.add_argument('key', metavar='key to encrypt',type=int)
+    parser = argparse.ArgumentParser(description='Takes a file as argument and encrypts it')
 
-args = parser.parse_args()
+    parser.add_argument('file', metavar='file to be encrypted', type=str)
+    parser.add_argument('key', metavar='key to encrypt',type=int)
+    parser.add_argument('mode', metavar='Select the mode (encrypt, decrypt)', type=str)
 
-file_content = get_file_content(args.file)
+    args = parser.parse_args()
 
-new_file = store_file_content(encrypt(file_content, args.key), 'encriptado.txt')
+    try:
+        eval(args.mode)(args.file, args.key)
 
-print(f'content stored on {new_file}')
+    except NameError:
+        print(f'The mode {args.mode} does not exists')
+
+
+def encrypt(file, key):
+
+    try:
+        file_content = get_file_content(file)
+
+        if file_content:
+            new_file = store_file_content(caesar_cipher.encrypt(file_content, key), 'encriptado.txt')
+            print(f'content stored on {new_file}')
+
+        else:
+            print(f'The file {file} is empty')
+
+    except FileNotFoundError:
+        print(f'The file {file} does not exists')
+    
+
+
+def decrypt(file, key):
+    try:
+        file_content = get_file_content(file)
+
+        if file_content:
+            new_file = store_file_content(caesar_cipher.decrypt(file_content, key), 'decriptado.txt')
+            print(f'Content stored on {new_file}')
+
+        else:
+            print(f'The file {file} is empty')
+
+    except FileNotFoundError:
+        print(f'The file {file} does not exists')
+
+
+if __name__ == "__main__":
+    main()