commit 03b4771c43064fc1bb1c9cf75ac3e73eab3c30e8
Author: Raine <raine@ixvd.net>
Date:   Fri Oct 6 17:52:09 2023 +0200

    init: initial commit

diff --git a/.gitignore b/.gitignore
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--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*.txt
diff --git a/README.md b/README.md
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--- /dev/null
+++ b/README.md
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+# Logical Alternating Shift Cypher
+
+Made to talk with a friend without eavedroppers.
+
+## Usage
+The tool uses a numerical key to shift the message's characters.  
+Only alphabetical characters are shifted.
diff --git a/cypher.py b/cypher.py
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+++ b/cypher.py
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+import argparse 
+
+def encode_shift_cipher(text, key):
+    result = ""
+    alphabet = 'abcdefghijklmnopqrstuvwxyz'
+    shift_direction = 1
+    shift_count = 0
+    
+    for char in text:
+        if char.isalpha():
+            shift = int(key[shift_count]) * shift_direction
+            index = alphabet.index(char.lower())
+            
+            # Calculate the new index and wrap around if it's less than 0
+            new_index = (index + shift) % 26
+            if new_index < 0:
+                new_index += 26  # Wrap around to 'z'
+            
+            result += alphabet[new_index]
+            
+            shift_direction *= -1
+            shift_count = (shift_count + 1) % len(key)
+        else:
+            result += char
+    
+    return result
+
+def decode_shift_cipher(text, key):
+    result = ""
+    alphabet = 'abcdefghijklmnopqrstuvwxyz'
+    shift_direction = 1
+    shift_count = 0
+    
+    for char in text:
+        if char.isalpha():
+            shift = int(key[shift_count]) * shift_direction
+            index = alphabet.index(char.lower())
+            
+            # Calculate the new index and wrap around if it's less than 0
+            new_index = (index - shift) % 26
+            if new_index < 0:
+                new_index += 26  # Wrap around to 'z'
+            
+            result += alphabet[new_index]
+            
+            shift_direction *= -1
+            shift_count = (shift_count + 1) % len(key)
+        else:
+            result += char
+    
+    return result
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Shift Cipher Encoder/Decoder")
+    parser.add_argument("-e", "--encode", action="store_true", help="Encode the input")
+    parser.add_argument("-d", "--decode", action="store_true", help="Decode the input")
+    parser.add_argument("-k", "--key", required=True, help="Encryption/Decryption key (e.g., '1234')")
+    parser.add_argument("-i", "--input", help="Input file to process")
+    parser.add_argument("-o", "--output", help="Output file (optional)")
+    parser.add_argument("-s", "--string", help="Input string to process")
+
+    args = parser.parse_args()
+
+    if not args.encode and not args.decode:
+        print("Please specify whether to encode or decode using -e or -d.")
+        return
+
+    if args.encode and args.decode:
+        print("Please choose either -e (encode) or -d (decode), not both.")
+        return
+
+    if args.input and args.string:
+        print("Please choose either -i (input file) or -s (input string), not both.")
+        return
+
+    if args.input:
+        # Read input from a file
+        try:
+            with open(args.input, "r") as file:
+                input_text = file.read()
+        except FileNotFoundError:
+            print(f"Error: Input file '{args.input}' not found.")
+            return
+    elif args.string:
+        # Use the input string
+        input_text = args.string
+    else:
+        # Read input from the command line
+        input_text = input("Enter the text to encode/decode: ")
+
+    key = args.key
+
+    if args.encode:
+        output_text = encode_shift_cipher(input_text, key)
+    else:
+        output_text = decode_shift_cipher(input_text, key)
+
+    if args.output:
+        # Write the result to an output file
+        with open(args.output, "w") as file:
+            file.write(output_text)
+        print(f"Output written to '{args.output}'")
+    else:
+        # Print the result to the console
+        print("Result:")
+        print(output_text)
+
+if __name__ == "__main__":
+    main()