From 3b59fcf9f63abcf62c53c84d14d15c486ae7618d Mon Sep 17 00:00:00 2001
From: Daniel Tschertkow <daniel.tschertkow@posteo.de>
Date: Mon, 23 Nov 2020 01:12:31 +0100
Subject: [PATCH] =?UTF-8?q?f=C3=BCgt=20mono.py=20hinzu?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/mono/mono.py | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100755 src/mono/mono.py

diff --git a/src/mono/mono.py b/src/mono/mono.py
new file mode 100755
index 0000000..c63bf75
--- /dev/null
+++ b/src/mono/mono.py
@@ -0,0 +1,64 @@
+#!/usr/bin/env python
+"""
+Module to encrypt and decrypt a monoalphabetic cipher.
+"""
+
+from string import ascii_lowercase
+from collections import OrderedDict
+
+def subs_alphabet(key):
+    return list(OrderedDict.fromkeys(key + ascii_lowercase))
+
+
+def mono_encrypt(plaintext, key):
+    subs_dict = OrderedDict(zip( ascii_lowercase, subs_alphabet(key) ))
+    enc = ""
+    for char in plaintext.lower():
+        enc += subs_dict[char]
+    return enc
+
+def mono_decrypt(ciphertext, key):
+    subs_dict = OrderedDict(zip( subs_alphabet(key), ascii_lowercase ))
+    dec = ""
+    for char in ciphertext.lower():
+        dec += subs_dict[char]
+    return dec
+
+
+if __name__ == "__main__":
+    import sys, os
+    import argparse
+
+    # cannot import from a parent package if called directly
+    # without modifying PYTHONPATH or sys.path
+    file_dir = os.path.dirname(os.path.abspath(__file__))
+    file_parent_dir = os.path.dirname(file_dir)
+    sys.path.append(file_parent_dir)
+
+    from libex01 import read_text
+
+    def parse_args(sys_argv):
+        parser = argparse.ArgumentParser()
+        parser.add_argument("FILE")
+        command_group = parser.add_mutually_exclusive_group(required=True)
+        command_group.add_argument("--encrypt", metavar="KEY")
+        command_group.add_argument("--decrypt", metavar="KEY")
+        parser.add_argument("--out", metavar="FILE")
+        return parser.parse_args(sys_argv[1:])
+
+    def write_output(output, outfile=None):
+        if outfile != None:
+            with open(outfile, 'w') as f:
+                f.write(output)
+        else:
+            print(output)
+
+    args = parse_args(sys.argv)
+
+    txt = read_text(args.FILE)
+    if args.encrypt:
+        enc = mono_encrypt(txt, args.encrypt)
+        write_output(enc, args.out)
+    else:
+        dec = mono_decrypt(txt, args.decrypt)
+        write_output(dec, args.out)