flexible Baconian cipher encoding and decoding

ciphers/flexible_baconian_cipher

@@ -0,0 +1,94 @@
+encode_dict = {
+    "a": "AAAAA",
+    "b": "AAAAB",
+    "c": "AAABA",
+    "d": "AAABB",
+    "e": "AABAA",
+    "f": "AABAB",
+    "g": "AABBA",
+    "h": "AABBB",
+    "i": "ABAAA",
+    "j": "BBBAA",
+    "k": "ABAAB",
+    "l": "ABABA",
+    "m": "ABABB",
+    "n": "ABBAA",
+    "o": "ABBAB",
+    "p": "ABBBA",
+    "q": "ABBBB",
+    "r": "BAAAA",
+    "s": "BAAAB",
+    "t": "BAABA",
+    "u": "BAABB",
+    "v": "BBBAB",
+    "w": "BABAA",
+    "x": "BABAB",
+    "y": "BABBA",
+    "z": "BABBB",
+    " ": " ",
+}
+
+decode_dict = {value: key for key, value in encode_dict.items()}
+
+def encode(word: str, symbols=("A","B")) -> str:
+    a_sym, b_sym = symbols
+    encoded = ""
+    for letter in word.lower():
+        if letter.isalpha() or letter == " ":
+            # replace A with a_symbol, B with b_symbol
+            bacon = encode_dict[letter]
+            bacon_custom = bacon.replace("A", a_sym).replace("B", b_sym)
+            encoded += bacon_custom
+        else:
+            raise Exception("encode() accepts only letters of the alphabet and spaces")
+    return encoded
+
+def decode(coded: str, symbols=("A","B")) -> str:
+    sym1, sym2 = symbols
+    #  check if we need to remap
+    unique_symbols = set(coded.replace(" ", ""))
+    if unique_symbols - {sym1, sym2} != set():
+        raise Exception(f"decode() accepts only symbols {sym1} and {sym2} and spaces")
+
+    # Try both mappings: symbol1 maps to A, symbol2 maps to B or symbol1 maps to B, symbol2 maps A
+    candidates = []
+    for mapping in [(sym1, sym2), (sym2, sym1)]:
+        s1, s2 = mapping
+        # convert coded symbols to standard A/B
+        standard = coded.replace(s1, "A").replace(s2, "B")
+        try:
+            decoded = ""
+            for word in standard.split():
+                while len(word) != 0:
+                    chunk = word[:5]
+                    if chunk not in decode_dict:
+                        raise ValueError
+                    decoded += decode_dict[chunk]
+                    word = word[5:]
+                decoded += " "
+            candidates.append(decoded.strip())
+        except ValueError:
+            candidates.append(None)
+
+    # return the valid decoding
+    for candidate in candidates:
+        if candidate is not None:
+            return candidate
+    raise Exception("No valid decoding found with the given symbols")
+def detect_unique_char (cipher):
+    #CD CD DC returns C, D
+    cipher = cipher.replace(" ","")
+    unique_chars = set(cipher)
+    unique_letters = [char for char in unique_chars if char.isalpha()]
+    if len(unique_letters) != 2:
+        raise Exception("Cipher must contain exactly two unique alphabetic characters for encoding.")
+    else:
+        list_unique = list(unique_letters)
+        return list_unique[0], list_unique[1]
+
+if __name__ == "__main__":
+    # Example usage
+    cipher_text = "FEEFE EEFFF EEFEE EFFFF FEEFF EFEEE EEEFE EFEEF EEEEF FEEEE EFFEF FEFEE EFFEE EEFEF EFFEF FEFEF"
+    symbol_1, symbol_2 = detect_unique_char(cipher_text)
+    decoded = decode(cipher_text, symbols=(symbol_1, symbol_2))
+    print(decoded)  # prints the quick brown fox