Tirsvad
9d8beb3aef
- Replace separate encrypt/decrypt with shared caesar() function - Add direction constants (DIRECTION_ENCODE, DIRECTION_DECODE) and prompts - Update main.py to support interactive encode/decode loop - Keep encrypt/decrypt as wrappers for backward compatibility - Add tests for caesar() with both directions and error handling - Update tests for main.py with interactive scenario tests
45 lines
1.7 KiB
Python
45 lines
1.7 KiB
Python
## @file cipher.py
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# @brief Caesar cipher: one shared function for encoding and decoding.
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from caesar_cipher.constants import ALPHABET, DIRECTION_DECODE, DIRECTION_ENCODE
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def caesar(text: str, shift: int, direction: str) -> str:
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## @brief Encode or decode a text with the Caesar cipher.
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# @param text Text to transform.
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# @param shift Positions to move each letter (may be negative or > 26).
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# @param direction DIRECTION_ENCODE or DIRECTION_DECODE.
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# @return The transformed text; non-letters are kept, case is preserved.
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# @throws ValueError If direction is not a known direction.
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if direction == DIRECTION_DECODE:
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shift = -shift
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elif direction != DIRECTION_ENCODE:
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raise ValueError(f"Unknown direction: {direction!r}")
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result = []
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for char in text:
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lower = char.lower()
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if lower in ALPHABET:
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new_position = (ALPHABET.index(lower) + shift) % len(ALPHABET)
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new_char = ALPHABET[new_position]
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result.append(new_char.upper() if char.isupper() else new_char)
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else:
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result.append(char)
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return "".join(result)
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def encrypt(text: str, shift: int) -> str:
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## @brief Encrypt a text with the Caesar cipher.
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# @param text Original text.
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# @param shift Number of positions to shift forward.
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# @return The encrypted text.
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return caesar(text, shift, DIRECTION_ENCODE)
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def decrypt(text: str, shift: int) -> str:
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## @brief Decrypt a Caesar-cipher text.
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# @param text Encrypted text.
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# @param shift Shift that was used to encrypt.
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# @return The original text.
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return caesar(text, shift, DIRECTION_DECODE)
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