Added enigma machine emulator (#2345)

* Added Enigma machine file

Added Enigma machine file to 'ciphers' section

* Added doctest to validator

* Fixed typo

* Shortened some lines

* Shortened some lines

* Update enigma_machine.py

* Shortened some lines

* Update enigma_machine.py

* Update enigma_machine.py

* Update enigma_machine2.py

* Update enigma_machine2.py

* added f-strings

* Update enigma_machine2.py

* Update enigma_machine2.py

* Updated some numbers

* Plugboard improvement

Added option to separate pair for plugboard by spaces

* renamed variable

* renamed some variables

* improved plugboard exception

* Update enigma_machine2.py

* Update enigma_machine2.py

Author: TrapinchO

ciphers/enigma_machine2.py

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+"""
+Wikipedia: https://en.wikipedia.org/wiki/Enigma_machine
+Video explanation: https://youtu.be/QwQVMqfoB2E
+Also check out Numberphile's and Computerphile's videos on this topic
+
+This module contains function 'enigma' which emulates
+the famous Enigma machine from WWII.
+Module includes:
+- enigma function
+- showcase of function usage
+- 9 randnomly generated rotors
+- reflector (aka static rotor)
+- original alphabet
+
+Created by TrapinchO
+"""
+
+# used alphabet --------------------------
+# from string.ascii_uppercase
+abc = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+
+# -------------------------- default selection --------------------------
+# rotors --------------------------
+rotor1 = 'EGZWVONAHDCLFQMSIPJBYUKXTR'
+rotor2 = 'FOBHMDKEXQNRAULPGSJVTYICZW'
+rotor3 = 'ZJXESIUQLHAVRMDOYGTNFWPBKC'
+# reflector --------------------------
+reflector = {'A': 'N', 'N': 'A', 'B': 'O', 'O': 'B', 'C': 'P', 'P': 'C', 'D': 'Q',
+             'Q': 'D', 'E': 'R', 'R': 'E', 'F': 'S', 'S': 'F', 'G': 'T', 'T': 'G',
+             'H': 'U', 'U': 'H', 'I': 'V', 'V': 'I', 'J': 'W', 'W': 'J', 'K': 'X',
+             'X': 'K', 'L': 'Y', 'Y': 'L', 'M': 'Z', 'Z': 'M'}
+
+# -------------------------- extra rotors --------------------------
+rotor4 = 'RMDJXFUWGISLHVTCQNKYPBEZOA'
+rotor5 = 'SGLCPQWZHKXAREONTFBVIYJUDM'
+rotor6 = 'HVSICLTYKQUBXDWAJZOMFGPREN'
+rotor7 = 'RZWQHFMVDBKICJLNTUXAGYPSOE'
+rotor8 = 'LFKIJODBEGAMQPXVUHYSTCZRWN'
+rotor9 = 'KOAEGVDHXPQZMLFTYWJNBRCIUS'
+
+
+def _validator(rotpos: tuple, rotsel: tuple, pb: str) -> tuple:
+    """
+    Checks if the values can be used for the 'enigma' function
+
+    >>> _validator((1,1,1), (rotor1, rotor2, rotor3), 'POLAND')
+    ((1, 1, 1), ('EGZWVONAHDCLFQMSIPJBYUKXTR', 'FOBHMDKEXQNRAULPGSJVTYICZW', \
+'ZJXESIUQLHAVRMDOYGTNFWPBKC'), \
+{'P': 'O', 'O': 'P', 'L': 'A', 'A': 'L', 'N': 'D', 'D': 'N'})
+
+    :param rotpos: rotor_positon
+    :param rotsel: rotor_selection
+    :param pb: plugb -> validated and transformed
+    :return: (rotpos, rotsel, pb)
+    """
+    # Checks if there are 3 unique rotors
+
+    unique_rotsel = len(set(rotsel))
+    if unique_rotsel < 3:
+        raise Exception(f'Please use 3 unique rotors (not {unique_rotsel})')
+
+    # Checks if rotor positions are valid
+    rotorpos1, rotorpos2, rotorpos3 = rotpos
+    if not 0 < rotorpos1 <= len(abc):
+        raise ValueError(f'First rotor position is not within range of 1..26 ('
+                         f'{rotorpos1}')
+    if not 0 < rotorpos2 <= len(abc):
+        raise ValueError(f'Second rotor position is not within range of 1..26 ('
+                         f'{rotorpos2})')
+    if not 0 < rotorpos3 <= len(abc):
+        raise ValueError(f'Third rotor position is not within range of 1..26 ('
+                         f'{rotorpos3})')
+
+    # Validates string and returns dict
+    pb = _plugboard(pb)
+
+    return rotpos, rotsel, pb
+
+
+def _plugboard(pbstring: str) -> dict:
+    """
+    https://en.wikipedia.org/wiki/Enigma_machine#Plugboard
+
+    >>> _plugboard('PICTURES')
+    {'P': 'I', 'I': 'P', 'C': 'T', 'T': 'C', 'U': 'R', 'R': 'U', 'E': 'S', 'S': 'E'}
+    >>> _plugboard('POLAND')
+    {'P': 'O', 'O': 'P', 'L': 'A', 'A': 'L', 'N': 'D', 'D': 'N'}
+
+    In the code, 'pb' stands for 'plugboard'
+
+    Pairs can be separated by spaces
+    :param pbstring: string containing plugboard setting for the Enigma machine
+    :return: dictionary containing converted pairs
+    """
+
+    # tests the input string if it
+    # a) is type string
+    # b) has even length (so pairs can be made)
+    if not isinstance(pbstring, str):
+        raise TypeError(f'Plugboard setting isn\'t type string ({type(pbstring)})')
+    elif len(pbstring) % 2 != 0:
+        raise Exception(f'Odd number of symbols ({len(pbstring)})')
+    elif pbstring == '':
+        return {}
+
+    pbstring.replace(' ', '')
+
+    # Checks if all characters are unique
+    tmppbl = set()
+    for i in pbstring:
+        if i not in abc:
+            raise Exception(f'\'{i}\' not in list of symbols')
+        elif i in tmppbl:
+            raise Exception(f'Duplicate symbol ({i})')
+        else:
+            tmppbl.add(i)
+    del tmppbl
+
+    # Created the dictionary
+    pb = {}
+    for i in range(0, len(pbstring) - 1, 2):
+        pb[pbstring[i]] = pbstring[i + 1]
+        pb[pbstring[i + 1]] = pbstring[i]
+
+    return pb
+
+
+def enigma(text: str, rotor_position: tuple,
+           rotor_selection: tuple = (rotor1, rotor2, rotor3), plugb: str = '') -> str:
+    """
+    The only difference with real-world enigma is that I allowed string input.
+    All characters are converted to uppercase. (non-letter symbol are ignored)
+    How it works:
+    (for every letter in the message)
+
+    - Input letter goes into the plugboard.
+    If it is connected to another one, switch it.
+
+    - Letter goes through 3 rotors.
+    Each rotor can be represented as 2 sets of symbol, where one is shuffled.
+    Each symbol from the first set has corresponding symbol in
+    the second set and vice versa.
+
+    example:
+    | ABCDEFGHIJKLMNOPQRSTUVWXYZ | e.g. F=D and D=F
+    | VKLEPDBGRNWTFCJOHQAMUZYIXS |
+
+    - Symbol then goes through reflector (static rotor).
+    There it is switched with paired symbol
+    The reflector can be represented as2 sets, each with half of the alphanet.
+    There are usually 10 pairs of letters.
+
+    Example:
+    | ABCDEFGHIJKLM | e.g. E is paired to X
+    | ZYXWVUTSRQPON | so when E goes in X goes out and vice versa
+
+    - Letter then goes through the rotors again
+
+    - If the letter is connected to plugboard, it is switched.
+
+    - Return the letter
+
+    >>> enigma('Hello World!', (1, 2, 1), plugb='pictures')
+    'KORYH JUHHI!'
+    >>> enigma('KORYH, juhhi!', (1, 2, 1), plugb='pictures')
+    'HELLO, WORLD!'
+    >>> enigma('hello world!', (1, 1, 1), plugb='pictures')
+    'FPNCZ QWOBU!'
+    >>> enigma('FPNCZ QWOBU', (1, 1, 1), plugb='pictures')
+    'HELLO WORLD'
+
+
+    :param text: input message
+    :param rotor_position: tuple with 3 values in range 1..26
+    :param rotor_selection: tuple with 3 rotors ()
+    :param plugb: string containing plugboard configuration (default '')
+    :return: en/decrypted string
+    """
+
+    text = text.upper()
+    rotor_position, rotor_selection, plugboard = _validator(
+        rotor_position, rotor_selection, plugb.upper())
+
+    rotorpos1, rotorpos2, rotorpos3 = rotor_position
+    rotor1, rotor2, rotor3 = rotor_selection
+    rotorpos1 -= 1
+    rotorpos2 -= 1
+    rotorpos3 -= 1
+    plugboard = plugboard
+
+    result = []
+
+    # encryption/decryption process --------------------------
+    for symbol in text:
+        if symbol in abc:
+
+            # 1st plugboard --------------------------
+            if symbol in plugboard:
+                symbol = plugboard[symbol]
+
+            # rotor ra --------------------------
+            index = abc.index(symbol) + rotorpos1
+            symbol = rotor1[index % len(abc)]
+
+            # rotor rb --------------------------
+            index = abc.index(symbol) + rotorpos2
+            symbol = rotor2[index % len(abc)]
+
+            # rotor rc --------------------------
+            index = abc.index(symbol) + rotorpos3
+            symbol = rotor3[index % len(abc)]
+
+            # reflector --------------------------
+            # this is the reason you don't need another machine to decipher
+
+            symbol = reflector[symbol]
+
+            # 2nd rotors
+            symbol = abc[rotor3.index(symbol) - rotorpos3]
+            symbol = abc[rotor2.index(symbol) - rotorpos2]
+            symbol = abc[rotor1.index(symbol) - rotorpos1]
+
+            # 2nd plugboard
+            if symbol in plugboard:
+                symbol = plugboard[symbol]
+
+            # moves/resets rotor positions
+            rotorpos1 += 1
+            if rotorpos1 >= len(abc):
+                rotorpos1 = 0
+                rotorpos2 += 1
+            if rotorpos2 >= len(abc):
+                rotorpos2 = 0
+                rotorpos3 += 1
+            if rotorpos3 >= len(abc):
+                rotorpos3 = 0
+
+        # else:
+        #    pass
+        #    Error could be also raised
+        #    raise ValueError(
+        #       'Invalid symbol('+repr(symbol)+')')
+        result.append(symbol)
+
+    return "".join(result)
+
+
+if __name__ == '__main__':
+    message = 'This is my Python script that emulates the Enigma machine from WWII.'
+    rotor_pos = (1, 1, 1)
+    pb = 'pictures'
+    rotor_sel = (rotor2, rotor4, rotor8)
+    en = enigma(message, rotor_pos, rotor_sel, pb)
+
+    print('Encrypted message:', en)
+    print('Decrypted message:', enigma(en, rotor_pos, rotor_sel, pb))