From f75ab4735704ff853368e08c0f9f3d67b1856ff4 Mon Sep 17 00:00:00 2001
From: Vinicius Cordeiro <marcos.cordeiroal@gmail.com>
Date: Mon, 18 Oct 2021 09:23:57 -0300
Subject: [PATCH 1/2] Add polybius cipher

---
 ciphers/polybius.py | 96 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 ciphers/polybius.py

diff --git a/ciphers/polybius.py b/ciphers/polybius.py
new file mode 100644
index 000000000000..bc8264c67cac
--- /dev/null
+++ b/ciphers/polybius.py
@@ -0,0 +1,96 @@
+#!/usr/bin/env python3
+
+"""
+A Polybius Square is a table that allows someone to translate letters into numbers.
+
+https://www.braingle.com/brainteasers/codes/polybius.php
+"""
+
+import numpy as np
+
+
+class PolybiusCipher:
+    def __init__(self) -> None:
+        SQUARE = [
+            ["a", "b", "c", "d", "e"],
+            ["f", "g", "h", "i", "k"],
+            ["l", "m", "n", "o", "p"],
+            ["q", "r", "s", "t", "u"],
+            ["v", "w", "x", "y", "z"],
+        ]
+        self.SQUARE = np.array(SQUARE)
+
+    def letter_to_numbers(self, letter: str) -> np.ndarray:
+        """
+        Return the pair of numbers that represents the given letter in the
+        polybius square
+        >>> np.array_equal(PolybiusCipher().letter_to_numbers('a'), [1,1])
+        True
+
+        >>> np.array_equal(PolybiusCipher().letter_to_numbers('u'), [4,5])
+        True
+        """
+        index1, index2 = np.where(self.SQUARE == letter)
+        indexes = np.concatenate([index1 + 1, index2 + 1])
+        return indexes
+
+    def numbers_to_letter(self, index1: int, index2: int) -> str:
+        """
+        Return the letter corresponding to the position [index1, index2] in
+        the polybius square
+
+        >>> PolybiusCipher().numbers_to_letter(4, 5)
+        "u"
+
+        >>> PolybiusCipher().numbers_to_letter(1, 1)
+        "a"
+        """
+        letter = self.SQUARE[index1 - 1, index2 - 1]
+        return letter
+
+    def encode(self, message: str) -> str:
+        """
+        Return the encoded version of message according to the polybius cipher
+
+        >>> PolybiusCipher().encode("test message")
+        "44154344 32154343112215"
+
+        >>> PolybiusCipher().encode("Test Message")
+        "44154344 32154343112215"
+        """
+        message = message.lower()
+        message = message.replace("j", "i")
+
+        encoded_message = ""
+        for letter_index in range(len(message)):
+            if message[letter_index] != " ":
+                numbers = self.letter_to_numbers(message[letter_index])
+                encoded_message = encoded_message + str(numbers[0]) + str(numbers[1])
+            elif message[letter_index] == " ":
+                encoded_message = encoded_message + " "
+
+        return encoded_message
+
+    def decode(self, message: str) -> str:
+        """
+        Return the decoded version of message according to the polybius cipher
+
+        >>> PolybiusCipher().decode("44154344 32154343112215")
+        "test message"
+
+        >>> PolybiusCipher().decode("4415434432154343112215")
+        "testmessage"
+        """
+        message = message.replace(" ", "  ")
+        decoded_message = ""
+        for numbers_index in range(int(len(message) / 2)):
+            if message[numbers_index * 2] != " ":
+                index1 = message[numbers_index * 2]
+                index2 = message[numbers_index * 2 + 1]
+
+                letter = self.numbers_to_letter(int(index1), int(index2))
+                decoded_message = decoded_message + letter
+            elif message[numbers_index * 2] == " ":
+                decoded_message = decoded_message + " "
+
+        return decoded_message

From 650b4fec1a9ff786f39a3da61ab149aa549b4f0e Mon Sep 17 00:00:00 2001
From: Vinicius Cordeiro <marcos.cordeiroal@gmail.com>
Date: Mon, 18 Oct 2021 14:10:01 -0300
Subject: [PATCH 2/2] Fix polybius.py build issues and add test

---
 ciphers/polybius.py | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/ciphers/polybius.py b/ciphers/polybius.py
index bc8264c67cac..9e1dc4cbb5a8 100644
--- a/ciphers/polybius.py
+++ b/ciphers/polybius.py
@@ -39,11 +39,11 @@ def numbers_to_letter(self, index1: int, index2: int) -> str:
         Return the letter corresponding to the position [index1, index2] in
         the polybius square
 
-        >>> PolybiusCipher().numbers_to_letter(4, 5)
-        "u"
+        >>> PolybiusCipher().numbers_to_letter(4, 5) == "u"
+        True
 
-        >>> PolybiusCipher().numbers_to_letter(1, 1)
-        "a"
+        >>> PolybiusCipher().numbers_to_letter(1, 1) == "a"
+        True
         """
         letter = self.SQUARE[index1 - 1, index2 - 1]
         return letter
@@ -52,11 +52,11 @@ def encode(self, message: str) -> str:
         """
         Return the encoded version of message according to the polybius cipher
 
-        >>> PolybiusCipher().encode("test message")
-        "44154344 32154343112215"
+        >>> PolybiusCipher().encode("test message") == "44154344 32154343112215"
+        True
 
-        >>> PolybiusCipher().encode("Test Message")
-        "44154344 32154343112215"
+        >>> PolybiusCipher().encode("Test Message") == "44154344 32154343112215"
+        True
         """
         message = message.lower()
         message = message.replace("j", "i")
@@ -75,11 +75,11 @@ def decode(self, message: str) -> str:
         """
         Return the decoded version of message according to the polybius cipher
 
-        >>> PolybiusCipher().decode("44154344 32154343112215")
-        "test message"
+        >>> PolybiusCipher().decode("44154344 32154343112215") == "test message"
+        True
 
-        >>> PolybiusCipher().decode("4415434432154343112215")
-        "testmessage"
+        >>> PolybiusCipher().decode("4415434432154343112215") == "testmessage"
+        True
         """
         message = message.replace(" ", "  ")
         decoded_message = ""