merge conflict (#240)

config.json

@@ -336,7 +336,15 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 3
-      }       
+      },
+      {
+        "slug": "affine-cipher",
+        "name": "Affine Cipher",
+        "uuid": "85dae1ac-f9e5-411d-920e-bfa988c49876",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      }
     ]
   },
   "concepts": [

exercises/practice/affine-cipher/.docs/instructions.md

@@ -0,0 +1,74 @@
+# Description
+
+Create an implementation of the affine cipher, an ancient encryption system created in the Middle East.
+
+The affine cipher is a type of monoalphabetic substitution cipher.
+Each character is mapped to its numeric equivalent, encrypted with a mathematical function and then converted to the letter relating to its new numeric value.
+Although all monoalphabetic ciphers are weak, the affine cipher is much stronger than the atbash cipher, because it has many more keys.
+
+[comment]: # ( monoalphabetic as spelled by Merriam-Webster, compare to polyalphabetic )
+
+## Encryption
+
+The encryption function is:
+
+```text
+E(x) = (ai + b) mod m
+```
+
+Where:
+
+- `i` is the letter's index from `0` to the length of the alphabet - 1
+- `m` is the length of the alphabet.
+  For the Roman alphabet `m` is `26`.
+- `a` and `b` are integers which make the encryption key
+
+Values `a` and `m` must be *coprime* (or, *relatively prime*) for automatic decryption to succeed, i.e., they have number `1` as their only common factor (more information can be found in the [Wikipedia article about coprime integers][coprime-integers]).
+In case `a` is not coprime to `m`, your program should indicate that this is an error.
+Otherwise it should encrypt or decrypt with the provided key.
+
+For the purpose of this exercise, digits are valid input but they are not encrypted.
+Spaces and punctuation characters are excluded.
+Ciphertext is written out in groups of fixed length separated by space, the traditional group size being `5` letters.
+This is to make it harder to guess encrypted text based on word boundaries.
+
+## Decryption
+
+The decryption function is:
+
+```text
+D(y) = (a^-1)(y - b) mod m
+```
+
+Where:
+
+- `y` is the numeric value of an encrypted letter, i.e., `y = E(x)`
+- it is important to note that `a^-1` is the modular multiplicative inverse (MMI) of `a mod m`
+- the modular multiplicative inverse only exists if `a` and `m` are coprime.
+
+The MMI of `a` is `x` such that the remainder after dividing `ax` by `m` is `1`:
+
+```text
+ax mod m = 1
+```
+
+More information regarding how to find a Modular Multiplicative Inverse and what it means can be found in the [related Wikipedia article][mmi].
+
+## General Examples
+
+- Encrypting `"test"` gives `"ybty"` with the key `a = 5`, `b = 7`
+- Decrypting `"ybty"` gives `"test"` with the key `a = 5`, `b = 7`
+- Decrypting `"ybty"` gives `"lqul"` with the wrong key `a = 11`, `b = 7`
+- Decrypting `"kqlfd jzvgy tpaet icdhm rtwly kqlon ubstx"` gives `"thequickbrownfoxjumpsoverthelazydog"` with the key `a = 19`, `b = 13`
+- Encrypting `"test"` with the key `a = 18`, `b = 13` is an error because `18` and `26` are not coprime
+
+## Example of finding a Modular Multiplicative Inverse (MMI)
+
+Finding MMI for `a = 15`:
+
+- `(15 * x) mod 26 = 1`
+- `(15 * 7) mod 26 = 1`, ie. `105 mod 26 = 1`
+- `7` is the MMI of `15 mod 26`
+
+[mmi]: https://en.wikipedia.org/wiki/Modular_multiplicative_inverse
+[coprime-integers]: https://en.wikipedia.org/wiki/Coprime_integers

exercises/practice/affine-cipher/.meta/config.json

@@ -0,0 +1,13 @@
+{
+  "blurb": "Create an implementation of the Affine cipher, an ancient encryption algorithm from the Middle East.",
+  "authors": ["dwivedirahul44"],
+  "contributors": [
+  ],
+  "files": {
+    "solution": ["zcl_affine_cipher.clas.abap"],
+    "test": ["zcl_affine_cipher.clas.testclasses.abap"],
+    "example": [".meta/zcl_affine_cipher.clas.abap"]
+  },
+  "source": "Wikipedia",
+  "source_url": "http://en.wikipedia.org/wiki/Affine_cipher"
+}

exercises/practice/affine-cipher/.meta/zcl_affine_cipher.clas.abap

@@ -0,0 +1,133 @@
+CLASS zcl_affine_cipher DEFINITION
+  PUBLIC
+  FINAL
+  CREATE PUBLIC.
+
+  PUBLIC SECTION.
+    TYPES: BEGIN OF key,
+             a TYPE i,
+             b TYPE i,
+           END OF key.
+
+    METHODS:
+      encode IMPORTING phrase        TYPE string
+                       key           TYPE key
+             RETURNING VALUE(cipher) TYPE string
+             RAISING   cx_parameter_invalid,
+      decode IMPORTING cipher        TYPE string
+                       key           TYPE key
+             RETURNING VALUE(phrase) TYPE string
+             RAISING   cx_parameter_invalid.
+  PROTECTED SECTION.
+  PRIVATE SECTION.
+    TYPES: ty_char1 TYPE c LENGTH 1.
+    CONSTANTS:
+      max_len TYPE i VALUE 26.
+    METHODS:
+      is_coprime         IMPORTING VALUE(a)    TYPE i
+                         RETURNING VALUE(flag) TYPE abap_bool,
+      ret_mmi            IMPORTING VALUE(a)   TYPE i
+                         RETURNING VALUE(mmi) TYPE i,
+      ret_upper_nth_char IMPORTING str           TYPE string
+                                   n             TYPE i
+                         RETURNING VALUE(letter) TYPE ty_char1,
+      ret_nth_letter     IMPORTING n             TYPE i
+                         RETURNING VALUE(letter) TYPE ty_char1,
+      ret_letter_index   IMPORTING letter       TYPE ty_char1
+                         RETURNING VALUE(index) TYPE i.
+
+ENDCLASS.
+
+
+
+CLASS zcl_affine_cipher IMPLEMENTATION.
+  METHOD encode.
+    IF is_coprime( key-a ) = abap_false.
+      RAISE EXCEPTION TYPE cx_parameter_invalid.
+    ENDIF.
+    DATA(str) = replace( val   = phrase
+                         with  = ``
+                         regex = '[\,\s\.]'
+                         occ   = 0 ).
+    cipher = REDUCE string(
+               INIT result TYPE string
+                    cur_letter = ''
+               FOR i = 0 UNTIL i = strlen( str )
+               NEXT cur_letter = ret_upper_nth_char( str = str
+                                                       n = i )
+                    result &&= |{
+                      COND string(
+                        WHEN i MOD 5 = 0 AND i > 0
+                          THEN ` `
+                          ELSE `` ) }{
+                      to_lower(
+                        COND string(
+                          WHEN cur_letter CA sy-abcde
+                            THEN ret_nth_letter(
+                                   ( ( ( key-a * ret_letter_index( cur_letter ) ) + key-b ) MOD max_len ) )
+                            ELSE cur_letter ) ) }| ).
+  ENDMETHOD.
+
+  METHOD ret_upper_nth_char.
+    letter = to_upper( substring( val = str off = n len = 1 ) ).
+  ENDMETHOD.
+
+  METHOD ret_nth_letter.
+    letter = substring( val = sy-abcde off = n len = 1 ).
+  ENDMETHOD.
+
+  METHOD ret_letter_index.
+    index = find( val = sy-abcde sub = letter ).
+  ENDMETHOD.
+
+  METHOD decode.
+    DATA(mmi) = ret_mmi( key-a ).
+    IF mmi = 0.
+      RAISE EXCEPTION TYPE cx_parameter_invalid.
+    ENDIF.
+
+    DATA(str) = condense( val = cipher from = ` ` to = `` ).
+    phrase = REDUCE string(
+               INIT result TYPE string
+                    cur_letter = ''
+               FOR i = 0 UNTIL i = strlen( str )
+               NEXT cur_letter = ret_upper_nth_char( str = str
+                                                       n = i )
+                    result &&= |{
+                      COND string(
+                        WHEN cur_letter CA sy-abcde
+                          THEN to_lower(
+                                 ret_nth_letter(
+                                   ( ( mmi * ( ret_letter_index( cur_letter ) - key-b ) MOD max_len ) ) ) )
+                          ELSE cur_letter ) }| ).
+
+  ENDMETHOD.
+
+  METHOD is_coprime.
+    DATA(m) = max_len.
+    WHILE a <> 0 AND m <> 0.
+      IF a = nmax( val1 = a val2 = m ).
+        a = a MOD m.
+      ELSE.
+        m = m MOD a.
+      ENDIF.
+    ENDWHILE.
+    IF nmax( val1 = a val2 = m ) = 1.
+      flag = abap_true.
+    ENDIF.
+  ENDMETHOD.
+
+  METHOD ret_mmi.
+    DATA(i) = 0.
+    DATA(x) = 0.
+    WHILE i < max_len.
+      x = ( ( a MOD max_len ) * ( i MOD max_len ) ) MOD max_len.
+      IF x = 1.
+        mmi = i.
+        EXIT.
+      ENDIF.
+      i += 1.
+    ENDWHILE.
+  ENDMETHOD.
+
+ENDCLASS.

exercises/practice/affine-cipher/package.devc.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<abapGit version="v1.0.0" serializer="LCL_OBJECT_DEVC" serializer_version="v1.0.0">
+ <asx:abap xmlns:asx="http://www.sap.com/abapxml" version="1.0">
+  <asx:values>
+   <DEVC>
+    <CTEXT>Exercism: Affine-Cipher</CTEXT>
+   </DEVC>
+  </asx:values>
+ </asx:abap>
+</abapGit>

exercises/practice/affine-cipher/zcl_affine_cipher.clas.abap

@@ -0,0 +1,36 @@
+CLASS zcl_affine_cipher DEFINITION
+  PUBLIC
+  FINAL
+  CREATE PUBLIC.
+
+  PUBLIC SECTION.
+    TYPES: BEGIN OF key,
+             a TYPE i,
+             b TYPE i,
+           END OF key.
+
+    METHODS:
+      encode IMPORTING phrase        TYPE string
+                       key           TYPE key
+             RETURNING VALUE(cipher) TYPE string
+             RAISING   cx_parameter_invalid,
+      decode IMPORTING cipher        TYPE string
+                       key           TYPE key
+             RETURNING VALUE(phrase) TYPE string
+             RAISING   cx_parameter_invalid.
+  PROTECTED SECTION.
+  PRIVATE SECTION.
+ENDCLASS.
+
+
+
+CLASS zcl_affine_cipher IMPLEMENTATION.
+  METHOD encode.
+    "Implement solution
+  ENDMETHOD.
+
+  METHOD decode.
+    "Implement solution
+  ENDMETHOD.
+
+ENDCLASS.

exercises/practice/affine-cipher/zcl_affine_cipher.clas.testclasses.abap

@@ -0,0 +1,161 @@
+CLASS ltcl_crypto_square DEFINITION FINAL FOR TESTING
+  DURATION SHORT
+  RISK LEVEL HARMLESS.
+
+  PRIVATE SECTION.
+    DATA cut TYPE REF TO zcl_affine_cipher.
+    METHODS setup.
+    METHODS:
+      encode_yes                  FOR TESTING,
+      encode_no                   FOR TESTING,
+      encode_omg                  FOR TESTING,
+      encode_o_m_g                FOR TESTING,
+      encode_string               FOR TESTING,
+      encode_sentence_with_number FOR TESTING,
+      encode_sentence             FOR TESTING,
+      encode_all_letters          FOR TESTING,
+      encode_no_coprime           FOR TESTING,
+      decode_exercism             FOR TESTING,
+      decode_sentence             FOR TESTING,
+      decode_sentence_with_number FOR TESTING,
+      decode_all_letters          FOR TESTING,
+      decode_multi_space          FOR TESTING,
+      decode_no_coprime           FOR TESTING.
+ENDCLASS.
+
+
+CLASS ltcl_crypto_square IMPLEMENTATION.
+  METHOD setup.
+    cut = NEW zcl_affine_cipher( ).
+  ENDMETHOD.
+
+  METHOD encode_yes.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `xbt`
+      act = cut->encode(
+              phrase = `yes`
+              key    = VALUE #( a = 5 b = 7 ) ) ).
+  ENDMETHOD.
+
+  METHOD encode_no.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `fu`
+      act = cut->encode(
+              phrase = `no`
+              key    = VALUE #( a = 15 b = 18 ) ) ).
+  ENDMETHOD.
+
+  METHOD encode_omg.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `lvz`
+      act = cut->encode(
+              phrase = `OMG`
+              key    = VALUE #( a = 21 b = 3 ) ) ).
+  ENDMETHOD.
+
+  METHOD encode_o_m_g.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `hjp`
+      act = cut->encode(
+              phrase = `O M G`
+              key    = VALUE #( a = 25 b = 47 ) ) ).
+  ENDMETHOD.
+
+  METHOD encode_string.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `rzcwa gnxzc dgt`
+      act = cut->encode(
+              phrase = `mindblowingly`
+              key    = VALUE #( a = 11 b = 15 ) ) ).
+  ENDMETHOD.
+
+  METHOD encode_sentence_with_number.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `jqgjc rw123 jqgjc rw`
+      act = cut->encode(
+              phrase = `Testing,1 2 3, testing.`
+              key    = VALUE #( a = 3 b = 4 ) ) ).
+  ENDMETHOD.
+
+  METHOD encode_sentence.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `iynia fdqfb ifje`
+      act = cut->encode(
+              phrase = `Truth is fiction.`
+              key    = VALUE #( a = 5 b = 17 ) ) ).
+  ENDMETHOD.
+
+  METHOD encode_all_letters.
+    DATA(exp) = `swxtj npvyk lruol iejdc blaxk swxmh qzglf`.
+    DATA(phrase) = `The quick brown fox jumps over the lazy dog.`.
+    cl_abap_unit_assert=>assert_equals(
+      exp = exp
+      act = cut->encode(
+              phrase = phrase
+              key    = VALUE #( a = 17 b = 33 ) ) ).
+  ENDMETHOD.
+
+  METHOD encode_no_coprime.
+    TRY.
+        cut->encode(
+          phrase = `Test`
+          key    = VALUE #( a = 6 b = 17 ) ).
+        cl_abap_unit_assert=>fail( ).
+      CATCH cx_parameter_invalid.
+    ENDTRY.
+  ENDMETHOD.
+
+  METHOD decode_exercism.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `exercism`
+      act = cut->decode(
+              cipher = `tytgn fjr`
+              key    = VALUE #( a = 3 b = 7 ) ) ).
+  ENDMETHOD.
+
+  METHOD decode_sentence.
+    DATA(cipher) = `qdwju nqcro muwhn odqun oppmd aunwd o`.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `anobstacleisoftenasteppingstone`
+      act = cut->decode(
+              cipher = cipher
+              key    = VALUE #( a = 19 b = 16 ) ) ).
+  ENDMETHOD.
+
+  METHOD decode_sentence_with_number.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `testing123testing`
+      act = cut->decode(
+              cipher = `odpoz ub123 odpoz ub`
+              key    = VALUE #( a = 25 b = 7 ) ) ).
+  ENDMETHOD.
+
+  METHOD decode_all_letters.
+    DATA(cipher) = `swxtj npvyk lruol iejdc blaxk swxmh qzglf`.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `thequickbrownfoxjumpsoverthelazydog`
+      act = cut->decode(
+              cipher = cipher
+              key    = VALUE #( a = 17 b = 33 ) ) ).
+  ENDMETHOD.
+
+  METHOD decode_multi_space.
+    DATA(cipher) = `vszzm    cly   yd cg    qdp`.
+    cl_abap_unit_assert=>assert_equals(
+      exp = `jollygreengiant`
+      act = cut->decode(
+              cipher = cipher
+              key    = VALUE #( a = 15 b = 16 ) ) ).
+  ENDMETHOD.
+
+  METHOD decode_no_coprime.
+    TRY.
+        cut->decode(
+          cipher = `Test`
+          key    = VALUE #( a = 13 b = 5 ) ).
+        cl_abap_unit_assert=>fail( ).
+      CATCH cx_parameter_invalid.
+    ENDTRY.
+  ENDMETHOD.
+
+ENDCLASS.

exercises/practice/affine-cipher/zcl_affine_cipher.clas.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<abapGit version="v1.0.0" serializer="LCL_OBJECT_CLAS" serializer_version="v1.0.0">
+ <asx:abap xmlns:asx="http://www.sap.com/abapxml" version="1.0">
+  <asx:values>
+   <VSEOCLASS>
+    <CLSNAME>ZCL_AFFINE_CIPHER</CLSNAME>
+    <LANGU>E</LANGU>
+    <DESCRIPT>Exercism: Affine Cipher</DESCRIPT>
+    <STATE>1</STATE>
+    <CLSCCINCL>X</CLSCCINCL>
+    <FIXPT>X</FIXPT>
+    <UNICODE>X</UNICODE>
+    <WITH_UNIT_TESTS>X</WITH_UNIT_TESTS>
+   </VSEOCLASS>
+  </asx:values>
+ </asx:abap>
+</abapGit>