rotaitional_chiper

elixir/rotational-cipher/.exercism/config.json

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+{
+  "authors": [
+    "DoggettCK"
+  ],
+  "contributors": [
+    "angelikatyborska",
+    "Cohen-Carlisle",
+    "devonestes",
+    "neenjaw",
+    "sotojuan"
+  ],
+  "files": {
+    "solution": [
+      "lib/rotational_cipher.ex"
+    ],
+    "test": [
+      "test/rotational_cipher_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Caesar_cipher"
+}

elixir/rotational-cipher/.exercism/metadata.json

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+{"track":"elixir","exercise":"rotational-cipher","id":"bd76a5d1822947e48b10bad622ce9d75","url":"https://exercism.org/tracks/elixir/exercises/rotational-cipher","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/rotational-cipher/.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

elixir/rotational-cipher/.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+rotational_cipher-*.tar
+

elixir/rotational-cipher/HELP.md

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+# Help
+
+## Running the tests
+
+From the terminal, change to the base directory of the exercise then execute the tests with:
+
+```bash
+$ mix test
+```
+
+This will execute the test file found in the `test` subfolder -- a file ending in `_test.exs`
+
+Documentation:
+
+* [`mix test` - Elixir's test execution tool](https://hexdocs.pm/mix/Mix.Tasks.Test.html)
+* [`ExUnit` - Elixir's unit test library](https://hexdocs.pm/ex_unit/ExUnit.html)
+
+## Pending tests
+
+In test suites of practice exercises, all but the first test have been tagged to be skipped.
+
+Once you get a test passing, you can unskip the next one by commenting out the relevant `@tag :pending` with a `#` symbol.
+
+For example:
+
+```elixir
+# @tag :pending
+test "shouting" do
+  assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
+end
+```
+
+If you wish to run all tests at once, you can include all skipped test by using the `--include` flag on the `mix test` command:
+
+```bash
+$ mix test --include pending
+```
+
+Or, you can enable all the tests by commenting out the `ExUnit.configure` line in the file `test/test_helper.exs`.
+
+```elixir
+# ExUnit.configure(exclude: :pending, trace: true)
+```
+
+## Useful `mix test` options
+
+* `test/<FILE>.exs:LINENUM` - runs only a single test, the test from `<FILE>.exs` whose definition is on line `LINENUM`
+* `--failed` - runs only tests that failed the last time they ran
+* `--max-failures` - the suite stops evaluating tests when this number of test failures
+is reached
+* `--seed 0` - disables randomization so the tests in a single file will always be ran
+in the same order they were defined in
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit lib/rotational_cipher.ex` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Elixir track's documentation](https://exercism.org/docs/tracks/elixir)
+- The [Elixir track's programming category on the forum](https://forum.exercism.org/c/programming/elixir)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+If you're stuck on something, it may help to look at some of the [available resources](https://exercism.org/docs/tracks/elixir/resources) out there where answers might be found.

elixir/rotational-cipher/README.md

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+# Rotational Cipher
+
+Welcome to Rotational Cipher on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.
+
+The Caesar cipher is a simple shift cipher that relies on transposing all the letters in the alphabet using an integer key between `0` and `26`.
+Using a key of `0` or `26` will always yield the same output due to modular arithmetic.
+The letter is shifted for as many values as the value of the key.
+
+The general notation for rotational ciphers is `ROT + <key>`.
+The most commonly used rotational cipher is `ROT13`.
+
+A `ROT13` on the Latin alphabet would be as follows:
+
+```text
+Plain:  abcdefghijklmnopqrstuvwxyz
+Cipher: nopqrstuvwxyzabcdefghijklm
+```
+
+It is stronger than the Atbash cipher because it has 27 possible keys, and 25 usable keys.
+
+Ciphertext is written out in the same formatting as the input including spaces and punctuation.
+
+## Examples
+
+- ROT5 `omg` gives `trl`
+- ROT0 `c` gives `c`
+- ROT26 `Cool` gives `Cool`
+- ROT13 `The quick brown fox jumps over the lazy dog.` gives `Gur dhvpx oebja sbk whzcf bire gur ynml qbt.`
+- ROT13 `Gur dhvpx oebja sbk whzcf bire gur ynml qbt.` gives `The quick brown fox jumps over the lazy dog.`
+
+## Source
+
+### Created by
+
+- @DoggettCK
+
+### Contributed to by
+
+- @angelikatyborska
+- @Cohen-Carlisle
+- @devonestes
+- @neenjaw
+- @sotojuan
+
+### Based on
+
+Wikipedia - https://en.wikipedia.org/wiki/Caesar_cipher

elixir/rotational-cipher/lib/rotational_cipher.ex

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+defmodule RotationalCipher do
+  @moduledoc """
+  Generates a simple Caesar cipher by rotating the alphabet by a given amount.
+  Use for that shifted alphabet generation function and transliteration table based on two alphabets.
+  """
+
+  @alphabet ?a..?z
+            |> Enum.to_list()
+            |> to_string()
+            |> String.split("", trim: true)
+
+  # Generates a shifted alphabet based on the given shift amount.
+  # If swaped is true, the function will return a map with the index as the key and the character as the value,
+  # otherwise the function will return a map with the character as the key and the index as the value.
+
+  defp alphabet(shift \\ 0, swaped \\ false) when shift < 26 and shift >= 0 do
+    @alphabet
+    |> Enum.with_index(fn char, index ->
+      position = if index + shift >= 26, do: index + shift - 26, else: index + shift
+      if swaped == true, do: {position, char}, else: {char, position}
+    end)
+    |> Enum.into(%{})
+  end
+
+  # Generates a transliteration table based on the given shift amount.
+
+  defp transliterate_table(shift) do
+    transliterated = alphabet(shift, true)
+
+    alphabet()
+    |> Enum.reduce(%{}, fn {char, index}, acc ->
+      Map.merge(acc, %{
+        transliterated[index] => char,
+        String.upcase(transliterated[index]) => String.upcase(char)
+      })
+    end)
+  end
+
+  defp rotate_char(char, table), do: table[char] || char
+
+  @doc """
+  Given a plaintext and amount to shift by, return a rotated string.
+
+  Example:
+  iex> RotationalCipher.rotate("Attack at dawn", 13)
+  "Nggnpx ng qnja"
+  """
+
+  @spec rotate(text :: String.t(), shift :: integer) :: String.t()
+  def rotate(text, shift) when shift == 0 or shift == 26, do: text
+
+  def rotate(text, shift) do
+    table = transliterate_table(shift)
+
+    text
+    |> String.graphemes()
+    |> Enum.map(&rotate_char(&1, table))
+    |> Enum.join()
+  end
+end

elixir/rotational-cipher/mix.exs

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+defmodule RotationalCipher.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :rotational_cipher,
+      version: "0.1.0",
+      # elixir: "~> 1.8",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

elixir/rotational-cipher/test/rotational_cipher_test.exs

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+defmodule RotationalCipherTest do
+  use ExUnit.Case
+
+  test "rotate a by 1" do
+    plaintext = "a"
+    shift = 1
+    assert RotationalCipher.rotate(plaintext, shift) == "b"
+  end
+
+  test "rotate a by 26, same output as input" do
+    plaintext = "a"
+    shift = 26
+    assert RotationalCipher.rotate(plaintext, shift) == "a"
+  end
+
+  test "rotate a by 0, same output as input" do
+    plaintext = "a"
+    shift = 0
+    assert RotationalCipher.rotate(plaintext, shift) == "a"
+  end
+
+  test "rotate m by 13" do
+    plaintext = "m"
+    shift = 13
+    assert RotationalCipher.rotate(plaintext, shift) == "z"
+  end
+
+  test "rotate n by 13 with wrap around alphabet" do
+    plaintext = "n"
+    shift = 13
+    assert RotationalCipher.rotate(plaintext, shift) == "a"
+  end
+
+  test "rotate capital letters" do
+    plaintext = "OMG"
+    shift = 5
+    assert RotationalCipher.rotate(plaintext, shift) == "TRL"
+  end
+
+  test "rotate spaces" do
+    plaintext = "O M G"
+    shift = 5
+    assert RotationalCipher.rotate(plaintext, shift) == "T R L"
+  end
+
+  test "rotate numbers" do
+    plaintext = "Testing 1 2 3 testing"
+    shift = 4
+    assert RotationalCipher.rotate(plaintext, shift) == "Xiwxmrk 1 2 3 xiwxmrk"
+  end
+
+  test "rotate punctuation" do
+    plaintext = "Let's eat, Grandma!"
+    shift = 21
+    assert RotationalCipher.rotate(plaintext, shift) == "Gzo'n zvo, Bmviyhv!"
+  end
+
+  test "rotate all letters" do
+    plaintext = "The quick brown fox jumps over the lazy dog."
+    shift = 13
+
+    assert RotationalCipher.rotate(plaintext, shift) ==
+             "Gur dhvpx oebja sbk whzcf bire gur ynml qbt."
+  end
+end

elixir/rotational-cipher/test/test_helper.exs

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+ExUnit.start()
+ExUnit.configure(exclude: :pending, trace: true)