From 66f0e9c6f884cfbb4035d91f513a6f27e18537b4 Mon Sep 17 00:00:00 2001
From: Danylo Negrienko <danil@negrienko.com>
Date: Sat, 29 Jun 2024 17:39:58 -0400
Subject: [PATCH] atbash

---
 elixir/atbash-cipher/.exercism/config.json   | 36 +++++++++
 elixir/atbash-cipher/.exercism/metadata.json |  1 +
 elixir/atbash-cipher/.formatter.exs          |  4 +
 elixir/atbash-cipher/.gitignore              | 24 ++++++
 elixir/atbash-cipher/HELP.md                 | 75 +++++++++++++++++++
 elixir/atbash-cipher/README.md               | 60 +++++++++++++++
 elixir/atbash-cipher/lib/atbash.ex           | 48 ++++++++++++
 elixir/atbash-cipher/mix.exs                 | 28 +++++++
 elixir/atbash-cipher/test/atbash_test.exs    | 77 ++++++++++++++++++++
 elixir/atbash-cipher/test/test_helper.exs    |  2 +
 10 files changed, 355 insertions(+)
 create mode 100644 elixir/atbash-cipher/.exercism/config.json
 create mode 100644 elixir/atbash-cipher/.exercism/metadata.json
 create mode 100644 elixir/atbash-cipher/.formatter.exs
 create mode 100644 elixir/atbash-cipher/.gitignore
 create mode 100644 elixir/atbash-cipher/HELP.md
 create mode 100644 elixir/atbash-cipher/README.md
 create mode 100644 elixir/atbash-cipher/lib/atbash.ex
 create mode 100644 elixir/atbash-cipher/mix.exs
 create mode 100644 elixir/atbash-cipher/test/atbash_test.exs
 create mode 100644 elixir/atbash-cipher/test/test_helper.exs

diff --git a/elixir/atbash-cipher/.exercism/config.json b/elixir/atbash-cipher/.exercism/config.json
new file mode 100644
index 0000000..c58d6db
--- /dev/null
+++ b/elixir/atbash-cipher/.exercism/config.json
@@ -0,0 +1,36 @@
+{
+  "authors": [
+    "rubysolo"
+  ],
+  "contributors": [
+    "andrewsardone",
+    "angelikatyborska",
+    "Br1ght0ne",
+    "Cohen-Carlisle",
+    "dalexj",
+    "devonestes",
+    "jinyeow",
+    "kytrinyx",
+    "lpil",
+    "mhinz",
+    "neenjaw",
+    "parkerl",
+    "sotojuan",
+    "Teapane",
+    "waiting-for-dev"
+  ],
+  "files": {
+    "solution": [
+      "lib/atbash.ex"
+    ],
+    "test": [
+      "test/atbash_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Atbash"
+}
diff --git a/elixir/atbash-cipher/.exercism/metadata.json b/elixir/atbash-cipher/.exercism/metadata.json
new file mode 100644
index 0000000..5468982
--- /dev/null
+++ b/elixir/atbash-cipher/.exercism/metadata.json
@@ -0,0 +1 @@
+{"track":"elixir","exercise":"atbash-cipher","id":"156913b0379c4b8886dff7de48ab370e","url":"https://exercism.org/tracks/elixir/exercises/atbash-cipher","handle":"negrienko","is_requester":true,"auto_approve":false}
\ No newline at end of file
diff --git a/elixir/atbash-cipher/.formatter.exs b/elixir/atbash-cipher/.formatter.exs
new file mode 100644
index 0000000..d2cda26
--- /dev/null
+++ b/elixir/atbash-cipher/.formatter.exs
@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]
diff --git a/elixir/atbash-cipher/.gitignore b/elixir/atbash-cipher/.gitignore
new file mode 100644
index 0000000..73a4714
--- /dev/null
+++ b/elixir/atbash-cipher/.gitignore
@@ -0,0 +1,24 @@
+# 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").
+atbash_cipher-*.tar
+
diff --git a/elixir/atbash-cipher/HELP.md b/elixir/atbash-cipher/HELP.md
new file mode 100644
index 0000000..4f0d18d
--- /dev/null
+++ b/elixir/atbash-cipher/HELP.md
@@ -0,0 +1,75 @@
+# 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/atbash.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.
\ No newline at end of file
diff --git a/elixir/atbash-cipher/README.md b/elixir/atbash-cipher/README.md
new file mode 100644
index 0000000..2182c9b
--- /dev/null
+++ b/elixir/atbash-cipher/README.md
@@ -0,0 +1,60 @@
+# Atbash Cipher
+
+Welcome to Atbash 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 atbash cipher, an ancient encryption system created in the Middle East.
+
+The Atbash cipher is a simple substitution cipher that relies on transposing all the letters in the alphabet such that the resulting alphabet is backwards.
+The first letter is replaced with the last letter, the second with the second-last, and so on.
+
+An Atbash cipher for the Latin alphabet would be as follows:
+
+```text
+Plain:  abcdefghijklmnopqrstuvwxyz
+Cipher: zyxwvutsrqponmlkjihgfedcba
+```
+
+It is a very weak cipher because it only has one possible key, and it is a simple mono-alphabetic substitution cipher.
+However, this may not have been an issue in the cipher's time.
+
+Ciphertext is written out in groups of fixed length, the traditional group size being 5 letters, leaving numbers unchanged, and punctuation is excluded.
+This is to make it harder to guess things based on word boundaries.
+All text will be encoded as lowercase letters.
+
+## Examples
+
+- Encoding `test` gives `gvhg`
+- Encoding `x123 yes` gives `c123b vh`
+- Decoding `gvhg` gives `test`
+- Decoding `gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt` gives `thequickbrownfoxjumpsoverthelazydog`
+
+## Source
+
+### Created by
+
+- @rubysolo
+
+### Contributed to by
+
+- @andrewsardone
+- @angelikatyborska
+- @Br1ght0ne
+- @Cohen-Carlisle
+- @dalexj
+- @devonestes
+- @jinyeow
+- @kytrinyx
+- @lpil
+- @mhinz
+- @neenjaw
+- @parkerl
+- @sotojuan
+- @Teapane
+- @waiting-for-dev
+
+### Based on
+
+Wikipedia - https://en.wikipedia.org/wiki/Atbash
\ No newline at end of file
diff --git a/elixir/atbash-cipher/lib/atbash.ex b/elixir/atbash-cipher/lib/atbash.ex
new file mode 100644
index 0000000..e4afae2
--- /dev/null
+++ b/elixir/atbash-cipher/lib/atbash.ex
@@ -0,0 +1,48 @@
+defmodule Atbash do
+  @letters ?a..?z
+           |> Enum.to_list
+           |> to_string
+           |> String.graphemes()
+
+  @digits ?0..?9
+          |> Enum.to_list
+          |> to_string
+          |> String.graphemes()
+
+  @table Map.new(Enum.zip(@letters, Enum.reverse(@letters)))
+
+  defguardp is_letter(char) when char in @letters
+  defguardp is_digit(char) when char in @digits
+
+  @doc """
+  Encode a given plaintext to the corresponding ciphertext
+
+  ## Examples
+
+  iex> Atbash.encode("completely insecure")
+  "xlnko vgvob rmhvx fiv"
+  """
+  @spec encode(String.t()) :: String.t()
+  def encode(plaintext) do
+    plaintext
+    |> transpose()
+    |> String.graphemes()
+    |> Enum.chunk_every(5)
+    |> Enum.join(" ")
+  end
+
+  @spec decode(String.t()) :: String.t()
+  def decode(cipher), do: transpose(cipher)
+
+  defp transpose(string) do
+    string
+    |> String.downcase()
+    |> String.graphemes()
+    |> Enum.map(&code/1)
+    |> Enum.join()
+  end
+
+  defp code(char) when is_digit(char), do: char
+  defp code(char) when is_letter(char), do: @table[char]
+  defp code(_char), do: nil
+end
diff --git a/elixir/atbash-cipher/mix.exs b/elixir/atbash-cipher/mix.exs
new file mode 100644
index 0000000..b4a8636
--- /dev/null
+++ b/elixir/atbash-cipher/mix.exs
@@ -0,0 +1,28 @@
+defmodule Atbash.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :atbash,
+      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
diff --git a/elixir/atbash-cipher/test/atbash_test.exs b/elixir/atbash-cipher/test/atbash_test.exs
new file mode 100644
index 0000000..94f3fc5
--- /dev/null
+++ b/elixir/atbash-cipher/test/atbash_test.exs
@@ -0,0 +1,77 @@
+defmodule AtbashTest do
+  use ExUnit.Case
+
+  describe "encode" do
+    test "yes" do
+      assert Atbash.encode("yes") == "bvh"
+    end
+
+    test "no" do
+      assert Atbash.encode("no") == "ml"
+    end
+
+    test "OMG" do
+      assert Atbash.encode("OMG") == "lnt"
+    end
+
+    test "O M G" do
+      assert Atbash.encode("O M G") == "lnt"
+    end
+
+    test "mindblowingly" do
+      assert Atbash.encode("mindblowingly") == "nrmwy oldrm tob"
+    end
+
+    test "numbers" do
+      assert Atbash.encode("Testing, 1 2 3, testing.") == "gvhgr mt123 gvhgr mt"
+    end
+
+    test "deep thought" do
+      assert Atbash.encode("Truth is fiction.") == "gifgs rhurx grlm"
+    end
+
+    test "all the letters" do
+      plaintext = "The quick brown fox jumps over the lazy dog."
+      cipher = "gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt"
+      assert Atbash.encode(plaintext) == cipher
+    end
+  end
+
+  describe "decode" do
+    test "exercism" do
+      cipher = "vcvix rhn"
+      plaintext = "exercism"
+      assert Atbash.decode(cipher) == plaintext
+    end
+
+    test "a sentence" do
+      cipher = "zmlyh gzxov rhlug vmzhg vkkrm thglm v"
+      plaintext = "anobstacleisoftenasteppingstone"
+      assert Atbash.decode(cipher) == plaintext
+    end
+
+    test "numbers" do
+      cipher = "gvhgr mt123 gvhgr mt"
+      plaintext = "testing123testing"
+      assert Atbash.decode(cipher) == plaintext
+    end
+
+    test "all the letters" do
+      cipher = "gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt"
+      plaintext = "thequickbrownfoxjumpsoverthelazydog"
+      assert Atbash.decode(cipher) == plaintext
+    end
+
+    test "with too many spaces" do
+      cipher = "vc vix    r hn"
+      plaintext = "exercism"
+      assert Atbash.decode(cipher) == plaintext
+    end
+
+    test "with no spaces" do
+      cipher = "zmlyhgzxovrhlugvmzhgvkkrmthglmv"
+      plaintext = "anobstacleisoftenasteppingstone"
+      assert Atbash.decode(cipher) == plaintext
+    end
+  end
+end
diff --git a/elixir/atbash-cipher/test/test_helper.exs b/elixir/atbash-cipher/test/test_helper.exs
new file mode 100644
index 0000000..35fc5bf
--- /dev/null
+++ b/elixir/atbash-cipher/test/test_helper.exs
@@ -0,0 +1,2 @@
+ExUnit.start()
+ExUnit.configure(exclude: :pending, trace: true)