Add first pass

README.md

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+# Admonition Block Formatter
+
+This is the code that formats admonition blocks for Exercism.
+It ensures that blocks always use four tildes.
+
+For example: it converts
+````
+```exercism/note
+something
+```
+````
+
+to
+
+```
+~~~~exercism/note
+something
+~~~~
+```
+
+## Tests
+
+The code requires Ruby, but no other dependencies.
+
+Run the tests by running `rake`.

Rakefile

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+require "rake/testtask"
+
+Rake::TestTask.new(:test) do |t|
+  t.libs << "test"
+  t.libs << "lib"
+  t.warning = false
+  t.test_files = FileList["test/**/*_test.rb"]
+end
+
+task default: :test
+

lib/admonition_block_formatter.rb

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+class AdmonitionBlockFormatter
+  def self.format(code)
+    [:format_four, :format_three].each do |meth|
+      while code != (new_code = send(meth, code))
+        code = new_code
+      end
+    end
+
+    code
+  end
+
+  def self.format_three(code)
+    matches = THREE_TILDE_REGEX.match(code)
+    return code unless matches
+
+    matches['before'] + "~~~~" + matches['type'] + matches['admonition'] + "~~~~" + matches['after']
+  end
+
+  def self.format_four(code)
+    matches = FOUR_TILDE_REGEX.match(code)
+    return code unless matches
+
+    matches['before'] + "~~~~" + matches['type'] + matches['admonition'] + "~~~~" + matches['after']
+  end
+
+  THREE_TILDE_REGEX = /(?<before>[\s\S]*)(?<start>```)(?<type>exercism\/[a-z]+)(?<admonition>[\s\S]*?)(?<end>```)(?<after>[\s\S]*)/.freeze
+  FOUR_TILDE_REGEX = /(?<before>[\s\S]*)(?<start>````)(?<type>exercism\/[a-z]+)(?<admonition>[\s\S]*?)(?<end>````)(?<after>[\s\S]*)/.freeze
+end
+

test/four_tildes_test.rb

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+require 'test_helper'
+
+class FourTildesTest < Minitest::Test
+  def test_basic
+    input = <<~INPUT
+    ````exercism/note
+    something
+    ````
+    INPUT
+
+    output = <<~OUTPUT
+    ~~~~exercism/note
+    something
+    ~~~~
+    OUTPUT
+
+    assert_equal output, AdmonitionBlockFormatter.format(input)
+  end
+
+  def test_fuller
+    input = <<~INPUT
+    something
+
+    ````exercism/note
+    some code
+    with a `variable` here
+    some other code
+    ````
+
+    endstuff
+    INPUT
+
+    output = <<~OUTPUT
+    something
+
+    ~~~~exercism/note
+    some code
+    with a `variable` here
+    some other code
+    ~~~~
+
+    endstuff
+    OUTPUT
+
+    assert_equal output, AdmonitionBlockFormatter.format(input)
+  end
+
+  def test_multiple
+    input = <<~INPUT
+    something
+
+    ````exercism/note
+    some code
+    ````
+
+    else
+
+    ````exercism/note
+    other code
+    ````
+
+    endstuff
+    INPUT
+
+    output = <<~OUTPUT
+    something
+
+    ~~~~exercism/note
+    some code
+    ~~~~
+
+    else
+
+    ~~~~exercism/note
+    other code
+    ~~~~
+
+    endstuff
+    OUTPUT
+
+    assert_equal output, AdmonitionBlockFormatter.format(input)
+  end
+
+  def test_nested
+    input = <<~INPUT
+    ````exercism/note
+    before
+    ```ruby
+    code1
+    ```
+    middle
+    ```
+    code2
+    ```
+    after
+    ````
+
+    ```
+    code3
+    ```
+    INPUT
+
+    output = <<~OUTPUT
+    ~~~~exercism/note
+    before
+    ```ruby
+    code1
+    ```
+    middle
+    ```
+    code2
+    ```
+    after
+    ~~~~
+
+    ```
+    code3
+    ```
+    OUTPUT
+
+    assert_equal output, AdmonitionBlockFormatter.format(input)
+  end
+end
+

test/mixed_test.rb

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+require 'test_helper'
+
+class MixedTest < Minitest::Test
+  def test_three_then_four_then_three
+    input = <<~INPUT
+    something
+
+    ```exercism/note
+    code 1
+    ```
+
+    ````exercism/note
+    code 2
+    ````
+
+    ```exercism/note
+    code 3
+    ```
+
+    end bit
+    INPUT
+
+    output = <<~OUTPUT
+    something
+
+    ~~~~exercism/note
+    code 1
+    ~~~~
+
+    ~~~~exercism/note
+    code 2
+    ~~~~
+
+    ~~~~exercism/note
+    code 3
+    ~~~~
+
+    end bit
+    OUTPUT
+
+    assert_equal output, AdmonitionBlockFormatter.format(input)
+  end
+
+  def test_four_then_three_then_four
+    input = <<~INPUT
+    something
+
+    ````exercism/note
+    code 1
+    ````
+
+    ```exercism/note
+    code 2
+    ```
+
+    ````exercism/note
+    code 3
+    ````
+
+    end bit
+    INPUT
+
+    output = <<~OUTPUT
+    something
+
+    ~~~~exercism/note
+    code 1
+    ~~~~
+
+    ~~~~exercism/note
+    code 2
+    ~~~~
+
+    ~~~~exercism/note
+    code 3
+    ~~~~
+
+    end bit
+    OUTPUT
+
+    assert_equal output, AdmonitionBlockFormatter.format(input)
+  end
+
+end
+

test/test_helper.rb

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+# gem "minitest"
+require "minitest/autorun"
+# require "minitest/pride"
+# require "minitest/mock"
+# require "mocha/minitest"
+
+$LOAD_PATH.unshift File.expand_path('lib', __dir__)
+require "admonition_block_formatter"

test/three_tildes_test.rb

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+require 'test_helper'
+
+class ThreeTildesTest < Minitest::Test
+  def test_basic
+    input = <<~INPUT
+    ```exercism/note
+    something
+    ```
+    INPUT
+
+    output = <<~OUTPUT
+    ~~~~exercism/note
+    something
+    ~~~~
+    OUTPUT
+
+    assert_equal output, AdmonitionBlockFormatter.format(input)
+  end
+
+  def test_fuller
+    input = <<~INPUT
+    something
+
+    ```exercism/note
+    some code
+    with a `variable` here
+    some other code
+    ```
+
+    endstuff
+    INPUT
+
+    output = <<~OUTPUT
+    something
+
+    ~~~~exercism/note
+    some code
+    with a `variable` here
+    some other code
+    ~~~~
+
+    endstuff
+    OUTPUT
+
+    assert_equal output, AdmonitionBlockFormatter.format(input)
+  end
+
+  def test_multiple
+    input = <<~INPUT
+    something
+
+    ```exercism/note
+    some code
+    ```
+
+    else
+
+    ```exercism/note
+    other code
+    ```
+
+    endstuff
+    INPUT
+
+    output = <<~OUTPUT
+    something
+
+    ~~~~exercism/note
+    some code
+    ~~~~
+
+    else
+
+    ~~~~exercism/note
+    other code
+    ~~~~
+
+    endstuff
+    OUTPUT
+
+    assert_equal output, AdmonitionBlockFormatter.format(input)
+  end
+end