Add keymap replacement strategy

Adds a replacement strategy which uses knowledge of a particular keyboard
layout to create typos which would be easy mistakes on the configured
layout.

Seems to be pivoting off the wrong character in the source text right now,
but is otherwise working.

data/keymaps/en-US_qwerty.yml

@@ -0,0 +1,146 @@
+---
+data:
+  '`':
+    shift: '~'
+    neighbors: ['1']
+  '1':
+    shift: '!'
+    neighbors: ['`', 'q']
+  '2':
+    shift: '@'
+    neighbors: ['1', 'q', '3']
+  '3':
+    shift: '#'
+    neighbors: ['2', 'w', 'e', '4']
+  '4':
+    shift: '$'
+    neighbors: ['3', 'e', 'r', '5']
+  '5':
+    shift: '%'
+    neighbors: ['4', 'r', 't', '6']
+  '6':
+    shift: '^'
+    neighbors: ['5', 't', 'y', '7']
+  '7':
+    shift: '&'
+    neighbors: ['6', 'y', 'u', '8']
+  '8':
+    shift: '*'
+    neighbors: ['7', 'u', 'i', '9']
+  '9':
+    shift: '('
+    neighbors: ['8', 'i', 'o', '0']
+  '0':
+    shift: ')'
+    neighbors: ['9', 'o', 'p', '-']
+  '-':
+    shift: '_'
+    neighbors: ['0', 'p', '[', '=']
+  '=':
+    shift: '+'
+    neighbors: ['-', '[', ']']
+  q:
+    shift: 'Q'
+    neighbors: ['1', '2', 'w', 'a']
+  w:
+    shift: 'W'
+    neighbors: ['q', '2', '3', 'e', 'a', 's']
+  e:
+    shift: 'E'
+    neighbors: ['w', '3', '4', 'r', 'd', 's']
+  r:
+    shift: 'R'
+    neighbors: ['e', '4', '5', 't', 'f', 'd']
+  t:
+    shift: 'T'
+    neighbors: ['r', '5', '6', 'y', 'g', 'f']
+  y:
+    shift: 'Y'
+    neighbors: ['t', '6', '7', 'u', 'h', 'g']
+  u:
+    shift: 'U'
+    neighbors: ['y', '7', '8', 'i', 'j', 'h']
+  i:
+    shift: 'I'
+    neighbors: ['u', '8', '9', 'o', 'k', 'j']
+  o:
+    shift: 'O'
+    neighbors: ['i', '9', '0', 'p', 'l', 'k']
+  p:
+    shift: 'P'
+    neighbors: ['o', '0', '-', '[', ';', 'l']
+  '[':
+    shift: '{'
+    neighbors: ['p', '-', '=', ']', "'", ';']
+  ']':
+    shift: '}'
+    neighbors: ['[', '=', '\', "'"]
+  '\':
+    shift: '|'
+    neighbors: [']']
+  a:
+    shift: 'A'
+    neighbors: ['q', 'w', 's', 'z']
+  s:
+    shift: 'S'
+    neighbors: ['a', 'w', 'e', 'd', 'x', 'z']
+  d:
+    shift: 'D'
+    neighbors: ['s', 'e', 'r', 'f', 'c', 'x']
+  f:
+    shift: 'F'
+    neighbors: ['d', 'r', 't', 'g', 'v', 'c']
+  g:
+    shift: 'G'
+    neighbors: ['f', 't', 'y', 'h', 'b', 'v']
+  h:
+    shift: 'H'
+    neighbors: ['g', 'y', 'u', 'j', 'n', 'b']
+  j:
+    shift: 'J'
+    neighbors: ['h', 'u', 'i', 'k', 'm', 'n']
+  k:
+    shift: 'K'
+    neighbors: ['j', 'i', 'o', 'l', ',', 'm']
+  l:
+    shift: 'L'
+    neighbors: ['k', 'o', 'p', ';', '.', ',']
+  ';':
+    shift: ':'
+    neighbors: ['l', 'p', '[', "'", '/', '.']
+  "'":
+    shift: '"'
+    neighbors: [';', '[', ']', '/']
+  z:
+    shift: 'Z'
+    neighbors: ['a', 's', 'x']
+  x:
+    shift: 'X'
+    neighbors: ['z', 's', 'd', 'c']
+  c:
+    shift: 'C'
+    neighbors: ['x', 'd', 'f', 'v']
+  v:
+    shift: 'V'
+    neighbors: ['c', 'f', 'g', 'b']
+  b:
+    shift: 'B'
+    neighbors: ['v', 'g', 'h', 'n']
+  n:
+    shift: 'N'
+    neighbors: ['b', 'h', 'j', 'm']
+  m:
+    shift: 'M'
+    neighbors: ['n', 'j', 'k', ',']
+  ',':
+    shift: '<'
+    neighbors: ['m', 'k', 'l', '.']
+  '.':
+    shift: '>'
+    neighbors: [',', 'l', ';', '/']
+  '/':
+    shift: '?'
+    neighbors: ['.', ';', "'"]
+  ' ':
+    shift: ' '
+    neighbors: ['x', 'c', 'v', 'b', 'n', 'm', ',']

src/typhar.cr

@@ -1,5 +1,6 @@
 require "cli"
 require "secure_random"
+require "yaml"
 require "./typhar/*"
 
 module Typhar

src/typhar/cli.cr

@@ -83,6 +83,9 @@ module Typhar
         when "n-shifter"
           codepoint_shift = options.codepoint_shift.to_i
           Typhar::ReplacementStrategies::NShifter.new(seed, codepoint_shift)
+        when "keymap"
+          keymap_name = "en-US_qwerty"
+          Typhar::ReplacementStrategies::Keymap.new(seed, keymap_name)
         else
           raise StrategyDoesNotExistException.new("'#{strategy}' does not exist.")
         end

src/typhar/exceptions.cr

@@ -4,4 +4,7 @@ module Typhar
 
   class StrategyDoesNotExistException < Exception
   end
+
+  class UnknownKeyError < Exception
+  end
 end

src/typhar/strategies/replacement/keymap.cr

@@ -0,0 +1,30 @@
+module Typhar
+  module ReplacementStrategies
+    class Keymap < Base
+      @keymap : Typhar::Types::Keymap
+
+      getter keymap_name
+      getter keymap
+
+      def initialize(@seed : UInt32, @keymap_name : String)
+        keymap_yml = File.read("./data/keymaps/#{keymap_name}.yml")
+        @keymap = Typhar::Types::Keymap.from_yaml(keymap_yml).not_nil!
+        @keymap.dereference!
+      end
+
+      def replace(to_replace : String | Char) : String | Char
+        keymap_entry = keymap[to_replace]?
+
+        if keymap_entry
+          keymap_entry.neighbors.sample(sampler)
+        else
+          raise UnknownKeyError.new("Unknown key '#{to_replace}' in keymap")
+        end
+      end
+
+      private def sampler
+        @sampler ||= Random.new(seed)
+      end
+    end
+  end
+end

src/typhar/transformer.cr

@@ -1,3 +1,4 @@
+require "./types/*"
 require "./strategies/*"
 
 module Typhar

src/typhar/types/keymap.cr

@@ -0,0 +1,39 @@
+module Typhar
+  module Types
+    class Keymap
+      YAML.mapping(
+        data: {
+          type: Hash(String, KeymapEntry)
+        }
+      )
+
+      def [](key)
+        data[key]?.not_nil!
+      end
+
+      def []?(key)
+        data.fetch(key.to_s) do |key|
+          result = data.find { |k, v| v.shift == key }
+          if result
+            result[1]
+          else
+            nil
+          end
+        end
+      end
+
+      def dereference!
+        data.map do |key, value|
+          value.neighbors = value.neighbors.flat_map do |neighbor|
+            if data[neighbor]?
+              neighbor_entry = data[neighbor]
+              [neighbor, neighbor_entry.shift]
+            else
+              raise UnknownKeyError.new("Unknown key '#{neighbor}' in keymap")
+            end
+          end
+        end
+      end
+    end
+  end
+end

src/typhar/types/keymap_entry.cr

@@ -0,0 +1,10 @@
+module Typhar
+  module Types
+    class KeymapEntry
+      YAML.mapping(
+        shift: String,
+        neighbors: Array(String)
+      )
+    end
+  end
+end