Initial implementation of script

mutate.cr

@@ -0,0 +1,58 @@
+require "random"
+
+class String
+  @@nearby_chars = {
+    'q' => ['w', 'a'],
+    'w' => ['q', 'e', 's'],
+    'e' => ['w', 'r', 'd'],
+    'r' => ['e', 't', 'f'],
+    't' => ['r', 'y', 'g'],
+    'y' => ['t', 'h', 'u'],
+    'u' => ['y', 'j', 'i'],
+    'i' => ['u', 'k', 'o'],
+    'o' => ['i', 'l', 'p'],
+    'p' => ['o', 'l'],
+    'a' => ['q', 's', 'z'],
+    's' => ['w', 'r', 'a', 'x'],
+    'd' => ['s', 'e', 'f', 'x', 'c'],
+    'f' => ['d', 'r', 'x', 'c', 'v'],
+    'g' => ['f', 't', 'h', 'v', 'b'],
+    'h' => ['g', 'y', 'j', 'b', 'n'],
+    'j' => ['h', 'u', 'k', 'n', 'm'],
+    'k' => ['j', 'i', 'l', 'm'],
+    'l' => ['k', 'o', 'p'],
+    'z' => ['a', 's', 'x'],
+    'x' => ['z', 's', 'd', 'c'],
+    'c' => ['x', 'd', 'f', 'v'],
+    'v' => ['c', 'f', 'g', 'b'],
+    'b' => ['v', 'g', 'h', 'n'],
+    'n' => ['b', 'h', 'j', 'm'],
+    'm' => ['n', 'j', 'k', 'l'],
+    ' ' => [' ']
+  }
+
+  def mutate
+    return self if Random.rand > 0.1
+    mutations = [
+      ->mutate_modify,
+      ->mutate_insert
+    ]
+    return mutations.sample(1)[0].call.mutate
+  end
+
+  def mutate_modify
+    index = Random.rand(size)
+    was_upcase = self[index].uppercase?
+    char = self[index].downcase
+    char = @@nearby_chars[char].sample(1)[0]
+    char = char.upcase if was_upcase
+    new_chars = chars
+    new_chars[index] = char
+    return new_chars.join("")
+  end
+
+  def mutate_insert
+    index = Random.rand(size)
+    return insert(index, ' ')
+  end
+end