module RegexpExamples
  # The maximum variance for any given repeater, to prevent a huge/infinite number of
  # examples from being listed. For example, if MaxRepeaterVariance = 2 then:
  # .* is equivalent to .{0,2}
  # .+ is equivalent to .{1,3}
  # .{2,} is equivalent to .{2,4}
  # .{,3} is equivalent to .{0,2}
  # .{3,8} is equivalent to .{3,5}
  MaxRepeaterVariance = 2

  # Maximum number of characters returned from a char set, to reduce output spam
  # For example:
  # If MaxGroupResults = 5, then
  # \d = [0, 1, 2, 3, 4]
  MaxGroupResults = 5

  module CharSets
    Lower      = Array('a'..'z')
    Upper      = Array('A'..'Z')
    Digit      = Array('0'..'9')
    Punct      = [33..47, 58..64, 91..96, 123..126].map { |r| r.map { |val| val.chr } }.flatten
    Hex        = Array('a'..'f') | Array('A'..'F') | Digit
    Whitespace = [' ', "\t", "\n", "\r", "\v", "\f"]
    Any        = Lower | Upper | Digit | Punct
  end

  # Map of special regex characters, to their associated character sets
  BackslashCharMap = {
    'd' => CharSets::Digit,
    'D' => CharSets::Lower | CharSets::Upper | CharSets::Punct,
    'w' => CharSets::Lower | CharSets::Upper | CharSets::Digit | ['_'],
    'W' => CharSets::Punct.reject { |val| val == '_' },
    's' => CharSets::Whitespace,
    'S' => CharSets::Any - CharSets::Whitespace,
    'h' => CharSets::Hex,
    'H' => CharSets::Any - CharSets::Hex,

    't' => ["\t"], # tab
    'n' => ["\n"], # new line
    'r' => ["\r"], # carriage return
    'f' => ["\f"], # form feed
    'a' => ["\a"], # alarm
    'v' => ["\v"], # vertical tab
    'e' => ["\e"], # escape
  }
end