# :nodoc:
module RegexpExamples
  # Configuration settings to limit the number/length of Regexp examples generated
  class Config
    class << self
      def with_configuration(**new_config)
        original_config = config.dup

        begin
          self.config = new_config
          result = yield
        ensure
          self.config = original_config
        end

        result
      end

      # Thread-safe getters and setters
      %i[max_repeater_variance max_group_results max_results_limit].each do |m|
        define_method(m) do
          config[m]
        end
        define_method("#{m}=") do |value|
          config[m] = value
        end
      end

      private

      def config=(**args)
        Thread.current[:regexp_examples_config].merge!(args)
      end

      def config
        Thread.current[:regexp_examples_config] ||= {
          max_repeater_variance: MAX_REPEATER_VARIANCE_DEFAULT,
          max_group_results: MAX_GROUP_RESULTS_DEFAULT,
          max_results_limit: MAX_RESULTS_LIMIT_DEFAULT
        }
      end
    end
    # The maximum variance for any given repeater, to prevent a huge/infinite number of
    # examples from being listed. For example, if self.max_repeater_variance = 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}
    MAX_REPEATER_VARIANCE_DEFAULT = 2

    # Maximum number of characters returned from a char set, to reduce output spam
    # For example, if self.max_group_results = 5 then:
    # \d is equivalent to [01234]
    # \w is equivalent to [abcde]
    MAX_GROUP_RESULTS_DEFAULT = 5

    # Maximum number of results to be generated, for Regexp#examples
    # This is to prevent the system "freezing" when given instructions like:
    # /[ab]{30}/.examples
    # (Which would attempt to generate 2**30 == 1073741824 examples!!!)
    MAX_RESULTS_LIMIT_DEFAULT = 10_000
  end

  # Definitions of various special characters, used in regular expressions.
  # For example, `/\h/.examples` will return the value of `Hex` in this module
  module CharSets
    Lower        = Array('a'..'z')
    Upper        = Array('A'..'Z')
    Digit        = Array('0'..'9')
    Punct        = %w[! " # % & ' ( ) * , - . / : ; ? @ [ \\ ] _ { }] \
                     | (RUBY_VERSION >= '2.4.0' ? %w[$ + < = > ^ ` | ~] : [])
    Hex          = Array('a'..'f') | Array('A'..'F') | Digit
    Word         = Lower | Upper | Digit | ['_']
    Whitespace   = [' ', "\t", "\n", "\r", "\v", "\f"].freeze
    Control      = (0..31).map(&:chr) | ["\x7f"]
    # Ensure that the "common" characters appear first in the array
    # Also, ensure "\n" comes first, to make it obvious when included
    Any          = ["\n"] | Lower | Upper | Digit | Punct | (0..127).map(&:chr)
    AnyNoNewLine = Any - ["\n"]
  end.freeze

  # Map of special regex characters, to their associated character sets
  BackslashCharMap = {
    'd' => CharSets::Digit,
    'D' => CharSets::Any - CharSets::Digit,
    'w' => CharSets::Word,
    'W' => CharSets::Any - CharSets::Word,
    '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
  }.freeze

  POSIXCharMap = {
    'alnum'  => CharSets::Upper | CharSets::Lower | CharSets::Digit,
    'alpha'  => CharSets::Upper | CharSets::Lower,
    'blank'  => [' ', "\t"],
    'cntrl'  => CharSets::Control,
    'digit'  => CharSets::Digit,
    'graph'  => (CharSets::Any - CharSets::Control) - [' '], #  Visible chars
    'lower'  => CharSets::Lower,
    'print'  => CharSets::Any - CharSets::Control,
    'punct'  => CharSets::Punct,
    'space'  => CharSets::Whitespace,
    'upper'  => CharSets::Upper,
    'xdigit' => CharSets::Hex,
    'word'   => CharSets::Word,
    'ascii'  => CharSets::Any
  }.freeze

  NamedPropertyCharMap = UnicodeCharRanges.new
end