class Regexp
  def self.allocate
    Rubinius.primitive :regexp_allocate
    raise PrimitiveFailure, "Regexp.allocate primitive failed"
  end

  class << self
    alias_method :compile, :new
  end

  def self.try_convert(obj)
    Rubinius::Type.try_convert obj, Regexp, :to_regexp
  end

  def self.convert(pattern)
    return pattern if pattern.kind_of? Regexp
    if pattern.kind_of? Array
      return union(*pattern)
    else
      return Regexp.quote(pattern.to_s)
    end
  end

  def self.compatible?(*patterns)
    encodings = patterns.map{ |r| convert(r).encoding }
    last_enc = encodings.pop
    encodings.each do |encoding|
      raise ArgumentError, "incompatible encodings: #{encoding} and #{last_enc}" unless Encoding.compatible?(last_enc, encoding)
      last_enc = encoding
    end
  end

  def self.union(*patterns)
    case patterns.size
    when 0
      return %r/(?!)/
    when 1
      pat = patterns.first
      case pat
      when Array
        return union(*pat)
      when Regexp
        return pat
      else
        return Regexp.new(Regexp.quote(StringValue(pat)))
      end
    else
      compatible?(*patterns)
      enc = convert(patterns.first).encoding
    end

    str = "".encode(enc)
    sep = "|".encode(enc)
    patterns.each_with_index do |pat, idx|
      str << sep if idx != 0
      if pat.kind_of? Regexp
        str << pat.to_s
      else
        str << Regexp.quote(StringValue(pat))
      end
    end

    Regexp.new(str)
  end

  def self.escape(str)
    str = str.to_s if str.is_a?(Symbol)
    escaped = StringValue(str).transform(ESCAPE_TABLE)
    if escaped.ascii_only?
      escaped.force_encoding Encoding::US_ASCII
    elsif str.valid_encoding?
      escaped.force_encoding str.encoding
    else
      escaped.force_encoding Encoding::ASCII_8BIT
    end
  end

  class << self
    alias_method :quote, :escape
  end

  ##
  # See Regexp.new. This may be overridden by subclasses.

  def compile(pattern, opts)
    Rubinius.primitive :regexp_initialize
    raise PrimitiveFailure, "Regexp.compile(#{pattern.inspect}, #{opts}) primitive failed"
  end

  private :compile

  def search_region(str, start, finish, forward) # equiv to MRI's re_search
    Rubinius.primitive :regexp_search_region
    raise PrimitiveFailure, "Regexp#search_region primitive failed"
  end

  def match_start(str, offset) # equiv to MRI's re_match
    Rubinius.primitive :regexp_match_start
    raise PrimitiveFailure, "Regexp#match_start primitive failed"
  end

  def search_from(str, offset) # equiv to MRI's rb_reg_search
    Rubinius.primitive :regexp_search_from
    raise PrimitiveFailure, "Regexp#search_from primitive failed"
  end

  def options
    Rubinius.primitive :regexp_options
    raise PrimitiveFailure, "Regexp#options primitive failed"
  end

  def self.last_match(field=nil)
    Rubinius.primitive :regexp_last_match

    return last_match(Integer(field)) if field
    raise PrimitiveFailure, "Regexp#last_match primitive failed"
  end

  def self.last_match=(match)
    Rubinius.primitive :regexp_set_last_match

    unless match.kind_of? MatchData
      raise TypeError, "Expected MatchData, got #{match.inspect}"
    end

    raise PrimitiveFailure, "Regexp#set_last_match primitive failed"
  end

  def self.propagate_last_match
    Rubinius.primitive :regexp_propagate_last_match
    raise PrimitiveFailure, "Regexp#propagate_last_match primitive failed"
  end

  def self.set_block_last_match
    Rubinius.primitive :regexp_set_block_last_match
    raise PrimitiveFailure, "Regexp#set_block_last_match primitive failed"
  end

  def fixed_encoding?
    Rubinius.primitive :regexp_fixed_encoding_p
    raise PrimitiveFailure, "Regexp.fixed_encoding? primitive failed"
  end

  def initialize(pattern, opts=nil, lang=nil)
    if pattern.kind_of?(Regexp)
      opts = pattern.options
      pattern = pattern.source
    elsif pattern.kind_of?(Fixnum) or pattern.kind_of?(Float)
      raise TypeError, "can't convert Fixnum into String"
    elsif opts.kind_of?(Fixnum)
      opts = opts & (OPTION_MASK | KCODE_MASK) if opts > 0
    elsif opts
      opts = IGNORECASE
    else
      opts = 0
    end

    code = lang[0] if lang
    opts |= NOENCODING if code == ?n or code == ?N

    compile pattern, opts
  end

  private :initialize

  def initialize_copy(other)
    initialize other.source, other.options
  end

  private :initialize_copy

  def match(str, pos=0)
    unless str
      Regexp.last_match = nil
      return nil
    end

    str = str.to_s if str.is_a?(Symbol)
    str = StringValue(str)

    m = Rubinius::Mirror.reflect str
    pos = pos < 0 ? pos + str.size : pos
    pos = m.character_to_byte_index pos
    result = search_region(str, pos, str.bytesize, true)
    Regexp.last_match = result

    if result && block_given?
      yield result
    else
      result
    end
  end

  def match?(str, pos=0)
    return false unless str

    str = str.to_s if str.is_a?(Symbol)
    str = StringValue(str)

    m = Rubinius::Mirror.reflect str
    pos = pos < 0 ? pos + str.size : pos
    pos = m.character_to_byte_index pos

    search_region(str, pos, str.bytesize, true) ? true : false
  end

  # Returns the index of the first character in the region that
  # matched or nil if there was no match. See #match for returning
  # the MatchData instead.
  def =~(str)
    str = str.to_s if str.is_a?(Symbol)
    # unless str.nil? because it's nil and only nil, not false.
    str = StringValue(str) unless str.nil?

    match = match_from(str, 0)
    if match
      Regexp.last_match = match
      return match.begin(0)
    else
      Regexp.last_match = nil
      return nil
    end
  end

  def ===(other)
    if other.kind_of? Symbol
      other = other.to_s
    elsif !other.kind_of? String
      other = Rubinius::Type.check_convert_type other, String, :to_str
      unless other
        Regexp.last_match = nil
        return false
      end
    end

    if match = match_from(other, 0)
      Regexp.last_match = match
      true
    else
      Regexp.last_match = nil
      false
    end
  end

  def eql?(other)
    return false unless other.kind_of?(Regexp)
    return false unless source == other.source
    (options & ~NOENCODING) == (other.options & ~NOENCODING)
  end

  alias_method :==, :eql?

  def hash
    str = '/' << source << '/' << option_to_string(options)
    str.hash
  end

  def inspect
    # the regexp matches any / that is after anything except for a \
    escape = source.gsub(%r!(\\.)|/!) { $1 || '\/' }
    str = "/#{escape}/#{option_to_string(options)}"
    str << 'n' if (options & NOENCODING) > 0
    str
  end

  def encoding
    source.encoding
  end


  def source
    @source.dup
  end

  def ~
    line = $_

    unless line.kind_of?(String)
      Regexp.last_match = nil
      return nil
    end

    res = match(line)
    return res ? res.begin(0) : nil
  end

  def match_all(str)
    start = 0
    arr = []
    while match = self.match_from(str, start)
      arr << match
      if match.collapsing?
        start += 1
      else
        start = match.full.at(1)
      end
    end
    arr
  end

  def casefold?
    (options & IGNORECASE) > 0 ? true : false
  end

  def match_from(str, count)
    return nil unless str
    search_region(str, count, str.bytesize, true)
  end

  class SourceParser
    class Part
      attr_accessor :options
      attr_accessor :source

      def initialize(source="")
        @source = source
        @options = []
        @negated_options = []
      end

      private :initialize

      def <<(str)
        @source << str
      end

      def empty?
        @source.empty?
      end

      def flatten
      end

      def to_s
        # Put in the proper \'s to escape /'s
        # This is the same regexp used by #inspect
        source.gsub(%r!(\\.)|/!) { $1 || '\/' }
      end

      def has_options!
        @has_options = true
      end

      def has_options?
        @has_options
      end
    end

    class OptionsGroupPart < Part
      def to_s
        @flatten ? "#{source}" : "(#{options_string}#{source})"
      end

      def push_option!(identifier)
        @options << identifier
      end

      def push_negated_option!(identifier)
        @negated_options << identifier
      end

      def flatten
        @flatten = true
      end

      def options_string
        string = @options.join + (@negated_options.empty? ? "" : @negated_options.join)
        "?#{string}:"
      end
      private :options_string
    end

    class LookAheadGroupPart < Part
      def to_s
        "(#{source})"
      end
    end

    def initialize(source, options = 0)
      @source = source
      @options = options
      @parts = [Part.new]
    end

    private :initialize

    def string
      "(?#{options_string}:#{parts_string})"
    end

    def parts_string
      if parts.size == 1 && parts.first.has_options?
        parts.first.flatten
      end
      parts.map { |part| part.to_s }.join
    end

    def parts
      return @parts if @already_parsed
      @index = 0
      create_parts
      @parts.reject! { |part| part.empty? }
      @already_parsed = true
      @parts
    end

    # TODO: audit specs for this method when specs are running
    def create_parts
      while @index < @source.size
        if @source[@index].chr == '('
          escaped = @index > 0 && @source[@index - 1].chr == '\\'

          idx = @index + 1
          if idx < @source.size and @source[idx].chr == '?' and !escaped
            process_group
          else
            push_current_character!
          end
        else
          push_current_character!
        end
      end
    end

    def process_group
      @index += 1
      @parts << group_part_class.new

      if in_group_with_options?
        @index += 1
        process_group_options
      end

      process_look_ahead if in_lookahead_group?
      process_until_group_finished
      add_part!
    end

    def group_part_class
      if in_group_with_options?
        OptionsGroupPart
      else
        LookAheadGroupPart
      end
    end

    def in_lookahead_group?
      @source[@index, 2] == "?=" || @source[@index, 2] == "?!"
    end

    def process_look_ahead
      push_current_character!
      push_current_character!
    end

    def in_group_with_options?
      return false if @source[@index, 1] != '?'

      @source[@index + 1..-1].each_byte do |b|
        c = b.chr
        return true if ':' == c
        return false unless %w[m i x -].include? c
      end
    end

    def process_group_options
      @parts.last.has_options!
      case @source[@index].chr
      when ')'
        return
      when ':'
        @index += 1
        return
      else
        push_option!
        process_group_options
      end
    end

    def process_until_group_finished
      push_current_character! until @source[@index].chr == ")"
      @index += 1
    end

    def push_current_character!
      @parts.last << @source[@index].chr
      @index += 1
    end

    def push_option!
      @parts.last.push_option!(@source[@index].chr)
      @index += 1
    end

    def add_part!
      @parts << Part.new
    end

    def options_string
      chosen_options = []
      possible_options = PossibleOptions
      possible_options.each do |flag, identifier|
        chosen_options << identifier if @options & flag > 0
      end

      if parts.size == 1
        chosen_options.concat parts.first.options
      end

      excluded_options = possible_options.map { |e| e.last }.select do |identifier|
        !chosen_options.include?(identifier)
      end

      options_to_return = chosen_options
      if !excluded_options.empty?
        options_to_return << "-" << excluded_options
      end
      options_to_return.join
    end

  end

  def to_s
    SourceParser.new(source, options).string
  end

  def option_to_string(option)
    string = ""
    string << 'm' if (option & MULTILINE) > 0
    string << 'i' if (option & IGNORECASE) > 0
    string << 'x' if (option & EXTENDED) > 0
    string
  end

  def name_table
    @names
  end

  #
  # call-seq:
  #    rxp.named_captures  => hash
  #
  # Returns a hash representing information about named captures of <i>rxp</i>.
  #
  # A key of the hash is a name of the named captures.
  # A value of the hash is an array which is list of indexes of corresponding
  # named captures.
  #
  #    /(?<foo>.)(?<bar>.)/.named_captures
  #    #=> {"foo"=>[1], "bar"=>[2]}
  #
  #    /(?<foo>.)(?<foo>.)/.named_captures
  #    #=> {"foo"=>[1, 2]}
  #
  # If there are no named captures, an empty hash is returned.
  #
  #    /(.)(.)/.named_captures
  #    #=> {}
  #
  def named_captures
    hash = {}

    if @names
      @names.sort_by { |a,b| b.first }.each do |k, v| # LookupTable is unordered
        hash[k.to_s] = v
      end
    end

    return hash
  end

  #
  # call-seq:
  #    rxp.names   => [name1, name2, ...]
  #
  # Returns a list of names of captures as an array of strings.
  #
  #     /(?<foo>.)(?<bar>.)(?<baz>.)/.names
  #     #=> ["foo", "bar", "baz"]
  #
  #     /(?<foo>.)(?<foo>.)/.names
  #     #=> ["foo"]
  #
  #     /(.)(.)/.names
  #     #=> []
  #
  def names
    if @names
      @names.sort_by { |a,b| b.first }.map { |x| x.first.to_s } # LookupTable is unordered
    else
      []
    end
  end
end