require "webrat/core/xml"

module Webrat
  module Matchers

    class HaveXpath #:nodoc:
      def initialize(expected, options = {}, &block)
        @expected = expected
        @options  = options
        @block    = block
      end

      def matches?(stringlike, &block)
        @block ||= block
        matched = matches(stringlike)

        @block.call(matched) if @block

        if @options[:count]
          matched.size == @options[:count].to_i
        else
          matched.any?
        end
      end

      def matches(stringlike)
        nokogiri_matches(stringlike)
      end

      def nokogiri_matches(stringlike)
        if Nokogiri::XML::NodeSet === stringlike
          @query = query.gsub(%r'^//', './/')
        else
          @query = query
        end

        add_options_conditions_to(@query)

        @document = Webrat::XML.document(stringlike)
        @document.xpath(*@query)
      end

      def add_options_conditions_to(query)
        add_attributes_conditions_to(query)
        add_content_condition_to(query)
      end

      def add_attributes_conditions_to(query)
        attribute_conditions = []

        @options.each do |key, value|
          next if [:content, :count].include?(key)
          attribute_conditions << "@#{key} = #{xpath_escape(value)}"
        end

        if attribute_conditions.any?
          query << "[#{attribute_conditions.join(' and ')}]"
        end
      end

      def add_content_condition_to(query)
        if @options[:content]
          query << "[contains(., #{xpath_escape(@options[:content])})]"
        end
      end

      def query
        @expected
      end

      # ==== Returns
      # String:: The failure message.
      def failure_message
        "expected following text to match xpath #{@expected}:\n#{@document}"
      end

      # ==== Returns
      # String:: The failure message to be displayed in negative matches.
      def negative_failure_message
        "expected following text to not match xpath #{@expected}:\n#{@document}"
      end

    protected

      def xpath_escape(string)
        if string.include?("'") && string.include?('"')
          parts = string.split("'").map do |part|
            "'#{part}'"
          end

          "concat(" + parts.join(", \"'\", ") + ")"
        elsif string.include?("'")
          "\"#{string}\""
        else
          "'#{string}'"
        end
      end

    end

    # Matches HTML content against an XPath query
    #
    # ==== Parameters
    # expected<String>:: The XPath query to look for.
    #
    # ==== Returns
    # HaveXpath:: A new have xpath matcher.
    def have_xpath(expected, options = {}, &block)
      HaveXpath.new(expected, options, &block)
    end
    alias_method :match_xpath, :have_xpath

    def assert_have_xpath(expected, options = {}, &block)
      hs = HaveXpath.new(expected, options, &block)
      assert hs.matches?(response_body), hs.failure_message
    end

    def assert_have_no_xpath(expected, options = {}, &block)
      hs = HaveXpath.new(expected, options, &block)
      assert !hs.matches?(response_body), hs.negative_failure_message
    end

  end
end