module Merb::Test::Rspec::ViewMatchers
  
  class HaveXpath
    def initialize(expected, &block)
      # Require nokogiri and fall back on rexml
      begin
        require "nokogiri"
      rescue LoadError => e
        if require "rexml/document"
          require "merb-core/vendor/nokogiri/css"
          warn("Standard REXML library is slow. Please consider installing nokogiri.\nUse \"sudo gem install nokogiri\"")
        end
      end
      
      @expected = expected
      @block    = block
    end
    
    def matches?(stringlike)
      if defined?(Nokogiri::XML)
        matches_nokogiri?(stringlike)
      else
        matches_rexml?(stringlike)
      end
    end
    
    def matches_rexml?(stringlike)
      stringlike = stringlike.body.to_s if stringlike.respond_to?(:body)
      
      @document = case stringlike
      when REXML::Document
        stringlike.root
      when REXML::Node
        stringlike
      when StringIO, String
        begin
          REXML::Document.new(stringlike.to_s).root
        rescue REXML::ParseException => e
          if e.message.include?("second root element")
            REXML::Document.new("<fake-root-element>#{stringlike}</fake-root-element>").root
          else
            raise e
          end
        end
      end
      
      query.all? do |q|
        matched = REXML::XPath.match(@document, q)
        matched.any? && (!block_given? || matched.all?(&@block))
      end
    end
    
    def matches_nokogiri?(stringlike)
      stringlike = stringlike.body.to_s if stringlike.respond_to?(:body)
      
      @document = case stringlike
      when Nokogiri::HTML::Document, Nokogiri::XML::NodeSet
        stringlike
      when StringIO
        Nokogiri::HTML(stringlike.string)
      else
        Nokogiri::HTML(stringlike.to_s)
      end
      @document.xpath(*query).any?
    end
    
    def query
      [@expected].flatten.compact
    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    
  end
  
  class HaveSelector < HaveXpath

    # ==== Returns
    # String:: The failure message.
    def failure_message
      "expected following text to match selector #{@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 selector #{@expected}:\n#{@document}"
    end
    
    def query
      Nokogiri::CSS::Parser.parse(*super).map { |ast| ast.to_xpath }
    end
  
  end
  
  class HaveTag < HaveSelector
    
    # ==== Returns
    # String:: The failure message.
    def failure_message
      "expected following output to contain a #{tag_inspect} tag:\n#{@document}"
    end
    
    # ==== Returns
    # String:: The failure message to be displayed in negative matches.
    def negative_failure_message
      "expected following output to omit a #{tag_inspect}:\n#{@document}"
    end
    
    def tag_inspect
      options = @expected.last.dup
      content = options.delete(:content)
      
      html = "<#{@expected.first}"
      options.each do |k,v|
        html << " #{k}='#{v}'"
      end
      
      if content
        html << ">#{content}</#{@expected.first}>"
      else
        html << "/>"
      end
      
      html
    end
    
    def query
      options  = @expected.last.dup
      selector = @expected.first.to_s
      
      selector << ":contains('#{options.delete(:content)}')" if options[:content]
      
      options.each do |key, value|
        selector << "[#{key}='#{value}']"
      end
      
      Nokogiri::CSS::Parser.parse(selector).map { |ast| ast.to_xpath }
    end
    
  end

  class HasContent
    def initialize(content)
      @content = content
    end

    def matches?(element)
      element = element.body.to_s if element.respond_to?(:body)
      @element = element
      
      case @content
      when String
        @element.contains?(@content)
      when Regexp
        @element.matches?(@content)
      end
    end
    
    # ==== Returns
    # String:: The failure message.
    def failure_message
      "expected the following element's content to #{content_message}:\n#{@element.inner_text}"
    end

    # ==== Returns
    # String:: The failure message to be displayed in negative matches.
    def negative_failure_message
      "expected the following element's content to not #{content_message}:\n#{@element.inner_text}"
    end
    
    def content_message
      case @content
      when String
        "include \"#{@content}\""
      when Regexp
        "match #{@content.inspect}"
      end
    end
  end

  # Matches HTML content against a CSS 3 selector.
  #
  # ==== Parameters
  # expected<String>:: The CSS selector to look for.
  #
  # ==== Returns
  # HaveSelector:: A new have selector matcher.
  # ---
  # @api public
  def have_selector(expected)
    HaveSelector.new(expected)
  end
  alias_method :match_selector, :have_selector

  # Matches HTML content against an XPath query
  #
  # ==== Parameters
  # expected<String>:: The XPath query to look for.
  #
  # ==== Returns
  # HaveXpath:: A new have xpath matcher.
  # ---
  # @api public
  def have_xpath(expected)
    HaveXpath.new(expected)
  end
  alias_method :match_xpath, :have_xpath
  
  def have_tag(name, attributes = {})
    HaveTag.new([name, attributes])
  end
  alias_method :match_tag, :have_tag
  
  # Matches the contents of an HTML document with
  # whatever string is supplied
  #
  # ---
  # @api public
  def contain(content)
    HasContent.new(content)
  end
end