module ActionView
  module Assertions
    NO_STRIP = %w{pre script style textarea}

    # Adds the +assert_select+ method for use in Rails functional
    # test cases, which can be used to make assertions on the response HTML of a controller
    # action. You can also call +assert_select+ within another +assert_select+ to
    # make assertions on elements selected by the enclosing assertion.
    #
    # Use +css_select+ to select elements without making an assertions, either
    # from the response HTML or elements selected by the enclosing assertion.
    #
    # In addition to HTML responses, you can make the following assertions:
    #
    # * +assert_select_encoded+ - Assertions on HTML encoded inside XML, for example for dealing with feed item descriptions.
    # * +assert_select_email+ - Assertions on the HTML body of an e-mail.
    module SelectorAssertions
      # Select and return all matching elements.
      #
      # If called with a single argument, uses that argument as a selector
      # to match all elements of the current page. Returns an empty
      # Nokogiri::XML::NodeSet if no match is found.
      #
      # If called with two arguments, uses the first argument as the root
      # element and the second argument as the selector. Attempts to match the
      # root element and any of its children.
      # Returns an empty Nokogiri::XML::NodeSet if no match is found.
      #
      # The selector may be a CSS selector expression (String).
      #
      #   # Selects all div tags
      #   divs = css_select("div")
      #
      #   # Selects all paragraph tags and does something interesting
      #   pars = css_select("p")
      #   pars.each do |par|
      #     # Do something fun with paragraphs here...
      #   end
      #
      #   # Selects all list items in unordered lists
      #   items = css_select("ul>li")
      #
      #   # Selects all form tags and then all inputs inside the form
      #   forms = css_select("form")
      #   forms.each do |form|
      #     inputs = css_select(form, "input")
      #     ...
      #   end
      def css_select(*args)
        raise ArgumentError, "you at least need a selector argument" if args.empty?

        root = args.size == 1 ? response_from_page : args.shift
        selector = args.first

        root.css(selector).tap do |matches|
          if matches.empty? && root.matches?(selector)
            return Nokogiri::XML::NodeSet.new(root.document, [root])
          end
        end
      end

      # An assertion that selects elements and makes one or more equality tests.
      #
      # If the first argument is an element, selects all matching elements
      # starting from (and including) that element and all its children in
      # depth-first order.
      #
      # If no element is specified, calling +assert_select+ selects from the
      # response HTML unless +assert_select+ is called from within an +assert_select+ block.
      #
      # When called with a block +assert_select+ passes an array of selected elements
      # to the block. Calling +assert_select+ from the block, with no element specified,
      # runs the assertion on the complete set of elements selected by the enclosing assertion.
      # Alternatively the array may be iterated through so that +assert_select+ can be called
      # separately for each element.
      #
      #
      # ==== Example
      # If the response contains two ordered lists, each with four list elements then:
      #   assert_select "ol" do |elements|
      #     elements.each do |element|
      #       assert_select element, "li", 4
      #     end
      #   end
      #
      # will pass, as will:
      #   assert_select "ol" do
      #     assert_select "li", 8
      #   end
      #
      # The selector may be a CSS selector expression (String) or an expression
      # with substitution values (Array).
      # Substitution uses a custom pseudo class match. Pass in whatever attribute you want to match (enclosed in quotes) and a ? for the substitution.
      #
      # assert_select "div:match('id', ?)", /\d+/
      #
      # === Equality Tests
      #
      # The equality test may be one of the following:
      # * <tt>true</tt> - Assertion is true if at least one element selected.
      # * <tt>false</tt> - Assertion is true if no element selected.
      # * <tt>String/Regexp</tt> - Assertion is true if the text value of at least
      #   one element matches the string or regular expression.
      # * <tt>Integer</tt> - Assertion is true if exactly that number of
      #   elements are selected.
      # * <tt>Range</tt> - Assertion is true if the number of selected
      #   elements fit the range.
      # If no equality test specified, the assertion is true if at least one
      # element selected.
      #
      # To perform more than one equality tests, use a hash with the following keys:
      # * <tt>:text</tt> - Narrow the selection to elements that have this text
      #   value (string or regexp).
      # * <tt>:html</tt> - Narrow the selection to elements that have this HTML
      #   content (string or regexp).
      # * <tt>:count</tt> - Assertion is true if the number of selected elements
      #   is equal to this value.
      # * <tt>:minimum</tt> - Assertion is true if the number of selected
      #   elements is at least this value.
      # * <tt>:maximum</tt> - Assertion is true if the number of selected
      #   elements is at most this value.
      #
      # If the method is called with a block, once all equality tests are
      # evaluated the block is called with an array of all matched elements.
      #
      #   # At least one form element
      #   assert_select "form"
      #
      #   # Form element includes four input fields
      #   assert_select "form input", 4
      #
      #   # Page title is "Welcome"
      #   assert_select "title", "Welcome"
      #
      #   # Page title is "Welcome" and there is only one title element
      #   assert_select "title", {count: 1, text: "Welcome"},
      #       "Wrong title or more than one title element"
      #
      #   # Page contains no forms
      #   assert_select "form", false, "This page must contain no forms"
      #
      #   # Test the content and style
      #   assert_select "body div.header ul.menu"
      #
      #   # Use substitution values
      #   assert_select "ol>li:match('id', ?)", /item-\d+/
      #
      #   # All input fields in the form have a name
      #   assert_select "form input" do
      #     assert_select ":match('name', ?)", /.+/  # Not empty
      #   end
      def assert_select(*args, &block)
        @selected ||= nil

        selector = HTMLSelector.new(@selected, response_from_page, args)

        matches = selector.select
        assert_size_match!(matches.size, selector.equality_tests, selector.source, selector.message)

        # Set @selected to allow nested assert_select.
        # Can be nested several levels deep.
        if block_given? && !matches.empty?
          begin
            in_scope, @selected = @selected, matches
            yield matches
          ensure
            @selected = in_scope
          end
        end

        matches
      end

      def count_description(min, max, count) #:nodoc:
        pluralize = lambda {|word, quantity| word << (quantity == 1 ? '' : 's')}

        if min && max && (max != min)
          "between #{min} and #{max} elements"
        elsif min && max && max == min && count
          "exactly #{count} #{pluralize['element', min]}"
        elsif min && !(min == 1 && max == 1)
          "at least #{min} #{pluralize['element', min]}"
        elsif max
          "at most #{max} #{pluralize['element', max]}"
        end
      end

      # Extracts the content of an element, treats it as encoded HTML and runs
      # nested assertion on it.
      #
      # You typically call this method within another assertion to operate on
      # all currently selected elements. You can also pass an element or array
      # of elements.
      #
      # The content of each element is un-encoded, and wrapped in the root
      # element +encoded+. It then calls the block with all un-encoded elements.
      #
      #   # Selects all bold tags from within the title of an Atom feed's entries (perhaps to nab a section name prefix)
      #   assert_select "feed[xmlns='http://www.w3.org/2005/Atom']" do
      #     # Select each entry item and then the title item
      #     assert_select "entry>title" do
      #       # Run assertions on the encoded title elements
      #       assert_select_encoded do
      #         assert_select "b"
      #       end
      #     end
      #   end
      #
      #
      #   # Selects all paragraph tags from within the description of an RSS feed
      #   assert_select "rss[version=2.0]" do
      #     # Select description element of each feed item.
      #     assert_select "channel>item>description" do
      #       # Run assertions on the encoded elements.
      #       assert_select_encoded do
      #         assert_select "p"
      #       end
      #     end
      #   end
      def assert_select_encoded(element = nil, &block)
        case element
          when Array
            elements = element
          when Nokogiri::XML::Node
            elements = [element]
          when nil
            unless elements = @selected
              raise ArgumentError, "First argument is optional, but must be called from a nested assert_select"
            end
          else
            raise ArgumentError, "Argument is optional, and may be node or array of nodes"
        end

        content = elements.map do |elem|
          elem.children.select(&:cdata?).map(&:content)
        end.join
        selected = Loofah.fragment(content)

        begin
          old_selected, @selected = @selected, selected
          if content.empty?
            yield selected
          else
            assert_select ":root", &block
          end
        ensure
          @selected = old_selected
        end
      end

      # Extracts the body of an email and runs nested assertions on it.
      #
      # You must enable deliveries for this assertion to work, use:
      #   ActionMailer::Base.perform_deliveries = true
      #
      #  assert_select_email do
      #    assert_select "h1", "Email alert"
      #  end
      #
      #  assert_select_email do
      #    items = assert_select "ol>li"
      #    items.each do
      #       # Work with items here...
      #    end
      #  end
      def assert_select_email(&block)
        deliveries = ActionMailer::Base.deliveries
        assert !deliveries.empty?, "No e-mail in delivery list"

        deliveries.each do |delivery|
          (delivery.parts.empty? ? [delivery] : delivery.parts).each do |part|
            if part["Content-Type"].to_s =~ /^text\/html\W/
              root = Loofah.fragment(part.body.to_s)
              assert_select root, ":root", &block
            end
          end
        end
      end

      protected
        # +equals+ must contain :minimum, :maximum and :count keys
        def assert_size_match!(size, equals, css_selector, message = nil)
          min, max, count = equals[:minimum], equals[:maximum], equals[:count]

          message ||= %(Expected #{count_description(min, max, count)} matching "#{css_selector}", found #{size}.)
          if count
            assert_equal size, count, message
          else
            assert_operator size, :>=, min, message if min
            assert_operator size, :<=, max, message if max
          end
        end

        # +html_document+ is used in testing/integration.rb
        def html_document
          @html_document ||= if @response.content_type =~ /xml$/
            Loofah.xml_document(@response.body)
          else
            Loofah.document(@response.body)
          end
        end

        def response_from_page
          html_document.root
        end

        class HTMLSelector #:nodoc:
          attr_accessor :root, :css_selector, :equality_tests, :message

          alias :source :css_selector

          def initialize(selected, page, args)
            # Start with optional element followed by mandatory selector.
            @root = determine_root_from(args.first, page, selected)

            # First or second argument is the selector
            selector = @css_selector_is_second_argument ? args.shift(2).last : args.shift
            @css_selector = selector_from(selector, args)

            @equality_tests = equality_tests_from(args.shift)
            @message = args.shift

            if args.shift
              raise ArgumentError, "Not expecting that last argument, you either have too many arguments, or they're the wrong type"
            end
          end

          def select
            filter root.css(css_selector, context)
          end

          def filter(matches)
            match_with = equality_tests[:text] || equality_tests[:html]
            return matches if matches.empty? || !match_with

            content_mismatch = nil
            text_matches = equality_tests.has_key?(:text)

            remaining = matches.reject do |match|
              # Preserve markup with to_s for html elements
              content = text_matches ? match.text : match.children.to_s

              content.strip! unless NO_STRIP.include?(match.name)
              content.sub!(/\A\n/, '') if text_matches && match.name == "textarea"

              unless match_with.is_a?(Regexp) ? (content =~ match_with) : (content == match_with.to_s)
                content_mismatch ||= sprintf("<%s> expected but was\n<%s>.", match_with, content)
                true
              end
            end

            # Expecting foo found bar element only if found zero, not if
            # found one but expecting two.
            self.message ||= content_mismatch if remaining.empty?

            Nokogiri::XML::NodeSet.new(matches.document, remaining)
          end

          def determine_root_from(root_or_selector, page, previous_selection = nil)
            @css_selector_is_second_argument = false
            if root_or_selector == nil
              raise ArgumentError, "First argument is either selector or element to select, but nil found. Perhaps you called assert_select with an element that does not exist?"
            elsif root_or_selector.is_a?(Nokogiri::XML::Node) || root_or_selector.is_a?(Nokogiri::XML::NodeSet)
              # First argument is a node (tag or text, but also HTML root),
              # so we know what we're selecting from.
              @css_selector_is_second_argument = true

              root_or_selector
            elsif previous_selection
              if previous_selection.is_a?(Array)
                Nokogiri::XML::NodeSet.new(previous_selection[0].document, previous_selection)
              else
                previous_selection
              end
            else
              page
            end
          end

          def selector_from(selector, substitution_values)
            unless selector.is_a? String
              raise ArgumentError, "Expecting a selector as the first argument"
            end
            context.substitute!(selector, substitution_values)
          end

          def equality_tests_from(comparator)
              comparisons = {}
              case comparator
                when Hash
                  comparisons = comparator
                when String, Regexp
                  comparisons[:text] = comparator
                when Integer
                  comparisons[:count] = comparator
                when Range
                  comparisons[:minimum] = comparator.begin
                  comparisons[:maximum] = comparator.end
                when FalseClass
                  comparisons[:count] = 0
                when NilClass, TrueClass
                  comparisons[:minimum] = 1
                else raise ArgumentError, "I don't understand what you're trying to match"
              end

              # By default we're looking for at least one match.
              if comparisons[:count]
                comparisons[:minimum] = comparisons[:maximum] = comparisons[:count]
              else
                comparisons[:minimum] ||= 1
              end
            comparisons
          end

          def context
            @context ||= SubstitutionContext.new
          end

          class SubstitutionContext
            def initialize(substitute = '?')
              @substitute = substitute
              @regexes = []
            end

            def add_regex(regex)
              # Nokogiri doesn't like arbitrary values without quotes, hence inspect.
              return regex.inspect unless regex.is_a?(Regexp)
              @regexes.push(regex)
              last_id.to_s # avoid implicit conversions of Fixnum to String
            end

            def last_id
              @regexes.count - 1
            end

            def match(matches, attribute, id)
              matches.find_all { |node| node[attribute] =~ @regexes[id] }
            end

            def substitute!(selector, values)
              while !values.empty? && selector.index(@substitute)
                selector.sub!(@substitute, add_regex(values.shift))
              end
              selector
            end
          end
        end
    end
  end
end