require 'nokogiri'
require 'spidr/extensions/uri'

module Spidr
  class Page
    include Enumerable

    #
    # The title of the HTML page.
    #
    # @return [String]
    #   The inner-text of the title element of the page.
    #
    def title
      if (node = at('//title'))
        node.inner_text
      end
    end

    #
    # Enumerates over the meta-redirect links in the page.
    #
    # @yield [link]
    #   If a block is given, it will be passed every meta-redirect link
    #   from the page.
    #
    # @yieldparam [String] link
    #   A meta-redirect link from the page.
    #
    # @return [Enumerator]
    #   If no block is given, an enumerator object will be returned.
    #
    # @since 0.3.0
    #
    def each_meta_redirect
      return enum_for(__method__) unless block_given?

      if (html? && doc)
        search('//meta[@http-equiv and @content]').each do |node|
          if node.get_attribute('http-equiv') =~ /refresh/i
            content = node.get_attribute('content')

            if (redirect = content.match(/url=(\S+)$/))
              yield redirect[1]
            end
          end
        end
      end
    end

    #
    # Returns a boolean indicating whether or not page-level meta
    # redirects are present in this page.
    #
    # @return [Boolean]
    #   Specifies whether the page includes page-level redirects.
    #
    def meta_redirect?
      !each_meta_redirect.first.nil?
    end

    #
    # The meta-redirect links of the page.
    #
    # @return [Array<String>]
    #   All meta-redirect links in the page.
    #
    # @since 0.3.0
    #
    def meta_redirects
      each_meta_redirect.to_a
    end

    #
    # The meta-redirect links of the page.
    #
    # @return [Array<String>]
    #   All meta-redirect links in the page.
    #
    # @deprecated
    #   Deprecated in 0.3.0 and will be removed in 0.4.0.
    #   Use {#meta_redirects} instead.
    #
    def meta_redirect
      warn 'DEPRECATION: Spidr::Page#meta_redirect will be removed in 0.3.0'
      warn 'DEPRECATION: Use Spidr::Page#meta_redirects instead'

      meta_redirects
    end

    #
    # Enumerates over every HTTP or meta-redirect link in the page.
    #
    # @yield [link]
    #   The given block will be passed every redirection link from the page.
    #
    # @yieldparam [String] link
    #   A HTTP or meta-redirect link from the page.
    #
    # @return [Enumerator]
    #   If no block is given, an enumerator object will be returned.
    #
    # @since 0.3.0
    #
    def each_redirect(&block)
      return enum_for(__method__) unless block

      if (locations = @response.get_fields('Location'))
        # Location headers override any meta-refresh redirects in the HTML
        locations.each(&block)
      else
        # check page-level meta redirects if there isn't a location header
        each_meta_redirect(&block)
      end
    end

    #
    # URLs that this document redirects to.
    #
    # @return [Array<String>]
    #   The links that this page redirects to (usually found in a
    #   location header or by way of a page-level meta redirect).
    #
    def redirects_to
      each_redirect.to_a
    end

    #
    # Enumerates over every `mailto:` link in the page.
    #
    # @yield [link]
    #   The given block will be passed every `mailto:` link from the page.
    #
    # @yieldparam [String] link
    #   A `mailto:` link from the page.
    #
    # @return [Enumerator]
    #   If no block is given, an enumerator object will be returned.
    #
    # @since 0.5.0
    #
    def each_mailto
      return enum_for(__method__) unless block_given?

      if (html? && doc)
        doc.search('//a[starts-with(@href,"mailto:")]').each do |a|
          yield a.get_attribute('href')[7..-1]
        end
      end
    end

    #
    # `mailto:` links in the page.
    #
    # @return [Array<String>]
    #   The `mailto:` links found within the page.
    #
    # @since 0.5.0
    #
    def mailtos
      each_mailto.to_a
    end

    #
    # Enumerates over every link in the page.
    #
    # @yield [link]
    #   The given block will be passed every non-empty link in the page.
    #
    # @yieldparam [String] link
    #   A link in the page.
    #
    # @return [Enumerator]
    #   If no block is given, an enumerator object will be returned.
    #
    # @since 0.3.0
    #
    def each_link
      return enum_for(__method__) unless block_given?

      filter = lambda { |url|
        yield url unless (url.nil? || url.empty?)
      }

      each_redirect(&filter) if is_redirect?

      if (html? && doc)
        doc.search('//a[@href]').each do |a|
          filter.call(a.get_attribute('href'))
        end

        doc.search('//frame[@src]').each do |iframe|
          filter.call(iframe.get_attribute('src'))
        end

        doc.search('//iframe[@src]').each do |iframe|
          filter.call(iframe.get_attribute('src'))
        end

        doc.search('//link[@href]').each do |link|
          filter.call(link.get_attribute('href'))
        end

        doc.search('//script[@src]').each do |script|
          filter.call(script.get_attribute('src'))
        end
      end
    end

    #
    # The links from within the page.
    #
    # @return [Array<String>]
    #   All links within the HTML page, frame/iframe source URLs and any
    #   links in the `Location` header.
    #
    def links
      each_link.to_a
    end

    #
    # Enumerates over every absolute URL in the page.
    #
    # @yield [url]
    #   The given block will be passed every URL in the page.
    #
    # @yieldparam [URI::HTTP] url
    #   An absolute URL in the page.
    #
    # @return [Enumerator]
    #   If no block is given, an enumerator object will be returned.
    #
    # @since 0.3.0
    #
    def each_url
      return enum_for(__method__) unless block_given?

      each_link do |link|
        if (url = to_absolute(link))
          yield url
        end
      end
    end

    alias each each_url

    #
    # Absolute URIs from within the page.
    #
    # @return [Array<URI::HTTP>]
    #   The links from within the page, converted to absolute URIs.
    #
    def urls
      each_url.to_a
    end

    #
    # Normalizes and expands a given link into a proper URI.
    #
    # @param [String] link
    #   The link to normalize and expand.
    #
    # @return [URI::HTTP]
    #   The normalized URI.
    #
    def to_absolute(link)
      link    = link.to_s
      new_url = begin
                  url.merge(link)
                rescue Exception
                  return
                end

      if (!new_url.opaque) && (path = new_url.path)
        # ensure that paths begin with a leading '/' for URI::FTP
        if (new_url.scheme == 'ftp' && !path.start_with?('/'))
          path.insert(0,'/')
        end

        # make sure the path does not contain any .. or . directories,
        # since URI::Generic#merge cannot normalize paths such as
        # "/stuff/../"
        new_url.path = URI.expand_path(path)
      end

      return new_url
    end
  end
end