module ProxyFetcher
  module Providers
    # HTTPTunnel provider class.
    class HTTPTunnel < Base
      # Provider URL to fetch proxy list
      PROVIDER_URL = 'http://www.httptunnel.ge/ProxyListForFree.aspx'.freeze

      # Fetches HTML content by sending HTTP request to the provider URL and
      # parses the document (built as abstract <code>ProxyFetcher::Document</code>)
      # to return all the proxy entries (HTML nodes).
      #
      # @return [Array<ProxyFetcher::Document::Node>]
      #   Collection of extracted HTML nodes with full proxy info
      #
      def load_proxy_list(*)
        doc = load_document(PROVIDER_URL)
        doc.xpath('//table[contains(@id, "GridView")]/tr[(count(td)>2)]')
      end

      # Converts HTML node (entry of N tags) to <code>ProxyFetcher::Proxy</code>
      # object.
      #
      # @param html_node [Object]
      #   HTML node from the <code>ProxyFetcher::Document</code> DOM model.
      #
      # @return [ProxyFetcher::Proxy]
      #   Proxy object
      #
      def to_proxy(html_node)
        ProxyFetcher::Proxy.new.tap do |proxy|
          uri = parse_proxy_uri(html_node)
          proxy.addr = uri.host
          proxy.port = uri.port

          proxy.country = parse_country(html_node)
          proxy.anonymity = parse_anonymity(html_node)
          proxy.type = ProxyFetcher::Proxy::HTTP
        end
      end

      private

      # Parses HTML node to extract URI object with proxy host and port.
      #
      # @param html_node [Object]
      #   HTML node from the <code>ProxyFetcher::Document</code> DOM model.
      #
      # @return [URI]
      #   URI object
      #
      def parse_proxy_uri(html_node)
        full_addr = html_node.content_at('td[1]')
        URI.parse("http://#{full_addr}")
      end

      # Parses HTML node to extract proxy country.
      #
      # @param html_node [Object]
      #   HTML node from the <code>ProxyFetcher::Document</code> DOM model.
      #
      # @return [String]
      #   Country code
      #
      def parse_country(html_node)
        html_node.find('.//img').attr('title')
      end

      # Parses HTML node to extract proxy anonymity level.
      #
      # @param html_node [Object]
      #   HTML node from the <code>ProxyFetcher::Document</code> DOM model.
      #
      # @return [String]
      #   Anonymity level
      #
      def parse_anonymity(html_node)
        transparency = html_node.content_at('td[5]').to_sym

        {
          A: 'Anonymous',
          E: 'Elite',
          T: 'Transparent',
          U: 'Unknown'
        }.fetch(transparency, 'Unknown')
      end
    end

    ProxyFetcher::Configuration.register_provider(:http_tunnel, HTTPTunnel)
  end
end