require 'cgi'
require 'net/http'

module Rack
  class Request
    
    HEADERS_IGNORED_WHEN_FORWARDING = ['HTTP_HOST', 'HTTP_VERSION']
    
    # Forward this request to a different URL.
    # 
    # +options+ is a hash of rewrites of the request for the purpose of
    # forwarding.
    # You can override the port, path, querystring, data and method to use
    # with the forwarded request.
    def forward_to(host, options={})
      # Get some info from the request
      port = options[:port] || self.port
      path = options[:path] || self.path_info
      querystring = options[:querystring] || self.query_string
      data = options[:data] || @env['rack.input'].read
      method = options[:method] || self.request_method

      # Construct URI string
      uri = 'http://' + host + (port ? ":#{port}" : '') + path
      uri += '?' + querystring unless querystring == ''
      LOGGER.debug "Preparing to send request to " + uri
      uri = URI.parse(uri)
      
      # Construct the request from the URI
      http_request = eval("Net::HTTP::" + method[0,1].upcase + method[1..-1].downcase + ".new('#{uri}')")
      
      # Add headers
      headers = {}
      @env.each do |header_key, header_value| 
        if !(HEADERS_IGNORED_WHEN_FORWARDING.member?(header_key))
          if header_key =~ /^HTTP\_/
            header_key = normalise_header_key(header_key)
          elsif header_key =~ /CONTENT_TYPE/
            header_key = 'Content-Type'
          else
            header_key = nil
          end
          headers[header_key] = header_value unless header_key.nil?
        end
      end
      
      headers.each do |key, value|
        LOGGER.debug "Adding header #{key} to request before forwarding"
        http_request.add_field(key, value)
      end
      
      # Set an attribute for the data being sent, so we can show it
      # when we call to_s on the HTTP request.
      http_request.data = data
      
      LOGGER.debug "Forwarding request: " + http_request.to_s
      
      # Send the request
      http_response = Net::HTTP.start(uri.host, uri.port) do |http|
        http.request(http_request, data)
      end
      
      # Send back the response from the proxied URL
      http_response
    end
    
    private
    # Turn Rack headers into proper HTTP headers
    def normalise_header_key(header_key)
      header_key = header_key.gsub("HTTP_", "").gsub("_", "-")
      
      if header_key == "SOAPACTION"
        header_key = "SOAPAction"
      end
      header_key
    end
    
  end
end