require 'cgi'
require 'digest/sha1'
require 'base64'
require 'time'
require 'base64'
require 'digest/sha1'
require 'restclient'

module RTurk
  class Requester
    class << self
      include RTurk::Utilities

      # @param [Hash] params
      # @option [String] 'Operation' The operation - Required
      # @option [String] Any Pass any other params and they will be included in the request
      #
      def request(params = {})
        params.delete_if {|k,v| v.nil? }
        params = stringify_keys(params)
        base_params = {
          'Service'=>'AWSMechanicalTurkRequester',
          'AWSAccessKeyId' => credentials.access_key,
          'Timestamp' => Time.now.utc.iso8601,
          'Version' => RTurk::API_VERSION
        }

        params.merge!(base_params)
        signature = sign(credentials.secret_key, params['Service'], params['Operation'], params["Timestamp"])
        params['Signature'] = signature

        querystring = params.inject([]) do |pairs, (key, value)|
          if value.is_a?(Array)
            value.each do |multi_value|
              pairs << [CGI.escape(key.to_s), CGI.escape(multi_value.to_s)].join('=')
            end
          elsif value.is_a?(Hash)
            value.each do |multi_key, multi_value|
              pairs << [CGI.escape("#{key}.#{multi_key}"), CGI.escape(multi_value.to_s)].join('=')
            end
          else
            pairs << [CGI.escape(key.to_s), CGI.escape(value.to_s)].join('=')
          end
          pairs
        end.join('&') # order doesn't matter for the actual request

        RTurk.logger.debug "Sending request:\n\t #{credentials.host}?#{querystring}"
        begin
          RestClient.post(credentials.host, querystring)
        rescue RestClient::Exception => e
          raise ServiceUnavailable if e.http_code == 503
          raise
        end
      end

      private

        def credentials
          RTurk
        end

        def stubbed_response
          @stubbed_responses ||= []
          @stubbed_responses.each do |sr|
            return sr.response if sr.matches(params)
          end
        end

        def sign(secret_key, service, method, time)
          msg = "#{service}#{method}#{time}"
          return hmac_sha1(secret_key, msg )
        end

        def hmac_sha1(key, s)
          ipad = [].fill(0x36, 0, 64)
          opad = [].fill(0x5C, 0, 64)
          key = key.unpack("C*")
          key += [].fill(0, 0, 64-key.length) if key.length < 64

          inner = []
          64.times { |i| inner.push(key[i] ^ ipad[i]) }
          inner += s.unpack("C*")

          outer = []
          64.times { |i| outer.push(key[i] ^ opad[i]) }
          outer = outer.pack("c*")
          outer += Digest::SHA1.digest(inner.pack("c*"))

          return Base64::encode64(Digest::SHA1.digest(outer)).chomp
        end
    end
  end

  def self.Request(*args)
    RTurk::Requester.request(*args)
  end
end