module ActiveShipping

  # Carrier is abstract the base class for all supported carriers.
  #
  # To implement support for a carrier, you should subclass this class and
  # implement all the methods the carrier supports.
  #
  # @see #find_rates
  # @see #create_shipment
  # @see #find_tracking_info
  #
  # @!attribute test_mode
  #   Whether to interact with the carrier's sandbox environment.
  #   @return [Boolean]
  #
  # @!attribute last_request
  #   The last request performed against the carrier's API.
  #   @see #save_request
  class Carrier
    include Quantified

    attr_reader :last_request
    attr_accessor :test_mode
    alias_method :test_mode?, :test_mode

    # Credentials should be in options hash under keys :login, :password and/or :key.
    # @param options [Hash] The details needed to connect to the carrier's API.
    # @option options [Boolean] :test Set this to true to connect to the carrier's
    #   sandbox environment instead of the production environment.
    def initialize(options = {})
      requirements.each { |key| requires!(options, key) }
      @options = options
      @last_request = nil
      @test_mode = @options[:test]
    end

    # Asks the carrier for rate estimates for a given shipment.
    #
    # @note Override with whatever you need to get the rates from the carrier.
    #
    # @param origin [ActiveShipping::Location] Where the shipment will originate from.
    # @param destination [ActiveShipping::Location] Where the package will go.
    # @param packages [Array<ActiveShipping::Package>] The list of packages that will
    #   be in the shipment.
    # @param options [Hash] Carrier-specific parameters.
    # @return [ActiveShipping::RateResponse] The response from the carrier, which
    #   includes 0 or more rate estimates for different shipping products
    def find_rates(origin, destination, packages, options = {})
      raise NotImplementedError, "#find_rates is not supported by #{self.class.name}."
    end

    # Registers a new shipment with the carrier, to get a tracking number and
    # potentially shipping labels
    #
    # @note Override with whatever you need to register a shipment, and obtain
    #   shipping labels if supported by the carrier.
    #
    # @param origin [ActiveShipping::Location] Where the shipment will originate from.
    # @param destination [ActiveShipping::Location] Where the package will go.
    # @param packages [Array<ActiveShipping::Package>] The list of packages that will
    #   be in the shipment.
    # @param options [Hash] Carrier-specific parameters.
    # @return [ActiveShipping::ShipmentResponse] The response from the carrier. This
    #   response should include a shipment identifier or tracking_number if successful,
    #   and potentially shipping labels.
    def create_shipment(origin, destination, packages, options = {})
      raise NotImplementedError, "#create_shipment is not supported by #{self.class.name}."
    end

    # Retrieves tracking information for a previous shipment
    #
    # @note Override with whatever you need to get a shipping label
    #
    # @param tracking_number [String] The unique identifier of the shipment to track.
    # @param options [Hash] Carrier-specific parameters.
    # @return [ActiveShipping::TrackingResponse] The response from the carrier. This
    #   response should a list of shipment tracking events if successful.
    def find_tracking_info(tracking_number, options = {})
      raise NotImplementedError, "#find_tracking_info is not supported by #{self.class.name}."
    end

    # Validate credentials with a call to the API.
    #
    # By default this just does a `find_rates` call with the orgin and destination both as
    # the carrier's default_location. Override to provide alternate functionality, such as
    # checking for `test_mode` to use test servers, etc.
    #
    # @return [Boolean] Should return `true` if the provided credentials proved to work,
    #   `false` otherswise.
    def valid_credentials?
      location = self.class.default_location
      find_rates(location, location, Package.new(100, [5, 15, 30]), :test => test_mode)
    rescue ActiveShipping::ResponseError
      false
    else
      true
    end

    # The maximum weight the carrier will accept.
    # @return [Quantified::Mass]
    def maximum_weight
      Mass.new(150, :pounds)
    end

    protected

    include ActiveUtils::RequiresParameters
    include ActiveUtils::PostsData

    # Returns the keys that are required to be passed to the options hash
    # @note Override to return required keys in options hash for initialize method.
    # @return [Array<Symbol>]
    def requirements
      []
    end

    # The default location to use for {#valid_credentials?}.
    # @note Override for non-U.S.-based carriers.
    # @return [ActiveShipping::Location]
    def self.default_location
      Location.new( :country => 'US',
                    :state => 'CA',
                    :city => 'Beverly Hills',
                    :address1 => '455 N. Rexford Dr.',
                    :address2 => '3rd Floor',
                    :zip => '90210',
                    :phone => '1-310-285-1013',
                    :fax => '1-310-275-8159')
    end

    # Use after building the request to save for later inspection.
    # @return [void]
    def save_request(r)
      @last_request = r
    end

    # Calculates a timestamp that corresponds a given number if business days in the future
    #
    # @param [Integer] The number of business days from now.
    # @return [DateTime] A timestamp, the provided number of business days in the future.
    def timestamp_from_business_day(days)
      return unless days
      date = DateTime.now.utc
      days.times do
        begin
          date = date + 1
        end while [0, 6].include?(date.wday)
      end
      date
    end
  end
end