handling.go

package shipping

// TODO: It would make sense to have this in its own package. Unfortunately,
// then there would be a circular dependency between the cargo and handling
// packages since cargo.Delivery would use handling.HandlingEvent and
// handling.HandlingEvent would use cargo.TrackingID. Also,
// HandlingEventFactory depends on the cargo repository.
//
// It would make sense not having the cargo package depend on handling.

import (
	"errors"
	"time"
)

// HandlingActivity represents how and where a cargo can be handled, and can
// be used to express predictions about what is expected to happen to a cargo
// in the future.
type HandlingActivity struct {
	Type         HandlingEventType
	Location     UNLocode
	VoyageNumber VoyageNumber
}

// HandlingEvent is used to register the event when, for instance, a cargo is
// unloaded from a carrier at a some location at a given time.
type HandlingEvent struct {
	TrackingID TrackingID
	Activity   HandlingActivity
}

// HandlingEventType describes type of a handling event.
type HandlingEventType int

// Valid handling event types.
const (
	NotHandled HandlingEventType = iota
	Load
	Unload
	Receive
	Claim
	Customs
)

func (t HandlingEventType) String() string {
	switch t {
	case NotHandled:
		return "Not Handled"
	case Load:
		return "Load"
	case Unload:
		return "Unload"
	case Receive:
		return "Receive"
	case Claim:
		return "Claim"
	case Customs:
		return "Customs"
	}

	return ""
}

// HandlingHistory is the handling history of a cargo.
type HandlingHistory struct {
	HandlingEvents []HandlingEvent
}

// MostRecentlyCompletedEvent returns most recently completed handling event.
func (h HandlingHistory) MostRecentlyCompletedEvent() (HandlingEvent, error) {
	if len(h.HandlingEvents) == 0 {
		return HandlingEvent{}, errors.New("delivery history is empty")
	}

	return h.HandlingEvents[len(h.HandlingEvents)-1], nil
}

// HandlingEventRepository provides access a handling event store.
type HandlingEventRepository interface {
	Store(e HandlingEvent)
	QueryHandlingHistory(TrackingID) HandlingHistory
}

// HandlingEventFactory creates handling events.
type HandlingEventFactory struct {
	CargoRepository    CargoRepository
	VoyageRepository   VoyageRepository
	LocationRepository LocationRepository
}

// CreateHandlingEvent creates a validated handling event.
func (f *HandlingEventFactory) CreateHandlingEvent(registered time.Time, completed time.Time, id TrackingID,
	voyageNumber VoyageNumber, unLocode UNLocode, eventType HandlingEventType) (HandlingEvent, error) {

	if _, err := f.CargoRepository.Find(id); err != nil {
		return HandlingEvent{}, err
	}

	if _, err := f.VoyageRepository.Find(voyageNumber); err != nil {
		// TODO: This is pretty ugly, but when creating a Receive event, the voyage number is not known.
		if len(voyageNumber) > 0 {
			return HandlingEvent{}, err
		}
	}

	if _, err := f.LocationRepository.Find(unLocode); err != nil {
		return HandlingEvent{}, err
	}

	return HandlingEvent{
		TrackingID: id,
		Activity: HandlingActivity{
			Type:         eventType,
			Location:     unLocode,
			VoyageNumber: voyageNumber,
		},
	}, nil
}