go-cart-actor/cart-grain.go

package main

import (
	"encoding/json"
	"fmt"
	"slices"
	"sync"
	"time"

	messages "git.tornberg.me/go-cart-actor/proto"
)

type CartId [16]byte

func (id CartId) MarshalJSON() ([]byte, error) {
	return json.Marshal(id.String())
}

func (id *CartId) UnmarshalJSON(data []byte) error {
	var str string
	err := json.Unmarshal(data, &str)
	if err != nil {
		return err
	}
	copy(id[:], []byte(str))
	return nil
}

type CartItem struct {
	Id       int    `json:"id"`
	Sku      string `json:"sku"`
	Name     string `json:"name"`
	Price    int64  `json:"price"`
	Quantity int    `json:"qty"`
	Image    string `json:"image"`
}

type CartDelivery struct {
	Provider string `json:"provider"`
	Price    int64  `json:"price"`
	Items    []int  `json:"items"`
}

type CartGrain struct {
	mu              sync.RWMutex
	lastItemId      int
	lastDeliveryId  int
	storageMessages []Message
	Id              CartId         `json:"id"`
	Items           []*CartItem    `json:"items"`
	TotalPrice      int64          `json:"totalPrice"`
	Deliveries      []CartDelivery `json:"deliveries,omitempty"`
}

type Grain interface {
	GetId() CartId
	HandleMessage(message *Message, isReplay bool) ([]byte, error)
}

func (c *CartGrain) GetId() CartId {
	return c.Id
}

func (c *CartGrain) GetLastChange() int64 {
	if len(c.storageMessages) == 0 {
		return 0
	}
	return *c.storageMessages[len(c.storageMessages)-1].TimeStamp
}

func getItemData(sku string, qty int) (*messages.AddItem, error) {
	item, err := FetchItem(sku)
	if err != nil {
		return nil, err
	}
	price := 0
	priceField, ok := item.Fields[4]
	if ok {
		priceFloat, ok := priceField.(float64)
		if !ok {
			price, ok = priceField.(int)
			if !ok {
				return nil, fmt.Errorf("invalid price type")
			}
		} else {
			price = int(priceFloat)
		}
	}
	if price == 0 {
		return nil, fmt.Errorf("invalid price")
	}

	return &messages.AddItem{
		Quantity: int32(qty),
		Price:    int64(price),
		Sku:      sku,
		Name:     item.Title,
		Image:    item.Img,
	}, nil
}

func (c *CartGrain) AddItem(sku string, qty int) ([]byte, error) {
	cartItem, err := getItemData(sku, qty)
	if err != nil {
		return nil, err
	}
	return c.HandleMessage(&Message{
		Type:    2,
		Content: cartItem,
	}, false)
}

func (c *CartGrain) GetStorageMessage(since int64) []StorableMessage {
	c.mu.RLock()
	defer c.mu.RUnlock()
	ret := make([]StorableMessage, 0)

	for _, message := range c.storageMessages {
		if *message.TimeStamp > since {
			ret = append(ret, message)
		}
	}
	return ret
}

func (c *CartGrain) GetState() ([]byte, error) {
	return json.Marshal(c)
}

func (c *CartGrain) ItemsWithDelivery() []int {
	ret := make([]int, 0, len(c.Items))
	for _, item := range c.Items {
		for _, delivery := range c.Deliveries {
			for _, id := range delivery.Items {
				if item.Id == id {
					ret = append(ret, id)
				}
			}
		}
	}
	return ret
}

func (c *CartGrain) ItemsWithoutDelivery() []int {
	ret := make([]int, 0, len(c.Items))
	hasDelivery := c.ItemsWithDelivery()
	for _, item := range c.Items {
		found := false
		for _, id := range hasDelivery {
			if item.Id == id {
				found = true
				break
			}
		}

		if !found {
			ret = append(ret, item.Id)
		}
	}
	return ret
}

func (c *CartGrain) HandleMessage(message *Message, isReplay bool) ([]byte, error) {
	if message.TimeStamp == nil {
		now := time.Now().Unix()
		message.TimeStamp = &now
	}
	grainMutations.Inc()
	var err error
	switch message.Type {
	case AddRequestType:
		msg, ok := message.Content.(*messages.AddRequest)
		if !ok {
			err = fmt.Errorf("expected AddRequest")
		} else {
			return c.AddItem(msg.Sku, 1) // extent AddRequest to include quantity
		}
	case AddItemType:
		msg, ok := message.Content.(*messages.AddItem)
		if !ok {
			err = fmt.Errorf("expected AddItem")
		} else {
			found := false
			if msg.Quantity < 1 {
				return nil, fmt.Errorf("invalid quantity")
			}
			for _, item := range c.Items {
				if item.Sku == msg.Sku {
					found = true
					item.Quantity += int(msg.Quantity)
					c.TotalPrice += item.Price * int64(msg.Quantity)
					break
				}
			}
			if !found {
				c.mu.Lock()
				c.lastItemId++
				c.Items = append(c.Items, &CartItem{
					Id:       c.lastItemId,
					Quantity: int(msg.Quantity),
					Sku:      msg.Sku,
					Name:     msg.Name,
					Price:    msg.Price,
					Image:    msg.Image,
				})
				c.TotalPrice += msg.Price * int64(msg.Quantity)
				c.mu.Unlock()
			}
		}
	case ChangeQuantityType:
		msg, ok := message.Content.(*messages.ChangeQuantity)
		if !ok {
			err = fmt.Errorf("expected RemoveItem")
		} else {
			for i, item := range c.Items {
				if item.Id == int(msg.Id) {
					if item.Quantity <= int(msg.Quantity) {
						c.Items = append(c.Items[:i], c.Items[i+1:]...)

					} else {
						item.Quantity -= int(msg.Quantity)
					}
					c.TotalPrice -= item.Price * int64(msg.Quantity)

					break
				}
			}
		}
	case RemoveItemType:
		msg, ok := message.Content.(*messages.RemoveItem)
		if !ok {
			err = fmt.Errorf("expected RemoveItem")
		} else {
			for i, item := range c.Items {
				if item.Id == int(msg.Id) {
					c.TotalPrice -= item.Price * int64(item.Quantity)
					c.Items = append(c.Items[:i], c.Items[i+1:]...)
					break
				}
			}
		}
	case SetDeliveryType:
		msg, ok := message.Content.(*messages.SetDelivery)
		if !ok {
			err = fmt.Errorf("expected SetDelivery")
		} else {
			c.lastDeliveryId++
			items := make([]int, 0)
			withDelivery := c.ItemsWithDelivery()
			if len(msg.Items) == 0 {
				items = append(items, c.ItemsWithoutDelivery()...)
			} else {
				for _, id := range msg.Items {
					for _, item := range c.Items {
						if item.Id == int(id) {
							if slices.Contains(withDelivery, item.Id) {
								return nil, fmt.Errorf("item already has delivery")
							}
							items = append(items, int(item.Id))
							break
						}
					}
				}
			}
			c.Deliveries = append(c.Deliveries, CartDelivery{
				Provider: msg.Provider,
				Price:    49,
				Items:    items,
			})
		}
	case RemoveDeliveryType:
	default:
		err = fmt.Errorf("unknown message type %d", message.Type)
	}
	if err != nil {
		return nil, err
	}

	if !isReplay {
		c.mu.Lock()
		c.storageMessages = append(c.storageMessages, *message)
		c.mu.Unlock()
	}
	return json.Marshal(c)
}