package main

import (
	"encoding/json"
	"fmt"
	"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 {
	Sku   string `json:"sku"`
	Name  string `json:"name"`
	Price int64  `json:"price"`
	Image string `json:"image"`
}

type CartGrain struct {
	storageMessages []Message
	Id              CartId     `json:"id"`
	Items           []CartItem `json:"items"`
	TotalPrice      int64      `json:"totalPrice"`
}

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) (*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: 1,
		Price:    int64(price),
		Sku:      sku,
		Name:     item.Title,
		Image:    item.Img,
	}, nil
}

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

func (c *CartGrain) GetStorageMessage(since int64) []StorableMessage {

	ret := make([]StorableMessage, 0)
	for _, message := range c.storageMessages {
		if *message.TimeStamp > since {
			ret = append(ret, message)
		}
	}
	return ret
}

func (c *CartGrain) HandleMessage(message *Message, isReplay bool) ([]byte, error) {
	if message.TimeStamp == nil {
		now := time.Now().Unix()
		message.TimeStamp = &now
	}
	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)
		}
	case AddItemType:
		msg, ok := message.Content.(*messages.AddItem)
		if !ok {
			err = fmt.Errorf("expected AddItem")
		} else {
			c.Items = append(c.Items, CartItem{
				Sku:   msg.Sku,
				Name:  msg.Name,
				Price: msg.Price,
				Image: msg.Image,
			})
			c.TotalPrice += msg.Price
		}
	default:
		err = fmt.Errorf("unknown message type %d", message.Type)
	}
	if err != nil {
		return nil, err
	}
	if !isReplay {
		c.storageMessages = append(c.storageMessages, *message)
	}
	return json.Marshal(c)
}