package entity

import (
	"fmt"
	"time"

	"github.com/genex/trading-service/internal/domain/vo"
)

const (
	// TakerFeeRate is the fee rate charged to the taker (0.5%).
	TakerFeeRate = 0.005
	// MakerFeeRate is the fee rate charged to the maker (0.1%).
	MakerFeeRate = 0.001
)

// Trade represents an executed trade between a buyer and seller.
type Trade struct {
	ID          string   `json:"id"`
	CouponID    string   `json:"couponId"`
	BuyOrderID  string   `json:"buyOrderId"`
	SellOrderID string   `json:"sellOrderId"`
	BuyerID     string   `json:"buyerId"`
	SellerID    string   `json:"sellerId"`
	Price       vo.Price `json:"price"`
	Quantity    int      `json:"quantity"`
	BuyerFee    float64  `json:"buyerFee"`
	SellerFee   float64  `json:"sellerFee"`
	CreatedAt   time.Time `json:"createdAt"`
}

// NewTrade creates a new Trade from matched orders.
func NewTrade(id string, buyOrder, sellOrder *Order, price vo.Price, matchQty int) (*Trade, error) {
	if id == "" {
		return nil, fmt.Errorf("trade ID cannot be empty")
	}
	if matchQty <= 0 {
		return nil, fmt.Errorf("trade quantity must be positive")
	}

	notional := price.Multiply(matchQty)
	takerFee := notional * TakerFeeRate
	makerFee := notional * MakerFeeRate

	return &Trade{
		ID:          id,
		CouponID:    buyOrder.CouponID,
		BuyOrderID:  buyOrder.ID,
		SellOrderID: sellOrder.ID,
		BuyerID:     buyOrder.UserID,
		SellerID:    sellOrder.UserID,
		Price:       price,
		Quantity:    matchQty,
		BuyerFee:    takerFee,
		SellerFee:   makerFee,
		CreatedAt:   time.Now(),
	}, nil
}

// Notional returns the total value of the trade (price * quantity).
func (t *Trade) Notional() float64 {
	return t.Price.Multiply(t.Quantity)
}

// TotalFees returns the sum of buyer and seller fees.
func (t *Trade) TotalFees() float64 {
	return t.BuyerFee + t.SellerFee
}