package handler

import (
	"fmt"
	"net/http"
	"strconv"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/genex/trading-service/internal/domain/entity"
	"github.com/genex/trading-service/internal/matching"
)

type TradeHandler struct {
	engine *matching.Engine
}

func NewTradeHandler(engine *matching.Engine) *TradeHandler {
	return &TradeHandler{engine: engine}
}

type PlaceOrderReq struct {
	CouponID string  `json:"couponId" binding:"required"`
	Side     string  `json:"side" binding:"required,oneof=buy sell"`
	Type     string  `json:"type" binding:"required,oneof=limit market"`
	Price    float64 `json:"price"`
	Quantity int     `json:"quantity" binding:"required,min=1"`
}

func (h *TradeHandler) PlaceOrder(c *gin.Context) {
	var req PlaceOrderReq
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": -1, "message": err.Error()})
		return
	}

	userID := c.GetString("userId")
	order := &entity.Order{
		ID:           generateID(),
		UserID:       userID,
		CouponID:     req.CouponID,
		Side:         entity.OrderSide(req.Side),
		Type:         entity.OrderType(req.Type),
		Price:        req.Price,
		Quantity:     req.Quantity,
		RemainingQty: req.Quantity,
		Status:       entity.OrderPending,
	}

	result := h.engine.PlaceOrder(order)
	c.JSON(http.StatusOK, gin.H{"code": 0, "data": gin.H{
		"order":  result.UpdatedOrder,
		"trades": result.Trades,
	}})
}

func (h *TradeHandler) CancelOrder(c *gin.Context) {
	couponID := c.Query("couponId")
	orderID := c.Param("id")
	side := entity.OrderSide(c.Query("side"))

	success := h.engine.CancelOrder(couponID, orderID, side)
	if !success {
		c.JSON(http.StatusNotFound, gin.H{"code": -1, "message": "Order not found"})
		return
	}
	c.JSON(http.StatusOK, gin.H{"code": 0, "data": nil})
}

func (h *TradeHandler) GetOrderBook(c *gin.Context) {
	couponID := c.Param("couponId")
	depth, _ := strconv.Atoi(c.DefaultQuery("depth", "20"))

	bids, asks := h.engine.GetOrderBookSnapshot(couponID, depth)
	c.JSON(http.StatusOK, gin.H{"code": 0, "data": gin.H{
		"couponId": couponID,
		"bids":     bids,
		"asks":     asks,
	}})
}

func generateID() string {
	return fmt.Sprintf("ord-%d", time.Now().UnixNano())
}