package handler

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

	"github.com/gin-gonic/gin"
	"gorm.io/gorm"

	"github.com/wangjia/jiu/backend/internal/middleware"
	"github.com/wangjia/jiu/backend/internal/model"
	"github.com/wangjia/jiu/backend/internal/util"
)

type InventoryHandler struct {
	db *gorm.DB
}

func NewInventoryHandler(db *gorm.DB) *InventoryHandler {
	return &InventoryHandler{db: db}
}

// inventoryRow is the response shape for GET /api/v1/inventory
type inventoryRow struct {
	ID             uint64   `json:"id"`
	ShopID         uint64   `json:"shop_id"`
	WarehouseID    *uint64  `json:"warehouse_id"`
	ProductID      *uint64  `json:"product_id"`
	StockInItemID  *uint64  `json:"stock_in_item_id"`
	Quantity       float64  `json:"quantity"`
	ProductCode    string   `json:"product_code"`
	ProductName    string   `json:"product_name"`
	Series         string   `json:"series"`
	Spec           string   `json:"spec"`
	Unit           string   `json:"unit"`
	WarehouseName  string   `json:"warehouse_name"`
	UnitPrice      *float64 `json:"unit_price"`
	ProductionDate *string  `json:"production_date"`
	BatchNo        string   `json:"batch_no"`
	SupplierName   string   `json:"supplier_name"`
	Remark         string   `json:"remark"`
	Brand          string   `json:"brand"`
	MinStock       *int     `json:"min_stock"`
	CreatedAt      string   `json:"created_at"`
}

// List GET /api/v1/inventory
func (h *InventoryHandler) List(c *gin.Context) {
	shopID := middleware.GetShopID(c)
	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
	pageSize, _ := strconv.Atoi(c.DefaultQuery("page_size", "20"))
	if page < 1 {
		page = 1
	}
	if pageSize < 1 {
		pageSize = 20
	}
	// 超出上限钳到上限（此前是回退默认 20，导致出库选货请求大 page_size 被打回只剩 20 条）
	if pageSize > 5000 {
		pageSize = 5000
	}

	baseWhere := "inv.shop_id = ? AND inv.deleted_at IS NULL"
	args := []interface{}{shopID}

	keyword := c.Query("keyword")
	warehouseIDStr := c.Query("warehouse_id")
	inStock := c.Query("in_stock")
	seriesStr := c.Query("series")
	specStr := c.Query("spec")

	if keyword != "" {
		baseWhere += " AND (COALESCE(NULLIF(p.name,''), NULLIF(sii.product_name,''), inv.product_name) LIKE ? OR COALESCE(NULLIF(p.code,''), NULLIF(sii.product_code,''), inv.product_code) LIKE ? OR p.name_pinyin LIKE ? OR p.name_initials LIKE ?)"
		like := "%" + keyword + "%"
		args = append(args, like, like, like, like)
	}
	if warehouseIDStr != "" {
		baseWhere += " AND inv.warehouse_id = ?"
		args = append(args, warehouseIDStr)
	}
	if inStock == "1" {
		baseWhere += " AND inv.quantity > 0"
	}
	if seriesStr != "" {
		parts := strings.Split(seriesStr, ",")
		placeholders := strings.Repeat("?,", len(parts))
		baseWhere += " AND COALESCE(NULLIF(p.series,''), inv.series, '') IN (" + placeholders[:len(placeholders)-1] + ")"
		for _, s := range parts {
			args = append(args, strings.TrimSpace(s))
		}
	}
	if specStr != "" {
		parts := strings.Split(specStr, ",")
		placeholders := strings.Repeat("?,", len(parts))
		baseWhere += " AND COALESCE(NULLIF(p.spec,''), inv.spec, '') IN (" + placeholders[:len(placeholders)-1] + ")"
		for _, s := range parts {
			args = append(args, strings.TrimSpace(s))
		}
	}

	// Count query
	countSQL := `
		SELECT COUNT(*)
		FROM inventories inv
		LEFT JOIN stock_in_items sii ON sii.id = inv.stock_in_item_id
		LEFT JOIN products p ON p.id = inv.product_id AND p.deleted_at IS NULL
		LEFT JOIN warehouses w ON w.id = inv.warehouse_id
		WHERE ` + baseWhere

	var total int64
	if err := h.db.Raw(countSQL, args...).Scan(&total).Error; err != nil {
		util.RespondError(c, http.StatusInternalServerError, "QUERY_ERROR", "查询失败")
		return
	}

	// Data query
	dataSQL := `
		SELECT
		  inv.id, inv.shop_id, inv.warehouse_id, inv.product_id, inv.stock_in_item_id,
		  inv.quantity,
		  COALESCE(NULLIF(p.code,''), NULLIF(sii.product_code,''), inv.product_code, '') AS product_code,
		  COALESCE(NULLIF(p.name,''), NULLIF(sii.product_name,''), inv.product_name, '') AS product_name,
		  COALESCE(NULLIF(p.series,''), NULLIF(sii.series,''), inv.series, '') AS series,
		  COALESCE(NULLIF(p.spec,''), NULLIF(sii.spec,''), inv.spec, '') AS spec,
		  COALESCE(NULLIF(p.unit,''), inv.unit, '') AS unit,
		  COALESCE(NULLIF(w.name,''), inv.warehouse_name, '') AS warehouse_name,
		  COALESCE(sii.unit_price, inv.unit_price) AS unit_price,
		  COALESCE(DATE(sii.production_date), DATE(inv.production_date)) AS production_date,
		  COALESCE(NULLIF(sii.batch_no,''), inv.batch_no, '') AS batch_no,
		  inv.supplier_name,
		  inv.remark,
		  COALESCE(p.brand, '') AS brand,
		  p.min_stock,
		  inv.created_at
		FROM inventories inv
		LEFT JOIN stock_in_items sii ON sii.id = inv.stock_in_item_id
		LEFT JOIN products p ON p.id = inv.product_id AND p.deleted_at IS NULL
		LEFT JOIN warehouses w ON w.id = inv.warehouse_id
		WHERE ` + baseWhere + `
		ORDER BY inv.id DESC
		LIMIT ? OFFSET ?`

	dataArgs := append(args, pageSize, (page-1)*pageSize)

	var rows []inventoryRow
	if err := h.db.Raw(dataSQL, dataArgs...).Scan(&rows).Error; err != nil {
		util.RespondError(c, http.StatusInternalServerError, "QUERY_ERROR", "查询失败")
		return
	}

	c.JSON(http.StatusOK, gin.H{"data": rows, "total": total, "page": page, "page_size": pageSize})
}

// Logs GET /api/v1/inventory/logs
func (h *InventoryHandler) Logs(c *gin.Context) {
	shopID := middleware.GetShopID(c)
	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
	pageSize, _ := strconv.Atoi(c.DefaultQuery("page_size", "20"))
	pageSize = util.ValidatePageSize(pageSize, 20, 500)

	query := h.db.Model(&model.InventoryLog{}).Where("shop_id = ?", shopID)

	if productID := c.Query("product_id"); productID != "" {
		query = query.Where("product_id = ?", productID)
	}

	var total int64
	query.Count(&total)

	logs := make([]model.InventoryLog, 0)
	query.Preload("Product").Preload("Warehouse").Offset((page-1)*pageSize).Limit(pageSize).Order("id DESC").Find(&logs)

	c.JSON(http.StatusOK, gin.H{"data": logs, "total": total, "page": page, "page_size": pageSize})
}

// CreateCheck POST /api/v1/inventory/checks
func (h *InventoryHandler) CreateCheck(c *gin.Context) {
	shopID := middleware.GetShopID(c)
	operatorID := middleware.GetUserID(c)

	var req model.InventoryCheck
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	req.ShopID = shopID
	req.OperatorID = operatorID
	req.Status = "draft"

	// 自动填入系统库存数量（SUM 聚合）
	for i := range req.Items {
		req.Items[i].ShopID = shopID
		warehouseID := req.WarehouseID
		productID := req.Items[i].ProductID
		var systemQty float64
		h.db.Model(&model.Inventory{}).
			Where("shop_id = ? AND warehouse_id = ? AND product_id = ? AND deleted_at IS NULL",
				shopID, warehouseID, productID).
			Select("COALESCE(SUM(quantity), 0)").Scan(&systemQty)
		req.Items[i].SystemQty = systemQty
	}

	if err := h.db.Create(&req).Error; err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
		return
	}
	util.RespondCreated(c, req)
}

// GetCheck GET /api/v1/inventory/checks/:id
func (h *InventoryHandler) GetCheck(c *gin.Context) {
	shopID := middleware.GetShopID(c)
	var check model.InventoryCheck
	if err := h.db.Preload("Items.Product").
		Where("id = ? AND shop_id = ?", c.Param("id"), shopID).
		First(&check).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"error": "not found"})
		return
	}
	util.RespondSuccess(c, check)
}

// CompleteCheck PUT /api/v1/inventory/checks/:id/complete
func (h *InventoryHandler) CompleteCheck(c *gin.Context) {
	shopID := middleware.GetShopID(c)
	checkID, _ := strconv.ParseUint(c.Param("id"), 10, 64)

	var check model.InventoryCheck
	if err := h.db.Preload("Items.Product").
		Where("id = ? AND shop_id = ?", checkID, shopID).
		First(&check).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"error": "not found"})
		return
	}
	if check.Status == "completed" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "已完成"})
		return
	}

	tx := h.db.Begin()
	now := time.Now()

	for _, item := range check.Items {
		diff := item.ActualQty - item.SystemQty
		if diff == 0 {
			continue
		}

		if diff > 0 {
			// 盘盈：新增一条库存批次记录
			checkIDCopy := checkID
			productIDCopy := item.ProductID
			warehouseIDCopy := check.WarehouseID

			productCode := ""
			productName := ""
			series := ""
			spec := ""
			unit := ""
			if item.Product != nil {
				productCode = item.Product.Code
				productName = item.Product.Name
				series = item.Product.Series
				spec = item.Product.Spec
				unit = item.Product.Unit
			}

			inv := model.Inventory{
				ShopID:           shopID,
				WarehouseID:      &warehouseIDCopy,
				ProductID:        &productIDCopy,
				InventoryCheckID: &checkIDCopy,
				Quantity:         diff,
				ProductCode:      productCode,
				ProductName:      productName,
				Series:           series,
				Spec:             spec,
				Unit:             unit,
			}
			tx.Create(&inv)
		} else {
			// 盘亏：FIFO 扣减
			remaining := -diff
			var batches []model.Inventory
			tx.Set("gorm:query_option", "FOR UPDATE").
				Where("shop_id = ? AND warehouse_id = ? AND product_id = ? AND quantity > 0 AND deleted_at IS NULL",
					shopID, check.WarehouseID, item.ProductID).
				Order("created_at ASC").Find(&batches)
			for i := range batches {
				if remaining <= 0 {
					break
				}
				b := &batches[i]
				if b.Quantity <= remaining {
					remaining -= b.Quantity
					tx.Model(b).Updates(map[string]interface{}{"quantity": 0, "deleted_at": now})
				} else {
					tx.Model(b).Update("quantity", gorm.Expr("quantity - ?", remaining))
					remaining = 0
				}
			}
		}
	}

	tx.Model(&check).Update("status", "completed")
	if err := tx.Commit().Error; err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
		return
	}
	c.JSON(http.StatusOK, gin.H{"message": "盘点完成"})
}

// UpdateRemark PUT /api/v1/inventory/:id/remark
func (h *InventoryHandler) UpdateRemark(c *gin.Context) {
	shopID := middleware.GetShopID(c)
	id, err := strconv.ParseUint(c.Param("id"), 10, 64)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid id"})
		return
	}
	var req struct {
		Remark string `json:"remark"`
	}
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}
	result := h.db.Model(&model.Inventory{}).
		Where("id = ? AND shop_id = ? AND deleted_at IS NULL", id, shopID).
		Update("remark", req.Remark)
	if result.Error != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": result.Error.Error()})
		return
	}
	if result.RowsAffected == 0 {
		c.JSON(http.StatusNotFound, gin.H{"error": "库存记录不存在"})
		return
	}
	c.JSON(http.StatusOK, gin.H{"ok": true})
}