package erp

import (
	"fmt"
	"math"
	"time"

	"server/models"

	"github.com/beego/beego/v2/client/orm"
)

// Movement 一次库存变动的入参。库存结存只能由本引擎经流水驱动。
type Movement struct {
	TenantID     string
	ProductID    uint64
	WarehouseID  uint64
	BatchNo      string
	Direction    int8 // models.ErpStockIn / ErpStockOut
	Qty          float64
	UnitCost     float64 // 入库=进价/成本；出库传 0 表示按当前加权成本
	DocType      string
	DocID        uint64
	DocNo        string
	DocItemID    uint64
	OperatorID   string
	OperatorName string
	Remark       string
	// 批次效期随入库流水落地，出库/调拨沿用同批次快照
	ProductionDate *time.Time
	ExpireDate     *time.Time
}

// StockError 库存不足等业务错误（调用方可据 ErrInsufficientStock 区分文案）。
type StockError struct {
	ProductName  string
	Requested    float64
	Available    float64
	Insufficient bool
}

func (e *StockError) Error() string {
	if e.Insufficient {
		return fmt.Sprintf("商品「%s」库存不足：可用 %.4f，本次需要 %.4f", e.ProductName, e.Available, e.Requested)
	}
	return fmt.Sprintf("商品「%s」库存异常", e.ProductName)
}

// ApplyMovement 在事务内执行一条库存变动：
//  1. 定位/创建结存行（tenant+product+warehouse+batch 唯一）；
//  2. 出库时校验可用量（负库存开关取自基础设置）；
//  3. 入库按移动加权平均重算单位成本；出库成本=出库时加权成本（记入流水，毛利口径）；
//  4. 写库存流水 + 更新结存。
//
// 返回出库时点的单位成本（销售成本/退货回冲依据）。
func ApplyMovement(o orm.QueryExecutor, mv *Movement) (float64, error) {
	if mv.Qty <= 0 {
		return 0, fmt.Errorf("库存变动数量必须大于0")
	}
	if mv.WarehouseID == 0 || mv.ProductID == 0 {
		return 0, fmt.Errorf("库存变动缺少商品或仓库")
	}

	settings := GetSettings(mv.TenantID)

	var product models.ErpProduct
	if err := o.QueryTable(new(models.ErpProduct)).
		Filter("id", mv.ProductID).Filter("tenant_id", mv.TenantID).One(&product); err != nil {
		return 0, fmt.Errorf("商品不存在(id=%d)", mv.ProductID)
	}

	var stock models.ErpStock
	err := o.QueryTable(new(models.ErpStock)).
		Filter("tenant_id", mv.TenantID).
		Filter("product_id", mv.ProductID).
		Filter("warehouse_id", mv.WarehouseID).
		Filter("batch_no", mv.BatchNo).
		ForUpdate().One(&stock)
	if err == orm.ErrNoRows {
		stock = models.ErpStock{
			TenantID: mv.TenantID, ProductID: mv.ProductID,
			WarehouseID: mv.WarehouseID, BatchNo: mv.BatchNo,
			Quantity: 0, CostPrice: product.PurchasePrice,
			UpdateTime: time.Now(),
		}
		id, ierr := o.Insert(&stock)
		if ierr != nil {
			return 0, fmt.Errorf("初始化库存结存失败: %v", ierr)
		}
		stock.ID = uint64(id)
	} else if err != nil {
		return 0, fmt.Errorf("查询库存失败: %v", err)
	}

	before := stock.Quantity
	dir := mv.Direction
	unitCost := mv.UnitCost
	outCost := stock.CostPrice // 出库成本口径：当前加权成本

	if dir == models.ErpStockOut {
		if !settings.NegativeAllowed && before-mv.Qty < -0.000001 {
			return 0, &StockError{
				ProductName:  product.ProductName,
				Requested:    mv.Qty,
				Available:    before,
				Insufficient: true,
			}
		}
		after := before - mv.Qty
		if unitCost <= 0 {
			unitCost = outCost
		}
		if err := writeLedger(o, mv, dir, before, after, unitCost); err != nil {
			return 0, err
		}
		if _, err := o.QueryTable(new(models.ErpStock)).Filter("id", stock.ID).
			Update(orm.Params{"quantity": after, "update_time": time.Now()}); err != nil {
			return 0, fmt.Errorf("更新库存结存失败: %v", err)
		}
		return unitCost, nil
	}

	// 入库：移动加权平均
	if unitCost <= 0 {
		unitCost = product.PurchasePrice
	}
	after := before + mv.Qty
	newCost := unitCost
	if after > 0.000001 {
		newCost = (before*stock.CostPrice + mv.Qty*unitCost) / after
	}
	if err := writeLedger(o, mv, dir, before, after, unitCost); err != nil {
		return 0, err
	}
	if _, err := o.QueryTable(new(models.ErpStock)).Filter("id", stock.ID).
		Update(orm.Params{"quantity": after, "cost_price": newCost, "update_time": time.Now()}); err != nil {
		return 0, fmt.Errorf("更新库存结存失败: %v", err)
	}
	return unitCost, nil
}

func writeLedger(o orm.QueryExecutor, mv *Movement, dir int8, before, after, unitCost float64) error {
	now := time.Now()
	ledger := models.ErpStockLedger{
		TenantID: mv.TenantID, ProductID: mv.ProductID, WarehouseID: mv.WarehouseID,
		BatchNo: mv.BatchNo, Direction: dir, Quantity: mv.Qty,
		BeforeQty: before, AfterQty: after,
		UnitCost: unitCost, TotalCost: round2(unitCost * mv.Qty),
		DocType: mv.DocType, DocID: mv.DocID, DocNo: mv.DocNo, DocItemID: mv.DocItemID,
		ProductionDate: mv.ProductionDate, ExpireDate: mv.ExpireDate,
		OperatorID: mv.OperatorID, OperatorName: mv.OperatorName,
		Remark: mv.Remark, CreateTime: now,
	}
	if _, err := o.Insert(&ledger); err != nil {
		return fmt.Errorf("写入库存流水失败: %v", err)
	}
	return nil
}

// RefOutboundCost 取某条出库流水记录的出库成本（销售退货回冲入库成本用）。
func RefOutboundCost(o orm.QueryExecutor, tenantID string, docItemID uint64) float64 {
	if docItemID == 0 {
		return 0
	}
	var led models.ErpStockLedger
	if err := o.QueryTable(new(models.ErpStockLedger)).
		Filter("tenant_id", tenantID).
		Filter("doc_item_id", docItemID).
		Filter("direction", models.ErpStockOut).
		OrderBy("-id").One(&led); err != nil {
		return 0
	}
	return led.UnitCost
}

func round2(v float64) float64 {
	return math.Round(v*100) / 100
}

func round4(v float64) float64 {
	return math.Round(v*10000) / 10000
}

func absf(v float64) float64 {
	if v < 0 {
		return -v
	}
	return v
}