package service

import (
	"time"

	"github.com/shopspring/decimal"
	"github.com/wmms/wmms/internal/model"
	"github.com/wmms/wmms/internal/repository"
)

type InboundService struct {
	inboundRepo *repository.InboundRepo
	materialSvc *MaterialService
	stockRepo   *repository.StockRepo
}

func NewInboundService() *InboundService {
	return &InboundService{
		inboundRepo: repository.NewInboundRepo(),
		materialSvc: NewMaterialService(),
		stockRepo:   repository.NewStockRepo(),
	}
}

func (s *InboundService) Create(req *model.CreateInboundRequest) (*model.InboundOrder, error) {
	order := &model.InboundOrder{
		InboundDate: time.Now(),
		Handler:     req.Handler,
		Supplier:    req.Supplier,
		Items:       make([]model.InboundItem, len(req.Items)),
	}

	// Validate all items first (outside transaction)
	for i, item := range req.Items {
		exists, err := s.materialSvc.Exists(item.MaterialID)
		if err != nil {
			return nil, err
		}
		if !exists {
			return nil, ErrMaterialNotFound
		}
		if item.WarningStock != nil && item.WarningStock.IsNegative() {
			return nil, ErrInvalidWarningStock
		}
		order.Items[i] = model.InboundItem{
			MaterialID: item.MaterialID,
			Quantity:   item.Quantity,
		}
	}

	// Start transaction
	tx, err := repository.BeginTx()
	if err != nil {
		return nil, err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	// Create inbound order within transaction
	err = s.inboundRepo.CreateTx(tx, order)
	if err != nil {
		return nil, err
	}

	// Update stock and create logs within transaction
	for i := range order.Items {
		item := &order.Items[i]
		// 这里必须用赋值而不是 := ，否则 err 会被遮蔽，defer 里的回滚判断看不到它。
		var material *model.Material
		material, err = s.materialSvc.GetByID(item.MaterialID)
		if err != nil {
			return nil, err
		}
		item.MaterialCode = material.MaterialCode
		item.MaterialName = material.Name

		err = s.stockRepo.UpdateStockTx(tx, item.MaterialID, decimal.NewFromInt(int64(item.Quantity)))
		if err != nil {
			return nil, err
		}

		// 入库明细上带的预警阈值在同一个事务里写入，保证物料的第一个阈值和第一行库存
		// 同时落库。阈值为 nil 表示本次不改动已存的值。
		if warningStock := req.Items[i].WarningStock; warningStock != nil {
			err = s.stockRepo.UpdateWarningStockTx(tx, item.MaterialID, *warningStock, true)
			if err != nil {
				return nil, err
			}
		}

		stockLog := &model.StockLog{
			MaterialID:       item.MaterialID,
			Type:             "in",
			Quantity:         item.Quantity,
			RelatedOrderType: "inbound",
			RelatedOrderID:   order.ID,
		}
		err = s.stockRepo.CreateLogTx(tx, stockLog)
		if err != nil {
			return nil, err
		}
	}

	// Commit transaction
	if err = tx.Commit(); err != nil {
		return nil, err
	}

	order.Status = "completed"
	return order, nil
}

func (s *InboundService) GetByID(id int64) (*model.InboundOrder, error) {
	return s.inboundRepo.GetByID(id)
}

func (s *InboundService) List(search string, limit, offset int) ([]model.InboundOrder, int64, error) {
	return s.inboundRepo.List(search, limit, offset)
}

func (s *InboundService) GetByMaterialID(materialID int64) ([]model.InboundRecord, error) {
	return s.inboundRepo.GetByMaterialID(materialID)
}

func (s *InboundService) Delete(id int64) error {
	// Get the inbound order with items
	order, err := s.inboundRepo.GetByID(id)
	if err != nil {
		return err
	}

	// Start transaction
	tx, err := repository.BeginTx()
	if err != nil {
		return err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	// Reverse stock for each item within transaction
	for _, item := range order.Items {
		err = s.stockRepo.UpdateStockTx(tx, item.MaterialID, decimal.NewFromInt(int64(-item.Quantity)))
		if err != nil {
			return err
		}
	}

	// Delete stock logs within transaction
	err = s.stockRepo.DeleteLogsTx(tx, "inbound", id)
	if err != nil {
		return err
	}

	// Delete the inbound order (items will be cascade deleted)
	err = s.inboundRepo.DeleteTx(tx, id)
	if err != nil {
		return err
	}

	// Commit transaction
	if err = tx.Commit(); err != nil {
		return err
	}

	return nil
}

func (s *InboundService) Update(id int64, req *model.UpdateInboundRequest) (*model.InboundOrder, error) {
	// Get old order data
	oldOrder, err := s.inboundRepo.GetByID(id)
	if err != nil {
		return nil, err
	}

	// 阈值校验放在事务之外，避免为非法输入白开一个事务
	for _, item := range req.Items {
		if item.WarningStock != nil && item.WarningStock.IsNegative() {
			return nil, ErrInvalidWarningStock
		}
	}

	// Start transaction
	tx, err := repository.BeginTx()
	if err != nil {
		return nil, err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	// Reverse stock for old items (subtract what was previously added)
	for _, item := range oldOrder.Items {
		_, err = s.stockRepo.GetStockForUpdateTx(tx, item.MaterialID)
		if err != nil {
			return nil, err
		}
		err = s.stockRepo.UpdateStockTx(tx, item.MaterialID, decimal.NewFromInt(int64(-item.Quantity)))
		if err != nil {
			return nil, err
		}
	}

	// Delete old stock logs
	err = s.stockRepo.DeleteLogsTx(tx, "inbound", id)
	if err != nil {
		return nil, err
	}

	// Update order in repository
	err = s.inboundRepo.UpdateTx(tx, id, req)
	if err != nil {
		return nil, err
	}

	// Add stock for new items and create logs
	for _, item := range req.Items {
		_, err = s.stockRepo.GetStockForUpdateTx(tx, item.MaterialID)
		if err != nil {
			return nil, err
		}
		err = s.stockRepo.UpdateStockTx(tx, item.MaterialID, decimal.NewFromInt(int64(item.Quantity)))
		if err != nil {
			return nil, err
		}

		// 阈值随明细一起更新，nil 表示不改动已存的值，避免编辑旧入库单时把刚调好的
		// 阈值覆盖回旧数。
		if item.WarningStock != nil {
			err = s.stockRepo.UpdateWarningStockTx(tx, item.MaterialID, *item.WarningStock, true)
			if err != nil {
				return nil, err
			}
		}

		stockLog := &model.StockLog{
			MaterialID:       item.MaterialID,
			Type:             "in",
			Quantity:         item.Quantity,
			RelatedOrderType: "inbound",
			RelatedOrderID:   id,
		}
		err = s.stockRepo.CreateLogTx(tx, stockLog)
		if err != nil {
			return nil, err
		}
	}

	// Commit transaction
	if err = tx.Commit(); err != nil {
		return nil, err
	}

	// Get updated order with material details
	updatedOrder, err := s.inboundRepo.GetByID(id)
	if err != nil {
		return nil, err
	}
	updatedOrder.Status = "completed"

	return updatedOrder, nil
}