package service

import (
	"errors"
	"sort"
	"time"

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

var ErrInsufficientStock = errors.New("insufficient stock")

type OutboundService struct {
	outboundRepo *repository.OutboundRepo
	materialSvc  *MaterialService
	stockRepo    *repository.StockRepo
}

func NewOutboundService() *OutboundService {
	return &OutboundService{
		outboundRepo: repository.NewOutboundRepo(),
		materialSvc:  NewMaterialService(),
		stockRepo:    repository.NewStockRepo(),
	}
}

func (s *OutboundService) Create(organizationID int64, req *model.CreateOutboundRequest, operator string) (*model.OutboundOrder, error) {
	order := &model.OutboundOrder{
		OutboundDate: time.Now(),
		Operator:     operator,
		Handler:      operator,
		Receiver:     req.Receiver,
		Remark:       req.Remark,
		Items:        make([]model.OutboundItem, len(req.Items)),
	}

	// 库存维度由服务端按当前公司解析：本公司的唯一启用仓库和库位。缺失或停用回
	// ErrInventoryScopeUnavailable，Handler 映射为 409。
	scope, err := ResolveInventoryScope(organizationID, true)
	if err != nil {
		return nil, err
	}

	// Validate all items first (outside transaction)
	for i, item := range req.Items {
		exists, err := s.materialSvc.Exists(organizationID, item.MaterialID)
		if err != nil {
			return nil, err
		}
		if !exists {
			return nil, ErrMaterialNotFound
		}
		active, err := s.materialSvc.IsActive(organizationID, item.MaterialID)
		if err != nil {
			return nil, err
		}
		if !active {
			return nil, ErrMaterialObsolete
		}

		currentStock, err := s.stockRepo.GetStock(scope, item.MaterialID)
		if err != nil {
			return nil, err
		}
		if currentStock.LessThan(decimal.NewFromInt(int64(item.Quantity))) {
			return nil, ErrInsufficientStock
		}

		order.Items[i] = model.OutboundItem{
			MaterialID: item.MaterialID,
			Quantity:   item.Quantity,
		}
	}

	// Start transaction for stock update (prevents race condition)
	tx, err := repository.BeginTx()
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	// 按物料 ID 升序条件扣减，避免并发事务以不同顺序加锁造成死锁；条件扣减只在余额
	// 存在且足够时更新，余额不存在按 0 处理，因此不会透支、也不会锁到别家公司的余额。
	itemIDs := make([]int64, len(order.Items))
	for i := range order.Items {
		itemIDs[i] = order.Items[i].MaterialID
	}
	for _, idx := range materialSortedIndexes(itemIDs) {
		item := &order.Items[idx]
		err := s.stockRepo.DeductStockTx(tx, scope, item.MaterialID, decimal.NewFromInt(int64(item.Quantity)))
		if err != nil {
			if errors.Is(err, repository.ErrInsufficientStock) {
				return nil, ErrInsufficientStock
			}
			return nil, err
		}
	}

	// Create outbound order
	err = s.outboundRepo.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]
		material, err := s.materialSvc.GetByID(organizationID, item.MaterialID)
		if err != nil {
			return nil, err
		}
		item.MaterialCode = material.MaterialCode
		item.MaterialName = material.Name

		// Create stock log within transaction
		stockLog := &model.StockLog{
			OrganizationID:   scope.OrganizationID,
			WarehouseID:      scope.WarehouseID,
			LocationID:       scope.LocationID,
			MaterialID:       item.MaterialID,
			Type:             "out",
			Quantity:         item.Quantity,
			RelatedOrderType: "outbound",
			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
}

// materialSortedIndexes 返回按物料 ID 升序排列的下标，用于固定同一维度下多物料的
// 加锁顺序，避免并发事务互相等待造成死锁。
func materialSortedIndexes(materialIDs []int64) []int {
	indexes := make([]int, len(materialIDs))
	for i := range materialIDs {
		indexes[i] = i
	}
	sort.SliceStable(indexes, func(a, b int) bool {
		return materialIDs[indexes[a]] < materialIDs[indexes[b]]
	})
	return indexes
}

func (s *OutboundService) GetByID(id int64) (*model.OutboundOrder, error) {
	return s.outboundRepo.GetByID(id)
}

func (s *OutboundService) List(search string, limit, offset int) ([]model.OutboundOrder, int64, error) {
	return s.outboundRepo.List(search, limit, offset)
}

func (s *OutboundService) GetByMaterialID(materialID int64) ([]model.OutboundRecord, error) {
	return s.outboundRepo.GetByMaterialID(materialID)
}

func (s *OutboundService) Delete(organizationID, id int64) error {
	// Get the outbound order with items
	order, err := s.outboundRepo.GetByID(id)
	if err != nil {
		return err
	}

	// 冲销必须在当前公司启用的库存维度上进行。
	scope, err := ResolveInventoryScope(organizationID, true)
	if err != nil {
		return err
	}

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

	// 按物料 ID 升序把库存加回，固定加锁顺序。
	itemIDs := make([]int64, len(order.Items))
	for i := range order.Items {
		itemIDs[i] = order.Items[i].MaterialID
	}
	for _, idx := range materialSortedIndexes(itemIDs) {
		item := order.Items[idx]
		err = s.stockRepo.UpdateStockTx(tx, scope, item.MaterialID, decimal.NewFromInt(int64(item.Quantity)))
		if err != nil {
			return err
		}
	}

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

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

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

	return nil
}

func (s *OutboundService) Update(organizationID, id int64, req *model.UpdateOutboundRequest, operator string) (*model.OutboundOrder, error) {
	// Get old order data
	oldOrder, err := s.outboundRepo.GetByID(id)
	if err != nil {
		return nil, err
	}

	// 库存维度由服务端按当前公司解析。
	scope, err := ResolveInventoryScope(organizationID, true)
	if err != nil {
		return nil, err
	}

	// Validate all new items first (outside transaction)
	for _, item := range req.Items {
		exists, err := s.materialSvc.Exists(organizationID, item.MaterialID)
		if err != nil {
			return nil, err
		}
		if !exists {
			return nil, ErrMaterialNotFound
		}
		active, err := s.materialSvc.IsActive(organizationID, item.MaterialID)
		if err != nil {
			return nil, err
		}
		if !active {
			return nil, ErrMaterialObsolete
		}

		currentStock, err := s.stockRepo.GetStock(scope, item.MaterialID)
		if err != nil {
			return nil, err
		}
		// Calculate effective stock: current + old outbound quantity - new outbound quantity
		oldQty := 0
		for _, oldItem := range oldOrder.Items {
			if oldItem.MaterialID == item.MaterialID {
				oldQty = oldItem.Quantity
				break
			}
		}
		effectiveStock := currentStock.Add(decimal.NewFromInt(int64(oldQty)))
		if effectiveStock.LessThan(decimal.NewFromInt(int64(item.Quantity))) {
			return nil, ErrInsufficientStock
		}
	}

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

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

	// Update order in repository
	// 客户端不能指定操作人；编辑也由当前登录用户接管操作人和兼容字段 handler。
	req.Handler = operator
	req.Operator = operator
	err = s.outboundRepo.UpdateTx(tx, id, req)
	if err != nil {
		return nil, err
	}

	// 旧明细（冲销）与新明细（扣减）合并后，按物料 ID 统一升序处理，逐物料先冲销旧量、
	// 再条件扣减新量。两个并发的 Update 即便交换物料（tx1 旧={5}→新={3}、tx2 旧={3}→新={5}），
	// 也会以相同的全局顺序加锁，不会反过来锁住彼此持有的行造成死锁。
	oldQtyByMaterial := make(map[int64]int)
	involved := make(map[int64]bool)
	for _, item := range oldOrder.Items {
		oldQtyByMaterial[item.MaterialID] += item.Quantity
		involved[item.MaterialID] = true
	}
	newItemIndexes := make(map[int64][]int)
	for i := range req.Items {
		materialID := req.Items[i].MaterialID
		newItemIndexes[materialID] = append(newItemIndexes[materialID], i)
		involved[materialID] = true
	}
	materialIDs := make([]int64, 0, len(involved))
	for materialID := range involved {
		materialIDs = append(materialIDs, materialID)
	}
	for _, idx := range materialSortedIndexes(materialIDs) {
		materialID := materialIDs[idx]
		if qty := oldQtyByMaterial[materialID]; qty > 0 {
			err = s.stockRepo.UpdateStockTx(tx, scope, materialID, decimal.NewFromInt(int64(qty)))
			if err != nil {
				return nil, err
			}
		}
		for _, i := range newItemIndexes[materialID] {
			item := req.Items[i]
			err = s.stockRepo.DeductStockTx(tx, scope, materialID, decimal.NewFromInt(int64(item.Quantity)))
			if err != nil {
				if errors.Is(err, repository.ErrInsufficientStock) {
					return nil, ErrInsufficientStock
				}
				return nil, err
			}

			stockLog := &model.StockLog{
				OrganizationID:   scope.OrganizationID,
				WarehouseID:      scope.WarehouseID,
				LocationID:       scope.LocationID,
				MaterialID:       materialID,
				Type:             "out",
				Quantity:         item.Quantity,
				RelatedOrderType: "outbound",
				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.outboundRepo.GetByID(id)
	if err != nil {
		return nil, err
	}
	updatedOrder.Status = "completed"

	return updatedOrder, nil
}