package usecase

import (
	"context"
	"math"

	"code.30cm.net/digimon/app-cloudep-product-service/pkg/domain/entity"
	"code.30cm.net/digimon/app-cloudep-product-service/pkg/domain/product"
	"code.30cm.net/digimon/app-cloudep-product-service/pkg/domain/repository"
	"code.30cm.net/digimon/app-cloudep-product-service/pkg/domain/usecase"
	"code.30cm.net/digimon/library-go/errs"
	"github.com/shopspring/decimal"
	"github.com/zeromicro/go-zero/core/logx"
)

type ProductItemUseCaseParam struct {
	ProductItems repository.ProductItemRepository
	TagRepo      repository.TagRepo
}

type ProductItemUseCase struct {
	ProductItemUseCaseParam
}

func MustProductItemUseCase(param ProductItemUseCaseParam) usecase.ProductItemUseCase {
	return &ProductItemUseCase{
		param,
	}
}

// --- 輔助函式 ---

// 將 usecase.ProductItems 轉換為 entity.ProductItems（用於 Create）
func toEntity(u *usecase.ProductItems) (entity.ProductItems, error) {
	// 將價格字串轉換為 decimal.Decimal
	priceDec, err := decimal.NewFromString(u.Price)
	if err != nil {
		return entity.ProductItems{}, err
	}

	return entity.ProductItems{
		// ID 在新增時通常由資料庫自動產生
		ReferenceID:      u.ReferenceID,
		Name:             u.Name,
		Description:      u.Description,
		ShortDescription: u.ShortDescription,
		IsUnLimit:        u.IsUnLimit,
		IsFree:           u.IsFree,
		Stock:            u.Stock,
		Price:            priceDec,
		SKU:              u.SKU,
		TimeSeries:       u.TimeSeries,
		Media:            convertMediaToEntity(u.Media),
		Status:           u.Status,
		Freight:          convertCustomFieldsToEntity(u.Freight),
		CustomFields:     convertCustomFieldsToEntity(u.CustomFields),
	}, nil
}

// 將 entity.ProductItems 轉換為 usecase.ProductItems（用於 Get 與 List）
func fromEntity(e *entity.ProductItems) *usecase.ProductItems {
	return &usecase.ProductItems{
		ID:               e.ID.Hex(),
		ReferenceID:      e.ReferenceID,
		Name:             e.Name,
		Description:      e.Description,
		ShortDescription: e.ShortDescription,
		IsUnLimit:        e.IsUnLimit,
		IsFree:           e.IsFree,
		Stock:            e.Stock,
		Price:            e.Price.String(),
		SKU:              e.SKU,
		TimeSeries:       e.TimeSeries,
		Media:            convertEntityMedia(e.Media),
		Status:           e.Status,
		Freight:          convertEntityCustomFields(e.Freight),
		CustomFields:     convertEntityCustomFields(e.CustomFields),
		SalesCount:       e.SalesCount,
		UpdatedAt:        e.UpdatedAt,
		CreatedAt:        e.CreatedAt,
	}
}

// Media 轉換：usecase.Media -> entity.Media
func convertMediaToEntity(meds []usecase.Media) []entity.Media {
	res := make([]entity.Media, len(meds))
	for i, m := range meds {
		res[i] = entity.Media{
			Sort: m.Sort,
			Type: m.Type,
			URL:  m.URL,
		}
	}

	return res
}

// Media 轉換：entity.Media -> usecase.Media
func convertEntityMedia(meds []entity.Media) []usecase.Media {
	res := make([]usecase.Media, len(meds))
	for i, m := range meds {
		res[i] = usecase.Media{
			Sort: m.Sort,
			Type: m.Type,
			URL:  m.URL,
		}
	}

	return res
}

// CustomFields 轉換：usecase.CustomFields -> entity.CustomFields
func convertCustomFieldsToEntity(cfs []usecase.CustomFields) []entity.CustomFields {
	res := make([]entity.CustomFields, len(cfs))
	for i, cf := range cfs {
		res[i] = entity.CustomFields{
			Key:   cf.Key,
			Value: cf.Value,
		}
	}

	return res
}

// CustomFields 轉換：entity.CustomFields -> usecase.CustomFields
func convertEntityCustomFields(cfs []entity.CustomFields) []usecase.CustomFields {
	res := make([]usecase.CustomFields, len(cfs))
	for i, cf := range cfs {
		res[i] = usecase.CustomFields{
			Key:   cf.Key,
			Value: cf.Value,
		}
	}

	return res
}

// --- 實作 ProductItemUseCase interface ---

func (use *ProductItemUseCase) Create(ctx context.Context, productItem *usecase.ProductItems) error {
	// 轉換成 entity 層型別
	ent, err := toEntity(productItem)
	if err != nil {
		return errs.InvalidFormatL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "product_id", Value: productItem},
				{Key: "func", Value: "ProductItemUseCase.Create"},
				{Key: "err", Value: err.Error()},
			}, "failed to change use case into entity")
	}

	err = use.ProductItemUseCaseParam.ProductItems.Insert(ctx, []entity.ProductItems{ent})
	if err != nil {
		return errs.DBErrorL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "req", Value: productItem},
				{Key: "func", Value: "ProductItemUseCaseParam.ProductItems.Insert"},
				{Key: "err", Value: err.Error()},
			}, "failed to insert product item")
	}

	return nil
}

func (use *ProductItemUseCase) Get(ctx context.Context, id string) (*usecase.ProductItems, error) {
	ent, err := use.ProductItemUseCaseParam.ProductItems.FindByID(ctx, id)
	if err != nil {
		return nil, errs.DBErrorL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "id", Value: id},
				{Key: "func", Value: "ProductItemUseCaseParam.ProductItems.FindByID"},
				{Key: "err", Value: err.Error()},
			}, "failed to create product items")
	}

	return fromEntity(ent), nil
}

func (use *ProductItemUseCase) DeleteByReferenceID(ctx context.Context, id string) error {
	err := use.ProductItems.DeleteByReferenceID(ctx, id)
	if err != nil {
		return errs.DBErrorL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "id", Value: id},
				{Key: "func", Value: "ProductItemUseCaseParam.ProductItems.DeleteByReferenceID"},
				{Key: "err", Value: err.Error()},
			}, "failed to delete product items")
	}
	return nil
}

func (use *ProductItemUseCase) Update(ctx context.Context, id string, data *usecase.UpdateProductItems) error {
	// 構建更新參數（僅更新部分欄位）
	update := &repository.ProductUpdateItem{}
	if data.Name != nil {
		update.Name = data.Name
	}
	if data.Description != nil {
		update.Description = data.Description
	}
	if data.ShortDescription != nil {
		update.ShortDescription = data.ShortDescription
	}
	if data.IsUnLimit != nil {
		update.IsUnLimit = data.IsUnLimit
	}
	if data.IsFree != nil {
		update.IsFree = data.IsFree
	}
	if data.Stock != nil {
		if *data.Stock > math.MaxInt64 {
			return errs.InvalidFormatL(logx.WithContext(ctx),
				[]logx.LogField{
					{Key: "id", Value: id},
					{Key: "data.Stock ", Value: *data.Stock},
				}, "data.Stock  too large to convert to int64")
		}
		// data.Stock 為 *uint64，需先解引用再轉換為 int64
		s := int64(*data.Stock)
		update.Stock = &s
	}
	if data.Price != nil {
		// data.Price 為 *string，需先解引用並轉換為 decimal.Decimal
		dec, err := decimal.NewFromString(*data.Price)
		if err != nil {
			return errs.InvalidFormat("failed to convert price to decimal")
		}
		update.Price = &dec
	}
	if data.SKU != nil {
		update.SKU = data.SKU
	}
	// 假設有 TimeSeries 欄位也需要更新（若有定義的話）
	if data.TimeSeries != nil {
		update.TimeSeries = data.TimeSeries
	}
	if len(data.Media) > 0 {
		update.Media = convertMediaToEntity(data.Media)
	}
	if len(data.CustomFields) > 0 {
		update.CustomFields = convertCustomFieldsToEntity(data.CustomFields)
	}
	if len(data.Freight) > 0 {
		update.Freight = convertCustomFieldsToEntity(data.Freight)
	}
	if err := use.ProductItemUseCaseParam.ProductItems.Update(ctx, id, update); err != nil {
		return errs.DBErrorL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "id", Value: id},
				{Key: "req", Value: data},
				{Key: "func", Value: "ProductItemUseCaseParam.ProductItems.Update"},
				{Key: "err", Value: err.Error()},
			}, "failed to update product item")
	}

	return nil
}

func (use *ProductItemUseCase) UpdateStatus(ctx context.Context, id string, status product.ItemStatus) error {
	err := use.ProductItemUseCaseParam.ProductItems.UpdateStatus(ctx, id, status)
	if err != nil {
		return errs.DBErrorL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "id", Value: id},
				{Key: "status", Value: status},
				{Key: "func", Value: "ProductItemUseCaseParam.ProductItems.UpdateStatus"},
				{Key: "err", Value: err.Error()},
			}, "failed to update product item status")
	}

	return nil
}

func (use *ProductItemUseCase) IncSalesCount(ctx context.Context, id string, saleCount uint64) error {
	if saleCount > math.MaxInt64 {
		return errs.InvalidFormatL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "id", Value: id},
				{Key: "saleCount", Value: saleCount},
			}, "saleCount too large to convert to int64")
	}
	// repository 方法使用 int64，故需轉型
	if err := use.ProductItemUseCaseParam.ProductItems.IncSalesCount(ctx, id, int64(saleCount)); err != nil {
		return errs.DBErrorL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "id", Value: id},
				{Key: "saleCount", Value: saleCount},
				{Key: "func", Value: "ProductItemUseCaseParam.ProductItems.IncSalesCount"},
				{Key: "err", Value: err.Error()},
			}, "failed to insert product item")
	}

	return nil
}

func (use *ProductItemUseCase) DecSalesCount(ctx context.Context, id string, saleCount uint64) error {
	if saleCount > math.MaxInt64 {
		return errs.InvalidFormatL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "id", Value: id},
				{Key: "saleCount", Value: saleCount},
			}, "saleCount too large to convert to int64")
	}

	if err := use.ProductItemUseCaseParam.ProductItems.DecSalesCount(ctx, id, int64(saleCount)); err != nil {
		return errs.DBErrorL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "id", Value: id},
				{Key: "saleCount", Value: saleCount},
				{Key: "func", Value: "ProductItemUseCaseParam.ProductItems.DecSalesCount"},
				{Key: "err", Value: err.Error()},
			}, "failed to Dec product item")
	}

	return nil
}

func (use *ProductItemUseCase) Delete(ctx context.Context, ids []string) error {
	// repository.Delete 接收 slice，因此將 id 放入 slice 中
	if err := use.ProductItemUseCaseParam.ProductItems.Delete(ctx, ids); err != nil {
		return errs.DBErrorL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "id", Value: ids},
				{Key: "func", Value: "ProductItemUseCaseParam.ProductItems.Delete"},
				{Key: "err", Value: err.Error()},
			}, "failed to delete product item")
	}

	return nil
}

func (use *ProductItemUseCase) List(ctx context.Context, filter usecase.QueryProductItemParam) ([]*usecase.ProductItems, int64, error) {
	repoQuery := repository.ProductItemQueryParams{
		PageSize:    filter.PageSize,
		PageIndex:   filter.PageIndex,
		ReferenceID: filter.ReferenceID,
		IsFree:      filter.IsFree,
		Status:      filter.Status,
		IsUnlimited: filter.IsUnLimit,
		// 注意：若需要依 IsUnLimit 過濾，需擴充 repository.ProductItemQueryParams 結構
	}
	entities, total, err := use.ProductItemUseCaseParam.ProductItems.ListProductItem(ctx, repoQuery)
	if err != nil {
		return nil, 0, errs.DBErrorL(logx.WithContext(ctx),
			[]logx.LogField{
				{Key: "filter", Value: filter},
				{Key: "func", Value: "ProductItemUseCaseParam.ProductItems.ListProductItem"},
				{Key: "err", Value: err.Error()},
			}, "failed to list product item")
	}
	result := make([]*usecase.ProductItems, 0, len(entities))
	for i := range entities {
		// 逐筆轉換 entity -> usecase 型別
		result = append(result, fromEntity(&entities[i]))
	}

	return result, total, nil
}