package service

import (
	"context"
	"fmt"
	"io"
	"log/slog"
	"mime/multipart"
	"time"

	"go.opentelemetry.io/otel/trace"

	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/global"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/dto"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/mysqldao"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/mysqlmodel"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/pkg/classification"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/pkg/errcode"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/pkg/matting"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/pkg/upload"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// imageProcessSem 限制异步抠图处理的并发数，避免瞬时大量上传打满下游抠图/分类服务。
var imageProcessSem = make(chan struct{}, 10)

// ClothesService 衣物业务服务。
type ClothesService struct {
	clothesDao *mysqldao.ClothesDao
	userDao    *mysqldao.UserDao
}

// NewClothesService 创建衣物服务。
func NewClothesService() *ClothesService {
	return &ClothesService{
		clothesDao: mysqldao.NewClothesDao(),
		userDao:    mysqldao.NewUserDao(),
	}
}

// Upload 上传衣物图片：同步完成校验、扣额度、建记录后立即返回，
// 抠图与分类在后台 goroutine 异步执行并回填状态。
func (s *ClothesService) Upload(ctx context.Context, userID int64, fileHeader *multipart.FileHeader) (*dto.ClothesUploadResponse, *errcode.Error) {
	ctx, span := global.Tracer.Start(ctx, "svc.ClothesUpload")
	defer span.End()

	if fileHeader == nil || fileHeader.Size == 0 {
		return nil, errcode.UploadFileEmpty
	}

	// 1. 校验扩展名与大小。
	ext := upload.FileGetExt(fileHeader.Filename)
	if !upload.FileCheckAllowExt(ext, global.UploadSetting.AllowedExtensions) {
		return nil, errcode.UploadFileExtNotAllow
	}
	if !upload.FileCheckMaxSize(fileHeader.Size, int64(global.UploadSetting.MaxSizeMB)) {
		return nil, errcode.UploadFileTooLarge
	}

	// 2. 读取原图字节（必须同步读取，请求返回后 multipart 临时文件会被清理）。
	src, oerr := fileHeader.Open()
	if oerr != nil {
		return nil, errcode.UploadFileSaveFailed
	}
	imageData, rerr := io.ReadAll(src)
	_ = src.Close()
	if rerr != nil {
		return nil, errcode.UploadFileSaveFailed
	}

	// 3. 校验文件内容为真实图片（magic bytes），防止伪造扩展名上传恶意文件。
	if !upload.FileCheckImageMagic(imageData) {
		return nil, errcode.UploadFileExtNotAllow
	}

	// 4. 扣减 COS 上传额度（权威扣减，先到期凭证先用，再扣免费额度）。
	if qerr := consumeCosQuota(ctx, userID, 1, 0, "上传衣物消耗"); qerr != nil {
		return nil, qerr
	}

	// 5. 创建衣物记录，初始状态为排队中。
	clothesUUID := genUUID()
	clothes := &mysqlmodel.Clothes{
		ClothesUUID:        clothesUUID,
		UserID:             userID,
		ImageSize:          fileHeader.Size / 1024,
		ImageProcessStatus: ImageProcessQueuing,
	}
	if err := s.clothesDao.ClothesCreate(ctx, clothes); err != nil {
		// 建记录失败，回退已扣额度。
		refundCosQuota(ctx, userID, 1, 0, "上传失败回退")
		return nil, errcode.ClothesCreateFailed
	}

	// 6. 异步抠图 + 分类。
	go s.processImageAsync(ctx, userID, clothesUUID, imageData)

	return &dto.ClothesUploadResponse{
		ClothesUUID:        clothesUUID,
		ImageProcessStatus: clothes.ImageProcessStatus,
	}, nil
}

// processImageAsync 后台执行抠图、上传 COS、分类，并回填衣物记录。
func (s *ClothesService) processImageAsync(parentCtx context.Context, userID int64, clothesUUID string, imageData []byte) {
	// 限流：获取信号量，超出并发上限时阻塞等待。
	imageProcessSem <- struct{}{}
	defer func() { <-imageProcessSem }()

	// 派生独立 ctx：继承父 trace 信息，但切断取消信号，避免复用已结束的请求 ctx。
	ctx, cancel := context.WithTimeout(trace.ContextWithSpanContext(context.Background(), trace.SpanContextFromContext(parentCtx)), 3*time.Minute)
	defer cancel()

	ctx, span := global.Tracer.Start(ctx, "svc.ClothesProcessImageAsync")
	defer span.End()

	defer func() {
		if r := recover(); r != nil {
			slog.ErrorContext(ctx, "clothes image process panic", "clothes_uuid", clothesUUID, "recover", r)
			s.markProcessFailed(ctx, userID, clothesUUID, "内部错误")
		}
	}()

	dao := s.clothesDao

	// 1. 抠图。
	_ = dao.ClothesUpdateByUUID(ctx, clothesUUID, map[string]any{"image_process_status": ImageProcessMatting})
	mattingClient := matting.NewClient()
	processedData, err := retryCall(ctx, global.MattingModelSetting.MaxRetry, "matting", func() ([]byte, error) {
		return mattingClient.Matting(ctx, imageData)
	})
	if err != nil {
		slog.ErrorContext(ctx, "matting failed", "clothes_uuid", clothesUUID, "error", err)
		s.markProcessFailed(ctx, userID, clothesUUID, "图片抠图失败")
		return
	}

	// 2. 处理结果落临时目录并上传 COS。对象键结构：用户UUID/用户ID/图片文件名。
	processedName := genUUID() + ".png"
	// 获取用户 UUID，作为 COS 对象键第一层（uuid/userid/图片）。
	user, gerr := s.userDao.UserGetByID(ctx, userID)
	if gerr != nil {
		slog.ErrorContext(ctx, "get user for cos key failed", "clothes_uuid", clothesUUID, "error", gerr)
		s.markProcessFailed(ctx, userID, clothesUUID, "获取用户信息失败")
		return
	}
	subDir := fmt.Sprintf("%s/%d", user.UserUUID, userID)
	if _, serr := upload.FileSaveTmpBytes(ctx, processedData, processedName, subDir); serr != nil {
		slog.ErrorContext(ctx, "save processed image failed", "clothes_uuid", clothesUUID, "error", serr)
		s.markProcessFailed(ctx, userID, clothesUUID, "图片保存失败")
		return
	}
	cosKey := fmt.Sprintf("%s/%s", subDir, processedName)
	if uerr := upload.FileUploadCos(ctx, cosKey); uerr != nil {
		slog.ErrorContext(ctx, "upload processed image to cos failed", "clothes_uuid", clothesUUID, "error", uerr)
		s.markProcessFailed(ctx, userID, clothesUUID, "图片上传失败")
		return
	}

	// 上传成功后回填前检查衣物是否仍存在：用户可能在处理期间删除衣物，
	// 若已删除则清理刚上传的对象，避免 COS 残留（额度已由删除事务回退，无需再处理）。
	if _, gerr := dao.ClothesGetByUUID(ctx, clothesUUID); isNotFound(gerr) {
		if derr := upload.FileDeleteCos(ctx, cosKey); derr != nil {
			slog.ErrorContext(ctx, "delete orphan cos image failed", "clothes_uuid", clothesUUID, "cos_key", cosKey, "error", derr)
		}
		slog.InfoContext(ctx, "clothes deleted during processing, cleaned uploaded image", "clothes_uuid", clothesUUID)
		return
	}

	// 3. 分类。
	_ = dao.ClothesUpdateByUUID(ctx, clothesUUID, map[string]any{"image_process_status": ImageProcessClassifying})
	classifyClient := classification.NewClient()
	result, cerr := retryCall(ctx, global.ClassificationModelSetting.MaxRetry, "classify", func() (*classification.ClassifyResult, error) {
		return classifyClient.Classify(ctx, processedData)
	})
	if cerr != nil {
		slog.ErrorContext(ctx, "classify failed", "clothes_uuid", clothesUUID, "error", cerr)
		// 分类失败仍保留已抠图结果，但条件标记失败并回退以便用户手动补全。
		_ = dao.ClothesUpdateByUUID(ctx, clothesUUID, map[string]any{"processed_image": cosKey})
		s.markProcessFailed(ctx, userID, clothesUUID, "图片分类失败")
		return
	}

	// 4. 回填分类结果与处理后图片，标记成功。注意主色列名为 color。
	updates := map[string]any{
		"category_main":        result.CategoryMain,
		"category_sub":         result.CategorySub,
		"style":                result.Style,
		"name":                 buildDefaultClothesName(result),
		"color":                result.ColorMain,
		"color_sub":            result.ColorSub,
		"thickness":            result.Thickness,
		"version":              result.Version,
		"material":             result.Material,
		"pattern":              result.Pattern,
		"sleeve_type":          result.SleeveType,
		"clothes_type":         result.ClothesType,
		"neckline_type":        result.NecklineType,
		"formality":            result.Formality,
		"occasions":            result.Occasions,
		"visual_impact":        result.VisualImpact,
		"processed_image":      cosKey,
		"image_process_status": ImageProcessSuccess,
		"fail_reason":          "",
	}
	if uerr := dao.ClothesUpdateByUUID(ctx, clothesUUID, updates); uerr != nil {
		slog.ErrorContext(ctx, "update clothes after classify failed", "clothes_uuid", clothesUUID, "error", uerr)
	}
}

// buildDefaultClothesName 根据分类结果生成衣服默认名称（风格+小类+大类，空字段跳过）。
func buildDefaultClothesName(result *classification.ClassifyResult) string {
	name := ""
	if result.Style != "" {
		name += result.Style
	}
	if result.CategorySub != "" {
		name += result.CategorySub
	}
	if result.CategoryMain != "" {
		name += result.CategoryMain
	}
	return name
}

// retryCall 对 fn 进行最多 maxRetry 次额外重试（总尝试 maxRetry+1 次）。
// 重试间隔 1s；ctx 到期则提前终止并返回 ctx.Err()。
func retryCall[T any](ctx context.Context, maxRetry int, name string, fn func() (T, error)) (T, error) {
	var zero T
	var err error
	for attempt := 0; attempt <= maxRetry; attempt++ {
		result, e := fn()
		if e == nil {
			return result, nil
		}
		err = e
		if attempt >= maxRetry {
			break
		}
		slog.WarnContext(ctx, "model call failed, retrying", "name", name, "attempt", attempt+1, "error", e)
		select {
		case <-ctx.Done():
			return zero, ctx.Err()
		case <-time.After(time.Second):
		}
	}
	return zero, err
}

// markProcessFailed 标记处理失败并回退上传额度。
// 单事务（行锁 -> 置失败 -> 回退额度 + 写流水），与删除事务（FOR UPDATE）通过行锁互斥：
// 两路径串行化保证「处理失败回退」与「删除回退」恰好执行一次，消除漏退/双退窗口。
func (s *ClothesService) markProcessFailed(ctx context.Context, userID int64, clothesUUID, reason string) {
	vipExpire := getUserVIPExpire(ctx, userID)
	err := global.MysqlEngine.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var c mysqlmodel.Clothes
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
			Where("clothes_uuid = ?", clothesUUID).
			First(&c).Error; err != nil {
			if isNotFound(err) {
				// 衣物已删除：删除事务已回退额度，跳过。
				return nil
			}
			return err
		}
		// 已是失败态：说明失败回退已处理过，跳过。
		if c.ImageProcessStatus == ImageProcessFailed {
			return nil
		}

		// 置失败。
		if err := tx.Model(&mysqlmodel.Clothes{}).
			Where("clothes_uuid = ?", clothesUUID).
			Updates(map[string]any{"image_process_status": ImageProcessFailed, "fail_reason": reason}).Error; err != nil {
			return err
		}

		// 同事务回退额度（优先免费额度，不足回退凭证）。
		return refundCosQuotaTx(tx, userID, vipExpire, 1, 0, "衣物处理失败回退")
	})
	if err != nil {
		slog.ErrorContext(ctx, "mark process failed transaction error", "clothes_uuid", clothesUUID, "error", err)
	}
}

// ProcessStatusGetByUUID 查询衣物图片处理状态。
func (s *ClothesService) ProcessStatusGetByUUID(ctx context.Context, userID int64, request *dto.ClothesProcessStatusGetByUUIDRequest) (*dto.ClothesProcessStatusGetByUUIDResponse, *errcode.Error) {
	ctx, span := global.Tracer.Start(ctx, "svc.ClothesProcessStatusGetByUUID")
	defer span.End()

	clothes, cerr := s.getOwnedClothes(ctx, request.ClothesUUID, userID)
	if cerr != nil {
		return nil, cerr
	}
	return &dto.ClothesProcessStatusGetByUUIDResponse{
		ImageProcessStatus: clothes.ImageProcessStatus,
		FailReason:         clothes.FailReason,
	}, nil
}

// GetByUUID 获取衣物详情。
func (s *ClothesService) GetByUUID(ctx context.Context, userID int64, request *dto.ClothesGetByUUIDRequest) (*dto.ClothesGetByUUIDResponse, *errcode.Error) {
	ctx, span := global.Tracer.Start(ctx, "svc.ClothesGetByUUID")
	defer span.End()

	clothes, cerr := s.getOwnedClothes(ctx, request.ClothesUUID, userID)
	if cerr != nil {
		return nil, cerr
	}
	response := buildClothesResponse(clothes)
	return &response, nil
}

// UpdateByUUID 修改衣物属性（仅更新非空字段）。
func (s *ClothesService) UpdateByUUID(ctx context.Context, userID int64, request *dto.ClothesUpdateByUUIDRequest) (*dto.ClothesUpdateByUUIDResponse, *errcode.Error) {
	ctx, span := global.Tracer.Start(ctx, "svc.ClothesUpdateByUUID")
	defer span.End()

	if _, cerr := s.getOwnedClothes(ctx, request.ClothesUUID, userID); cerr != nil {
		return nil, cerr
	}

	updates := map[string]any{}
	setIfNotEmpty(updates, "category_main", request.CategoryMain)
	setIfNotEmpty(updates, "category_sub", request.CategorySub)
	setIfNotEmpty(updates, "style", request.Style)
	setIfNotEmpty(updates, "color", request.ColorMain) // 主色列名为 color
	setIfNotEmpty(updates, "color_sub", request.ColorSub)
	setIfNotEmpty(updates, "thickness", request.Thickness)
	setIfNotEmpty(updates, "version", request.Version)
	setIfNotEmpty(updates, "material", request.Material)
	setIfNotEmpty(updates, "pattern", request.Pattern)
	setIfNotEmpty(updates, "sleeve_type", request.SleeveType)
	setIfNotEmpty(updates, "clothes_type", request.ClothesType)
	setIfNotEmpty(updates, "neckline_type", request.NecklineType)
	setIfNotEmpty(updates, "formality", request.Formality)
	setIfNotEmpty(updates, "occasions", request.Occasions)
	setIfNotEmpty(updates, "visual_impact", request.VisualImpact)
	setIfNotEmpty(updates, "name", request.Name)
	setIfNotEmpty(updates, "remark", request.Remark)

	if len(updates) == 0 {
		return &dto.ClothesUpdateByUUIDResponse{}, nil
	}
	if err := s.clothesDao.ClothesUpdateByUUID(ctx, request.ClothesUUID, updates); err != nil {
		return nil, errcode.ClothesUpdateFailed
	}
	return &dto.ClothesUpdateByUUIDResponse{}, nil
}

// DeleteByUUID 删除衣物（软删除）。
func (s *ClothesService) DeleteByUUID(ctx context.Context, userID int64, request *dto.ClothesDeleteByUUIDRequest) (*dto.ClothesDeleteByUUIDResponse, *errcode.Error) {
	ctx, span := global.Tracer.Start(ctx, "svc.ClothesDeleteByUUID")
	defer span.End()

	if _, cerr := s.getOwnedClothes(ctx, request.ClothesUUID, userID); cerr != nil {
		return nil, cerr
	}

	// 事务内锁定衣物行 -> 读最新状态 -> 软删除 -> 条件回退额度 -> 写回退流水，
	// 数值变更与流水同事务强一致，并避免与异步处理失败回退并发导致漏退/双退。
	vipExpire := getUserVIPExpire(ctx, userID)
	var processedImage string
	err := global.MysqlEngine.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var c mysqlmodel.Clothes
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
			Where("clothes_uuid = ?", request.ClothesUUID).
			First(&c).Error; err != nil {
			return err
		}
		processedImage = c.ProcessedImage
		if err := tx.Where("clothes_uuid = ?", request.ClothesUUID).Delete(&mysqlmodel.Clothes{}).Error; err != nil {
			return err
		}
		// 失败状态已在处理失败路径回退，不再回退，避免双重回退。
		if c.ImageProcessStatus == ImageProcessFailed {
			return nil
		}
		// 同事务回退额度（优先免费额度，不足回退凭证）。
		return refundCosQuotaTx(tx, userID, vipExpire, 1, 0, "删除衣物回退")
	})
	if err != nil {
		if isNotFound(err) {
			return nil, errcode.ClothesNotFound
		}
		return nil, errcode.ClothesDeleteFailed
	}

	// 事务提交成功后清理 COS 图片（尽力而为，失败仅记录日志，不影响删除结果）。
	if processedImage != "" {
		if derr := upload.FileDeleteCos(ctx, processedImage); derr != nil {
			slog.WarnContext(ctx, "delete clothes cos image failed", "clothes_uuid", request.ClothesUUID, "cos_key", processedImage, "error", derr)
		}
	}

	return &dto.ClothesDeleteByUUIDResponse{}, nil
}

// List 分页查询用户衣物。
func (s *ClothesService) List(ctx context.Context, userID int64, request *dto.ClothesListRequest) (*dto.ClothesListResponse, *errcode.Error) {
	ctx, span := global.Tracer.Start(ctx, "svc.ClothesList")
	defer span.End()

	page, pageSize := normalizePage(request.Page, request.PageSize)

	list, total, err := s.clothesDao.ClothesListByUserID(ctx, userID, request.CategoryMain, request.CategorySub, page, pageSize)
	if err != nil {
		return nil, errcode.DatabaseError
	}

	items := make([]dto.ClothesGetByUUIDResponse, 0, len(list))
	for i := range list {
		items = append(items, buildClothesResponse(&list[i]))
	}

	return &dto.ClothesListResponse{
		PageResponse: dto.PageResponse{Total: total, Page: page, PageSize: pageSize},
		List:         items,
	}, nil
}

// getOwnedClothes 查询衣物并校验归属。
func (s *ClothesService) getOwnedClothes(ctx context.Context, clothesUUID string, userID int64) (*mysqlmodel.Clothes, *errcode.Error) {
	clothes, err := s.clothesDao.ClothesGetByUUID(ctx, clothesUUID)
	if err != nil {
		if isNotFound(err) {
			return nil, errcode.ClothesNotFound
		}
		return nil, errcode.DatabaseError
	}
	if clothes.UserID != userID {
		return nil, errcode.ClothesNoPermission
	}
	return clothes, nil
}

// buildClothesResponse 将衣物模型映射为响应，processed_image 转为可访问 URL。
func buildClothesResponse(c *mysqlmodel.Clothes) dto.ClothesGetByUUIDResponse {
	processed := c.ProcessedImage
	if processed != "" {
		processed = upload.GetCosUrl(processed)
	}
	return dto.ClothesGetByUUIDResponse{
		ClothesUUID:    c.ClothesUUID,
		CategoryMain:   c.CategoryMain,
		CategorySub:    c.CategorySub,
		Style:          c.Style,
		ColorMain:      c.ColorMain,
		ColorSub:       c.ColorSub,
		Thickness:      c.Thickness,
		Version:        c.Version,
		Material:       c.Material,
		Pattern:        c.Pattern,
		SleeveType:     c.SleeveType,
		ClothesType:    c.ClothesType,
		NecklineType:   c.NecklineType,
		Formality:      c.Formality,
		Occasions:      c.Occasions,
		VisualImpact:   c.VisualImpact,
		Name:           c.Name,
		Remark:         c.Remark,
		ProcessedImage: processed,
	}
}

// setIfNotEmpty 当值非空时写入 updates map。
func setIfNotEmpty(m map[string]any, key, val string) {
	if val != "" {
		m[key] = val
	}
}