backend/internal/service/upload_service.go

package service

import (
	"bytes"
	"cmp"
	"context"
	"crypto/sha256"
	"fmt"
	"image"
	"image/jpeg"
	"image/png"
	"io"
	"mime"
	"mime/multipart"
	"net/http"
	"path/filepath"
	"strings"

	"carrot_bbs/internal/pkg/s3"

	"github.com/disintegration/imaging"
	"go.uber.org/zap"

	_ "golang.org/x/image/bmp"
	_ "golang.org/x/image/tiff"
)

// UploadService 上传服务
type UploadService struct {
	s3Client    *s3.Client
	userService UserService
}

// 预览图配置
const (
	PreviewMaxWidth  = 300 // 列表/网格模式最大宽度
	PreviewMaxHeight = 800 // 详情页最大高度
	PreviewQuality   = 70  // WebP 质量
)

// NewUploadService 创建上传服务
func NewUploadService(s3Client *s3.Client, userService UserService) *UploadService {
	return &UploadService{
		s3Client:    s3Client,
		userService: userService,
	}
}

// UploadImage 上传图片（返回原图URL和预览图URL）
func (s *UploadService) UploadImage(ctx context.Context, file *multipart.FileHeader) (string, string, string, error) {
	processedData, contentType, ext, err := prepareImageForUpload(file)
	if err != nil {
		return "", "", "", err
	}

	// 压缩后再计算哈希，确保同一压缩结果映射同一对象名
	hash := sha256.Sum256(processedData)
	hashStr := fmt.Sprintf("%x", hash)

	// 上传原图
	objectName := fmt.Sprintf("images/%s%s", hashStr, ext)
	url, err := s.s3Client.UploadData(ctx, objectName, processedData, contentType)
	if err != nil {
		return "", "", "", fmt.Errorf("failed to upload to S3: %w", err)
	}

	// 生成预览图
	previewURL, previewURLLarge, err := s.GeneratePreviewImages(ctx, processedData, hashStr)
	if err != nil {
		zap.L().Warn("Failed to generate preview images",
			zap.Error(err),
		)
	}

	return url, previewURL, previewURLLarge, nil
}

// getExtFromContentType 根据Content-Type获取文件扩展名
func getExtFromContentType(contentType string) string {
	baseType, _, err := mime.ParseMediaType(contentType)
	if err == nil && baseType != "" {
		contentType = baseType
	}

	switch contentType {
	case "image/jpg", "image/jpeg":
		return ".jpg"
	case "image/png":
		return ".png"
	case "image/gif":
		return ".gif"
	case "image/webp":
		return ".webp"
	case "image/bmp", "image/x-ms-bmp":
		return ".bmp"
	case "image/tiff":
		return ".tiff"
	default:
		return ""
	}
}

// UploadAvatar 上传头像
func (s *UploadService) UploadAvatar(ctx context.Context, userID string, file *multipart.FileHeader) (string, error) {
	processedData, contentType, ext, err := prepareImageForUpload(file)
	if err != nil {
		return "", err
	}

	// 压缩后再计算哈希
	hash := sha256.Sum256(processedData)
	hashStr := fmt.Sprintf("%x", hash)

	objectName := fmt.Sprintf("avatars/%s%s", hashStr, ext)

	url, err := s.s3Client.UploadData(ctx, objectName, processedData, contentType)
	if err != nil {
		return "", fmt.Errorf("failed to upload to S3: %w", err)
	}

	// 更新用户头像
	if s.userService != nil {
		user, err := s.userService.GetUserByID(ctx, userID)
		if err == nil && user != nil {
			user.Avatar = url
			err = s.userService.UpdateUser(ctx, user)
			if err != nil {
				// 更新失败不影响上传结果，只记录日志
				fmt.Printf("[UploadAvatar] failed to update user avatar: %v\n", err)
			}
		}
	}

	return url, nil
}

// UploadCover 上传头图（个人主页封面）
func (s *UploadService) UploadCover(ctx context.Context, userID string, file *multipart.FileHeader) (string, error) {
	processedData, contentType, ext, err := prepareImageForUpload(file)
	if err != nil {
		return "", err
	}

	// 压缩后再计算哈希
	hash := sha256.Sum256(processedData)
	hashStr := fmt.Sprintf("%x", hash)

	objectName := fmt.Sprintf("covers/%s%s", hashStr, ext)

	url, err := s.s3Client.UploadData(ctx, objectName, processedData, contentType)
	if err != nil {
		return "", fmt.Errorf("failed to upload to S3: %w", err)
	}

	// 更新用户头图
	if s.userService != nil {
		user, err := s.userService.GetUserByID(ctx, userID)
		if err == nil && user != nil {
			user.CoverURL = url
			err = s.userService.UpdateUser(ctx, user)
			if err != nil {
				// 更新失败不影响上传结果，只记录日志
				fmt.Printf("[UploadCover] failed to update user cover: %v\n", err)
			}
		}
	}

	return url, nil
}

// GetURL 获取文件URL
func (s *UploadService) GetURL(ctx context.Context, objectName string) (string, error) {
	return s.s3Client.GetURL(ctx, objectName)
}

// Delete 删除文件
func (s *UploadService) Delete(ctx context.Context, objectName string) error {
	return s.s3Client.Delete(ctx, objectName)
}

func prepareImageForUpload(file *multipart.FileHeader) ([]byte, string, string, error) {
	f, err := file.Open()
	if err != nil {
		return nil, "", "", fmt.Errorf("failed to open file: %w", err)
	}
	defer f.Close()

	originalData, err := io.ReadAll(f)
	if err != nil {
		return nil, "", "", fmt.Errorf("failed to read file: %w", err)
	}

	// 优先从文件字节探测真实类型，避免前端压缩/转码后 header 与实际格式不一致
	detectedType := normalizeImageContentType(http.DetectContentType(originalData))
	headerType := normalizeImageContentType(file.Header.Get("Content-Type"))
	contentType := cmp.Or(detectedType, headerType, "application/octet-stream")

	compressedData, compressedType, err := compressImageData(originalData, contentType)
	if err != nil {
		// 压缩失败时回退到原图，保证上传可用性
		compressedData = originalData
		compressedType = contentType
	}

	compressedType = cmp.Or(compressedType, http.DetectContentType(compressedData))

	ext := cmp.Or(getExtFromContentType(compressedType), strings.ToLower(filepath.Ext(file.Filename)), ".jpg")

	return compressedData, compressedType, ext, nil
}

func compressImageData(data []byte, contentType string) ([]byte, string, error) {
	contentType = normalizeImageContentType(contentType)

	// GIF/WebP 等格式先保留原图，避免动画和透明通道丢失
	if contentType == "image/gif" || contentType == "image/webp" {
		return data, contentType, nil
	}

	if contentType != "image/jpeg" &&
		contentType != "image/png" &&
		contentType != "image/bmp" &&
		contentType != "image/x-ms-bmp" &&
		contentType != "image/tiff" {
		return data, contentType, nil
	}

	img, _, err := image.Decode(bytes.NewReader(data))
	if err != nil {
		return nil, "", fmt.Errorf("failed to decode image: %w", err)
	}

	var buf bytes.Buffer
	switch contentType {
	case "image/png":
		encoder := png.Encoder{CompressionLevel: png.BestCompression}
		if err := encoder.Encode(&buf, img); err != nil {
			return nil, "", fmt.Errorf("failed to encode png: %w", err)
		}
		return buf.Bytes(), "image/png", nil
	default:
		// BMP/TIFF 等无损大图统一压缩为 JPEG，控制体积
		if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: 82}); err != nil {
			return nil, "", fmt.Errorf("failed to encode jpeg: %w", err)
		}
		return buf.Bytes(), "image/jpeg", nil
	}
}

func normalizeImageContentType(contentType string) string {
	if contentType == "" {
		return ""
	}

	baseType, _, err := mime.ParseMediaType(contentType)
	if err == nil && baseType != "" {
		contentType = baseType
	}

	switch strings.ToLower(contentType) {
	case "image/jpg":
		return "image/jpeg"
	case "image/jpeg":
		return "image/jpeg"
	case "image/png":
		return "image/png"
	case "image/gif":
		return "image/gif"
	case "image/webp":
		return "image/webp"
	case "image/bmp", "image/x-ms-bmp":
		return "image/bmp"
	case "image/tiff":
		return "image/tiff"
	default:
		return contentType
	}
}

// GeneratePreviewImages 生成预览图
func (s *UploadService) GeneratePreviewImages(ctx context.Context, originalData []byte, hash string) (previewURL, previewURLLarge string, err error) {
	img, _, err := image.Decode(bytes.NewReader(originalData))
	if err != nil {
		return "", "", fmt.Errorf("failed to decode image: %w", err)
	}

	bounds := img.Bounds()
	originalWidth := bounds.Dx()
	originalHeight := bounds.Dy()

	// 生成普通预览图（列表/网格模式）
	previewURL, err = s.generatePreview(ctx, img, originalWidth, originalHeight, "preview", PreviewMaxWidth, hash)
	if err != nil {
		zap.L().Warn("Failed to generate preview",
			zap.Error(err),
		)
	}

	// 生成大预览图（详情页）
	previewURLLarge, err = s.generatePreview(ctx, img, originalWidth, originalHeight, "large", PreviewMaxHeight, hash)
	if err != nil {
		zap.L().Warn("Failed to generate large preview",
			zap.Error(err),
		)
	}

	return previewURL, previewURLLarge, nil
}

// generatePreview 生成单个预览图
func (s *UploadService) generatePreview(ctx context.Context, img image.Image, originalWidth, originalHeight int, mode string, maxDim int, hash string) (string, error) {
	var targetWidth, targetHeight int

	// 计算目标尺寸
	if originalWidth > originalHeight {
		// 宽图：按宽度缩放
		if originalWidth > maxDim {
			targetWidth = maxDim
			targetHeight = int(float64(originalHeight) * float64(maxDim) / float64(originalWidth))
		} else {
			return "", nil // 图片足够小，不需要生成预览图
		}
	} else {
		// 高图：按高度缩放
		if originalHeight > maxDim {
			targetHeight = maxDim
			targetWidth = int(float64(originalWidth) * float64(maxDim) / float64(originalHeight))
		} else {
			return "", nil // 图片足够小，不需要生成预览图
		}
	}

	// 缩放图片（使用高质量 Lanczos 算法）
	scaledImg := imaging.Resize(img, targetWidth, targetHeight, imaging.Lanczos)

	// 编码为 JPEG（WebP 在某些设备上可能不支持，使用 JPEG 保证兼容性）
	var buf bytes.Buffer
	if err := jpeg.Encode(&buf, scaledImg, &jpeg.Options{Quality: PreviewQuality}); err != nil {
		return "", fmt.Errorf("failed to encode jpeg: %w", err)
	}

	// 构建对象名：thumbnails/{hash}_{mode}.jpg
	objectName := fmt.Sprintf("thumbnails/%s_%s.jpg", hash, mode)

	// 上传到 S3
	url, err := s.s3Client.UploadData(ctx, objectName, buf.Bytes(), "image/jpeg")
	if err != nil {
		return "", fmt.Errorf("failed to upload preview: %w", err)
	}

	return url, nil
}