backend/internal/logic/fileStorage/upload_img_logic.go

package fileStorage

import (
	"backend/pkg/permission/domain/token"
	"context"
	"encoding/base64"
	"fmt"
	"strings"
	"time"

	"backend/internal/svc"
	"backend/internal/types"

	"github.com/google/uuid"
	"github.com/zeromicro/go-zero/core/logx"
)

type UploadImgLogic struct {
	logx.Logger
	ctx    context.Context
	svcCtx *svc.ServiceContext
}

// NewUploadImgLogic 上傳圖片檔案
func NewUploadImgLogic(ctx context.Context, svcCtx *svc.ServiceContext) *UploadImgLogic {
	return &UploadImgLogic{
		Logger: logx.WithContext(ctx),
		ctx:    ctx,
		svcCtx: svcCtx,
	}
}

func (l *UploadImgLogic) UploadImg(req *types.UploadImgReq) (resp *types.UploadResp, err error) {
	// 驗證 base64 格式
	content := req.Content
	if strings.HasPrefix(content, "data:image") {
		// 移除 data URL 前綴 (例如: data:image/png;base64,)
		parts := strings.SplitN(content, ",", 2)
		if len(parts) != 2 {
			return nil, fmt.Errorf("invalid base64 image format")
		}
		content = parts[1]
	}

	// 解碼 base64
	imgData, err := base64.StdEncoding.DecodeString(content)
	if err != nil {
		return nil, fmt.Errorf("failed to decode base64: %w", err)
	}

	// 驗證文件大小（10MB 限制）
	const maxImgSize = 10 << 20 // 10MB
	if len(imgData) > maxImgSize {
		return nil, fmt.Errorf("image size exceeds 10MB limit")
	}

	// 驗證圖片格式（檢查 magic bytes）
	mimeType, err := l.detectImageType(imgData)
	if err != nil {
		return nil, fmt.Errorf("invalid image format: %w", err)
	}

	// 生成唯一文件名
	fileExt := l.getExtensionFromMimeType(mimeType)
	fileName := fmt.Sprintf("%s%s", uuid.New().String(), fileExt)
	objectPath := fmt.Sprintf("images/%s/%d/%s", token.UID(l.ctx), time.Now().Year(), fileName)

	// 上傳到 S3
	fileStorageUC := l.svcCtx.FileStorageUC
	if err := fileStorageUC.UploadFromData(l.ctx, imgData, objectPath, mimeType); err != nil {
		return nil, fmt.Errorf("failed to upload image: %w", err)
	}

	// 獲取公開 URL
	fileUrl := fileStorageUC.GetPublicURL(l.ctx, objectPath)

	return &types.UploadResp{
		FileUrl:  fileUrl,
		FileSize: int64(len(imgData)),
		MimeType: mimeType,
	}, nil
}

// detectImageType 檢測圖片類型
func (l *UploadImgLogic) detectImageType(data []byte) (string, error) {
	if len(data) < 4 {
		return "", fmt.Errorf("file too small")
	}

	// 檢查常見圖片格式的 magic bytes
	if len(data) >= 2 && data[0] == 0xFF && data[1] == 0xD8 {
		return "image/jpeg", nil
	}
	if len(data) >= 8 && string(data[0:8]) == "\x89PNG\r\n\x1a\n" {
		return "image/png", nil
	}
	if len(data) >= 6 && (string(data[0:6]) == "GIF87a" || string(data[0:6]) == "GIF89a") {
		return "image/gif", nil
	}
	if len(data) >= 12 && string(data[8:12]) == "WEBP" {
		return "image/webp", nil
	}

	return "", fmt.Errorf("unsupported image format")
}

// getExtensionFromMimeType 根據 MIME 類型獲取文件擴展名
func (l *UploadImgLogic) getExtensionFromMimeType(mimeType string) string {
	switch mimeType {
	case "image/jpeg":
		return ".jpg"
	case "image/png":
		return ".png"
	case "image/gif":
		return ".gif"
	case "image/webp":
		return ".webp"
	default:
		return ".jpg"
	}
}