backend/internal/service/upload_service.go

package service

import (
	"carrotskin/pkg/storage"
	"context"
	"fmt"
	"path/filepath"
	"strings"
	"time"
)

// FileType 文件类型枚举
type FileType string

const (
	FileTypeAvatar  FileType = "avatar"
	FileTypeTexture FileType = "texture"
)

// UploadConfig 上传配置
type UploadConfig struct {
	AllowedExts map[string]bool // 允许的文件扩展名
	MinSize     int64           // 最小文件大小（字节）
	MaxSize     int64           // 最大文件大小（字节）
	Expires     time.Duration   // URL过期时间
}

// GetUploadConfig 根据文件类型获取上传配置
func GetUploadConfig(fileType FileType) *UploadConfig {
	switch fileType {
	case FileTypeAvatar:
		return &UploadConfig{
			AllowedExts: map[string]bool{
				".jpg":  true,
				".jpeg": true,
				".png":  true,
				".gif":  true,
				".webp": true,
			},
			MinSize: 1024,            // 1KB
			MaxSize: 5 * 1024 * 1024, // 5MB
			Expires: 15 * time.Minute,
		}
	case FileTypeTexture:
		return &UploadConfig{
			AllowedExts: map[string]bool{
				".png": true,
			},
			MinSize: 1024,             // 1KB
			MaxSize: 10 * 1024 * 1024, // 10MB
			Expires: 15 * time.Minute,
		}
	default:
		return nil
	}
}

// ValidateFileName 验证文件名
func ValidateFileName(fileName string, fileType FileType) error {
	if fileName == "" {
		return fmt.Errorf("文件名不能为空")
	}
	
	uploadConfig := GetUploadConfig(fileType)
	if uploadConfig == nil {
		return fmt.Errorf("不支持的文件类型")
	}
	
	ext := strings.ToLower(filepath.Ext(fileName))
	if !uploadConfig.AllowedExts[ext] {
		return fmt.Errorf("不支持的文件格式: %s", ext)
	}
	
	return nil
}

// uploadStorageClient 为上传服务定义的最小依赖接口，便于单元测试注入 mock
type uploadStorageClient interface {
	GetBucket(name string) (string, error)
	GeneratePresignedPostURL(ctx context.Context, bucketName, objectName string, minSize, maxSize int64, expires time.Duration) (*storage.PresignedPostPolicyResult, error)
}

// GenerateAvatarUploadURL 生成头像上传URL（对外导出）
func GenerateAvatarUploadURL(ctx context.Context, storageClient *storage.StorageClient, userID int64, fileName string) (*storage.PresignedPostPolicyResult, error) {
	return generateAvatarUploadURLWithClient(ctx, storageClient, userID, fileName)
}

// generateAvatarUploadURLWithClient 使用接口类型的内部实现，方便测试
func generateAvatarUploadURLWithClient(ctx context.Context, storageClient uploadStorageClient, userID int64, fileName string) (*storage.PresignedPostPolicyResult, error) {
	// 1. 验证文件名
	if err := ValidateFileName(fileName, FileTypeAvatar); err != nil {
		return nil, err
	}

	// 2. 获取上传配置
	uploadConfig := GetUploadConfig(FileTypeAvatar)

	// 3. 获取存储桶名称
	bucketName, err := storageClient.GetBucket("avatars")
	if err != nil {
		return nil, fmt.Errorf("获取存储桶失败: %w", err)
	}

	// 4. 生成对象名称（路径）
	// 格式: user_{userId}/timestamp_{originalFileName}
	timestamp := time.Now().Format("20060102150405")
	objectName := fmt.Sprintf("user_%d/%s_%s", userID, timestamp, fileName)

	// 5. 生成预签名POST URL (使用存储客户端内置的 PublicURL)
	result, err := storageClient.GeneratePresignedPostURL(
		ctx,
		bucketName,
		objectName,
		uploadConfig.MinSize,
		uploadConfig.MaxSize,
		uploadConfig.Expires,
	)
	if err != nil {
		return nil, fmt.Errorf("生成上传URL失败: %w", err)
	}

	return result, nil
}

// GenerateTextureUploadURL 生成材质上传URL（对外导出）
func GenerateTextureUploadURL(ctx context.Context, storageClient *storage.StorageClient, userID int64, fileName, textureType string) (*storage.PresignedPostPolicyResult, error) {
	return generateTextureUploadURLWithClient(ctx, storageClient, userID, fileName, textureType)
}

// generateTextureUploadURLWithClient 使用接口类型的内部实现，方便测试
func generateTextureUploadURLWithClient(ctx context.Context, storageClient uploadStorageClient, userID int64, fileName, textureType string) (*storage.PresignedPostPolicyResult, error) {
	// 1. 验证文件名
	if err := ValidateFileName(fileName, FileTypeTexture); err != nil {
		return nil, err
	}

	// 2. 验证材质类型
	if textureType != "SKIN" && textureType != "CAPE" {
		return nil, fmt.Errorf("无效的材质类型: %s", textureType)
	}

	// 3. 获取上传配置
	uploadConfig := GetUploadConfig(FileTypeTexture)

	// 4. 获取存储桶名称
	bucketName, err := storageClient.GetBucket("textures")
	if err != nil {
		return nil, fmt.Errorf("获取存储桶失败: %w", err)
	}

	// 5. 生成对象名称（路径）
	// 格式: user_{userId}/{textureType}/timestamp_{originalFileName}
	timestamp := time.Now().Format("20060102150405")
	textureTypeFolder := strings.ToLower(textureType)
	objectName := fmt.Sprintf("user_%d/%s/%s_%s", userID, textureTypeFolder, timestamp, fileName)

	// 6. 生成预签名POST URL (使用存储客户端内置的 PublicURL)
	result, err := storageClient.GeneratePresignedPostURL(
		ctx,
		bucketName,
		objectName,
		uploadConfig.MinSize,
		uploadConfig.MaxSize,
		uploadConfig.Expires,
	)
	if err != nil {
		return nil, fmt.Errorf("生成上传URL失败: %w", err)
	}

	return result, nil
}