backend/pkg/storage/minio.go

package storage

import (
	"context"
	"fmt"
	"io"
	"net/url"
	"strings"
	"time"

	"carrotskin/pkg/config"

	"github.com/minio/minio-go/v7"
	"github.com/minio/minio-go/v7/pkg/credentials"
)

// StorageClient S3兼容对象存储客户端包装 (支持RustFS、MinIO等)
type StorageClient struct {
	client    *minio.Client
	buckets   map[string]string
	publicURL string // 公开访问URL前缀
}

// NewStorage 创建新的对象存储客户端 (S3兼容，支持RustFS)
func NewStorage(cfg config.RustFSConfig) (*StorageClient, error) {
	// 创建S3兼容客户端
	// minio-go SDK支持所有S3兼容的存储，包括RustFS
	// 不指定Region，让SDK自动检测
	client, err := minio.New(cfg.Endpoint, &minio.Options{
		Creds:  credentials.NewStaticV4(cfg.AccessKey, cfg.SecretKey, ""),
		Secure: cfg.UseSSL,
	})
	if err != nil {
		return nil, fmt.Errorf("创建对象存储客户端失败: %w", err)
	}

	// 测试连接（如果AccessKey和SecretKey为空，跳过测试）
	if cfg.AccessKey != "" && cfg.SecretKey != "" {
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()

		_, err = client.ListBuckets(ctx)
		if err != nil {
			return nil, fmt.Errorf("对象存储连接测试失败: %w", err)
		}
	}

	// 构建公开访问URL
	publicURL := cfg.PublicURL
	if publicURL == "" {
		// 如果未配置 PublicURL，使用 Endpoint 构建
		protocol := "http"
		if cfg.UseSSL {
			protocol = "https"
		}
		publicURL = fmt.Sprintf("%s://%s", protocol, cfg.Endpoint)
	}

	storageClient := &StorageClient{
		client:    client,
		buckets:   cfg.Buckets,
		publicURL: publicURL,
	}

	return storageClient, nil
}

// GetClient 获取底层S3客户端
func (s *StorageClient) GetClient() *minio.Client {
	return s.client
}

// GetBucket 获取存储桶名称
func (s *StorageClient) GetBucket(name string) (string, error) {
	bucket, exists := s.buckets[name]
	if !exists {
		return "", fmt.Errorf("存储桶 %s 不存在", name)
	}
	return bucket, nil
}

// GeneratePresignedURL 生成预签名上传URL (PUT方法)
func (s *StorageClient) GeneratePresignedURL(ctx context.Context, bucketName, objectName string, expires time.Duration) (string, error) {
	url, err := s.client.PresignedPutObject(ctx, bucketName, objectName, expires)
	if err != nil {
		return "", fmt.Errorf("生成预签名URL失败: %w", err)
	}
	return url.String(), nil
}

// PresignedPostPolicyResult 预签名POST策略结果
type PresignedPostPolicyResult struct {
	PostURL  string            // POST的URL
	FormData map[string]string // 表单数据
	FileURL  string            // 文件的最终访问URL
}

// GeneratePresignedPostURL 生成预签名POST URL (支持表单上传)
// 注意：使用时必须确保file字段是表单的最后一个字段
func (s *StorageClient) GeneratePresignedPostURL(ctx context.Context, bucketName, objectName string, minSize, maxSize int64, expires time.Duration) (*PresignedPostPolicyResult, error) {
	// 创建上传策略
	policy := minio.NewPostPolicy()

	// 设置策略的基本信息
	policy.SetBucket(bucketName)
	policy.SetKey(objectName)
	policy.SetExpires(time.Now().UTC().Add(expires))

	// 设置文件大小限制
	if err := policy.SetContentLengthRange(minSize, maxSize); err != nil {
		return nil, fmt.Errorf("设置文件大小限制失败: %w", err)
	}

	// 使用MinIO客户端和策略生成预签名的POST URL和表单数据
	postURL, formData, err := s.client.PresignedPostPolicy(ctx, policy)
	if err != nil {
		return nil, fmt.Errorf("生成预签名POST URL失败: %w", err)
	}

	// 移除form_data中多余的bucket字段（MinIO Go SDK可能会添加这个字段，但会导致签名错误）
	// 注意：在Go中直接delete不存在的key是安全的
	delete(formData, "bucket")

	// 使用配置的公开访问URL构造文件的永久访问URL
	fileURL := s.BuildFileURL(bucketName, objectName)

	return &PresignedPostPolicyResult{
		PostURL:  postURL.String(),
		FormData: formData,
		FileURL:  fileURL,
	}, nil
}

// BuildFileURL 构建文件的公开访问URL
func (s *StorageClient) BuildFileURL(bucketName, objectName string) string {
	return fmt.Sprintf("%s/%s/%s", s.publicURL, bucketName, objectName)
}

// GetPublicURL 获取公开访问URL前缀
func (s *StorageClient) GetPublicURL() string {
	return s.publicURL
}

// ObjectInfo 对象信息
type ObjectInfo struct {
	Size         int64
	LastModified time.Time
	ContentType  string
	ETag         string
}

// GetObject 获取对象内容和信息
func (s *StorageClient) GetObject(ctx context.Context, bucketName, objectName string) (io.ReadCloser, *ObjectInfo, error) {
	obj, err := s.client.GetObject(ctx, bucketName, objectName, minio.GetObjectOptions{})
	if err != nil {
		return nil, nil, fmt.Errorf("获取对象失败: %w", err)
	}

	stat, err := obj.Stat()
	if err != nil {
		obj.Close()
		return nil, nil, fmt.Errorf("获取对象信息失败: %w", err)
	}

	info := &ObjectInfo{
		Size:         stat.Size,
		LastModified: stat.LastModified,
		ContentType:  stat.ContentType,
		ETag:         stat.ETag,
	}

	return obj, info, nil
}

// ParseFileURL 从文件URL中解析出bucket和objectName
// URL格式: {publicURL}/{bucket}/{objectName}
func (s *StorageClient) ParseFileURL(fileURL string) (bucket, objectName string, err error) {
	// 移除 publicURL 前缀
	if !strings.HasPrefix(fileURL, s.publicURL) {
		return "", "", fmt.Errorf("URL格式不正确，必须以 %s 开头", s.publicURL)
	}

	// 移除 publicURL 前缀和开头的 /
	path := strings.TrimPrefix(fileURL, s.publicURL)
	path = strings.TrimPrefix(path, "/")

	// 解析路径
	parts := strings.SplitN(path, "/", 2)
	if len(parts) < 2 {
		return "", "", fmt.Errorf("URL格式不正确，无法解析bucket和objectName")
	}

	bucket = parts[0]
	objectName = parts[1]

	// URL解码 objectName
	decoded, err := url.PathUnescape(objectName)
	if err == nil {
		objectName = decoded
	}

	return bucket, objectName, nil
}

// UploadObject 上传对象到存储
func (s *StorageClient) UploadObject(ctx context.Context, bucketName, objectName string, reader io.Reader, size int64, contentType string) error {
	_, err := s.client.PutObject(ctx, bucketName, objectName, reader, size, minio.PutObjectOptions{
		ContentType: contentType,
	})
	if err != nil {
		return fmt.Errorf("上传对象失败: %w", err)
	}
	return nil
}