package storage

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

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

// MinIOEngine MinIO 对象存储引擎
type MinIOEngine struct {
	Client     *minio.Client
	BucketName string
	Endpoint   string
	UseSSL     bool
}

// NewMinIOEngine 创建 MinIO 存储引擎实例
// endpoint 格式: host:port (如 localhost:9000), 不带 http://
func NewMinIOEngine(endpoint, accessKey, secretKey, bucket string, useSSL bool) (*MinIOEngine, error) {
	// 清理 endpoint: 去掉 http:// 或 https:// 前缀
	cleanEndpoint := endpoint
	if len(cleanEndpoint) > 7 && cleanEndpoint[:7] == "http://" {
		cleanEndpoint = cleanEndpoint[7:]
	}
	if len(cleanEndpoint) > 8 && cleanEndpoint[:8] == "https://" {
		cleanEndpoint = cleanEndpoint[8:]
	}
	// 去掉末尾的 /
	if len(cleanEndpoint) > 0 && cleanEndpoint[len(cleanEndpoint)-1] == '/' {
		cleanEndpoint = cleanEndpoint[:len(cleanEndpoint)-1]
	}

	// 支持匿名访问(公开桶不需要凭证)
	var creds *credentials.Credentials
	if accessKey != "" && secretKey != "" {
		creds = credentials.NewStaticV4(accessKey, secretKey, "")
	} else {
		creds = credentials.NewStaticV4("", "", "")
	}

	client, err := minio.New(cleanEndpoint, &minio.Options{
		Creds:  creds,
		Secure: useSSL,
	})
	if err != nil {
		return nil, fmt.Errorf("创建MinIO客户端失败: %w", err)
	}

	engine := &MinIOEngine{
		Client:     client,
		BucketName: bucket,
		Endpoint:   endpoint,
		UseSSL:     useSSL,
	}

	// 有凭证时确保 bucket 存在(匿名访问跳过)
	ctx := context.Background()
	if accessKey != "" {
		exists, checkErr := client.BucketExists(ctx, bucket)
		if checkErr != nil {
			return nil, fmt.Errorf("检查bucket失败: %w", checkErr)
		}
		if !exists {
			if err := client.MakeBucket(ctx, bucket, minio.MakeBucketOptions{}); err != nil {
				return nil, fmt.Errorf("创建bucket失败: %w", err)
			}
			// 设置 bucket 为公开读
			policy := fmt.Sprintf(`{
				"Version": "2012-10-17",
				"Statement": [{
					"Effect": "Allow",
					"Principal": {"AWS": ["*"]},
					"Action": ["s3:GetObject"],
					"Resource": ["arn:aws:s3:::%s/*"]
				}]
			}`, bucket)
			client.SetBucketPolicy(ctx, bucket, policy)
		}
	}

	return engine, nil
}

// Upload 上传文件到 MinIO
func (e *MinIOEngine) Upload(storageKey string, reader io.Reader, size int64) error {
	ctx := context.Background()
	_, err := e.Client.PutObject(ctx, e.BucketName, storageKey, reader, size, minio.PutObjectOptions{
		ContentType: "application/octet-stream",
	})
	if err != nil {
		return fmt.Errorf("MinIO上传失败: %w", err)
	}
	return nil
}

// Download 从 MinIO 下载文件
func (e *MinIOEngine) Download(storageKey string) (io.ReadCloser, error) {
	ctx := context.Background()
	object, err := e.Client.GetObject(ctx, e.BucketName, storageKey, minio.GetObjectOptions{})
	if err != nil {
		return nil, fmt.Errorf("MinIO下载失败: %w", err)
	}
	return object, nil
}

// Delete 从 MinIO 删除文件
func (e *MinIOEngine) Delete(storageKey string) error {
	ctx := context.Background()
	err := e.Client.RemoveObject(ctx, e.BucketName, storageKey, minio.RemoveObjectOptions{})
	if err != nil {
		return fmt.Errorf("MinIO删除失败: %w", err)
	}
	return nil
}

// Exists 判断文件是否存在于 MinIO
func (e *MinIOEngine) Exists(storageKey string) (bool, error) {
	ctx := context.Background()
	_, err := e.Client.StatObject(ctx, e.BucketName, storageKey, minio.StatObjectOptions{})
	if err != nil {
		// 检查是否是"不存在"的错误
		errResponse := minio.ToErrorResponse(err)
		if errResponse.Code == "NoSuchKey" {
			return false, nil
		}
		return false, err
	}
	return true, nil
}

// GetURL 获取文件的公开访问 URL
func (e *MinIOEngine) GetURL(storageKey string) string {
	scheme := "http"
	if e.UseSSL {
		scheme = "https"
	}
	return fmt.Sprintf("%s/%s/%s/%s", scheme+"://"+e.Endpoint, e.BucketName, storageKey, "")
}

// GetPresignedURL 生成预签名下载链接(临时授权)
// expiration: 链接有效期
func (e *MinIOEngine) GetPresignedURL(storageKey string, expiration time.Duration) (string, error) {
	ctx := context.Background()
	reqParams := make(url.Values)
	presignedURL, err := e.Client.PresignedGetObject(ctx, e.BucketName, storageKey, expiration, reqParams)
	if err != nil {
		return "", fmt.Errorf("生成预签名URL失败: %w", err)
	}
	return presignedURL.String(), nil
}

// GetPresignedPutURL 生成预签名上传链接(用于前端直传)
func (e *MinIOEngine) GetPresignedPutURL(storageKey string, expiration time.Duration) (string, error) {
	ctx := context.Background()
	presignedURL, err := e.Client.PresignedPutObject(ctx, e.BucketName, storageKey, expiration)
	if err != nil {
		return "", fmt.Errorf("生成预签名上传URL失败: %w", err)
	}
	return presignedURL.String(), nil
}

// GetPreviewURL 获取文件预览链接
// 对于图片/文本/PDF等可直接预览的文件, 返回公开URL
func (e *MinIOEngine) GetPreviewURL(storageKey string) string {
	scheme := "http"
	if e.UseSSL {
		scheme = "https"
	}
	return fmt.Sprintf("%s/%s/%s/%s", scheme+"://"+e.Endpoint, e.BucketName, storageKey, "")
}