package storage

import (
	"context"
	"crypto/md5"
	"encoding/hex"
	"fmt"
	"io"
	"path/filepath"
	"strings"
	"time"

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

// Client MinIO客户端
type Client struct {
	client *minio.Client
	config *Config
}

// NewClient 创建MinIO客户端
func NewClient(config *Config) (*Client, error) {
	client, err := minio.New(config.Endpoint, &minio.Options{
		Creds:  credentials.NewStaticV4(config.AccessKeyID, config.SecretAccessKey, ""),
		Secure: config.UseSSL,
	})
	if err != nil {
		return nil, fmt.Errorf("创建MinIO客户端失败: %w", err)
	}

	c := &Client{
		client: client,
		config: config,
	}

	// 确保默认桶存在
	if config.BucketName != "" {
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()

		exists, err := c.BucketExists(ctx, config.BucketName)
		if err != nil {
			return nil, fmt.Errorf("检查桶失败: %w", err)
		}
		if !exists {
			if err := c.CreateBucket(ctx, config.BucketName); err != nil {
				return nil, fmt.Errorf("创建桶失败: %w", err)
			}
		}
	}

	return c, nil
}

// UploadToken 上传凭证
type UploadToken struct {
	Key        string    `json:"key"`         // 文件存储路径
	UploadURL  string    `json:"upload_url"`  // 预签名上传URL
	ExpiresAt  time.Time `json:"expires_at"`  // 过期时间
	BucketName string    `json:"bucket_name"` // 桶名称
	AccessURL  string    `json:"access_url"`  // 访问URL（可选）
}

// DownloadToken 下载凭证
type DownloadToken struct {
	Key         string    `json:"key"`          // 文件key
	DownloadURL string    `json:"download_url"` // 预签名下载URL
	ExpiresAt   time.Time `json:"expires_at"`   // 过期时间
	Filename    string    `json:"filename"`     // 文件名（可选）
}

// FileInfo 文件信息
type FileInfo struct {
	Key          string            `json:"key"`           // 文件key
	Size         int64             `json:"size"`          // 文件大小
	ETag         string            `json:"etag"`          // ETag（MD5）
	ContentType  string            `json:"content_type"`  // Content-Type
	LastModified time.Time         `json:"last_modified"` // 最后修改时间
	Metadata     map[string]string `json:"metadata"`      // 元数据
	URL          string            `json:"url"`           // 访问URL
	Exists       bool              `json:"exists"`        // 是否存在
}

// GenerateUploadToken 生成上传凭证
func (c *Client) GenerateUploadToken(ctx context.Context, key string, bucketName ...string) (*UploadToken, error) {
	bucket := c.config.BucketName
	if len(bucketName) > 0 && bucketName[0] != "" {
		bucket = bucketName[0]
	}

	// 生成预签名PUT URL
	presignedURL, err := c.client.PresignedPutObject(ctx, bucket, key, c.config.PresignExpires)
	if err != nil {
		return nil, fmt.Errorf("生成上传凭证失败: %w", err)
	}

	token := &UploadToken{
		Key:        key,
		UploadURL:  presignedURL.String(),
		ExpiresAt:  time.Now().Add(c.config.PresignExpires),
		BucketName: bucket,
	}

	// 如果配置了CDN域名，生成访问URL
	if c.config.CDNDomain != "" {
		token.AccessURL = c.buildCDNURL(bucket, key)
	}

	return token, nil
}

// GenerateDownloadToken 生成下载凭证
func (c *Client) GenerateDownloadToken(ctx context.Context, key string, bucketName ...string) (*DownloadToken, error) {
	bucket := c.config.BucketName
	if len(bucketName) > 0 && bucketName[0] != "" {
		bucket = bucketName[0]
	}

	// 检查文件是否存在
	exists, err := c.FileExists(ctx, key, bucket)
	if err != nil {
		return nil, err
	}
	if !exists {
		return nil, fmt.Errorf("文件不存在: %s", key)
	}

	// 生成预签名GET URL
	presignedURL, err := c.client.PresignedGetObject(ctx, bucket, key, c.config.PresignExpires, nil)
	if err != nil {
		return nil, fmt.Errorf("生成下载凭证失败: %w", err)
	}

	token := &DownloadToken{
		Key:         key,
		DownloadURL: presignedURL.String(),
		ExpiresAt:   time.Now().Add(c.config.PresignExpires),
		Filename:    filepath.Base(key),
	}

	return token, nil
}

// VerifyFile 验证文件完整性
func (c *Client) VerifyFile(ctx context.Context, key string, expectedMD5 string, bucketName ...string) (*FileInfo, error) {
	bucket := c.config.BucketName
	if len(bucketName) > 0 && bucketName[0] != "" {
		bucket = bucketName[0]
	}

	// 获取文件信息
	stat, err := c.client.StatObject(ctx, bucket, key, minio.StatObjectOptions{})
	if err != nil {
		errResponse := minio.ToErrorResponse(err)
		if errResponse.Code == "NoSuchKey" {
			return &FileInfo{
				Key:    key,
				Exists: false,
			}, nil
		}
		return nil, fmt.Errorf("获取文件信息失败: %w", err)
	}

	fileInfo := &FileInfo{
		Key:          key,
		Size:         stat.Size,
		ETag:         strings.Trim(stat.ETag, "\""), // 去除引号
		ContentType:  stat.ContentType,
		LastModified: stat.LastModified,
		Metadata:     stat.UserMetadata,
		Exists:       true,
		URL:          c.buildAccessURL(bucket, key),
	}

	// 如果提供了期望的MD5，进行验证
	if expectedMD5 != "" {
		if !c.compareMD5(fileInfo.ETag, expectedMD5) {
			return fileInfo, fmt.Errorf("文件MD5不匹配，期望: %s, 实际: %s", expectedMD5, fileInfo.ETag)
		}
	}

	return fileInfo, nil
}

// CalculateFileMD5 计算文件MD5（从MinIO下载并计算）
func (c *Client) CalculateFileMD5(ctx context.Context, key string, bucketName ...string) (string, error) {
	bucket := c.config.BucketName
	if len(bucketName) > 0 && bucketName[0] != "" {
		bucket = bucketName[0]
	}

	// 下载文件
	object, err := c.client.GetObject(ctx, bucket, key, minio.GetObjectOptions{})
	if err != nil {
		return "", fmt.Errorf("下载文件失败: %w", err)
	}
	defer func() { _ = object.Close() }()

	// 计算MD5
	hash := md5.New()
	if _, err := io.Copy(hash, object); err != nil {
		return "", fmt.Errorf("计算MD5失败: %w", err)
	}

	return hex.EncodeToString(hash.Sum(nil)), nil
}

// FileExists 检查文件是否存在
func (c *Client) FileExists(ctx context.Context, key string, bucketName ...string) (bool, error) {
	bucket := c.config.BucketName
	if len(bucketName) > 0 && bucketName[0] != "" {
		bucket = bucketName[0]
	}

	_, err := c.client.StatObject(ctx, bucket, key, minio.StatObjectOptions{})
	if err != nil {
		errResponse := minio.ToErrorResponse(err)
		if errResponse.Code == "NoSuchKey" {
			return false, nil
		}
		return false, fmt.Errorf("检查文件失败: %w", err)
	}

	return true, nil
}

// DeleteFile 删除文件
func (c *Client) DeleteFile(ctx context.Context, key string, bucketName ...string) error {
	bucket := c.config.BucketName
	if len(bucketName) > 0 && bucketName[0] != "" {
		bucket = bucketName[0]
	}

	err := c.client.RemoveObject(ctx, bucket, key, minio.RemoveObjectOptions{})
	if err != nil {
		return fmt.Errorf("删除文件失败: %w", err)
	}

	return nil
}

// GetFileInfo 获取文件信息
func (c *Client) GetFileInfo(ctx context.Context, key string, bucketName ...string) (*FileInfo, error) {
	return c.VerifyFile(ctx, key, "", bucketName...)
}

// BucketExists 检查桶是否存在
func (c *Client) BucketExists(ctx context.Context, bucketName string) (bool, error) {
	exists, err := c.client.BucketExists(ctx, bucketName)
	if err != nil {
		return false, fmt.Errorf("检查桶失败: %w", err)
	}
	return exists, nil
}

// CreateBucket 创建桶
func (c *Client) CreateBucket(ctx context.Context, bucketName string) error {
	err := c.client.MakeBucket(ctx, bucketName, minio.MakeBucketOptions{
		Region: c.config.Region,
	})
	if err != nil {
		return fmt.Errorf("创建桶失败: %w", err)
	}
	return nil
}

// SetBucketPublic 设置桶为公开访问
func (c *Client) SetBucketPublic(ctx context.Context, bucketName string) error {
	policy := fmt.Sprintf(`{
		"Version": "2012-10-17",
		"Statement": [{
			"Effect": "Allow",
			"Principal": {"AWS": ["*"]},
			"Action": ["s3:GetObject"],
			"Resource": ["arn:aws:s3:::%s/*"]
		}]
	}`, bucketName)

	err := c.client.SetBucketPolicy(ctx, bucketName, policy)
	if err != nil {
		return fmt.Errorf("设置桶策略失败: %w", err)
	}
	return nil
}

// buildAccessURL 构建访问URL
func (c *Client) buildAccessURL(bucket, key string) string {
	if c.config.CDNDomain != "" {
		return c.buildCDNURL(bucket, key)
	}

	protocol := "http"
	if c.config.UseSSL {
		protocol = "https"
	}

	return fmt.Sprintf("%s://%s/%s/%s", protocol, c.config.Endpoint, bucket, key)
}

// buildCDNURL 构建CDN URL
func (c *Client) buildCDNURL(bucket, key string) string {
	return fmt.Sprintf("%s/%s/%s", strings.TrimRight(c.config.CDNDomain, "/"), bucket, key)
}

// compareMD5 比较MD5
func (c *Client) compareMD5(etag, md5 string) bool {
	etag = strings.ToLower(strings.Trim(etag, "\""))
	md5 = strings.ToLower(strings.Trim(md5, "\""))
	return etag == md5
}