package storage

import (
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"time"
)

// LocalEngine 本地磁盘存储引擎
type LocalEngine struct {
	BasePath       string // 存储根目录
	CDNHost        string // CDN地址, 如 http://localhost:3090
	CDNPathPrefix  string // CDN路径前缀, 如 /public
}

// NewLocalEngine 创建本地存储引擎实例
func NewLocalEngine(basePath string) *LocalEngine {
	os.MkdirAll(basePath, 0755)
	return &LocalEngine{BasePath: basePath}
}

// NewLocalEngineWithCDN 创建带CDN配置的本地存储引擎
func NewLocalEngineWithCDN(basePath, cdnHost, cdnPathPrefix string) *LocalEngine {
	os.MkdirAll(basePath, 0755)
	return &LocalEngine{
		BasePath:      basePath,
		CDNHost:       cdnHost,
		CDNPathPrefix: cdnPathPrefix,
	}
}

// Upload 上传文件到本地磁盘
func (e *LocalEngine) Upload(storageKey string, reader io.Reader, size int64) error {
	fullPath := filepath.Join(e.BasePath, storageKey)
	dir := filepath.Dir(fullPath)
	if err := os.MkdirAll(dir, 0755); err != nil {
		return fmt.Errorf("创建目录失败: %w", err)
	}

	dst, err := os.Create(fullPath)
	if err != nil {
		return fmt.Errorf("创建文件失败: %w", err)
	}
	defer dst.Close()

	if _, err := io.Copy(dst, reader); err != nil {
		os.Remove(fullPath)
		return fmt.Errorf("写入文件失败: %w", err)
	}
	return nil
}

// Download 从本地磁盘下载文件
func (e *LocalEngine) Download(storageKey string) (io.ReadCloser, error) {
	fullPath := filepath.Join(e.BasePath, storageKey)
	file, err := os.Open(fullPath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, fmt.Errorf("文件不存在: %s", storageKey)
		}
		return nil, fmt.Errorf("打开文件失败: %w", err)
	}
	return file, nil
}

// Delete 从本地磁盘删除文件
func (e *LocalEngine) Delete(storageKey string) error {
	fullPath := filepath.Join(e.BasePath, storageKey)
	err := os.Remove(fullPath)
	if err != nil && !os.IsNotExist(err) {
		return fmt.Errorf("删除文件失败: %w", err)
	}
	return nil
}

// Exists 判断文件是否存在于本地磁盘
func (e *LocalEngine) Exists(storageKey string) (bool, error) {
	fullPath := filepath.Join(e.BasePath, storageKey)
	_, err := os.Stat(fullPath)
	if err == nil {
		return true, nil
	}
	if os.IsNotExist(err) {
		return false, nil
	}
	return false, err
}

// GetURL 获取文件访问URL
// 配置了CDN: http://localhost:3090/public/2026/07/02/ab/xxx.txt
// 未配置CDN: /storage/2026/07/02/ab/xxx.txt
func (e *LocalEngine) GetURL(storageKey string) string {
	if e.CDNHost != "" {
		// 确保路径格式正确
		prefix := strings.TrimRight(e.CDNPathPrefix, "/")
		key := strings.TrimLeft(storageKey, "/")
		return fmt.Sprintf("%s%s/%s", e.CDNHost, prefix, key)
	}
	return "/storage/" + storageKey
}

// GetFullPath 获取文件在磁盘上的完整路径
func (e *LocalEngine) GetFullPath(storageKey string) string {
	return filepath.Join(e.BasePath, storageKey)
}

// GenerateStorageKey 生成存储路径
func GenerateStorageKey(md5, extension string) string {
	now := time.Now()
	day := now.Format("2006/01/02")
	if extension != "" {
		return fmt.Sprintf("%s/%s/%s.%s", day, md5[:2], md5, extension)
	}
	return fmt.Sprintf("%s/%s/%s", day, md5[:2], md5)
}