package storage

import (
	"context"
	"fmt"
	"io"
	"net/url"
	"os"
	"path"
	"path/filepath"
	"strings"

	"git.toowon.com/jimmy/go-common/config"
)

// LocalStorage 本地存储实现
// 将对象写入本地文件夹（BaseDir），对象键 objectKey 作为相对路径使用。
//
// 典型用法：
//   - 上传：Upload(ctx, "uploads/2026/01/01/a.png", reader)
//   - 查看：配合 ProxyHandler 或 http.FileServer 对外提供访问
type LocalStorage struct {
	baseDir   string
	publicURL string
}

// NewLocalStorage 创建本地存储实例
func NewLocalStorage(cfg *config.LocalStorageConfig) (*LocalStorage, error) {
	if cfg == nil {
		return nil, fmt.Errorf("LocalStorage config is nil")
	}
	if strings.TrimSpace(cfg.BaseDir) == "" {
		return nil, fmt.Errorf("LocalStorage baseDir is empty")
	}

	absBase, err := filepath.Abs(cfg.BaseDir)
	if err != nil {
		return nil, fmt.Errorf("failed to get absolute baseDir: %w", err)
	}

	// 确保根目录存在
	if err := os.MkdirAll(absBase, 0o755); err != nil {
		return nil, fmt.Errorf("failed to create baseDir: %w", err)
	}

	return &LocalStorage{
		baseDir:   absBase,
		publicURL: strings.TrimSpace(cfg.PublicURL),
	}, nil
}

// Upload 上传文件到本地文件夹
func (s *LocalStorage) Upload(ctx context.Context, objectKey string, reader io.Reader, contentType ...string) error {
	_ = ctx
	_ = contentType // 本地写文件不依赖 contentType；可由上层自行记录

	dstPath, err := s.resolvePath(objectKey)
	if err != nil {
		return err
	}

	// 确保目录存在
	if err := os.MkdirAll(filepath.Dir(dstPath), 0o755); err != nil {
		return fmt.Errorf("failed to create directory: %w", err)
	}

	// 原子写入：先写临时文件，再 rename
	tmp, err := os.CreateTemp(filepath.Dir(dstPath), ".upload-*")
	if err != nil {
		return fmt.Errorf("failed to create temp file: %w", err)
	}

	tmpName := tmp.Name()
	defer func() {
		_ = tmp.Close()
		_ = os.Remove(tmpName)
	}()

	if _, err := io.Copy(tmp, reader); err != nil {
		return fmt.Errorf("failed to write temp file: %w", err)
	}
	if err := tmp.Close(); err != nil {
		return fmt.Errorf("failed to close temp file: %w", err)
	}

	// 如果目标文件已存在，先删除（保证跨平台兼容 rename 行为）
	_ = os.Remove(dstPath)

	if err := os.Rename(tmpName, dstPath); err != nil {
		return fmt.Errorf("failed to move temp file to destination: %w", err)
	}

	return nil
}

// GetURL 获取本地文件访问URL
// - 若配置了 publicURL：
//   - 包含 "{objectKey}" 占位符：替换为 url.QueryEscape(objectKey)
//   - 否则认为是 URL 前缀：自动拼接 objectKey（用 path.Join 处理斜杠）
//
// - 未配置 publicURL：返回 objectKey（相对路径）
func (s *LocalStorage) GetURL(objectKey string, expires int64) (string, error) {
	_ = expires // 本地存储不提供签名URL，忽略 expires

	cleanKey, err := normalizeObjectKey(objectKey)
	if err != nil {
		return "", err
	}

	if s.publicURL == "" {
		return cleanKey, nil
	}

	if strings.Contains(s.publicURL, "{objectKey}") {
		return strings.ReplaceAll(s.publicURL, "{objectKey}", url.QueryEscape(cleanKey)), nil
	}

	// 作为前缀拼接
	trimmed := strings.TrimRight(s.publicURL, "/")
	return trimmed + "/" + path.Clean("/" + cleanKey)[1:], nil
}

// Delete 删除本地文件
func (s *LocalStorage) Delete(ctx context.Context, objectKey string) error {
	_ = ctx

	dstPath, err := s.resolvePath(objectKey)
	if err != nil {
		return err
	}

	if err := os.Remove(dstPath); err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return fmt.Errorf("failed to delete file: %w", err)
	}
	return nil
}

// Exists 检查本地文件是否存在
func (s *LocalStorage) Exists(ctx context.Context, objectKey string) (bool, error) {
	_ = ctx

	dstPath, err := s.resolvePath(objectKey)
	if err != nil {
		return false, err
	}

	info, err := os.Stat(dstPath)
	if err != nil {
		if os.IsNotExist(err) {
			return false, nil
		}
		return false, fmt.Errorf("failed to stat file: %w", err)
	}
	if info.IsDir() {
		return false, nil
	}
	return true, nil
}

// GetObject 获取本地文件内容
func (s *LocalStorage) GetObject(ctx context.Context, objectKey string) (io.ReadCloser, error) {
	_ = ctx

	dstPath, err := s.resolvePath(objectKey)
	if err != nil {
		return nil, err
	}

	f, err := os.Open(dstPath)
	if err != nil {
		return nil, fmt.Errorf("failed to open file: %w", err)
	}
	return f, nil
}

func (s *LocalStorage) resolvePath(objectKey string) (string, error) {
	cleanKey, err := normalizeObjectKey(objectKey)
	if err != nil {
		return "", err
	}
	// 将 URL 风格路径转换为 OS 路径
	full := filepath.Join(s.baseDir, filepath.FromSlash(cleanKey))

	// 防御：确保仍在 baseDir 下
	rel, err := filepath.Rel(s.baseDir, full)
	if err != nil {
		return "", fmt.Errorf("failed to resolve path: %w", err)
	}
	if rel == "." || strings.HasPrefix(rel, ".."+string(os.PathSeparator)) || rel == ".." {
		return "", fmt.Errorf("invalid objectKey: %s", objectKey)
	}

	return full, nil
}

func normalizeObjectKey(objectKey string) (string, error) {
	key := strings.TrimSpace(objectKey)
	if key == "" {
		return "", fmt.Errorf("objectKey is empty")
	}

	// 兼容 Windows 风格路径，统一为 URL 风格
	key = strings.ReplaceAll(key, "\\", "/")

	// 清洗路径，去除多余的 . / ..
	// 加前缀 "/" 让 Clean 以绝对路径方式处理，避免出现空结果
	clean := path.Clean("/" + key)
	clean = strings.TrimPrefix(clean, "/")
	if clean == "" || clean == "." {
		return "", fmt.Errorf("invalid objectKey: %s", objectKey)
	}

	// 不允许以 "/" 结尾（必须指向文件）
	if strings.HasSuffix(clean, "/") {
		return "", fmt.Errorf("objectKey cannot be a directory: %s", objectKey)
	}

	return clean, nil
}