package storage

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

// LocalStore 把文件落在本地磁盘（DataDir/uploads），零配置兜底。
// key 允许带「2026/09/」这类前缀，实现里做路径清洗防目录穿越。
type LocalStore struct {
	Root string
}

func NewLocal(root string) *LocalStore {
	return &LocalStore{Root: root}
}

func (s *LocalStore) path(key string) (string, error) {
	clean := filepath.Clean("/" + strings.TrimPrefix(key, "/"))[1:] // 锚到根再去掉，防 ../
	if clean == "" || strings.HasPrefix(clean, "..") {
		return "", fmt.Errorf("bad key: %q", key)
	}
	return filepath.Join(s.Root, filepath.FromSlash(clean)), nil
}

func (s *LocalStore) Put(ctx context.Context, key string, r io.Reader, size int64, contentType string) error {
	dst, err := s.path(key)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
		return err
	}
	tmp, err := os.CreateTemp(filepath.Dir(dst), ".upload-*")
	if err != nil {
		return err
	}
	defer os.Remove(tmp.Name())
	if _, err := io.Copy(tmp, r); err != nil {
		tmp.Close()
		return err
	}
	if err := tmp.Close(); err != nil {
		return err
	}
	return os.Rename(tmp.Name(), dst)
}

func (s *LocalStore) Open(ctx context.Context, key string) (io.ReadCloser, int64, error) {
	dst, err := s.path(key)
	if err != nil {
		return nil, 0, err
	}
	f, err := os.Open(dst)
	if err != nil {
		return nil, 0, err
	}
	st, err := f.Stat()
	if err != nil {
		f.Close()
		return nil, 0, err
	}
	return f, st.Size(), nil
}

func (s *LocalStore) Delete(ctx context.Context, key string) error {
	dst, err := s.path(key)
	if err != nil {
		return err
	}
	if err := os.Remove(dst); err != nil && !os.IsNotExist(err) {
		return err
	}
	return nil
}