package handler

import (
	"errors"
	"io/fs"
	"net/http"
	"os"
	"path/filepath"
	"strings"
)

type FileHandler struct {
	Root    string
	Default string
	http.FileSystem
}

func (f FileHandler) Open(name string) (http.File, error) {
	if strings.HasPrefix(name, "../") {
		return nil, errors.New("not permitted")
	}

	rPath := filepath.Join(f.Root, strings.TrimPrefix(name, "/"))
	if rPath == f.Root {
		if f.Default == "" {
			return nil, errors.New("not permit list dir")
		}
		rPath = filepath.Join(rPath, f.Default)
	}

	fInfo, _, err := FileExists(rPath)
	if err != nil {
		return nil, err
	}

	if fInfo.IsDir() {
		return nil, errors.New("not permit list dir")
	}

	if fInfo.Mode() == fs.ModeSymlink {
		return nil, errors.New("not permit follow symbol link")
	}
	return os.Open(rPath)
}

func FileExists(name string) (os.FileInfo, bool, error) {
	info, err := os.Stat(name)
	if err != nil {
		return nil, os.IsExist(err), err
	}
	return info, true, nil
}

func NewFileHandler(f FileHandler) http.Handler {
	return http.FileServer(f)
}