package storage

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

type Storage interface {
	Stat(path string) (os.FileInfo, error)
	Open(path string) (*os.File, error)
	Create(path string) (*os.File, error)
	Remove(path string) error
	Rename(oldPath, newPath string) error
	MkdirAll(path string) error
	List(path string) ([]os.FileInfo, error)
}

type Local struct{ Root string }

func (s Local) real(path string) (string, error) {
	root, err := filepath.Abs(s.Root)
	if err != nil {
		return "", err
	}
	p := strings.TrimPrefix(filepath.Clean("/"+path), string(filepath.Separator))
	full := filepath.Join(root, p)
	rel, err := filepath.Rel(root, full)
	if err != nil {
		return "", err
	}
	if rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) {
		return "", errors.New("path escapes storage root")
	}
	return full, nil
}
func (s Local) Stat(path string) (os.FileInfo, error) {
	p, e := s.real(path)
	if e != nil {
		return nil, e
	}
	return os.Stat(p)
}
func (s Local) Open(path string) (*os.File, error) {
	p, e := s.real(path)
	if e != nil {
		return nil, e
	}
	return os.Open(p)
}
func (s Local) Create(path string) (*os.File, error) {
	p, e := s.real(path)
	if e != nil {
		return nil, e
	}
	if e = os.MkdirAll(filepath.Dir(p), 0755); e != nil {
		return nil, e
	}
	return os.Create(p)
}
func (s Local) Remove(path string) error {
	p, e := s.real(path)
	if e != nil {
		return e
	}
	return os.RemoveAll(p)
}
func (s Local) Rename(a, b string) error {
	pa, e := s.real(a)
	if e != nil {
		return e
	}
	pb, e := s.real(b)
	if e != nil {
		return e
	}
	return os.Rename(pa, pb)
}
func (s Local) MkdirAll(path string) error {
	p, e := s.real(path)
	if e != nil {
		return e
	}
	return os.MkdirAll(p, 0755)
}
func (s Local) List(path string) ([]os.FileInfo, error) {
	p, e := s.real(path)
	if e != nil {
		return nil, e
	}
	f, e := os.Open(p)
	if e != nil {
		return nil, e
	}
	defer f.Close()
	return f.Readdir(-1)
}

var _ fs.FS