// Closer is the interface that wraps the basic Close method.
//
// The behavior of Close after the first call is undefined.
// Specific implementations may document their own behavior.
type Closer interface {
	Close() error
}

// File represents an open file descriptor.
type File struct {
	*file // os specific
}

// +build aix darwin dragonfly freebsd js,wasm linux netbsd openbsd solaris

// file is the real representation of *File.
// The extra level of indirection ensures that no clients of os
// can overwrite this data, which could cause the finalizer
// to close the wrong file descriptor.
type file struct {
	pfd         poll.FD
	name        string
	dirinfo     *dirInfo // nil unless directory being read
	nonblock    bool     // whether we set nonblocking mode
	stdoutOrErr bool     // whether this is stdout or stderr
	appendMode  bool     // whether file is opened for appending
}

// Close closes the File, rendering it unusable for I/O.
// On files that support SetDeadline, any pending I/O operations will
// be canceled and return immediately with an error.
// Close will return an error if it has already been called.
func (f *File) Close() error {
	if f == nil {
		return ErrInvalid
	}
	return f.file.close()
}

func (file *file) close() error {
	// ファイルが無い場合はエラーを返す
	if file == nil {
		return syscall.EINVAL
	}
	// ディレクトリ情報を持っている場合はそちらもCloseする
	if file.dirinfo != nil {
		file.dirinfo.close()
	}
	var err error
	// file構造体のpfdのCloseメソッドを呼び出す
	if e := file.pfd.Close(); e != nil {
		// エラーがpoll.ErrFileClosing変数と同じ場合はeにエラーを設定する
		if e == poll.ErrFileClosing {
			e = ErrClosed
		}
		// PathError構造体に、行った操作、パス、エラーを設定する
		err = &PathError{"close", file.name, e}
	}

	// no need for a finalizer anymore
	// fileに関連付けられているすべてのfinalizerをクリアする
	runtime.SetFinalizer(file, nil)
	return err
}

// PathError records an error and the operation and file path that caused it.
type PathError struct {
	Op   string
	Path string
	Err  error
}

func (e *PathError) Error() string { return e.Op + " " + e.Path + ": " + e.Err.Error() }

func (e *PathError) Unwrap() error { return e.Err }