package processlock

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
)

var ErrLocked = errors.New("进程锁已被占用")

type Lock struct {
	file *os.File
}

func Acquire(path string) (*Lock, error) {
	path = filepath.Clean(path)
	if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
		return nil, fmt.Errorf("创建进程锁目录失败：%w", err)
	}
	if info, err := os.Lstat(path); err == nil {
		if info.Mode()&os.ModeSymlink != 0 || !info.Mode().IsRegular() {
			return nil, errors.New("进程锁路径必须是普通文件")
		}
	} else if !errors.Is(err, os.ErrNotExist) {
		return nil, fmt.Errorf("检查进程锁失败：%w", err)
	}

	file, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0o600)
	if err != nil {
		return nil, fmt.Errorf("打开进程锁失败：%w", err)
	}
	if err := lockFile(file); err != nil {
		_ = file.Close()
		return nil, err
	}
	if err := os.Chmod(path, 0o600); err != nil {
		_ = unlockFile(file)
		_ = file.Close()
		return nil, fmt.Errorf("设置进程锁权限失败：%w", err)
	}
	return &Lock{file: file}, nil
}

func (lock *Lock) Close() error {
	if lock == nil || lock.file == nil {
		return nil
	}
	file := lock.file
	lock.file = nil
	return errors.Join(unlockFile(file), file.Close())
}