//go:build linux

package process

import (
	"fmt"
	"os"
	"path/filepath"
	"time"

	"golang.org/x/sys/unix"
)

// Lock 获取进程间互斥锁 (Linux: flock)
func (pm *ProcessManager) Lock() error {
	pm.mu.Lock()
	defer pm.mu.Unlock()

	if pm.locked {
		return nil
	}

	lockPath := filepath.Join(pm.dataDir, LockFileName)
	if err := os.MkdirAll(pm.dataDir, 0755); err != nil {
		return fmt.Errorf("创建数据目录失败: %w", err)
	}
	file, err := os.OpenFile(lockPath, os.O_CREATE|os.O_RDWR, 0644)
	if err != nil {
		return fmt.Errorf("打开锁文件失败: %w", err)
	}

	start := time.Now()
	for {
		err := unix.Flock(int(file.Fd()), unix.LOCK_EX|unix.LOCK_NB)
		if err == nil {
			pm.lockFile = file
			pm.locked = true
			return nil
		}
		if err != unix.EWOULDBLOCK {
			file.Close()
			return fmt.Errorf("获取锁失败: %w", err)
		}
		if time.Since(start) > LockAcquireTimeout {
			file.Close()
			return fmt.Errorf("获取锁超时 (超过 %v)", LockAcquireTimeout)
		}
		time.Sleep(LockRetryInterval)
	}
}

// Unlock 释放互斥锁 (Linux: flock)
func (pm *ProcessManager) Unlock() error {
	pm.mu.Lock()
	defer pm.mu.Unlock()

	if !pm.locked {
		return nil
	}
	if pm.lockFile != nil {
		unix.Flock(int(pm.lockFile.Fd()), unix.LOCK_UN)
		pm.lockFile.Close()
		pm.lockFile = nil
	}
	pm.locked = false
	return nil
}