/*
 * .============.
 * // M A K E / \
 * // C++ DEV / \
 * // E A S Y / \/ \
 * ++ ----------. \/\ .
 * \\ \ \ /\ /
 * \\ \ \ /
 * \\ \ \ /
 * -============'
 *
 * Copyright (c) 2018 Hevake and contributors, all rights reserved.
 *
 * This file is part of cpp-tbox (https://github.com/cpp-main/cpp-tbox)
 * Use of this source code is governed by MIT license that can be found
 * in the LICENSE file in the root of the source tree. All contributing
 * project authors may be found in the CONTRIBUTORS.md file in the root
 * of the source tree.
 */
#include "pid_file.h"

#include <unistd.h>
#include <fcntl.h>
#include <errno.h>

#include <cstring>

#include <iostream>
#include <tbox/base/scope_exit.hpp>

using namespace std;

namespace tbox {
namespace util {

PidFile::PidFile()
{ }

PidFile::~PidFile()
{
 unlock();
}

bool PidFile::lock(const std::string &pid_filename)
{
 if (fd_ >= 0) //! 已经 initialize() 过,直接返回
 return true;

 pid_filename_ = pid_filename;

 int fd = open(pid_filename_.c_str(), O_CREAT | O_WRONLY | O_CLOEXEC | O_TRUNC, 0644);
 if (fd < 0) {
 cerr << "Err: create pid file " << pid_filename_ << " fail. errno:" << errno << ", " << strerror(errno) << endl;
 return false;
 }

 //! 注册函数退出时 close(fd) 动作
 ScopeExitActionGuard close_fd([fd] { close(fd); });

 //! 加锁
 struct flock flock = {
 .l_type = F_WRLCK,
 .l_whence = SEEK_SET,
 .l_start = 0,
 .l_len = 0,
 };

 int ret = fcntl(fd, F_SETLK, &flock);
 if (ret < 0) {
 if (errno == EAGAIN) //! 已被其它进程锁住了
 return false;

 cerr << "Err: lock pid file fail, errno:" << errno << ", " << strerror(errno) << endl;
 return false;
 }

 //! 加锁成功,写入 pid
 pid_t pid = getpid();
 std::string pid_str = std::to_string(pid);
 ssize_t wsize = write(fd, pid_str.c_str(), pid_str.size());
 if (wsize < 0)
 cerr << "Warn: write pid fail. errno:" << errno << ", " << strerror(errno) << endl;

 close_fd.cancel(); //! 不要 close(fd);
 fd_ = fd;

 return true;
}

bool PidFile::unlock()
{
 if (fd_ < 0)
 return false;

 CHECK_CLOSE_RESET_FD(fd_);

 int ret = ::unlink(pid_filename_.c_str());
 if (ret < 0)
 cerr << "Warn: unlink pid file " << pid_filename_ << " fail. errno:" << errno << ", " << strerror(errno) << endl;

 return true;
}

}
}