/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * process.cpp - Process object
 */

#include "libcamera/internal/process.h"

#include <algorithm>
#include <dirent.h>
#include <fcntl.h>
#include <iostream>
#include <list>
#include <signal.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <vector>

#include "libcamera/internal/event_notifier.h"
#include "libcamera/internal/log.h"
#include "libcamera/internal/utils.h"

/**
 * \file process.h
 * \brief Process object
 */

namespace libcamera {

LOG_DEFINE_CATEGORY(Process)

/**
 * \class ProcessManager
 * \brief Manager of processes
 *
 * The ProcessManager singleton keeps track of all created Process instances,
 * and manages the signal handling involved in terminating processes.
 */

namespace {

void sigact(int signal, siginfo_t *info, void *ucontext)
{
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-result"
	/*
	 * We're in a signal handler so we can't log any message, and we need
	 * to continue anyway.
	 */
	char data = 0;
	write(ProcessManager::instance()->writePipe(), &data, sizeof(data));
#pragma GCC diagnostic pop

	const struct sigaction &oldsa = ProcessManager::instance()->oldsa();
	if (oldsa.sa_flags & SA_SIGINFO) {
		oldsa.sa_sigaction(signal, info, ucontext);
	} else {
		if (oldsa.sa_handler != SIG_IGN && oldsa.sa_handler != SIG_DFL)
			oldsa.sa_handler(signal);
	}
}

} /* namespace */

void ProcessManager::sighandler([[maybe_unused]] EventNotifier *notifier)
{
	char data;
	ssize_t ret = read(pipe_[0], &data, sizeof(data));
	if (ret < 0) {
		LOG(Process, Error)
			<< "Failed to read byte from signal handler pipe";
		return;
	}

	for (auto it = processes_.begin(); it != processes_.end(); ) {
		Process *process = *it;

		int wstatus;
		pid_t pid = waitpid(process->pid_, &wstatus, WNOHANG);
		if (process->pid_ != pid) {
			++it;
			continue;
		}

		it = processes_.erase(it);
		process->died(wstatus);
	}
}

/**
 * \brief Register process with process manager
 * \param[in] proc Process to register
 *
 * This method registers the \a proc with the process manager. It
 * shall be called by the parent process after successfully forking, in
 * order to let the parent signal process termination.
 */
void ProcessManager::registerProcess(Process *proc)
{
	processes_.push_back(proc);
}

ProcessManager *ProcessManager::self_ = nullptr;

/**
 * \brief Construct a ProcessManager instance
 *
 * The ProcessManager class is meant to only be instantiated once, by the
 * CameraManager.
 */
ProcessManager::ProcessManager()
{
	if (self_)
		LOG(Process, Fatal)
			<< "Multiple ProcessManager objects are not allowed";

	sigaction(SIGCHLD, NULL, &oldsa_);

	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_sigaction = &sigact;
	memcpy(&sa.sa_mask, &oldsa_.sa_mask, sizeof(sa.sa_mask));