#include <unistd.h>
#include <fcntl.h>
#include <sys/select.h>
#include <sys/epoll.h>
#include <stdio.h>
#include <sys/wait.h>
#include <sys/signalfd.h>
#include <sys/resource.h>

#include "process.h"
#include "debug.h"
#include "utils.h"

static int epoll_fd;
static unsigned int max_jobs;
static unsigned int max_jobs_pending;

struct work_struct {
	const char *name;
	int (*work_fn)(void *);
	void *arg;
	struct work_struct *next;
};

struct work_queue {
	struct work_struct *work;
	int length;
	char *name;
	struct mutex lock;
};

struct work_queue work_queues[WORK_PRIORITIES_NUM] = {
	{
		.name = "high priority",
		.lock = {
			.name = "high_prio_queue",
			.lock = PTHREAD_MUTEX_INITIALIZER,
		},
	},
	{
		.name = "low priority",
		.lock = {
			.name = "low_prio_queue",
			.lock = PTHREAD_MUTEX_INITIALIZER,
		},
	},
};

struct mutex work_stats_mutex = {
	.name = "work_stats",
	.lock = PTHREAD_MUTEX_INITIALIZER,
};
static int workers_active;
static int worker_count;

static int job_notify_fd[2];

static int run_work_on_queue(struct work_queue *queue)
{
	struct work_struct *work;

	mutex_lock(&queue->lock);

	if (!queue->work) {
		mutex_unlock(&queue->lock);
		return 0;
	}

	/* Take next work */
	work = queue->work;
	queue->work = work->next;
	queue->length--;

	mutex_unlock(&queue->lock);

	pr_info("Executing work %s from queue %s, %d still pending\n",
		work->name, queue->name, queue->length);

	work->work_fn(work->arg);
	pr_info("Work %s done\n", work->name);
	free(work);

	return 1;
}

static void *worker_thread(void *arg)
{
	int ret;
	char name[16];

	mutex_lock(&work_stats_mutex);
	snprintf(name, sizeof(name), "worker%d", worker_count);
	worker_count++;
	mutex_unlock(&work_stats_mutex);

	pthread_setname_np(pthread_self(), name);
	pthread_detach(pthread_self());

	pr_info("Worker started\n");

	/* Execute all high priority work from the queue */
	while (run_work_on_queue(&work_queues[WORK_PRIORITY_HIGH]))
		;
	/*
	 * All high priority work is now done, see if we have enough
	 * workers executing low priority worl. Continue from there if
	 * needed.
	 */
	mutex_lock(&work_stats_mutex);
	if (workers_active > max_jobs)
		goto out_unlock;

	mutex_unlock(&work_stats_mutex);

	/*
	 * Start executing the low priority work. Drop the nice value
	 * as this really is low priority stuff
	 */
	ret = nice(19);
	pr_info("Worker priority dropped to %d\n", ret);

	while (run_work_on_queue(&work_queues[WORK_PRIORITY_LOW]))
		;

	/* All done, exit */
	mutex_lock(&work_stats_mutex);
out_unlock:
	workers_active--;
	pr_info("Worker exiting, %d left active\n",
		workers_active);

	/*
	 * Last exiting worker zeroes the worker_count. This
	 * ensures next time we start spawning worker threads
	 * the first thread will have number zero on its name.
	 */
	if (!workers_active)
		worker_count = 0;

	/*
	 * Kick the job poller. If all jobs were active at this point
	 * the scheduler thread will wait indefinitely until someone
	 * tells it to do something. We may now know when next job is
	 * available, so it is better for the scheduler to recalculate
	 * its sleep time.
	 */
	notify_job_request();

	mutex_unlock(&work_stats_mutex);

	return NULL;
}

int queue_work(unsigned int priority, char *name,
	int (work_fn)(void *arg), void *arg)
{
	pthread_t *thread;
	struct work_queue *queue;
	struct work_struct *work, *last_work;

	if (priority >= WORK_PRIORITIES_NUM) {
		pr_err("Invalid priority: %d\n", priority);
		return -EINVAL;
	}

	work = calloc(sizeof(*work), 1);

	work->name = name;
	work->work_fn = work_fn;
	work->arg = arg;

	queue = &work_queues[priority];

	/* Insert new work at the end of the work queue */
	mutex_lock(&queue->lock);

	last_work = queue->work;
	while (last_work && last_work->next)
		last_work = last_work->next;

	if (!last_work)
		queue->work = work;
	else
		last_work->next = work;

	pr_info("Inserted work %s in queue %s, with %d pending items\n",
		work->name, queue->name, queue->length);
	queue->length++;
	mutex_unlock(&queue->lock);

	mutex_lock(&work_stats_mutex);
	pr_info("workers_active: %d, priority: %d\n", workers_active, priority);
	if (priority != WORK_PRIORITY_HIGH && workers_active >= max_jobs) {
		mutex_unlock(&work_stats_mutex);
		return 0;
	}
	workers_active++;
	mutex_unlock(&work_stats_mutex);

	pr_info("Creating new worker thread\n");
	/* We need a worker thread, create one */
	thread = calloc(sizeof(*thread), 1);
	pthread_create(thread, NULL, worker_thread, NULL);

	free(thread);

	return 0;
}

static int job_notify_handler(struct event_handler *h)
{
	int ret;
	char buf[64];

	ret = read(job_notify_fd[0], buf, sizeof(buf));
	if (ret < 0)
		pr_err("Failed to read: %m\n");

	return 0;
}

/*
 * Initialize the jobcontrol.
 *
 * Create the pipes that are used to grant children execution
 * permissions. If max_jobs is zero, count the number of CPUs from
 * /proc/cpuinfo and use that.
 */
int init_jobcontrol(int max_jobs_requested)
{
	static struct event_handler ev;
	FILE *file;
	int ret;
	char buf[256];
	char match[8];

	epoll_fd = epoll_create(1);
	if (epoll_fd == -1) {
		pr_err("Failed to epoll_create(): %m\n");
		return -1;
	}

	if (max_jobs_requested > 0) {
		max_jobs = max_jobs_requested;
		goto no_count_cpus;
	}
	max_jobs++;

	file = fopen("/proc/cpuinfo", "ro");
	if (!file) {
		pr_err("Failed to open /proc/cpuinfo: %m\n");
		goto open_fail;
	}

	/*
	 * The CPU count algorithm simply reads the first 8 bytes from
	 * the /proc/cpuinfo and then expects that line to be there as
	 * many times as there are CPUs.
	 */
	ret = fread(match, 1, sizeof(match), file);
	if (ret < sizeof(match)) {
		pr_err("read %d bytes when expecting %zd %m\n",
			ret, sizeof(match));
		goto read_fail;
	}

	while(fgets(buf, sizeof(buf), file)) {
		if (!strncmp(buf, match, sizeof(match)))
			max_jobs++;
	}

	ret = pipe(job_notify_fd);
	if (ret) {
		pr_err("pipe() failed: %m\n");
		return ret;
	}

	ev.fd = job_notify_fd[0];
	ev.events = EPOLLIN;
	ev.handle_event = job_notify_handler;
	ev.name = "job_notify";
	register_event_handler(&ev, EPOLL_CTL_ADD);

open_fail:
read_fail:
	fclose(file);

no_count_cpus:
	pr_info("Set maximum number of parallel jobs to %d\n", max_jobs);

	max_jobs_pending = max_jobs * 10 + 25;
	pr_info("Set maximum number of pending jobs to %d\n", max_jobs_pending);

	return 0;
}

int poll_job_requests(int timeout)
{
	struct epoll_event event;
	struct event_handler *job_handler;
	int ret;

	/* Convert positive seconds to milliseconds */
	timeout = timeout > 0 ? 1000 * timeout : timeout;

	ret = epoll_wait(epoll_fd, &event, 1, timeout);

	if (ret == -1) {
		if (errno != EINTR) {
			pr_err("epoll_wait: %m\n");
			return -1;
		}

		/*
		 * If epoll_wait() was interrupted, better start
		 * everything again from the beginning
		 */
		return 0;
	}

	if (ret == 0) {
		pr_info("Timed out\n");
		goto out;
	}

	job_handler = event.data.ptr;

	if (!job_handler || !job_handler->handle_event) {
		pr_err("Corrupted event handler for fd %d\n",
			event.data.fd);
		goto out;
	}

	pr_debug("Running handler %s to handle events from fd %d\n",
		job_handler->name, job_handler->fd);
	job_handler->handle_event(job_handler);

out:
	pr_info("Workers active: %u\n", workers_active);
	return ret;
}

int notify_job_request(void)
{
	int ret;
	char byte = 0;

	ret = write(job_notify_fd[1], &byte, sizeof(byte));
	if (ret < 0)
		pr_err("Failed to write: %m\n");

	return 0;
}

int do_fork(void)
{
	int child;
	child = fork();
	if (child < 0) {
		pr_err("fork() failed: %m\n");
		return -1;
	}

	if (child) {
		pr_debug("Fork child %d\n", child);
		return child;
	}

	return 0;
}

int clear_zombie(int pid)
{
	int status;
	struct rusage rusage;
	char *status_str = NULL;
	int code = 0;

	if (pid)
		pr_debug("Waiting on pid %d\n", pid);

	do {
		pid = wait4(pid, &status, 0, &rusage);
		if (pid < 0) {
			pr_err("Error on waitid(): %m\n");
			return 0;
		}
		/* Wait until the child has become a zombie */
	} while (!WIFEXITED(status) && !WIFSIGNALED(status));

	if (WIFEXITED(status)) {
		status_str = "exited with status";
		code = WEXITSTATUS(status);
	} else if (WIFSIGNALED(status)) {
		status_str = "killed by signal";
		code = WTERMSIG(status);
	}
	pr_debug("pid %d: %s %d.\n", pid,
		status_str, code);
	pr_debug("pid %d: User time: %ld.%03lds, System %ld.%03lds\n", pid,
		(long)rusage.ru_utime.tv_sec, rusage.ru_utime.tv_usec / 1000,
		(long)rusage.ru_stime.tv_sec, rusage.ru_stime.tv_usec / 1000);

	return 1;
}

/*
 * Runs a command cmd with params argv, connects stdin and stdout to
 * readfd and writefd
 *
 * Returns the pid of the executed process
 */
int run_piped(const char *cmd, char *const argv[],
	      int *stdinfd, int *stdoutfd, int *stderrfd)
{
	int ifd[2], ofd[2], efd[2], pid;

	pr_info("Running command %s\n", cmd);

	if (stdinfd && pipe(ifd)) {
		pr_err("pipe() failed: %m\n");
		return -1;
	}

	if (stdoutfd && pipe(ofd)) {
		pr_err("pipe() failed: %m\n");
		goto close_ifd;
	}

	if (stderrfd && pipe(efd)) {
		pr_err("pipe() failed: %m\n");
		goto close_ofd;
	}

	pid = do_fork();
	if (pid) { /* Parent side */
		if (stdinfd) {
			close(ifd[0]);
			*stdinfd = ifd[0];
		}

		if (stdoutfd) {
			close(ofd[1]);
			*stdoutfd = ofd[0];
		}

		if (stderrfd) {
			close(efd[1]);
			*stderrfd = efd[0];
		}

		return pid;
	}

	if (stdinfd) {
		close(ifd[1]);
		dup2(ifd[0], STDIN_FILENO);
	}

	if (stdoutfd) {
		close(ofd[0]);
		dup2(ofd[1], STDOUT_FILENO);
	}

	if (stderrfd) {
		close(efd[0]);
		dup2(efd[1], STDERR_FILENO);
	}

	/* Now we have redirected standard streams to parent process */
	execvp(cmd, argv);
	pr_err("Failed to execv command %s: %m\n", cmd);
	exit(1);

	return 0;

close_ofd:
	if (stdoutfd) {
		close(ofd[0]);
		close(ofd[1]);
	}
close_ifd:
	if (stdinfd) {
		close(ifd[0]);
		close(ifd[1]);
	}

	return -1;
}

/*
 * Runs a command cmd with params argv, connects stdin and stdout to
 * readfd and writefd
 *
 * Returns the pid of the executed process
 */
int run_piped_stream(const char *cmd, char *const argv[],
		     FILE **stdinf, FILE **stdoutf, FILE **stderrf)
{
	int ifd, ofd, efd, pid;
	int *i, *o, *e;

	if (stdinf)
		i = &ifd;
	else
		i = 0;
	if (stdoutf)
		o = &ofd;
	else
		o = 0;
	if (stderrf)
		e = &efd;
	else
		e = 0;

	pid = run_piped(cmd, argv, i, o, e);

	if (stdinf) {
		*stdinf = fdopen(ifd, "w");
		if (*stdinf == NULL) {
			pr_err("Error opening file stream for fd %d: %m\n",
			       ifd);
			return -1;
		}
	}

	if (stdoutf) {
		*stdoutf = fdopen(ofd, "r");
		if (*stdoutf == NULL) {
			pr_err("Error opening file stream for fd %d: %m\n",
			       ofd);
			return -1;
		}
	}

	if (stderrf) {
		*stderrf = fdopen(efd, "r");
		if (*stderrf == NULL) {
			pr_err("Error opening file stream for fd %d: %m\n",
			       efd);
			return -1;
		}
	}

	return pid;
}

/*
 * Forks a child and executes a command to run on parallel
 */

#define BUF_SIZE (128*1024)
int run(const char *cmd, char *const argv[])
{
	int child, error;
	int ofd, efd;
	fd_set rfds;
	int maxfd;
	int eof = 0;

	child = run_piped(cmd, argv, NULL, &ofd, &efd);

	FD_ZERO(&rfds);
	FD_SET(ofd, &rfds);
	FD_SET(efd, &rfds);

	while (!eof) {
		char *sptr , *eptr;
		char rbuf[BUF_SIZE];
		int bytes;
		int is_stderr = 0;

		maxfd = max(ofd, efd);
		error = select(maxfd, &rfds, NULL, NULL, NULL);

		if (error < 0) {
			pr_err("Error with select: %m\n");
			break;
		}

		if (FD_ISSET(ofd, &rfds)) {
			bytes = read(ofd, rbuf, BUF_SIZE);
			goto print;
		}

		if (FD_ISSET(efd, &rfds)) {
			is_stderr = 1;
			bytes = read(efd, rbuf, BUF_SIZE);
			goto print;
		}

		pr_err("select() returned unknown fd\n");
		break;

print:
		if (bytes < 0) {
			pr_err("read() failed: %m\n");
			break;
		}

		/*
		 * Workaround: When a process had die and it has only
		 * written to stderr, select() doesn't indicate that
		 * there might be something to read in stderr fd. To
		 * work around this issue, we try to read stderr just
		 * in case in order to ensure everything gets read.
		 */
		if (bytes == 0) {
			bytes = read(efd, rbuf, BUF_SIZE);
			is_stderr = 1;
			eof = 1;
		}

		sptr = eptr = rbuf;
		while (bytes--) {
			if (*eptr == '\n') {
				*eptr = 0;
				if (is_stderr)
					pr_err("%s: stderr: %s\n",
						cmd, sptr);
				else
					pr_info("%s: stdout: %s\n",
						cmd, sptr);
				sptr = eptr + 1;
			}
			eptr++;
		}
	}

	close(ofd);
	close(efd);

	clear_zombie(child);

	return 0;
}

int register_event_handler(struct event_handler *handler, int op)
{
	struct epoll_event ev;
	int ret;
	const char *str;

	if (handler->fd <= 0) {
		pr_err("Invalid file descriptor of %d\n", handler->fd);
		return -1;
	}

	if (!handler->handle_event) {
		pr_err("Handler callback missing\n");
		return -1;
	}

	switch (op) {
	case EPOLL_CTL_ADD:
		str = "register";
		break;

	case EPOLL_CTL_MOD:
		str = "modify";
		break;

	case EPOLL_CTL_DEL:
		str = "deregister";
		break;

	default:
		pr_err("Invalid op %d\n", op);
		return -1;
	}

	pr_info("Doing a epoll %s for handler %s, fd %d\n", str,
		handler->name, handler->fd);

	ev.data.fd = handler->fd;
	ev.data.ptr = handler;
	ev.events = handler->events;
	ret = epoll_ctl(epoll_fd, op, handler->fd, &ev);
	if (ret) {
		pr_err("Failed to do epoll_ctl %s: %m\n", str);
		return -1;
	}

	return 0;
}

void _mutex_lock_acquired(struct mutex *lock, char *file, int line)
{
	lock->line = line;
	lock->file = file;
	pthread_getname_np(pthread_self(),
			lock->owner_name, sizeof(lock->owner_name));
}

int _mutex_lock(struct mutex *lock, char *file, int line)
{
	int ret = 0;
	int contended = 0;

	if (!pthread_mutex_trylock(&lock->lock))
		goto out_lock;

	contended = 1;
	pr_debug("Lock contention at %s:%d on lock %s acquired by %s at %s:%d\n",
		file, line, lock->name,
		lock->owner_name, lock->file, lock->line);

	ret = pthread_mutex_lock(&lock->lock);
	if (ret)
		pr_err("Acquirin lock %s failed: %m, acquired on %s:%d\n",
			lock->name, lock->file, lock->line);

out_lock:
	if (contended)
		pr_debug("Lock %s acquired at %s:%d after contention\n",
			lock->name, file, line);
	_mutex_lock_acquired(lock, file, line);
	return ret;
}

int _mutex_unlock(struct mutex *lock)
{
	lock->line = 0;
	lock->file = NULL;
	pthread_mutex_unlock(&lock->lock);

	return 0;
}