/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * SPDX-License-Identifier: MPL-2.0
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0.  If a copy of the MPL was not distributed with this
 * file, you can obtain one at https://mozilla.org/MPL/2.0/.
 *
 * See the COPYRIGHT file distributed with this work for additional
 * information regarding copyright ownership.
 */

#include <inttypes.h>
#include <stdbool.h>

#include <isc/assertions.h>
#include <isc/condition.h>
#include <isc/error.h>
#include <isc/strerr.h>
#include <isc/thread.h>
#include <isc/time.h>
#include <isc/util.h>

#define LSIGNAL	   0
#define LBROADCAST 1

void
isc_condition_init(isc_condition_t *cond) {
	HANDLE h;

	REQUIRE(cond != NULL);

	cond->waiters = 0;
	/*
	 * This handle is shared across all threads
	 */
	h = CreateEvent(NULL, FALSE, FALSE, NULL);
	if (h == NULL) {
		char strbuf[ISC_STRERRORSIZE];
		DWORD err = GetLastError();
		strerror_r(err, strbuf, sizeof(strbuf));
		isc_error_fatal(__FILE__, __LINE__, "CreateEvent failed: %s",
				strbuf);
	}
	cond->events[LSIGNAL] = h;

	/*
	 * The threadlist will hold the actual events needed
	 * for the wait condition
	 */
	ISC_LIST_INIT(cond->threadlist);
}

/*
 * Add the thread to the threadlist along with the required events
 */
static isc_result_t
register_thread(unsigned long thrd, isc_condition_t *gblcond,
		isc_condition_thread_t **localcond) {
	HANDLE hc;
	isc_condition_thread_t *newthread;

	REQUIRE(localcond != NULL && *localcond == NULL);

	newthread = malloc(sizeof(isc_condition_thread_t));
	if (newthread == NULL) {
		return (ISC_R_NOMEMORY);
	}

	/*
	 * Create the thread-specific handle
	 */
	hc = CreateEvent(NULL, FALSE, FALSE, NULL);
	if (hc == NULL) {
		free(newthread);
		return (ISC_R_UNEXPECTED);
	}

	/*
	 * Add the thread ID and handles to list of threads for broadcast
	 */
	newthread->handle[LSIGNAL] = gblcond->events[LSIGNAL];
	newthread->handle[LBROADCAST] = hc;
	newthread->th = thrd;

	/*
	 * The thread is holding the manager lock so this is safe
	 */
	ISC_LINK_INIT(newthread, link);
	ISC_LIST_APPEND(gblcond->threadlist, newthread, link);
	*localcond = newthread;
	return (ISC_R_SUCCESS);
}

static isc_result_t
find_thread_condition(uintptr_t thrd, isc_condition_t *cond,
		      isc_condition_thread_t **threadcondp) {
	isc_condition_thread_t *threadcond;

	REQUIRE(threadcondp != NULL && *threadcondp == NULL);

	/*
	 * Look for the thread ID.
	 */
	for (threadcond = ISC_LIST_HEAD(cond->threadlist); threadcond != NULL;
	     threadcond = ISC_LIST_NEXT(threadcond, link))
	{
		if (threadcond->th == thrd) {
			*threadcondp = threadcond;
			return (ISC_R_SUCCESS);
		}
	}

	/*
	 * Not found, so add it.
	 */
	return (register_thread(thrd, cond, threadcondp));
}

isc_result_t
isc_condition_signal(isc_condition_t *cond) {
	/*
	 * Unlike pthreads, the caller MUST hold the lock associated with
	 * the condition variable when calling us.
	 */
	REQUIRE(cond != NULL);

	if (!SetEvent(cond->events[LSIGNAL])) {
		/* XXX */
		return (ISC_R_UNEXPECTED);
	}
	return (ISC_R_SUCCESS);
}

isc_result_t
isc_condition_broadcast(isc_condition_t *cond) {
	isc_condition_thread_t *threadcond;
	bool failed = false;

	/*
	 * Unlike pthreads, the caller MUST hold the lock associated with
	 * the condition variable when calling us.
	 */
	REQUIRE(cond != NULL);

	/*
	 * Notify every thread registered for this
	 */
	for (threadcond = ISC_LIST_HEAD(cond->threadlist); threadcond != NULL;
	     threadcond = ISC_LIST_NEXT(threadcond, link))
	{
		if (!SetEvent(threadcond->handle[LBROADCAST])) {
			failed = true;
		}
	}

	if (failed) {
		return (ISC_R_UNEXPECTED);
	}

	return (ISC_R_SUCCESS);
}

isc_result_t
isc_condition_destroy(isc_condition_t *cond) {
	isc_condition_thread_t *next, *threadcond;

	REQUIRE(cond != NULL);
	REQUIRE(cond->waiters == 0);

	(void)CloseHandle(cond->events[LSIGNAL]);

	/*
	 * Delete the threadlist
	 */
	threadcond = ISC_LIST_HEAD(cond->threadlist);

	while (threadcond != NULL) {
		next = ISC_LIST_NEXT(threadcond, link);
		DEQUEUE(cond->threadlist, threadcond, link);
		(void)CloseHandle(threadcond->handle[LBROADCAST]);
		free(threadcond);
		threadcond = next;
	}

	return (ISC_R_SUCCESS);
}

/*
 * This is always called when the mutex (lock) is held, but because
 * we are waiting we need to release it and reacquire it as soon as the wait
 * is over. This allows other threads to make use of the object guarded
 * by the mutex but it should never try to delete it as long as the
 * number of waiters > 0. Always reacquire the mutex regardless of the
 * result of the wait. Note that EnterCriticalSection will wait to acquire
 * the mutex.
 */
static isc_result_t
wait(isc_condition_t *cond, isc_mutex_t *mutex, DWORD milliseconds) {
	DWORD result;
	isc_result_t tresult;
	isc_condition_thread_t *threadcond = NULL;

	/*
	 * Get the thread events needed for the wait
	 */
	tresult = find_thread_condition(isc_thread_self(), cond, &threadcond);
	if (tresult != ISC_R_SUCCESS) {
		return (tresult);
	}

	cond->waiters++;
	LeaveCriticalSection(mutex);
	result = WaitForMultipleObjects(2, threadcond->handle, FALSE,
					milliseconds);
	EnterCriticalSection(mutex);
	cond->waiters--;
	if (result == WAIT_FAILED) {
		/* XXX */
		return (ISC_R_UNEXPECTED);
	}
	if (result == WAIT_TIMEOUT) {
		return (ISC_R_TIMEDOUT);
	}

	return (ISC_R_SUCCESS);
}

isc_result_t
isc_condition_wait(isc_condition_t *cond, isc_mutex_t *mutex) {
	return (wait(cond, mutex, INFINITE));
}

isc_result_t
isc_condition_waituntil(isc_condition_t *cond, isc_mutex_t *mutex,
			isc_time_t *t) {
	DWORD milliseconds;
	uint64_t microseconds;
	isc_time_t now;

	if (isc_time_now(&now) != ISC_R_SUCCESS) {
		/* XXX */
		return (ISC_R_UNEXPECTED);
	}

	microseconds = isc_time_microdiff(t, &now);
	if (microseconds > 0xFFFFFFFFi64 * 1000) {
		milliseconds = 0xFFFFFFFF;
	} else {
		milliseconds = (DWORD)(microseconds / 1000);
	}

	return (wait(cond, mutex, milliseconds));
}