/*
 * Copyright 2009-2010 Niels Provos and Nick Mathewson
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include "event2/event-config.h"

#ifdef WIN32
#include <winsock2.h>
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#undef WIN32_LEAN_AND_MEAN
#include <sys/locking.h>
#endif

struct event_base;
#include "event2/thread.h"

#include "mm-internal.h"
#include "evthread-internal.h"

#define SPIN_COUNT 2000

static void *
evthread_win32_lock_create(unsigned locktype)
{
	CRITICAL_SECTION *lock = mm_malloc(sizeof(CRITICAL_SECTION));
	if (!lock)
		return NULL;
	if (InitializeCriticalSectionAndSpinCount(lock, SPIN_COUNT) == 0) {
		mm_free(lock);
		return NULL;
	}
	return lock;
}

static void
evthread_win32_lock_free(void *_lock, unsigned locktype)
{
	CRITICAL_SECTION *lock = _lock;
	DeleteCriticalSection(lock);
	mm_free(lock);
}

static int
evthread_win32_lock(unsigned mode, void *_lock)
{
	CRITICAL_SECTION *lock = _lock;
	if ((mode & EVTHREAD_TRY)) {
		return ! TryEnterCriticalSection(lock);
	} else {
		EnterCriticalSection(lock);
		return 0;
	}
}

static int
evthread_win32_unlock(unsigned mode, void *_lock)
{
	CRITICAL_SECTION *lock = _lock;
	LeaveCriticalSection(lock);
	return 0;
}

static unsigned long
evthread_win32_get_id(void)
{
	return (unsigned long) GetCurrentThreadId();
}

#ifdef WIN32_HAVE_CONDITION_VARIABLES
static void WINAPI (*InitializeConditionVariable_fn)(PCONDITION_VARIABLE)
	= NULL;
static BOOL WINAPI (*SleepConditionVariableCS_fn)(
	PCONDITION_VARIABLE, PCRITICAL_SECTION, DWORD) = NULL;
static void WINAPI (*WakeAllConditionVariable_fn)(PCONDITION_VARIABLE) = NULL;
static void WINAPI (*WakeConditionVariable_fn)(PCONDITION_VARIABLE) = NULL;

static int
evthread_win32_condvar_init(void)
{
	HANDLE lib;

	lib = GetModuleHandle(TEXT("kernel32.dll"));
	if (lib == NULL)
		return 0;

#define LOAD(name)				\
	name##_fn = GetProcAddress(lib, #name)
	LOAD(InitializeConditionVariable);
	LOAD(SleepConditionVariable);
	LOAD(WakeAllConditionVariable);
	LOAD(WakeConditionVariable);

	return InitializeConditionVariable_fn && SleepConditionVariableCS_fn &&
	    WakeAllConditionVariable_fn && WakeConditionVariable_fn;
}

/* XXXX Even if we can build this, we don't necessarily want to: the functions
 * in question didn't exist before Vista, so we'd better LoadProc them. */
static void *
evthread_win32_condvar_alloc(unsigned condflags)
{
	CONDITION_VARIABLE *cond = mm_malloc(sizeof(CONDITION_VARIABLE));
	if (!cond)
		return NULL;
	InitializeConditionVariable_fn(cond);
	return cond;
}

static void
evthread_win32_condvar_free(void *_cond)
{
	CONDITION_VARIABLE *cond = _cond;
	/* There doesn't _seem_ to be a cleaup fn here... */
	mm_free(cond);
}

static int
evthread_win32_condvar_signal(void *_cond, int broadcast)
{
	CONDITION_VARIABLE *cond = _cond;
	if (broadcast)
		WakeAllConditionVariable_fn(cond);
	else
		WakeConditionVariable_fn(cond);
	return 0;
}

static int
evthread_win32_condvar_wait(void *_cond, void *_lock, const struct timeval *tv)
{
	CONDITION_VARIABLE *cond = _cond;
	CRITICAL_SECTION *lock = _lock;
	DWORD ms, err;
	BOOL result;

	if (tv)
		ms = evutil_tv_to_msec(tv);
	else
		ms = INFINITE;
	result = SleepConditionVariableCS_fn(cond, lock, ms);
	if (result) {
		if (GetLastError() == WAIT_TIMEOUT)
			return 1;
		else
			return -1;
	} else {
		return 0;
	}
}
#endif

struct evthread_win32_cond {
	HANDLE event;

	CRITICAL_SECTION lock;
	int n_waiting;
	int n_to_wake;
	int generation;
};

static void *
evthread_win32_cond_alloc(unsigned flags)
{
	struct evthread_win32_cond *cond;
	if (!(cond = mm_malloc(sizeof(struct evthread_win32_cond))))
		return NULL;
	if (InitializeCriticalSectionAndSpinCount(&cond->lock, SPIN_COUNT)==0) {
		mm_free(cond);
		return NULL;
	}
	if ((cond->event = CreateEvent(NULL,TRUE,FALSE,NULL)) == NULL) {
		DeleteCriticalSection(&cond->lock);
		mm_free(cond);
		return NULL;
	}
	cond->n_waiting = cond->n_to_wake = cond->generation = 0;
	return cond;
}

static void
evthread_win32_cond_free(void *_cond)
{
	struct evthread_win32_cond *cond = _cond;
	DeleteCriticalSection(&cond->lock);
	CloseHandle(cond->event);
	mm_free(cond);
}

static int
evthread_win32_cond_signal(void *_cond, int broadcast)
{
	struct evthread_win32_cond *cond = _cond;
	EnterCriticalSection(&cond->lock);
	if (broadcast)
		cond->n_to_wake = cond->n_waiting;
	else
		++cond->n_to_wake;
	cond->generation++;
	SetEvent(cond->event);
	LeaveCriticalSection(&cond->lock);
	return 0;
}

static int
evthread_win32_cond_wait(void *_cond, void *_lock, const struct timeval *tv)
{
	struct evthread_win32_cond *cond = _cond;
	CRITICAL_SECTION *lock = _lock;
	int generation_at_start;
	int waiting = 1;
	int result = -1;
	DWORD ms = INFINITE, ms_orig = INFINITE, startTime, endTime;
	if (tv)
		ms_orig = ms = evutil_tv_to_msec(tv);

	EnterCriticalSection(&cond->lock);
	++cond->n_waiting;
	generation_at_start = cond->generation;
	LeaveCriticalSection(&cond->lock);

	LeaveCriticalSection(lock);

	startTime = GetTickCount();
	do {
		DWORD res;
		res = WaitForSingleObject(cond->event, ms);
		EnterCriticalSection(&cond->lock);
		if (cond->n_to_wake &&
		    cond->generation != generation_at_start) {
			--cond->n_to_wake;
			--cond->n_waiting;
			result = 0;
			waiting = 0;
			goto out;
		} else if (res != WAIT_OBJECT_0) {
			result = (res==WAIT_TIMEOUT) ? 1 : -1;
			--cond->n_waiting;
			waiting = 0;
			goto out;
		} else if (ms != INFINITE) {
			endTime = GetTickCount();
			if (startTime + ms_orig <= endTime) {
				result = 1; /* Timeout */
				--cond->n_waiting;
				waiting = 0;
				goto out;
			} else {
				ms = startTime + ms_orig - endTime;
			}
		}
		/* If we make it here, we are still waiting. */
		if (cond->n_to_wake == 0) {
			/* There is nobody else who should wake up; reset
			 * the event. */
			ResetEvent(cond->event);
		}
	out:
		LeaveCriticalSection(&cond->lock);
	} while (waiting);

	EnterCriticalSection(lock);

	EnterCriticalSection(&cond->lock);
	if (!cond->n_waiting)
		ResetEvent(cond->event);
	LeaveCriticalSection(&cond->lock);

	return result;
}

int
evthread_use_windows_threads(void)
{
	struct evthread_lock_callbacks cbs = {
		EVTHREAD_LOCK_API_VERSION,
		EVTHREAD_LOCKTYPE_RECURSIVE,
		evthread_win32_lock_create,
		evthread_win32_lock_free,
		evthread_win32_lock,
		evthread_win32_unlock
	};


	struct evthread_condition_callbacks cond_cbs = {
		EVTHREAD_CONDITION_API_VERSION,
		evthread_win32_cond_alloc,
		evthread_win32_cond_free,
		evthread_win32_cond_signal,
		evthread_win32_cond_wait
	};
#ifdef WIN32_HAVE_CONDITION_VARIABLES
	struct evthread_condition_callbacks condvar_cbs = {
		EVTHREAD_CONDITION_API_VERSION,
		evthread_win32_condvar_alloc,
		evthread_win32_condvar_free,
		evthread_win32_condvar_signal,
		evthread_win32_condvar_wait
	};
#endif

	evthread_set_lock_callbacks(&cbs);
	evthread_set_id_callback(evthread_win32_get_id);
#ifdef WIN32_HAVE_CONDITION_VARIABLES
	if (evthread_win32_condvar_init()) {
		evthread_set_condition_callbacks(&condvar_cbs);
		return 0;
	}
#endif
	evthread_set_condition_callbacks(&cond_cbs);

	return 0;
}