/*
 * Copyright 2006-2013, Haiku, Inc. All Rights Reserved.
 * Distributed under the terms of the MIT License.
 *
 * Authors:
 *		Axel Dörfler, axeld@pinc-software.de
 */


#include "utility.h"

#include <ByteOrder.h>
#include <KernelExport.h>

#include <condition_variable.h>
#include <net_buffer.h>
#include <syscall_restart.h>
#include <util/AutoLock.h>

#include "stack_private.h"


//#define TRACE_UTILITY
#ifdef TRACE_UTILITY
#	define TRACE(x...) dprintf(x)
#else
#	define TRACE(x...) ;
#endif


// internal Fifo class which doesn't maintain it's own lock
// TODO: do we need this one for anything?
class Fifo {
public:
	Fifo(const char* name, size_t maxBytes);
	~Fifo();

	status_t InitCheck() const;

	status_t Enqueue(net_buffer* buffer);
	status_t EnqueueAndNotify(net_buffer* _buffer, net_socket* socket,
		uint8 event);
	status_t Wait(mutex* lock, bigtime_t timeout);
	net_buffer* Dequeue(bool clone);
	status_t Clear();

	void WakeAll();

	bool IsEmpty() const { return current_bytes == 0; }

//private:
	// these field names are kept so we can use templatized
	// functions together with net_fifo
	sem_id		notify;
	int32		waiting;
	size_t		max_bytes;
	size_t		current_bytes;
	struct list	buffers;
};



static struct list sTimers;
static mutex sTimerLock;
static sem_id sTimerWaitSem;
static ConditionVariable sWaitForTimerCondition;
static net_timer* sCurrentTimer;
static thread_id sTimerThread;
static bigtime_t sTimerTimeout;


static inline void
fifo_notify_one_reader(int32& waiting, sem_id sem)
{
	if (waiting > 0) {
		waiting--;
		release_sem_etc(sem, 1, B_DO_NOT_RESCHEDULE);
	}
}


template<typename FifoType> static inline status_t
base_fifo_init(FifoType* fifo, const char* name, size_t maxBytes)
{
	fifo->notify = create_sem(0, name);
	fifo->max_bytes = maxBytes;
	fifo->current_bytes = 0;
	fifo->waiting = 0;
	list_init(&fifo->buffers);

	return fifo->notify;
}


template<typename FifoType> static inline status_t
base_fifo_enqueue_buffer(FifoType* fifo, net_buffer* buffer)
{
	if (fifo->max_bytes > 0
		&& fifo->current_bytes + buffer->size > fifo->max_bytes)
		return ENOBUFS;

	list_add_item(&fifo->buffers, buffer);
	fifo->current_bytes += buffer->size;
	fifo_notify_one_reader(fifo->waiting, fifo->notify);

	return B_OK;
}


template<typename FifoType> static inline status_t
base_fifo_clear(FifoType* fifo)
{
	while (true) {
		net_buffer* buffer = (net_buffer*)list_remove_head_item(&fifo->buffers);
		if (buffer == NULL)
			break;

		gNetBufferModule.free(buffer);
	}

	fifo->current_bytes = 0;
	return B_OK;
}


// #pragma mark - UserBuffer


void*
UserBuffer::Push(void* source, size_t length)
{
	if (fStatus != B_OK)
		return NULL;

	if (fAvailable < length) {
		fStatus = ENOBUFS;
		return NULL;
	}

#ifdef _KERNEL_MODE
	fStatus = user_memcpy(fBuffer, source, length);
	if (fStatus != B_OK)
		return NULL;
#else
	memcpy(fBuffer, source, length);
#endif

	void* current = fBuffer;

	fAvailable -= length;
	fBuffer += length;

	return current;
}


status_t
UserBuffer::Pad(size_t length)
{
	if (fStatus != B_OK)
		return fStatus;

	if (fAvailable < length)
		return fStatus = ENOBUFS;

	fStatus = user_memset(fBuffer, 0, length);
	if (fStatus != B_OK)
		return fStatus;

	fAvailable -= length;
	fBuffer += length;

	return B_OK;
}


status_t
UserBuffer::PadToNext(size_t length)
{
	return Pad((BytesConsumed() + length - 1) / length - BytesConsumed());
}


// #pragma mark -


uint16
compute_checksum(uint8* _buffer, size_t length)
{
	uint16* buffer = (uint16*)_buffer;
	uint32 sum = 0;

	// TODO: unfold loop for speed
	// TODO: write processor dependent version for speed
	while (length >= 2) {
		sum += *buffer++;
		length -= 2;
	}

	if (length) {
		// give the last byte it's proper endian-aware treatment
#if B_HOST_IS_LENDIAN
		sum += *(uint8*)buffer;
#else
		uint8 ordered[2];
		ordered[0] = *(uint8*)buffer;
		ordered[1] = 0;
		sum += *(uint16*)ordered;
#endif
	}

	while (sum >> 16) {
		sum = (sum & 0xffff) + (sum >> 16);
	}

	return sum;
}


uint16
checksum(uint8* buffer, size_t length)
{
	return ~compute_checksum(buffer, length);
}


//	#pragma mark - Notifications


status_t
notify_socket(net_socket* socket, uint8 event, int32 value)
{
	return gNetSocketModule.notify(socket, event, value);
}


//	#pragma mark - FIFOs


Fifo::Fifo(const char* name, size_t maxBytes)
{
	base_fifo_init(this, name, maxBytes);
}


Fifo::~Fifo()
{
	Clear();
	delete_sem(notify);
}


status_t
Fifo::InitCheck() const
{
	return !(notify < B_OK);
}


status_t
Fifo::Enqueue(net_buffer* buffer)
{
	return base_fifo_enqueue_buffer(this, buffer);
}


status_t
Fifo::EnqueueAndNotify(net_buffer* _buffer, net_socket* socket, uint8 event)
{
	net_buffer *buffer = gNetBufferModule.clone(_buffer, false);
	if (buffer == NULL)
		return B_NO_MEMORY;

	status_t status = Enqueue(buffer);
	if (status < B_OK)
		gNetBufferModule.free(buffer);
	else
		notify_socket(socket, event, current_bytes);

	return status;
}


status_t
Fifo::Wait(mutex* lock, bigtime_t timeout)
{
	waiting++;
	mutex_unlock(lock);
	status_t status = acquire_sem_etc(notify, 1,
		B_CAN_INTERRUPT | B_ABSOLUTE_TIMEOUT, timeout);
	mutex_lock(lock);
	return status;
}


net_buffer*
Fifo::Dequeue(bool clone)
{
	net_buffer* buffer = (net_buffer*)list_get_first_item(&buffers);

	// assert(buffer != NULL);

	if (clone) {
		buffer = gNetBufferModule.clone(buffer, false);
		fifo_notify_one_reader(waiting, notify);
	}else {
		list_remove_item(&buffers, buffer);
		current_bytes -= buffer->size;
	}

	return buffer;
}


status_t
Fifo::Clear()
{
	return base_fifo_clear(this);
}


void
Fifo::WakeAll()
{
#ifdef __HAIKU__
	release_sem_etc(notify, 0, B_RELEASE_ALL);
#else
	release_sem_etc(notify, 0, waiting);
#endif
}


status_t
init_fifo(net_fifo* fifo, const char* name, size_t maxBytes)
{
	mutex_init_etc(&fifo->lock, name, MUTEX_FLAG_CLONE_NAME);

	status_t status = base_fifo_init(fifo, name, maxBytes);
	if (status < B_OK)
		mutex_destroy(&fifo->lock);

	return status;
}


void
uninit_fifo(net_fifo* fifo)
{
	clear_fifo(fifo);

	mutex_destroy(&fifo->lock);
	delete_sem(fifo->notify);
}


status_t
fifo_enqueue_buffer(net_fifo* fifo, net_buffer* buffer)
{
	MutexLocker locker(fifo->lock);
	return base_fifo_enqueue_buffer(fifo, buffer);
}


/*!	Gets the first buffer from the FIFO. If there is no buffer, it
	will wait depending on the \a flags and \a timeout.
	The following flags are supported (the rest is ignored):
		MSG_DONTWAIT - ignores the timeout and never wait for a buffer; if your
			socket is O_NONBLOCK, you should specify this flag. A \a timeout of
			zero is equivalent to this flag, though.
		MSG_PEEK - returns a clone of the buffer and keep the original
			in the FIFO.
*/
ssize_t
fifo_dequeue_buffer(net_fifo* fifo, uint32 flags, bigtime_t timeout,
	net_buffer** _buffer)
{
	MutexLocker locker(fifo->lock);
	bool dontWait = (flags & MSG_DONTWAIT) != 0 || timeout == 0;
	status_t status;

	while (true) {
		net_buffer* buffer = (net_buffer*)list_get_first_item(&fifo->buffers);
		if (buffer != NULL) {
			if ((flags & MSG_PEEK) != 0) {
				// we need to clone the buffer for inspection; we can't give a
				// handle to a buffer that we're still using
				buffer = gNetBufferModule.clone(buffer, false);
				if (buffer == NULL) {
					status = B_NO_MEMORY;
					break;
				}
			} else {
				list_remove_item(&fifo->buffers, buffer);
				fifo->current_bytes -= buffer->size;
			}

			*_buffer = buffer;
			status = B_OK;
			break;
		}

		if (!dontWait)
			fifo->waiting++;

		locker.Unlock();

		if (dontWait)
			return B_WOULD_BLOCK;

		// we need to wait until a new buffer becomes available
		status = acquire_sem_etc(fifo->notify, 1,
			B_CAN_INTERRUPT | B_RELATIVE_TIMEOUT, timeout);
		if (status < B_OK)
			return status;

		locker.Lock();
	}

	// if another thread is waiting for data, since we didn't
	// eat the buffer, it will get it
	if (flags & MSG_PEEK)
		fifo_notify_one_reader(fifo->waiting, fifo->notify);

	return status;
}


status_t
clear_fifo(net_fifo* fifo)
{
	MutexLocker locker(fifo->lock);
	return base_fifo_clear(fifo);
}


status_t
fifo_socket_enqueue_buffer(net_fifo* fifo, net_socket* socket, uint8 event,
	net_buffer* _buffer)
{
	net_buffer *buffer = gNetBufferModule.clone(_buffer, false);
	if (buffer == NULL)
		return B_NO_MEMORY;

	MutexLocker locker(fifo->lock);

	status_t status = base_fifo_enqueue_buffer(fifo, buffer);
	if (status < B_OK)
		gNetBufferModule.free(buffer);
	else
		notify_socket(socket, event, fifo->current_bytes);

	return status;
}


//	#pragma mark - Timer


static status_t
timer_thread(void* /*data*/)
{
	status_t status = B_OK;

	do {
		bigtime_t timeout = B_INFINITE_TIMEOUT;

		if (status == B_TIMED_OUT || status == B_OK) {
			// scan timers for new timeout and/or execute a timer
			mutex_lock(&sTimerLock);

			struct net_timer* timer = NULL;
			while (true) {
				timer = (net_timer*)list_get_next_item(&sTimers, timer);
				if (timer == NULL)
					break;

				if (timer->due < system_time()) {
					// execute timer
					list_remove_item(&sTimers, timer);
					timer->due = -1;
					sCurrentTimer = timer;

					mutex_unlock(&sTimerLock);
					timer->hook(timer, timer->data);
					mutex_lock(&sTimerLock);

					sCurrentTimer = NULL;
					sWaitForTimerCondition.NotifyAll();

					timer = NULL;
						// restart scanning as we unlocked the list
				} else {
					// calculate new timeout
					if (timer->due < timeout)
						timeout = timer->due;
				}
			}

			sTimerTimeout = timeout;
			mutex_unlock(&sTimerLock);
		}

		status = acquire_sem_etc(sTimerWaitSem, 1, B_ABSOLUTE_TIMEOUT, timeout);
			// the wait sem normally can't be acquired, so we
			// have to look at the status value the call returns:
			//
			// B_OK - a new timer has been added or canceled
			// B_TIMED_OUT - look for timers to be executed
			// B_BAD_SEM_ID - we are asked to quit
	} while (status != B_BAD_SEM_ID);

	return B_OK;
}


/*!
	Initializes a timer before use. You can also use this function to change
	a timer later on, but make sure you have canceled it before using set_timer().
*/
void
init_timer(net_timer* timer, net_timer_func hook, void* data)
{
	timer->hook = hook;
	timer->data = data;
	timer->due = 0;
	timer->flags = 0;
}


/*!	Sets or cancels a timer. When the \a delay is below zero, an eventually
	running timer is canceled, if not, it is scheduled to be executed after the
	specified \a delay.
	You need to have initialized the timer before calling this function.

	In case you need to change a running timer, you have to cancel it first,
	before making any changes.
*/
void
set_timer(net_timer* timer, bigtime_t delay)
{
	MutexLocker locker(sTimerLock);

	TRACE("set_timer %p, hook %p, data %p\n", timer, timer->hook, timer->data);

	if (timer->due > 0 && delay < 0) {
		// this timer is scheduled, cancel it
		list_remove_item(&sTimers, timer);
		timer->due = 0;
	}

	if (delay >= 0) {
		// reschedule or add this timer
		if (timer->due <= 0)
			list_add_item(&sTimers, timer);

		timer->due = system_time() + delay;

		// notify timer about the change if necessary
		if (sTimerTimeout > timer->due)
			release_sem(sTimerWaitSem);
	}
}


bool
cancel_timer(struct net_timer* timer)
{
	MutexLocker locker(sTimerLock);

	TRACE("cancel_timer %p, hook %p, data %p\n", timer, timer->hook,
		timer->data);

	if (timer->due <= 0)
		return false;

	// this timer is scheduled, cancel it
	list_remove_item(&sTimers, timer);
	timer->due = 0;
	return true;
}


status_t
wait_for_timer(struct net_timer* timer)
{
	if (find_thread(NULL) == sTimerThread) {
		// let's not wait for ourselves...
		return B_BAD_VALUE;
	}

	while (true) {
		MutexLocker locker(sTimerLock);

		if (timer->due <= 0 && sCurrentTimer != timer)
			return B_OK;

		// we actually need to wait for this timer
		ConditionVariableEntry entry;
		sWaitForTimerCondition.Add(&entry);

		locker.Unlock();

		entry.Wait();
	}

	return B_OK;
}


bool
is_timer_active(net_timer* timer)
{
	return timer->due > 0;
}


bool
is_timer_running(net_timer* timer)
{
	return timer == sCurrentTimer;
}


static int
dump_timer(int argc, char** argv)
{
	kprintf("timer       hook        data        due in\n");

	struct net_timer* timer = NULL;
	while (true) {
		timer = (net_timer*)list_get_next_item(&sTimers, timer);
		if (timer == NULL)
			break;

		kprintf("%p  %p  %p  %" B_PRId64 "\n", timer, timer->hook, timer->data,
			timer->due > 0 ? timer->due - system_time() : -1);
	}

	return 0;
}


status_t
init_timers(void)
{
	list_init(&sTimers);
	sTimerTimeout = B_INFINITE_TIMEOUT;

	status_t status = B_OK;
	mutex_init(&sTimerLock, "net timer");

	sTimerWaitSem = create_sem(0, "net timer wait");
	if (sTimerWaitSem < B_OK) {
		status = sTimerWaitSem;
		goto err1;
	}

	sTimerThread = spawn_kernel_thread(timer_thread, "net timer",
		B_NORMAL_PRIORITY, NULL);
	if (sTimerThread < B_OK) {
		status = sTimerThread;
		goto err2;
	}

	sWaitForTimerCondition.Init(NULL, "wait for net timer");

	add_debugger_command("net_timer", dump_timer,
		"Lists all active network timer");

	return resume_thread(sTimerThread);

err1:
	mutex_destroy(&sTimerLock);
err2:
	delete_sem(sTimerWaitSem);
	return status;
}


void
uninit_timers(void)
{
	delete_sem(sTimerWaitSem);

	status_t status;
	wait_for_thread(sTimerThread, &status);

	mutex_lock(&sTimerLock);

	mutex_destroy(&sTimerLock);

	remove_debugger_command("net_timer", dump_timer);
}


//	#pragma mark - Syscall restart


bool
is_syscall(void)
{
	return is_called_via_syscall();
}


bool
is_restarted_syscall(void)
{
	return syscall_restart_is_restarted();
}


void
store_syscall_restart_timeout(bigtime_t timeout)
{
	Thread* thread = thread_get_current_thread();
	if ((thread->flags & THREAD_FLAGS_SYSCALL) != 0)
		*(bigtime_t*)thread->syscall_restart.parameters = timeout;
}


bigtime_t
restore_syscall_restart_timeout(void)
{
	Thread* thread = thread_get_current_thread();
	return *(bigtime_t*)thread->syscall_restart.parameters;
}