/* fiber.c - fiber management
 *
 * Copyright (C) 2009 Timo Teräs <timo.teras@iki.fi>
 * All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 or later as
 * published by the Free Software Foundation.
 *
 * See http://www.gnu.org/ for details.
 */

#include <time.h>
#include <errno.h>
#include <unistd.h>
#include <libtf/fiber.h>
#include <libtf/scheduler.h>
#include "uctx.h"

#define TF_TIMEOUT_CHANGE_NEEDED			1
#define TF_TIMEOUT_CHANGE_NEW_VALUE			2

struct tf_fiber {
	unsigned int		ref_count;
	struct tf_scheduler *	scheduler;
	int			wakeup_type;
	unsigned int		timeout_change;
	tf_mtime_t		timeout;
	struct tf_list_node	queue_node;
	struct tf_heap_node	heap_node;
	struct tf_uctx		context;
	char			data[TF_EMPTY_ARRAY];
};

static inline
struct tf_fiber *tf_fiber_get_current(void)
{
	void *data = tf_scheduler_get_current()->active_fiber;
	return container_of(data, struct tf_fiber, data);
}

static void tf_fiber_main(void *user_data, void *arg)
{
	tf_fiber_proc proc = (tf_fiber_proc) arg;
	struct tf_fiber *f = user_data;

	proc(f->data);
	tf_fiber_exit();
}

void *__tf_fiber_create(tf_fiber_proc fiber_main, int private_size)
{
	struct tf_fiber *fiber;

	fiber = tf_uctx_create_embedded(
		TF_STACK_SIZE,
		sizeof(struct tf_fiber) + private_size,
		offsetof(struct tf_fiber, context),
		tf_fiber_main, fiber_main);
	if (fiber == NULL)
		return NULL;

	*fiber = (struct tf_fiber) {
		.ref_count = 1,
		.queue_node = TF_LIST_INITIALIZER(fiber->queue_node),
		.context = fiber->context,
	};

	return fiber->data;
}

void *tf_fiber_create(tf_fiber_proc fiber_main, int private_size)
{
	struct tf_fiber *fiber;
	struct tf_scheduler *sched;

	sched = tf_scheduler_get_current();
	if (tf_heap_prealloc(&sched->heap, sched->num_fibers + 1) < 0)
		return NULL;

	fiber = container_of(__tf_fiber_create(fiber_main, private_size),
			     struct tf_fiber, data);
	sched->num_fibers++;

	fiber->scheduler = sched;
	fiber->wakeup_type = TF_WAKEUP_NONE;
	tf_list_add_tail(&fiber->queue_node, &sched->scheduled_q);

	return tf_fiber_get(fiber->data);
}

void *tf_fiber_get(void *data)
{
	struct tf_fiber *fiber = container_of(data, struct tf_fiber, data);
	tf_atomic_inc(fiber->ref_count);
	return data;
}

static void __tf_fiber_destroy(struct tf_fiber *fiber)
{
	struct tf_scheduler *sched = fiber->scheduler;
	int main_fiber, num_fibers;

	/* decrease first the number of fibers as we might be
	 * killing the scheduler it self */
	num_fibers = --sched->num_fibers;

	main_fiber = (fiber->context.alloc == NULL);
	tf_heap_delete(&fiber->heap_node, &sched->heap);
	tf_uctx_destroy(&fiber->context);
	if (main_fiber)
		free(fiber);

	if (num_fibers == 1) {
		/* FIXME: Use proper fiber event*/
		__tf_fiber_wakeup(sched->main_fiber, TF_WAKEUP_IMMEDIATE);
	}
}

void tf_fiber_put(void *data)
{
	struct tf_fiber *fiber = container_of(data, struct tf_fiber, data);
	if (tf_atomic_dec(fiber->ref_count) == 0)
		__tf_fiber_destroy(fiber);
}

void __tf_fiber_wakeup(void *data, int wakeup_type)
{
	struct tf_fiber *fiber = container_of(data, struct tf_fiber, data);
	struct tf_scheduler *sched = fiber->scheduler;

	if (fiber->wakeup_type == TF_WAKEUP_NONE) {
		fiber->wakeup_type = wakeup_type;
		tf_list_add_tail(&fiber->queue_node, &sched->running_q);
	}
}

void __tf_fiber_wakeup_heapnode(struct tf_heap_node *node)
{
	__tf_fiber_wakeup(container_of(node, struct tf_fiber, heap_node)->data,
			  TF_WAKEUP_TIMEOUT);
}

int __tf_fiber_schedule(void)
{
	struct tf_scheduler *sched = tf_scheduler_get_current();
	struct tf_fiber *f = tf_fiber_get_current(), *nf;
	int wakeup;

	if (unlikely(f->timeout_change)) {
		if (f->timeout_change & TF_TIMEOUT_CHANGE_NEW_VALUE) {
			if (tf_mtime_diff(f->timeout, tf_scheduler_get_mtime()) <= 0) {
				f->timeout_change = TF_TIMEOUT_CHANGE_NEEDED;
				return TF_WAKEUP_TIMEOUT;
			}
			tf_heap_change(&f->heap_node, &sched->heap, f->timeout);
		} else
			tf_heap_delete(&f->heap_node, &sched->heap);
		f->timeout_change = 0;
	}

	/* Figure out the next fibre to run */
	if (unlikely(tf_list_empty(&sched->scheduled_q))) {
		tf_list_splice_tail(&sched->running_q,
				    &sched->scheduled_q);
		TF_BUG_ON(tf_list_empty(&sched->scheduled_q));
	}
	nf = tf_list_entry(tf_list_pop(&sched->scheduled_q),
			   struct tf_fiber, queue_node);
	sched->active_fiber = nf->data;
	tf_uctx_transfer(&f->context, &nf->context);

	wakeup = f->wakeup_type;
	f->wakeup_type = TF_WAKEUP_NONE;

	return wakeup;
}

int __tf_fiber_bind_scheduler(struct tf_scheduler *sched)
{
	struct tf_fiber *f;

	f = malloc(sizeof(struct tf_fiber));
	if (f == NULL)
		return -ENOMEM;

	/* Mark currently active main fiber as active */
	*f = (struct tf_fiber) {
		.ref_count = 1,
		.scheduler = sched,
		.queue_node = TF_LIST_INITIALIZER(f->queue_node),
	};
	tf_uctx_create_self(&f->context);
	sched->main_fiber = f->data;
	sched->active_fiber = f->data;
	sched->num_fibers++;

	/* Schedule scheduler fiber */
	f = container_of((void *) sched, struct tf_fiber, data);
	f->scheduler = sched;
	f->wakeup_type = TF_WAKEUP_IMMEDIATE;
	tf_list_add_tail(&f->queue_node, &sched->running_q);

	return 0;
}

int __tf_fiber_release_scheduler(struct tf_scheduler *sched)
{
	struct tf_fiber *f;

	/* Detach scheduler */
	f = container_of((void *) sched, struct tf_fiber, data);
	tf_list_del(&f->queue_node);

	/* Detach main stack from this scheduler */
	f = container_of((void *) sched->main_fiber, struct tf_fiber, data);
	tf_fiber_put(sched->main_fiber);
	sched->main_fiber = NULL;
	sched->num_fibers--;

	return 0;
}

void tf_fiber_exit(void)
{
	struct tf_scheduler *sched = tf_scheduler_get_current();
	struct tf_fiber *f = tf_fiber_get_current();
	struct tf_fiber *schedf = container_of((void *) sched, struct tf_fiber, data);

	tf_heap_delete(&f->heap_node, &sched->heap);
	schedf->wakeup_type = TF_WAKEUP_KILL;
	tf_uctx_transfer(&f->context, &schedf->context);
	TF_BUG_ON(1);
}

void tf_fiber_kill(void *fiber)
{
}

int tf_fiber_yield(void)
{
	struct tf_scheduler *sched = tf_scheduler_get_current();
	struct tf_fiber *f = tf_fiber_get_current();

	TF_BUG_ON(tf_list_hashed(&f->queue_node));
	f->wakeup_type = TF_WAKEUP_IMMEDIATE;
	tf_list_add_tail(&f->queue_node, &sched->running_q);

	return __tf_fiber_schedule();
}

void tf_timeout_push(struct tf_timeout *timeout, tf_mtime_diff_t milliseconds)
{
	struct tf_fiber *f = tf_fiber_get_current();
	tf_mtime_t abs = tf_scheduler_get_mtime() + milliseconds;
	int active;

	if (f->timeout_change)
		active = (f->timeout_change & TF_TIMEOUT_CHANGE_NEW_VALUE);
	else
		active = tf_heap_node_active(&f->heap_node);

	if (!active || tf_mtime_diff(abs, f->timeout) < 0) {
		/* Save previous timeout */
		timeout->saved_timeout = f->timeout;
		timeout->timeout_change = TF_TIMEOUT_CHANGE_NEEDED;
		if (active)
			timeout->timeout_change |= TF_TIMEOUT_CHANGE_NEW_VALUE;

		/* Make new timeout pending */
		f->timeout = abs;
		f->timeout_change = TF_TIMEOUT_CHANGE_NEEDED
				  | TF_TIMEOUT_CHANGE_NEW_VALUE;
	} else {
		timeout->timeout_change = 0;
	}
}

int __tf_timeout_pop(struct tf_timeout *timeout, int err)
{
	struct tf_fiber *f = tf_fiber_get_current();

	f->timeout = timeout->saved_timeout;
	f->timeout_change = timeout->timeout_change;
	if (err == TF_WAKEUP_TIMEOUT)
		err = TF_WAKEUP_THIS_TIMEOUT;
	return err;
}