#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <asm/uaccess.h>

#include <litmus/sched_plugin.h>
#include <litmus/preempt.h>
#include <litmus/debug_trace.h>

#include <litmus/litmus.h>
#include <litmus/jobs.h>
#include <litmus/budget.h>
#include <litmus/litmus_proc.h>
#include <litmus/sched_trace.h>

#include <litmus/reservations/ext_reservation.h>
#include <litmus/reservations/gedf_reservation.h>

struct gedf_reservation_environment* gedf_env;

struct cpu_time {
	struct hrtimer timer;
	lt_t last_update_time;
};

static DEFINE_PER_CPU(struct cpu_time, cpu_time);

static enum hrtimer_restart on_budget_timeout(struct hrtimer *timer)
{
	litmus_reschedule_local();
	return HRTIMER_NORESTART;
}

/*
static enum hrtimer_restart on_scheduling_timer(struct hrtimer *timer)
{
	unsigned long flags;
	enum hrtimer_restart restart = HRTIMER_NORESTART;
	struct pres_cpu_state *state;
	lt_t update, now;

	state = container_of(timer, struct pres_cpu_state, timer);

	// The scheduling timer should only fire on the local CPU, because
	// otherwise deadlocks via timer_cancel() are possible.
	// Note: this does not interfere with dedicated interrupt handling, as
	// even under dedicated interrupt handling scheduling timers for
	// budget enforcement must occur locally on each CPU.
	//
	BUG_ON(state->cpu != raw_smp_processor_id());

	raw_spin_lock_irqsave(&state->lock, flags);
	sup_update_time(&state->sup_env, litmus_clock());

	update = state->sup_env.next_scheduler_update;
	now = state->sup_env.env.current_time;

	TRACE_CUR("on_scheduling_timer at %llu, upd:%llu (for cpu=%d)\n",
		now, update, state->cpu);

	if (update <= now) {
		litmus_reschedule_local();
	} else if (update != SUP_NO_SCHEDULER_UPDATE) {
		hrtimer_set_expires(timer, ns_to_ktime(update));
		restart = HRTIMER_RESTART;
	}

	raw_spin_unlock_irqrestore(&state->lock, flags);

	return restart;
}
*/

static struct task_struct* ext_res_schedule(struct task_struct * prev)
{
	int cpu = smp_processor_id();
	lt_t delta, time_slice;
	struct cpu_time* entry;
	struct task_struct* next;

	entry = this_cpu_ptr(&cpu_time);
	delta = litmus_clock() - entry->last_update_time;

	//TODO: implement per cpu lt_t to track time

	gedf_env->env.ops->update_time(&gedf_env->env, delta, cpu);
	next = gedf_env->env.ops->dispatch(&gedf_env->env, &time_slice, cpu);

	entry->last_update_time = litmus_clock();

	if (time_slice != ULLONG_MAX) {
		hrtimer_start(&entry->timer,
			ns_to_ktime(entry->last_update_time + time_slice),
			HRTIMER_MODE_ABS_PINNED);
	} else
		hrtimer_try_to_cancel(&entry->timer);

	sched_state_task_picked();

	return next;
}

/* Called when a task should be removed from the ready queue.
 */
static void ext_res_task_block(struct task_struct *tsk)
{
	struct reservation* res;

	TRACE_TASK(tsk, "thread suspends at %llu \n", litmus_clock());

	res = (struct reservation*) tsk_rt(tsk)->plugin_state;
	res->par_env->ops->remove_res(res->par_env, res, 0, 0);
}


/* Called when the state of tsk changes back to TASK_RUNNING.
 * We need to requeue the task.
 */
static void ext_res_task_resume(struct task_struct  *tsk)
{
	struct reservation* res;

	TRACE_TASK(tsk, "thread wakes up at %llu\n", litmus_clock());

	res = (struct reservation*) tsk_rt(tsk)->plugin_state;
	res->par_env->ops->add_res(res->par_env, res, 0);
}

static long ext_res_admit_task(struct task_struct *tsk)
{
	long err = 0;

	struct gedf_task_reservation* gedf_task_res;

	err = alloc_gedf_task_reservation(&gedf_task_res, tsk);
	if (err)
		return err;
	tsk_rt(tsk)->plugin_state = gedf_task_res;

	gedf_task_res->gedf_res.res.par_env = &gedf_env->env;

	//TODO: for checkpoint 2, need to find component and insert into it

	return 0;
}

static void ext_res_task_new(struct task_struct *tsk, int on_runqueue,
			  int is_running)
{
	struct reservation* res;
	lt_t now = litmus_clock();

	TRACE_TASK(tsk, "new RT task %llu (on_rq:%d, running:%d)\n",
		   now, on_runqueue, is_running);

	res = (struct reservation*)tsk_rt(tsk)->plugin_state;

	release_at(tsk, now);
	res->replenishment_time = now;

	res->par_env->ops->add_res(res->par_env, res, 0);

	if (is_running)
		litmus_reschedule_local();
}

/*
static bool pres_fork_task(struct task_struct *tsk)
{
	TRACE_CUR("is forking\n");
	TRACE_TASK(tsk, "forked child rt:%d cpu:%d task_cpu:%d "
		        "wcet:%llu per:%llu\n",
		is_realtime(tsk),
		tsk_rt(tsk)->task_params.cpu,
		task_cpu(tsk),
		tsk_rt(tsk)->task_params.exec_cost,
		tsk_rt(tsk)->task_params.period);

	// We always allow forking.
	// The newly forked task will be in the same reservation.
	return true;
}
*/

static void ext_res_task_exit(struct task_struct *tsk)
{
	struct reservation* res;
	struct reservation_environment* par_env;

	res = (struct reservation*)tsk_rt(tsk)->plugin_state;
	par_env = res->par_env;

	par_env->ops->remove_res(par_env, res, 1, 0);

	TRACE_TASK(tsk, "task exits at %llu \n", litmus_clock());
}

/* used by task budget tracking in budget.c. Since we have tasks in containers that track
 * budget, we don't need this. Furthermore, this scheme doesn't work efficiently with
 * multicore reservations
 */
/*
static void pres_current_budget(lt_t *used_so_far, lt_t *remaining)
{
	struct pres_task_state *tstate = get_pres_state(current);
	struct pres_cpu_state *state;

	// FIXME: protect against concurrent task_exit()

	local_irq_disable();

	state = cpu_state_for(tstate->cpu);

	raw_spin_lock(&state->lock);

	sup_update_time(&state->sup_env, litmus_clock());
	if (remaining)
		*remaining = tstate->client->reservation->cur_budget;
	if (used_so_far)
		*used_so_far = tstate->client->reservation->budget_consumed;
	pres_update_timer_and_unlock(state);

	local_irq_enable();
}
*/

/*
static long do_pres_reservation_create(
	int res_type,
	struct reservation_config *config)
{
	struct pres_cpu_state *state;
	struct reservation* res;
	struct reservation* new_res = NULL;
	unsigned long flags;
	long err;

	// Allocate before we grab a spin lock.
	switch (res_type) {
		case PERIODIC_POLLING:
		case SPORADIC_POLLING:
			err = alloc_polling_reservation(res_type, config, &new_res);
			break;

		case TABLE_DRIVEN:
			err = alloc_table_driven_reservation(config, &new_res);
			break;

		default:
			err = -EINVAL;
			break;
	}

	if (err)
		return err;

	state = cpu_state_for(config->cpu);
	raw_spin_lock_irqsave(&state->lock, flags);

	res = sup_find_by_id(&state->sup_env, config->id);
	if (!res) {
		sup_add_new_reservation(&state->sup_env, new_res);
		err = config->id;
	} else {
		err = -EEXIST;
	}

	raw_spin_unlock_irqrestore(&state->lock, flags);

	if (err < 0)
		kfree(new_res);

	return err;
}
*/

/*
static long pres_reservation_create(int res_type, void* __user _config)
{
	struct reservation_config config;

	TRACE("Attempt to create reservation (%d)\n", res_type);

	if (copy_from_user(&config, _config, sizeof(config)))
		return -EFAULT;

	if (config.cpu < 0 || !cpu_online(config.cpu)) {
		printk(KERN_ERR "invalid polling reservation (%u): "
		       "CPU %d offline\n", config.id, config.cpu);
		return -EINVAL;
	}

	return do_pres_reservation_create(res_type, &config);
}
*/

static struct domain_proc_info ext_res_domain_proc_info;

static long ext_res_get_domain_proc_info(struct domain_proc_info **ret)
{
	*ret = &ext_res_domain_proc_info;
	return 0;
}

static void ext_res_setup_domain_proc(void)
{
	int i, cpu;
	int num_rt_cpus = num_online_cpus();

	struct cd_mapping *cpu_map, *domain_map;

	memset(&ext_res_domain_proc_info, 0, sizeof(ext_res_domain_proc_info));
	init_domain_proc_info(&ext_res_domain_proc_info, num_rt_cpus, num_rt_cpus);
	ext_res_domain_proc_info.num_cpus = num_rt_cpus;
	ext_res_domain_proc_info.num_domains = num_rt_cpus;

	i = 0;
	for_each_online_cpu(cpu) {
		cpu_map = &ext_res_domain_proc_info.cpu_to_domains[i];
		domain_map = &ext_res_domain_proc_info.domain_to_cpus[i];

		cpu_map->id = cpu;
		domain_map->id = i;
		cpumask_set_cpu(i, cpu_map->mask);
		cpumask_set_cpu(cpu, domain_map->mask);
		++i;
	}
}

static long ext_res_activate_plugin(void)
{
	int cpu;
	int num_cpus = num_online_cpus();
	struct cpu_time* entry;
	lt_t now = litmus_clock();

	alloc_gedf_reservation_environment(&gedf_env, num_cpus);

	for_each_online_cpu(cpu) {
		TRACE("Initializing CPU%d...\n", cpu);
		entry = per_cpu_ptr(&cpu_time, cpu);
		hrtimer_init(&entry->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
		entry->timer.function = on_budget_timeout;
		entry->last_update_time = now;
		gedf_env->cpu_entries[cpu].id = cpu;
		gedf_env->env.ops->resume(&gedf_env->env, cpu);
	}
	gedf_env->num_cpus = num_cpus;

	ext_res_setup_domain_proc();

	return 0;
}

static long ext_res_deactivate_plugin(void)
{
	int cpu;
	struct cpu_time* entry;

	gedf_env->env.ops->shutdown(&gedf_env->env);

	for_each_online_cpu(cpu) {
		entry = per_cpu_ptr(&cpu_time, cpu);
		hrtimer_cancel(&entry->timer);
	}

	destroy_domain_proc_info(&ext_res_domain_proc_info);
	return 0;
}

static struct sched_plugin ext_res_plugin = {
	.plugin_name		= "EXT-RES",
	.schedule		= ext_res_schedule,
	.task_block		= ext_res_task_block,
	.task_wake_up		= ext_res_task_resume,
	.admit_task		= ext_res_admit_task,
	.task_new		= ext_res_task_new,
	//.fork_task		= pres_fork_task,
	.task_exit		= ext_res_task_exit,
	.complete_job           = complete_job,
	.get_domain_proc_info   = ext_res_get_domain_proc_info,
	.activate_plugin	= ext_res_activate_plugin,
	.deactivate_plugin      = ext_res_deactivate_plugin,
	//.reservation_create     = pres_reservation_create,
	//.current_budget         = pres_current_budget,
};

static int __init init_ext_res(void)
{
	return register_sched_plugin(&ext_res_plugin);
}

module_init(init_ext_res);