/*
 * Copyright (c) 2018 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */
#include <timeout_q.h>
#include <drivers/system_timer.h>
#include <sys_clock.h>
#include <spinlock.h>
#include <ksched.h>
#include <syscall_handler.h>

#define LOCKED(lck) for (k_spinlock_key_t __i = {},			\
					  __key = k_spin_lock(lck);	\
			!__i.key;					\
			k_spin_unlock(lck, __key), __i.key = 1)

static u64_t curr_tick;

static sys_dlist_t timeout_list = SYS_DLIST_STATIC_INIT(&timeout_list);

static struct k_spinlock timeout_lock;

static bool can_wait_forever;

/* During a call to z_clock_announce(), the "current" time is "ahead"
 * of the reference used by timeout_list by this amount.
 */
static int announce_advance;

#if defined(CONFIG_TIMER_READS_ITS_FREQUENCY_AT_RUNTIME)
int z_clock_hw_cycles_per_sec = CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC;
#endif

static struct _timeout *first(void)
{
	sys_dnode_t *t = sys_dlist_peek_head(&timeout_list);

	return t == NULL ? NULL : CONTAINER_OF(t, struct _timeout, node);
}

static struct _timeout *next(struct _timeout *t)
{
	sys_dnode_t *n = sys_dlist_peek_next(&timeout_list, &t->node);

	return n == NULL ? NULL : CONTAINER_OF(n, struct _timeout, node);
}

static void remove(struct _timeout *t)
{
	if (next(t) != NULL) {
		next(t)->dticks += t->dticks;
	}

	sys_dlist_remove(&t->node);
	t->dticks = _INACTIVE;
}

static s32_t adjust_elapsed(s32_t ticks)
{
	ticks -= z_clock_elapsed();
	return ticks < 0 ? 0 : ticks;
}

void _add_timeout(struct _timeout *to, _timeout_func_t fn, s32_t ticks)
{
	__ASSERT(to->dticks < 0, "");
	to->fn = fn;

	LOCKED(&timeout_lock) {
		struct _timeout *t;

		to->dticks = adjust_elapsed(ticks) + announce_advance;
		for (t = first(); t != NULL; t = next(t)) {
			__ASSERT(t->dticks >= 0, "");

			if (t->dticks > to->dticks) {
				t->dticks -= to->dticks;
				sys_dlist_insert_before(&timeout_list,
							&t->node, &to->node);
				break;
			}
			to->dticks -= t->dticks;
		}

		if (t == NULL) {
			sys_dlist_append(&timeout_list, &to->node);
		}
	}

	z_clock_set_timeout(_get_next_timeout_expiry(), false);
}

int _abort_timeout(struct _timeout *to)
{
	int ret = _INACTIVE;

	LOCKED(&timeout_lock) {
		if (to->dticks != _INACTIVE) {
			remove(to);
			ret = 0;
		}
	}

	return ret;
}

s32_t z_timeout_remaining(struct _timeout *to)
{
	s32_t ticks = 0;

	if (to->dticks == _INACTIVE) {
		return 0;
	}

	LOCKED(&timeout_lock) {
		for (struct _timeout *t = first(); t != NULL; t = next(t)) {
			ticks += t->dticks;
			if (to == t) {
				break;
			}
		}
	}

	return ticks;
}

void z_clock_announce(s32_t ticks)
{
	struct _timeout *t = NULL;

#ifdef CONFIG_TIMESLICING
	z_time_slice(ticks);
#endif

	LOCKED(&timeout_lock) {
		curr_tick += ticks;
		announce_advance = ticks;
	}

	while (true) {
		LOCKED(&timeout_lock) {
			t = first();
			if (t != NULL) {
				if (t->dticks <= announce_advance) {
					announce_advance -= t->dticks;
					t->dticks = 0;
					remove(t);
				} else {
					t->dticks -= announce_advance;
					t = NULL;
				}
			}
		}

		if (t == NULL) {
			break;
		}

		t->fn(t);
	}

	announce_advance = 0;
	z_clock_set_timeout(_get_next_timeout_expiry(), false);
}

s32_t _get_next_timeout_expiry(void)
{
	s32_t ret = 0;
	int max = can_wait_forever ? K_FOREVER : INT_MAX;

	LOCKED(&timeout_lock) {
		struct _timeout *to = first();

		ret = to == NULL ? max : adjust_elapsed(to->dticks);
	}

#ifdef CONFIG_TIMESLICING
	if (_current_cpu->slice_ticks && _current_cpu->slice_ticks < ret) {
		ret = _current_cpu->slice_ticks;
	}
#endif
	return ret;
}

int k_enable_sys_clock_always_on(void)
{
	int ret = !can_wait_forever;

	can_wait_forever = 0;
	return ret;
}

void k_disable_sys_clock_always_on(void)
{
	can_wait_forever = 1;
}

s64_t z_tick_get(void)
{
	u64_t t = 0;

	LOCKED(&timeout_lock) {
		t = curr_tick + z_clock_elapsed();
	}
	return t;
}

u32_t z_tick_get_32(void)
{
#ifdef CONFIG_TICKLESS_KERNEL
	return (u32_t)z_tick_get();
#else
	return (u32_t)curr_tick;
#endif
}

u32_t _impl_k_uptime_get_32(void)
{
	return __ticks_to_ms(z_tick_get_32());
}

#ifdef CONFIG_USERSPACE
Z_SYSCALL_HANDLER(k_uptime_get_32)
{
	return _impl_k_uptime_get_32();
}
#endif

s64_t _impl_k_uptime_get(void)
{
	return __ticks_to_ms(z_tick_get());
}

#ifdef CONFIG_USERSPACE
Z_SYSCALL_HANDLER(k_uptime_get, ret_p)
{
	u64_t *ret = (u64_t *)ret_p;

	Z_OOPS(Z_SYSCALL_MEMORY_WRITE(ret, sizeof(*ret)));
	*ret = _impl_k_uptime_get();
	return 0;
}
#endif