/*
 * Copyright (c) 2016 Nordic Semiconductor ASA
 * Copyright (c) 2016 Vinayak Kariappa Chettimada
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <stdint.h>
#include "memq.h"
#include "mayfly.h"

#include "config.h"

static struct {
	void *head;
	void *tail;
} mft[MAYFLY_CALLEE_COUNT][MAYFLY_CALLER_COUNT];

static void *mfl[MAYFLY_CALLEE_COUNT][MAYFLY_CALLER_COUNT][2];

void mayfly_init(void)
{
	uint8_t callee_id;

	callee_id = MAYFLY_CALLEE_COUNT;
	while (callee_id--) {
		uint8_t caller_id;

		caller_id = MAYFLY_CALLER_COUNT;
		while (caller_id--) {
			memq_init(mfl[callee_id][caller_id],
				  &mft[callee_id][caller_id].head,
				  &mft[callee_id][caller_id].tail);
		}
	}
}

uint32_t mayfly_enqueue(uint8_t caller_id, uint8_t callee_id, uint8_t chain,
			struct mayfly *m)
{
	uint8_t state;
	uint8_t ack;

	chain = chain || !mayfly_prio_is_equal(caller_id, callee_id) ||
		!mayfly_is_enabled(caller_id, callee_id);

	/* shadow the ack */
	ack = m->_ack;

	/* already in queue */
	state = (m->_req - ack) & 0x03;
	if (state != 0) {
		if (chain) {
			if (state != 1) {
				/* mark as ready in queue */
				m->_req = ack + 1;

				/* pend the callee for execution */
				mayfly_pend(caller_id, callee_id);

				return 0;
			}

			/* already ready */
			return 1;
		}

		/* mark as done in queue, and fall thru */
		m->_req = ack + 2;
	}

	/* handle mayfly(s) that can be inline */
	if (!chain) {
		/* call fp */
		m->fp(m->param);

		return 0;
	}

	/* new, add as ready in the queue */
	m->_req = ack + 1;
	memq_enqueue(m, m->_link, &mft[callee_id][caller_id].tail);

	/* pend the callee for execution */
	mayfly_pend(caller_id, callee_id);

	return 0;
}

void mayfly_run(uint8_t callee_id)
{
	uint8_t caller_id;

	/* iterate through each caller queue to this callee_id */
	caller_id = MAYFLY_CALLER_COUNT;
	while (caller_id--) {
		void *link;
		struct mayfly *m = 0;

		/* fetch mayfly in callee queue, if any */
		link = memq_peek(mft[callee_id][caller_id].tail,
				 mft[callee_id][caller_id].head,
				 (void **)&m);
		while (link) {
			uint8_t state;
			uint8_t req;

			/* execute work if ready */
			req = m->_req;
			state = (req - m->_ack) & 0x03;
			if (state == 1) {
				/* mark mayfly as ran */
				m->_ack--;

				/* call the mayfly function */
				m->fp(m->param);
			}

			/* dequeue if not re-pended */
			req = m->_req;
			if (((req - m->_ack) & 0x03) != 1) {
				memq_dequeue(mft[callee_id][caller_id].tail,
					     &mft[callee_id][caller_id].head,
					     0);

				/* release link into dequeued mayfly struct */
				m->_link = link;

				/* reset mayfly state to idle */
				m->_ack = req;
			}

			/* fetch next mayfly in callee queue, if any */
			link = memq_peek(mft[callee_id][caller_id].tail,
					 mft[callee_id][caller_id].head,
					 (void **)&m);

			/* yield out of mayfly_run if a mayfly function was
			 * called.
			 */
			if (state == 1) {
				/* pend callee (tailchain) if mayfly queue is
				 * not empty.
				 */
				if (link) {
					mayfly_pend(callee_id, callee_id);
				}

				return;
			}
		}
	}
}