/*
 * melisma - extensible and scriptable audio engine
 * Copyright (C) 2026  Ludvig Gunne Lindström
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#include "mem.h"
#include "melisma/ring.h"

struct ml_ring
{
	_Atomic size_t  head;
	_Atomic size_t  tail;
	size_t          len;
	uint8_t         data[];
};


ml_ring *ml_ring_init(size_t len)
{
	size_t size = sizeof(ml_ring) + len;
	ml_ring *r = scalloc(1,size);
	r->len = len;
	return r;
}

void ml_ring_free(ml_ring *r)
{
	free(r);
}

int ml_ring_empty(ml_ring *r)
{
	size_t head = atomic_load_explicit(&r->head,memory_order_relaxed);
	size_t tail = atomic_load_explicit(&r->tail,memory_order_acquire);
	return tail == head;
}

int ml_ring_has_space(ml_ring *r, size_t len)
{
	size_t head = atomic_load_explicit(&r->head,memory_order_acquire);
	size_t tail = atomic_load_explicit(&r->tail,memory_order_relaxed);
	size_t used = tail >= head ? tail - head : r->len - head + tail;
	size_t free = r->len - 1 - used;
	return free >= len;
}

int ml_ring_put(ml_ring *r, uint8_t c)
{
	size_t tail = atomic_load_explicit(&r->tail,memory_order_relaxed);
	size_t head = atomic_load_explicit(&r->head,memory_order_acquire);
	size_t new_tail = (tail + 1) % r->len;

	if (new_tail == head)
	{
		return -1;
	}

	r->data[tail] = c;
	atomic_store_explicit(&r->tail,new_tail,memory_order_release);

	return 0;
}

int ml_ring_get(ml_ring *r, uint8_t *c)
{
	size_t tail = atomic_load_explicit(&r->tail,memory_order_acquire);
	size_t head = atomic_load_explicit(&r->head,memory_order_relaxed);
	size_t new_head = (head + 1) % r->len;

	if (head == tail)
	{
		return -1;
	}

	*c = r->data[head];
	atomic_store_explicit(&r->head,new_head,memory_order_release);

	return 0;
}

size_t ml_ring_write(ml_ring *r, const void *ptr, size_t len)
{
	size_t l = 0;
	const uint8_t *uptr = ptr;

	for (; l < len; l++)
	{
		if (ml_ring_put(r,uptr[l]) < 0)
		{
			break;
		}
	}

	return l;
}

size_t ml_ring_read(ml_ring *r, void *ptr, size_t len)
{
	size_t l = 0;
	uint8_t *uptr = ptr;

	for (; l < len; l++)
	{
		if (ml_ring_get(r,&uptr[l]) < 0)
		{
			break;
		}
	}

	return l;
}

void ml_ring_put_blocking(ml_ring *r, uint8_t c)
{
	while (ml_ring_put(r,c) < 0)
		;
}

uint8_t ml_ring_get_blocking(ml_ring *r)
{
	uint8_t c;
	while (ml_ring_get(r,&c) < 0)
		;
	return c;
}

void ml_ring_write_blocking(ml_ring *r, const void *ptr, size_t len)
{
	const uint8_t *uptr = ptr;

	while (len--)
	{
		ml_ring_put_blocking(r,*(uptr++));
	}
}

void ml_ring_read_blocking(ml_ring *r, void *ptr, size_t len)
{
	uint8_t *uptr = ptr;

	while (len--)
	{
		*(uptr++) = ml_ring_get_blocking(r);
	}
}