/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * SPDX-License-Identifier: MPL-2.0
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, you can obtain one at https://mozilla.org/MPL/2.0/.
 *
 * See the COPYRIGHT file distributed with this work for additional
 * information regarding copyright ownership.
 */

/*! \file */

#include <stdbool.h>
#include <stddef.h>

#include <isc/atomic.h>
#include <isc/counter.h>
#include <isc/magic.h>
#include <isc/mem.h>
#include <isc/refcount.h>
#include <isc/util.h>

#define COUNTER_MAGIC	 ISC_MAGIC('C', 'n', 't', 'r')
#define VALID_COUNTER(r) ISC_MAGIC_VALID(r, COUNTER_MAGIC)

struct isc_counter {
	unsigned int magic;
	isc_mem_t *mctx;
	isc_refcount_t references;
	atomic_uint_fast32_t limit;
	atomic_uint_fast32_t used;
};

void
isc_counter_create(isc_mem_t *mctx, int limit, isc_counter_t **counterp) {
	REQUIRE(counterp != NULL && *counterp == NULL);

	isc_counter_t *counter = isc_mem_get(mctx, sizeof(*counter));
	*counter = (isc_counter_t){
		.magic = COUNTER_MAGIC,
		.references = 1,
		.limit = limit,
	};

	isc_mem_attach(mctx, &counter->mctx);

	*counterp = counter;
}

isc_result_t
isc_counter_increment(isc_counter_t *counter) {
	uint_fast32_t used = atomic_fetch_add_relaxed(&counter->used, 1) + 1;
	uint_fast32_t limit = atomic_load_acquire(&counter->limit);

	if (limit != 0 && used >= limit) {
		return ISC_R_QUOTA;
	}

	return ISC_R_SUCCESS;
}

unsigned int
isc_counter_used(isc_counter_t *counter) {
	REQUIRE(VALID_COUNTER(counter));

	return atomic_load_relaxed(&counter->used);
}

void
isc_counter_setlimit(isc_counter_t *counter, int limit) {
	REQUIRE(VALID_COUNTER(counter));

	atomic_store_release(&counter->limit, limit);
}

unsigned int
isc_counter_getlimit(isc_counter_t *counter) {
	REQUIRE(VALID_COUNTER(counter));

	return atomic_load_acquire(&counter->limit);
}

static void
isc__counter_destroy(isc_counter_t *counter) {
	REQUIRE(VALID_COUNTER(counter));

	isc_refcount_destroy(&counter->references);
	counter->magic = 0;
	isc_mem_putanddetach(&counter->mctx, counter, sizeof(*counter));
}

ISC_REFCOUNT_IMPL(isc_counter, isc__counter_destroy);