/*

 * Copyright (c) 2017 Justin Zhu

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to

 * deal in the Software without restriction, including without limitation the

 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or

 * sell copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS

 * IN THE SOFTWARE.

 */

#include "h2o/balancer.h"

struct least_conn_t {

    h2o_balancer_t super;

    pthread_mutex_t mutex;

};

static size_t selector(h2o_balancer_t *_self, h2o_socketpool_target_vector_t *targets, char *tried)

{

    struct least_conn_t *self = (void *)_self;

    size_t i;

    size_t result_index = -1;

    size_t result_weight = 0;

    size_t result_leased = 1;

    uint64_t leftprod, rightprod;

    assert(targets->size != 0);

    pthread_mutex_lock(&self->mutex);

    for (i = 0; i < targets->size; i++) {

        leftprod = targets->entries[i]->_shared.leased_count;

        leftprod *= result_weight;

        rightprod = result_leased;

        rightprod *= ((unsigned)targets->entries[i]->conf.weight_m1) + 1;

        if (!tried[i] && leftprod < rightprod) {

            result_index = i;

            result_leased = targets->entries[i]->_shared.leased_count;

            result_weight = ((unsigned)targets->entries[i]->conf.weight_m1) + 1;

        }

    }

    pthread_mutex_unlock(&self->mutex);

    assert(result_index < targets->size);

    return result_index;

}

static void destroy(h2o_balancer_t *_self)

{

    struct least_conn_t *self = (void *)_self;

    pthread_mutex_destroy(&self->mutex);

    free(self);

}

h2o_balancer_t *h2o_balancer_create_lc(void)

{

    static const h2o_balancer_callbacks_t lc_callbacks = {selector, destroy};

    struct least_conn_t *self = h2o_mem_alloc(sizeof(*self));

    self->super.callbacks = &lc_callbacks;

    pthread_mutex_init(&self->mutex, NULL);

    return &self->super;

}