/*

 * 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 round_robin_t {

    h2o_balancer_t super;

    size_t pos;             /* current position */

    size_t consumed_weight; /* remained weight of current position */

    pthread_mutex_t mutex;

};

static inline void select_next(struct round_robin_t *self, h2o_socketpool_target_vector_t *targets)

{

    self->pos += 1;

    if (self->pos == targets->size)

        self->pos = 0;

    self->consumed_weight = 0;

}

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

{

    size_t i;

    size_t result = 0;

    struct round_robin_t *self = (void *)balancer;

    pthread_mutex_lock(&self->mutex);

    assert(targets->size != 0);

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

        if (!tried[self->pos]) {

            /* get the result */

            result = self->pos;

            if (++self->consumed_weight > targets->entries[self->pos]->conf.weight_m1)

                select_next(self, targets);

            pthread_mutex_unlock(&self->mutex);

            return result;

        } else {

            select_next(self, targets);

        }

    }

    h2o_fatal("unreachable");

}

static void destroy(h2o_balancer_t *balancer)

{

    struct round_robin_t *self = (void *)balancer;

    pthread_mutex_destroy(&self->mutex);

    free(self);

}

h2o_balancer_t *h2o_balancer_create_rr(void)

{

    static const h2o_balancer_callbacks_t rr_callbacks = {selector, destroy};

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

    pthread_mutex_init(&self->mutex, NULL);

    self->super.callbacks = &rr_callbacks;

    self->pos = 0;

    self->consumed_weight = 0;

    return &self->super;

}