#include <assert.h>
#include <stdlib.h>

#include "session_internal.h"
#include "session_pool.h"

struct session_pool
{
    uint64_t capacity;
    uint64_t used;
    uint64_t free;
    struct session_queue free_list;
};

struct session_pool *session_pool_new(uint64_t capacity)
{
    struct session_pool *pool = (struct session_pool *)calloc(1, sizeof(struct session_pool) + capacity * sizeof(struct session));
    if (pool == NULL)
    {
        return NULL;
    }
    pool->used = 0;
    pool->free = 0;
    pool->capacity = capacity;
    TAILQ_INIT(&pool->free_list);

    struct session *array = (struct session *)(pool + 1);
    for (uint64_t i = 0; i < capacity; i++)
    {
        struct session *sess = &array[i];
        TAILQ_INSERT_TAIL(&pool->free_list, sess, free_tqe);
        pool->free++;
    }

    return pool;
}

void session_pool_free(struct session_pool *pool)
{
    if (pool)
    {
        struct session *sess;
        while ((sess = TAILQ_FIRST(&pool->free_list)))
        {
            TAILQ_REMOVE(&pool->free_list, sess, free_tqe);
            pool->free--;
        }
        assert(pool->free == 0);
        assert(pool->used == 0);

        free(pool);
        pool = NULL;
    }
}

struct session *session_pool_acquire_sessoin(struct session_pool *pool)
{
    if (pool == NULL)
    {
        return NULL;
    }

    struct session *sess = TAILQ_FIRST(&pool->free_list);
    if (sess)
    {
        TAILQ_REMOVE(&pool->free_list, sess, free_tqe);
        pool->free--;
        pool->used++;
    }

    return sess;
}

void session_pool_release_sessoin(struct session_pool *pool, struct session *sess)
{
    if (pool == NULL || sess == NULL)
    {
        return;
    }

    TAILQ_INSERT_TAIL(&pool->free_list, sess, free_tqe);
    pool->free++;
    pool->used--;
}

const struct session *session_pool_get0(const struct session_pool *pool, uint64_t idx)
{
    if (pool == NULL || idx >= pool->capacity)
    {
        return NULL;
    }

    struct session *array = (struct session *)(pool + 1);
    return &array[idx];
}

uint64_t session_pool_get_free_num(const struct session_pool *pool)
{
    return pool->free;
}

uint64_t session_pool_get_used_num(const struct session_pool *pool)
{
    return pool->used;
}