#include <assert.h>

#define HASH_FUNCTION(keyptr, keylen, hashv) HASH_FUNCTION_OVERWRITE(keyptr, keylen, &hashv)
#define HASH_KEYCMP(a, b, len) HASH_KEYCMP_OVERWRITE(a, b, len)
#include "session_table.h"
#include "session_private.h"

struct session_table
{
    struct session *root;
    session_free_cb free_cb;
    void *arg;
    uint64_t count;

    struct session *least_recently_unused;
    struct session *least_recently_used;
};

/******************************************************************************
 * Private API
 ******************************************************************************/

static void HASH_FUNCTION_OVERWRITE(const struct tuple6 *tuple, unsigned int keylen, uint32_t *hashv)
{
    *hashv = tuple6_hash(tuple);
}

static int HASH_KEYCMP_OVERWRITE(const void *key_a, const void *key_b, size_t len)
{
    struct tuple6 *tuple_a = (struct tuple6 *)key_a;
    struct tuple6 *tuple_b = (struct tuple6 *)key_b;

    if (tuple6_cmp(tuple_a, tuple_b) == 0)
    {
        return 0;
    }

    struct tuple6 reversed;
    tuple6_reverse(tuple_b, &reversed);
    if (tuple6_cmp(tuple_a, &reversed) == 0)
    {
        return 0;
    }

    return -1;
}

static void session_table_add_session_to_linklist(struct session_table *table, struct session *sess)
{
    if (table == NULL || sess == NULL)
    {
        return;
    }

    if (table->least_recently_used == NULL)
    {
        table->least_recently_unused = sess;
        table->least_recently_used = sess;
        sess->prev_ptr = NULL;
        sess->next_ptr = NULL;
    }
    else
    {
        sess->next_ptr = table->least_recently_used;
        table->least_recently_used->prev_ptr = sess;
        sess->prev_ptr = NULL;
        table->least_recently_used = sess;
    }
}

static void session_table_del_session_from_linklist(struct session_table *table, struct session *sess)
{
    if (table == NULL || sess == NULL)
    {
        return;
    }

    if (sess->prev_ptr == NULL && sess->next_ptr == NULL)
    {
        table->least_recently_unused = NULL;
        table->least_recently_used = NULL;
    }
    else if (sess->prev_ptr == NULL && sess->next_ptr != NULL)
    {
        table->least_recently_used = sess->next_ptr;
        sess->next_ptr->prev_ptr = NULL;
    }
    else if (sess->prev_ptr != NULL && sess->next_ptr == NULL)
    {
        table->least_recently_unused = sess->prev_ptr;
        sess->prev_ptr->next_ptr = NULL;
    }
    else
    {
        sess->prev_ptr->next_ptr = sess->next_ptr;
        sess->next_ptr->prev_ptr = sess->prev_ptr;
    }
    sess->prev_ptr = NULL;
    sess->next_ptr = NULL;
}

/******************************************************************************
 * Public API
 ******************************************************************************/

struct session_table *session_table_new()
{
    struct session_table *table = (struct session_table *)calloc(1, sizeof(struct session_table));
    table->count = 0;
    table->least_recently_unused = NULL;
    table->least_recently_used = NULL;

    return table;
}

void session_table_free(struct session_table *table)
{
    if (table)
    {
        struct session *node = NULL;
        struct session *tmp = NULL;
        HASH_ITER(hh, table->root, node, tmp)
        {
            HASH_DELETE(hh, table->root, node);
            if (table->free_cb && node)
            {
                table->free_cb(node, table->arg);
            }
        }
        table->count--;

        free(table);
        table = NULL;
    }
}

uint64_t session_table_get_count(struct session_table *table)
{
    if (table == NULL)
    {
        return 0;
    }

    return table->count;
}

void session_table_set_freecb(struct session_table *table, session_free_cb free_cb, void *arg)
{
    if (table)
    {
        table->free_cb = free_cb;
        table->arg = arg;
    }
}

int session_table_add_session(struct session_table *table, const struct tuple6 *tuple, struct session *sess)
{
    if (table == NULL || sess == NULL)
    {
        return -1;
    }

    if (session_table_find_session(table, tuple))
    {
        return -1;
    }

    HASH_ADD(hh, table->root, tuple, sizeof(sess->tuple), sess);
    session_table_add_session_to_linklist(table, sess);
    table->count++;

    return 0;
}

void session_table_del_session(struct session_table *table, const struct tuple6 *tuple)
{
    if (table == NULL)
    {
        return;
    }

    struct session *sess = session_table_find_session(table, tuple);
    if (sess == NULL)
    {
        return;
    }

    HASH_DELETE(hh, table->root, sess);
    if (table->free_cb && sess)
    {
        table->free_cb(sess, table->arg);
    }
    session_table_del_session_from_linklist(table, sess);
    table->count--;
}

struct session *session_table_find_session(struct session_table *table, const struct tuple6 *tuple)
{
    if (table == NULL)
    {
        return NULL;
    }

    struct session *sess = NULL;
    HASH_FIND(hh, table->root, tuple, sizeof(struct tuple6), sess);
    if (sess == NULL)
    {
        struct tuple6 out;
        memset(&out, 0, sizeof(struct tuple6));
        tuple6_reverse(tuple, &out);
        HASH_FIND(hh, table->root, &out, sizeof(struct tuple6), sess);
    }

    if (sess)
    {
        session_table_del_session_from_linklist(table, sess);
        session_table_add_session_to_linklist(table, sess);
    }

    return sess;
}

struct session *session_table_find_least_recently_unused_session(struct session_table *table)
{
    if (table == NULL)
    {
        return NULL;
    }

    return table->least_recently_unused;
}

struct session *session_table_find_least_recently_used_session(struct session_table *table)
{
    if (table == NULL)
    {
        return NULL;
    }

    return table->least_recently_used;
}