/*
 * cache.c
 * package object cache
 *
 * Copyright (c) 2013 pkgconf authors (see AUTHORS).
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * This software is provided 'as is' and without any warranty, express or
 * implied.  In no event shall the authors be liable for any damages arising
 * from the use of this software.
 */

#include <libpkgconf/stdinc.h>
#include <libpkgconf/libpkgconf.h>

#include <assert.h>

/*
 * !doc
 *
 * libpkgconf `cache` module
 * =========================
 *
 * The libpkgconf `cache` module manages a package/module object cache, allowing it to
 * avoid loading duplicate copies of a package/module.
 *
 * A cache is tied to a specific pkgconf client object, so package objects should not
 * be shared across threads.
 */

static int
cache_member_cmp(const void *a, const void *b)
{
        const char *key = a;
        const pkgconf_pkg_t *pkg = *(void **) b;

        return strcmp(key, pkg->id);
}

static int
cache_member_sort_cmp(const void *a, const void *b)
{
        const pkgconf_pkg_t *pkgA = *(void **) a;
        const pkgconf_pkg_t *pkgB = *(void **) b;

        if (pkgA == NULL)
                return 1;

        if (pkgB == NULL)
                return -1;

        return strcmp(pkgA->id, pkgB->id);
}

static void
cache_dump(const pkgconf_client_t *client)
{
        size_t i;

        PKGCONF_TRACE(client, "dumping package cache contents");

        for (i = 0; i < client->cache_count; i++)
        {
                const pkgconf_pkg_t *pkg = client->cache_table[i];

                PKGCONF_TRACE(client, SIZE_FMT_SPECIFIER": %p(%s)",
                        i, pkg, pkg == NULL ? "NULL" : pkg->id);
        }
}

/*
 * !doc
 *
 * .. c:function:: pkgconf_pkg_t *pkgconf_cache_lookup(const pkgconf_client_t *client, const char *id)
 *
 *    Looks up a package in the cache given an `id` atom,
 *    such as ``gtk+-3.0`` and returns the already loaded version
 *    if present.
 *
 *    :param pkgconf_client_t* client: The client object to access.
 *    :param char* id: The package atom to look up in the client object's cache.
 *    :return: A package object if present, else ``NULL``.
 *    :rtype: pkgconf_pkg_t *
 */
pkgconf_pkg_t *
pkgconf_cache_lookup(pkgconf_client_t *client, const char *id)
{
        if (client->cache_table == NULL)
                return NULL;

        pkgconf_pkg_t **pkg;

        pkg = bsearch(id, client->cache_table,
                client->cache_count, sizeof (void *),
                cache_member_cmp);

        if (pkg != NULL)
        {
                PKGCONF_TRACE(client, "found: %s @%p", id, *pkg);
                return pkgconf_pkg_ref(client, *pkg);
        }

        PKGCONF_TRACE(client, "miss: %s", id);
        return NULL;
}

/*
 * !doc
 *
 * .. c:function:: void pkgconf_cache_add(pkgconf_client_t *client, pkgconf_pkg_t *pkg)
 *
 *    Adds an entry for the package to the package cache.
 *    The cache entry must be removed if the package is freed.
 *
 *    :param pkgconf_client_t* client: The client object to modify.
 *    :param pkgconf_pkg_t* pkg: The package object to add to the client object's cache.
 *    :return: nothing
 */
void
pkgconf_cache_add(pkgconf_client_t *client, pkgconf_pkg_t *pkg)
{
        if (pkg == NULL)
                return;

        pkgconf_pkg_ref(client, pkg);

        PKGCONF_TRACE(client, "added @%p to cache", pkg);

        /* mark package as cached */
        pkg->flags |= PKGCONF_PKG_PROPF_CACHED;

        ++client->cache_count;
        client->cache_table = pkgconf_reallocarray(client->cache_table,
                client->cache_count, sizeof (void *));
        client->cache_table[client->cache_count - 1] = pkg;

        qsort(client->cache_table, client->cache_count,
                sizeof(void *), cache_member_sort_cmp);
}

/*
 * !doc
 *
 * .. c:function:: void pkgconf_cache_remove(pkgconf_client_t *client, pkgconf_pkg_t *pkg)
 *
 *    Deletes a package from the client object's package cache.
 *
 *    :param pkgconf_client_t* client: The client object to modify.
 *    :param pkgconf_pkg_t* pkg: The package object to remove from the client object's cache.
 *    :return: nothing
 */
void
pkgconf_cache_remove(pkgconf_client_t *client, pkgconf_pkg_t *pkg)
{
        if (client->cache_table == NULL)
                return;

        if (pkg == NULL)
                return;

        if (!(pkg->flags & PKGCONF_PKG_PROPF_CACHED))
                return;

        PKGCONF_TRACE(client, "removed @%p from cache", pkg);

        pkgconf_pkg_t **slot;

        slot = bsearch(pkg->id, client->cache_table,
                client->cache_count, sizeof (void *),
                cache_member_cmp);

        if (slot == NULL)
                return;

        (*slot)->flags &= ~PKGCONF_PKG_PROPF_CACHED;
        pkgconf_pkg_unref(client, *slot);
        *slot = NULL;

        qsort(client->cache_table, client->cache_count,
                sizeof(void *), cache_member_sort_cmp);

        if (client->cache_table[client->cache_count - 1] != NULL)
        {
                PKGCONF_TRACE(client, "end of cache table refers to %p, not NULL",
                        client->cache_table[client->cache_count - 1]);
                cache_dump(client);
                abort();
        }

        client->cache_count--;
        if (client->cache_count > 0)
        {
                client->cache_table = pkgconf_reallocarray(client->cache_table,
                        client->cache_count, sizeof(void *));
        }
        else
        {
                free(client->cache_table);
                client->cache_table = NULL;
        }
}

/*
 * !doc
 *
 * .. c:function:: void pkgconf_cache_free(pkgconf_client_t *client)
 *
 *    Releases all resources related to a client object's package cache.
 *    This function should only be called to clear a client object's package cache,
 *    as it may release any package in the cache.
 *
 *    :param pkgconf_client_t* client: The client object to modify.
 */
void
pkgconf_cache_free(pkgconf_client_t *client)
{
        if (client->cache_table == NULL)
                return;

        while (client->cache_count > 0)
                pkgconf_cache_remove(client, client->cache_table[0]);

        free(client->cache_table);
        client->cache_table = NULL;
        client->cache_count = 0;

        PKGCONF_TRACE(client, "cleared package cache");
}