/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "fcgid_spawn_ctl.h"
#include "fcgid_conf.h"

#include "apr_strings.h"

#define REGISTER_LIFE 1
#define REGISTER_DEATH 2

struct fcgid_stat_node {
    apr_ino_t inode;
    dev_t deviceid;
    uid_t uid;
    gid_t gid;
    const char *cmdline;
    int vhost_id;
    int score;
    int process_counter;
    int max_class_process_count;
    int min_class_process_count;
    apr_time_t last_stat_time;
    struct fcgid_stat_node *next;
};

static apr_pool_t *g_stat_pool = NULL;
static struct fcgid_stat_node *g_stat_list_header = NULL;
static int g_total_process;

static void
register_life_death(server_rec * main_server,
                    fcgid_procnode * procnode, int life_or_death)
{
    struct fcgid_stat_node *previous_node, *current_node;
    fcgid_server_conf *sconf = ap_get_module_config(main_server->module_config,
                                                    &fcgid_module);
    apr_time_t now = apr_time_now();

    if (!g_stat_pool || !procnode)
        abort();

    /* Can I find the node base on inode, device id and cmdline? */
    previous_node = g_stat_list_header;
    for (current_node = previous_node;
         current_node != NULL; current_node = current_node->next) {
        if (current_node->inode == procnode->inode
            && current_node->deviceid == procnode->deviceid
            && !strcmp(current_node->cmdline, procnode->cmdline)
            && current_node->vhost_id == procnode->vhost_id
            && current_node->uid == procnode->uid
            && current_node->gid == procnode->gid)
            break;
        previous_node = current_node;
    }

    if (!current_node) {         /* I can't find it, create one */
        if (life_or_death == REGISTER_DEATH) {
            ap_log_error(APLOG_MARK, APLOG_CRIT, 0, main_server,
                         "stat node not found for exiting process %s",
                         procnode->cmdline);
            return;
        }
        current_node = apr_pcalloc(g_stat_pool, sizeof(*current_node));
        current_node->deviceid = procnode->deviceid;
        current_node->inode = procnode->inode;
        current_node->cmdline = apr_pstrdup(g_stat_pool, procnode->cmdline);
        current_node->vhost_id = procnode->vhost_id;
        current_node->uid = procnode->uid;
        current_node->gid = procnode->gid;
        current_node->last_stat_time = now;
        current_node->score = 0;
        current_node->process_counter = 0;
        current_node->max_class_process_count =
            procnode->cmdopts.max_class_process_count;
        current_node->min_class_process_count =
            procnode->cmdopts.min_class_process_count;
        current_node->next = NULL;

        /* append it to stat list for next search */
        if (!previous_node)
            g_stat_list_header = current_node;
        else
            previous_node->next = current_node;
    }

    /* Increase the score first */
    if (life_or_death == REGISTER_LIFE) {
        current_node->score += sconf->spawn_score;
        current_node->process_counter++;
    } else {
        current_node->score += sconf->termination_score;
        current_node->process_counter--;
    }

    /* Decrease the score based on elapsed time */
    current_node->score -= 
        sconf->time_score * 
        (int)(apr_time_sec(now) - apr_time_sec(current_node->last_stat_time));

    /* Make score reasonable */
    if (current_node->score < 0)
        current_node->score = 0;

    current_node->last_stat_time = now;
}

void spawn_control_init(server_rec * main_server, apr_pool_t * configpool)
{
    apr_status_t rv;

    if ((rv = apr_pool_create(&g_stat_pool, configpool)) != APR_SUCCESS) {
        /* Fatal error */
        ap_log_error(APLOG_MARK, APLOG_EMERG, rv, main_server,
                     "mod_fcgid: can't create stat pool");
        exit(1);
    }
}

void
register_termination(server_rec * main_server, fcgid_procnode * procnode)
{
    register_life_death(main_server, procnode, REGISTER_DEATH);
    g_total_process--;
}

void register_spawn(server_rec * main_server, fcgid_procnode * procnode)
{
    register_life_death(main_server, procnode, REGISTER_LIFE);
    g_total_process++;
}

/* 
 * Spawn control strategy:
 * 1. Add FcgidSpawnScore to score if application is terminated
 * 2. Add FcgidTerminationScore to score if application is spawned
 * 3. Subtract FcgidTimeScore from score each second while score is positive
 * 4. Ignore spawn request if score is higher than FcgidSpawnScoreUpLimit
 * 5. Ignore spawn request if total process count higher than
 *    FcgidSpawnScoreUpLimit
 * 6. Ignore spawn request if process count of this class is higher than
 *    FcgidMaxProcessesPerClass
 */
int is_spawn_allowed(server_rec * main_server, fcgid_command * command)
{
    struct fcgid_stat_node *current_node;
    fcgid_server_conf *sconf = ap_get_module_config(main_server->module_config,
                                                    &fcgid_module);

    if (!command || !g_stat_pool)
        return 1;

    /* Total process count higher than up limit? */
    if (g_total_process >= sconf->max_process_count) {
        ap_log_error(APLOG_MARK, APLOG_INFO, 0, main_server,
                     "mod_fcgid: %s total process count %d >= %d, skip the spawn request",
                     command->cgipath, g_total_process, sconf->max_process_count);
        return 0;
    }

    /* Can I find the node base on inode, device id and cmdline? */
    for (current_node = g_stat_list_header;
         current_node != NULL; current_node = current_node->next) {
        if (current_node->inode == command->inode
            && current_node->deviceid == command->deviceid
            && !strcmp(current_node->cmdline, command->cmdline)
            && current_node->vhost_id == sconf->vhost_id
            && current_node->uid == command->uid
            && current_node->gid == command->gid)
            break;
    }

    if (!current_node) {
        /* There are no existing processes for this class, so obviously 
         * no class-specific limits have been exceeded.
         */
        return 1;
    }
    else {
        apr_time_t now = apr_time_now();

        current_node->score -= 
          sconf->time_score * 
          (int)(apr_time_sec(now) - apr_time_sec(current_node->last_stat_time));
        current_node->last_stat_time = now;
        if (current_node->score < 0)
            current_node->score = 0;

        /* Score is higher than up limit? */
        if (current_node->score >= sconf->spawnscore_uplimit) {
            ap_log_error(APLOG_MARK, APLOG_INFO, 0, main_server,
                         "mod_fcgid: %s spawn score %d >= %d, skip the spawn request",
                         command->cgipath, current_node->score,
                         sconf->spawnscore_uplimit);
            return 0;
        }

        /* 
         * Process count of this class higher than up limit?
         */
        if (current_node->process_counter >= current_node->max_class_process_count) {
            ap_log_error(APLOG_MARK, APLOG_INFO, 0, main_server,
                         "mod_fcgid: too many %s processes (current:%d, max:%d), skip the spawn request",
                         command->cgipath, current_node->process_counter,
                         current_node->max_class_process_count);
            return 0;
        }

        return 1;
    }
}

int is_kill_allowed(server_rec * main_server, fcgid_procnode * procnode)
{
    struct fcgid_stat_node *current_node;

    if (!g_stat_pool || !procnode)
        return 0;

    /* Can I find the node base on inode, device id and cmdline? */
    for (current_node = g_stat_list_header;
         current_node != NULL; current_node = current_node->next) {
        if (current_node->inode == procnode->inode
            && current_node->deviceid == procnode->deviceid
            && !strcmp(current_node->cmdline, procnode->cmdline)
            && current_node->vhost_id == procnode->vhost_id
            && current_node->uid == procnode->uid
            && current_node->gid == procnode->gid)
            break;
    }

    if (current_node) {
        /* Found the node */
        if (current_node->process_counter <= current_node->min_class_process_count)
            return 0;
    }

    return 1;
}