<?php
/**
 * PHP Server Monitor
 * Monitor your servers and websites.
 *
 * This file is part of PHP Server Monitor.
 * PHP Server Monitor is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * PHP Server Monitor is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with PHP Server Monitor.  If not, see <http://www.gnu.org/licenses/>.
 *
 * @package     phpservermon
 * @author      Pepijn Over <pep@mailbox.org>
 *              Jérôme Cabanis <http://lauraly.com>
 * @copyright   Copyright (c) 2008-2017 Pepijn Over <pep@mailbox.org>
 * @license     http://www.gnu.org/licenses/gpl.txt GNU GPL v3
 * @version     Release: @package_version@
 * @link        http://www.phpservermonitor.org/
 **/

/**
 * The archiver class moves active data from the uptime table to the history table.
 *
 * Because the uptime table has a record for every single run of the status-check,
 * it will grow very large over time. For this reason, uptime records are only kept for a limited time
 * to provide detailed statistics. After that, the archiver comes in and saves the averages per day
 * in the history table. That way we can always show statistics regarding average latency and failed checks per day,
 * but we only need 1 record per server per day.
 *
 * @see \psm\Util\Updater\Autorun
 */
namespace psm\Util\Server\Archiver;
use psm\Service\Database;

class UptimeArchiver implements ArchiverInterface {

	/**
	 * Database service
	 * @var \psm\Service\Database $db
	 */
	protected $db;

	function __construct(Database $db) {
		$this->db = $db;
	}

	/**
	 * Archive all server status records older than 1 week.
	 *
	 * Archiving means calculating averages per day, and storing 1 single
	 * history row for each day for each server.
	 *
	 * @param int $server_id
	 */
	public function archive($server_id = null) {
		$latest_date = new \DateTime('-1 week 0:0:0');

		// Lock tables to prevent simultaneous archiving (by other sessions or the cron job)
		try {
			$this->db->pdo()->exec('LOCK TABLES '.PSM_DB_PREFIX.'servers_uptime WRITE, '.PSM_DB_PREFIX.'servers_history WRITE');
			$locked = true;
		} catch (\PDOException $e) {
			// user does not have lock rights, ignore
			$locked = false;
		}

		$latest_date_str = $latest_date->format('Y-m-d 00:00:00');

		$sql_where_server = $this->createSQLWhereServer($server_id);

		$records = $this->db->execute(
			"SELECT `server_id`,`date`,`status`,`latency`
				FROM `".PSM_DB_PREFIX."servers_uptime`
				WHERE {$sql_where_server} `date` < :latest_date",
			array('latest_date'	=> $latest_date_str));

		if (!empty($records)) {
			// first group all records by day and server_id
			$data_by_day = array();
			foreach ($records as $record) {
				$server_id = (int) $record['server_id'];
				$day = date('Y-m-d', strtotime($record['date']));
				if (!isset($data_by_day[$day][$server_id])) {
					$data_by_day[$day][$server_id] = array();
				}
				$data_by_day[$day][$server_id][] = $record;
			}

			// now get history data day by day
			$histories = array();
			foreach ($data_by_day as $day => $day_records) {
				foreach ($day_records as $server_id => $server_day_records) {
					$histories[] = $this->getHistoryForDay($day, $server_id, $server_day_records);
				}
			}

			// Save all
			$this->db->insertMultiple(PSM_DB_PREFIX.'servers_history', $histories);

			// now remove all records from the uptime table
			$this->db->execute(
				"DELETE FROM `".PSM_DB_PREFIX."servers_uptime` WHERE {$sql_where_server} `date` < :latest_date",
				array('latest_date' => $latest_date_str),
				false
			);
		}

		if ($locked) {
			$this->db->exec('UNLOCK TABLES');
		}

		return true;
	}

	public function cleanup(\DateTime $retention_date, $server_id = null) {
		$sql_where_server = $this->createSQLWhereServer($server_id);
		$this->db->execute(
			"DELETE FROM `".PSM_DB_PREFIX."servers_history` WHERE {$sql_where_server} `date` < :latest_date",
			array('latest_date' => $retention_date->format('Y-m-d 00:00:00')),
			false
		);
		return true;
	}

	/**
	 * Build a history array for a day records
	 * @param string $day
	 * @param int $server_id
	 * @param array $day_records
	 * @return array
	 */
	protected function getHistoryForDay($day, $server_id, $day_records) {
		$latencies = array();
		$checks_failed = 0;

		foreach ($day_records as $day_record) {
			$latencies[] = $day_record['latency'];

			if ($day_record['status'] == 0) {
				$checks_failed++;
			}
		}
		sort($latencies, SORT_NUMERIC);

		$history = array(
			'date' => $day,
			'server_id' => $server_id,
			'latency_min' => min($latencies),
			'latency_avg' => array_sum($latencies) / count($latencies),
			'latency_max' => max($latencies),
			'checks_total' => count($day_records),
			'checks_failed' => $checks_failed,
		);
		return $history;
	}

	protected function createSQLWhereServer($server_id) {
		$sql_where_server = ($server_id !== null)
				// this is obviously not the cleanest way to implement this when using paramter binding.. sorry.
				? ' `server_id` = '.intval($server_id).' AND '
				: '';

		return $sql_where_server;
	}
}