<?php

/**
 * @package     Joomla.Administrator
 * @subpackage  com_scheduler
 *
 * @copyright   (C) 2021 Open Source Matters, Inc. <https://www.joomla.org>
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */

namespace Joomla\Component\Scheduler\Administrator\Helper;

use Cron\CronExpression;
use Joomla\CMS\Date\Date;
use Joomla\CMS\Factory;
use Joomla\Component\Scheduler\Administrator\Task\Task;
use Joomla\Database\DatabaseDriver;
use Joomla\Utilities\ArrayHelper;

/**
 * Helper class for supporting task execution rules.
 *
 * @since  4.1.0
 * @todo   This helper should probably be merged into the {@see Task} class.
 */
class ExecRuleHelper
{
    /**
     * The execution rule type
     *
     * @var string
     * @since  4.1.0
     */
    private $type;

    /**
     * @var array
     * @since  4.1.0
     */
    private $task;

    /**
     * @var object
     * @since  4.1.0
     */
    private $rule;

    /**
     * @param   array|object  $task  A task entry
     *
     * @since  4.1.0
     */
    public function __construct($task)
    {
        $this->task = \is_array($task) ? $task : ArrayHelper::fromObject($task);
        $rule       = $this->getFromTask('cron_rules');
        $this->rule = \is_string($rule)
            ? (object) json_decode($rule)
            : (\is_array($rule) ? (object) $rule : $rule);
        $this->type = $this->rule->type;
    }

    /**
     * Get a property from the task array
     *
     * @param   string  $property  The property to get
     * @param   mixed   $default   The default value returned if property does not exist
     *
     * @return mixed
     *
     * @since  4.1.0
     */
    private function getFromTask(string $property, $default = null)
    {
        $property = ArrayHelper::getValue($this->task, $property);

        return $property ?? $default;
    }

    /**
     * @param   boolean  $string    If true, an SQL formatted string is returned.
     * @param   boolean  $basisNow  If true, the current date-time is used as the basis for projecting the next
     *                              execution.
     *
     * @return ?Date|string
     *
     * @since  4.1.0
     * @throws \Exception
     */
    public function nextExec(bool $string = true, bool $basisNow = false)
    {
        // Exception handling here
        switch ($this->type) {
            case 'interval':
                $lastExec = Factory::getDate($basisNow ? 'now' : $this->getFromTask('last_execution'), 'UTC');
                $interval = new \DateInterval($this->rule->exp);
                $nextExec = $lastExec->add($interval);
                $nextExec = $string ? $nextExec->toSql() : $nextExec;
                break;
            case 'cron-expression':
                // @todo: testing
                $cExp     = new CronExpression((string) $this->rule->exp);
                $nextExec = $cExp->getNextRunDate('now', 0, false, 'UTC');
                $nextExec = $string ? $this->dateTimeToSql($nextExec) : $nextExec;
                break;
            default:
                // 'manual' execution is handled here.
                $nextExec = null;
        }

        return $nextExec;
    }

    /**
     * Returns a sql-formatted string for a DateTime object.
     * Only needed for DateTime objects returned by CronExpression, JDate supports this as class method.
     *
     * @param   \DateTime  $dateTime  A DateTime object to format
     *
     * @return string
     *
     * @since  4.1.0
     */
    private function dateTimeToSql(\DateTime $dateTime): string
    {
        static $db;
        $db = $db ?? Factory::getContainer()->get(DatabaseDriver::class);

        return $dateTime->format($db->getDateFormat());
    }
}
