Proyectos de Subversion Moodle

<?php

// This file is part of Moodle - http://moodle.org/

//

// Moodle 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.

//

// Moodle 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 Moodle.  If not, see <http://www.gnu.org/licenses/>.

namespace core\local\guzzle;

/**

 * Class to define an interface for interacting with objects inside a cache.

 *

 * @package    core

 * @copyright  2022 safatshahin <safat.shahin@moodle.com>

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class cache_item {

    /**

     * Key to be used to store and identify the cache.

     *

     * @var string $key cache item key.

     */

    private string $key;

    /**

     * Actual data of the cache.

     *

     * @var mixed $value cache data.

     */

    private $value;

    /**

     * The expiry of the cache item according to TTL.

     *

     * @var \DateTime|null $expiration TTL time for the cache item.

     */

    private ?\DateTime $expiration;

    /**

     * Confirms if the cache item lookup resulted in a cache hit.

     *

     * @var bool $ishit determine the cache lookup.

     */

    private bool $ishit = false;

    /**

     * Constructor for the cache_item to get the key and module to retrieve or set the cache item.

     *

     * @param string $key The key for the current cache item.

     * @param string $module determines the location of the cache item.

     * @param int|null $ttl Time to live for the cache item.

     */

    public function __construct(string $key, string $module, ?int $ttl = null) {

        global $CFG, $USER;

        $this->key = $key;

        // Set the directory for cache.

        $dir = $CFG->cachedir . '/' . $module . '/';

        if (file_exists($dir)) {

            $filename = 'u' . $USER->id . '_' . md5(serialize($key));

            // If the cache fine exists, set the value from the cache file.

            if (file_exists($dir . $filename)) {

                $this->ishit = true;

                $this->expires_after($ttl);

                $fp = fopen($dir . $filename, 'rb');

                $size = filesize($dir . $filename);

                $content = fread($fp, $size);

                $this->value = unserialize($content);

            }

        }

    }

    /**

     * Returns the key for the current cache item.

     *

     * The key is loaded by the Implementing Library, but should be available to

     * the higher level callers when needed.

     *

     * @return string The key string for this cache item.

     */

    public function get_key(): string {

        return $this->key;

    }

    /**

     * Retrieves the value of the item from the cache associated with this object's key.

     *

     * The value returned must be identical to the value originally stored by set().

     *

     * If isHit() returns false, this method MUST return null. Note that null

     * is a legitimate cache value, so the isHit() method SHOULD be used to

     * differentiate between "null value was found" and "no value was found."

     *

     * @return mixed The value corresponding to this cache item's key, or null if not found.

     */

    public function get() {

        return $this->is_hit() ? $this->value : null;

    }

    /**

     * Confirms if the cache item lookup resulted in a cache hit.

     *

     * Note: This method MUST NOT have a race condition between calling isHit()

     * and calling get().

     *

     * @return bool True if the request resulted in a cache hit. False otherwise.

     */

    public function is_hit(): bool {

        if (!$this->ishit) {

            return false;

        }

        if ($this->expiration === null) {

            return true;

        }

        return $this->current_time()->getTimestamp() < $this->expiration->getTimestamp();

    }

    /**

     * Sets the value represented by this cache item.

     *

     * The $value argument may be any item that can be serialized by PHP,

     * although the method of serialization is left up to the Implementing

     * Library.

     *

     * @param mixed $value The serializable value to be stored.

     * @return static The invoked object.

     */

    public function set($value): cache_item {

        $this->ishit = true;

        $this->value = $value;

        return $this;

    }

    /**

     * Sets the absolute expiration time for this cache item.

     *

     * @param \DateTimeInterface|null $expiration

     *   The point in time after which the item MUST be considered expired.

     *   If null is passed explicitly, a default value MAY be used. If none is set,

     *   the value should be stored permanently or for as long as the

     *   implementation allows.

     *

     * @return static The called object.

     */

    public function expires_at($expiration): cache_item {

        if (null === $expiration || $expiration instanceof \DateTimeInterface) {

            $this->expiration = $expiration;

            return $this;

        }

        throw new \coding_exception('Invalid argument passed');

    }

    /**

     * Sets the relative expiration time for this cache item.

     *

     * @param int|\DateInterval|null $time

     *   The period of time from the present after which the item MUST be considered

     *   expired. An integer parameter is understood to be the time in seconds until

     *   expiration. If null is passed explicitly, a default value MAY be used.

     *   If none is set, the value should be stored permanently or for as long as the

     *   implementation allows.

     *

     * @return static The called object.

     */

    public function expires_after($time): cache_item {

        if (is_int($time) && $time >= 0) {

            $this->expiration = $this->current_time()->add(new \DateInterval("PT{$time}S"));

        } else if ($time instanceof \DateInterval) {

            $this->expiration = $this->current_time()->add($time);

        } else {

            $this->expiration = $time;

        }

        return $this;

    }

    /**

     * Gets the current time in the user timezone.

     *

     * @return \DateTime

     */

    private function current_time(): \DateTime {

        return new \DateTime('now', new \DateTimeZone(get_user_timezone()));

    }

}