<?php

/**
 * @package KantPHP
 * @author  Zhenqiang Zhang <zhenqiang.zhang@hotmail.com>
 * @copyright (c) KantPHP Studio, All rights reserved.
 * @license http://www.opensource.org/licenses/BSD-3-Clause  The BSD 3-Clause License
 */
namespace Kant\Behavior;

use Kant\Exception\InvalidCallException;
use Kant\Database\BaseActiveRecord;

/**
 * TimestampBehavior automatically fills the specified attributes with the current timestamp.
 *
 * To use TimestampBehavior, insert the following code to your ActiveRecord class:
 *
 * ```php
 * use Kant\Behavior\TimestampBehavior;
 *
 * public function behaviors()
 * {
 * return [
 * TimestampBehavior::className(),
 * ];
 * }
 * ```
 *
 * By default, TimestampBehavior will fill the `created_at` and `updated_at` attributes with the current timestamp
 * when the associated AR object is being inserted; it will fill the `updated_at` attribute
 * with the timestamp when the AR object is being updated. The timestamp value is obtained by `time()`.
 *
 * Because attribute values will be set automatically by this behavior, they are usually not user input and should therefore
 * not be validated, i.e. `created_at` and `updated_at` should not appear in the [[\Kant\Model\Model::rules()|rules()]] method of the model.
 *
 * For the above implementation to work with MySQL database, please declare the columns(`created_at`, `updated_at`) as int(11) for being UNIX timestamp.
 *
 * If your attribute names are different or you want to use a different way of calculating the timestamp,
 * you may configure the [[createdAtAttribute]], [[updatedAtAttribute]] and [[value]] properties like the following:
 *
 * ```php
 * use Kant\Database\Expression;
 *
 * public function behaviors()
 * {
 * return [
 * [
 * 'class' => TimestampBehavior::className(),
 * 'createdAtAttribute' => 'create_time',
 * 'updatedAtAttribute' => 'update_time',
 * 'value' => new Expression('NOW()'),
 * ],
 * ];
 * }
 * ```
 *
 * In case you use an [[\Kant\Database\Expression]] object as in the example above, the attribute will not hold the timestamp value, but
 * the Expression object itself after the record has been saved. If you need the value from DB afterwards you should call
 * the [[\Kant\Database\ActiveRecord::refresh()|refresh()]] method of the record.
 *
 * TimestampBehavior also provides a method named [[touch()]] that allows you to assign the current
 * timestamp to the specified attribute(s) and save them to the database. For example,
 *
 * ```php
 * $model->touch('creation_time');
 * ```
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @author Alexander Kochetov <creocoder@gmail.com>
 * @since 2.0
 */
class TimestampBehavior extends AttributeBehavior
{

    /**
     *
     * @var string the attribute that will receive timestamp value
     *      Set this property to false if you do not want to record the creation time.
     */
    public $createdAtAttribute = 'created_at';

    /**
     *
     * @var string the attribute that will receive timestamp value.
     *      Set this property to false if you do not want to record the update time.
     */
    public $updatedAtAttribute = 'updated_at';

    /**
     * @inheritdoc
     *
     * In case, when the value is `null`, the result of the PHP function [time()](http://php.net/manual/en/function.time.php)
     * will be used as value.
     */
    public $value;

    /**
     * @inheritdoc
     */
    public function init()
    {
        parent::init();
        
        if (empty($this->attributes)) {
            $this->attributes = [
                BaseActiveRecord::EVENT_BEFORE_INSERT => [
                    $this->createdAtAttribute,
                    $this->updatedAtAttribute
                ],
                BaseActiveRecord::EVENT_BEFORE_UPDATE => $this->updatedAtAttribute
            ];
        }
    }

    /**
     * @inheritdoc
     *
     * In case, when the [[value]] is `null`, the result of the PHP function [time()](http://php.net/manual/en/function.time.php)
     * will be used as value.
     */
    protected function getValue($event)
    {
        if ($this->value === null) {
            return time();
        }
        return parent::getValue($event);
    }

    /**
     * Updates a timestamp attribute to the current timestamp.
     *
     * ```php
     * $model->touch('lastVisit');
     * ```
     * 
     * @param string $attribute
     *            the name of the attribute to update.
     * @throws InvalidCallException if owner is a new record (since version 2.0.6).
     */
    public function touch($attribute)
    {
        /* @var $owner BaseActiveRecord */
        $owner = $this->owner;
        if ($owner->getIsNewRecord()) {
            throw new InvalidCallException('Updating the timestamp is not possible on a new record.');
        }
        $owner->updateAttributes(array_fill_keys((array) $attribute, $this->getValue(null)));
    }
}
