<?php
/**
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\base;

use Yii;
use yii\helpers\ArrayHelper;
use yii\web\Link;
use yii\web\Linkable;

/**
 * ArrayableTrait provides a common implementation of the [[Arrayable]] interface.
 *
 * ArrayableTrait implements [[toArray()]] by respecting the field definitions as declared
 * in [[fields()]] and [[extraFields()]].
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
trait ArrayableTrait
{
 /**
 * Returns the list of fields that should be returned by default by [[toArray()]] when no specific fields are specified.
 *
 * A field is a named element in the returned array by [[toArray()]].
 *
 * This method should return an array of field names or field definitions.
 * If the former, the field name will be treated as an object property name whose value will be used
 * as the field value. If the latter, the array key should be the field name while the array value should be
 * the corresponding field definition which can be either an object property name or a PHP callable
 * returning the corresponding field value. The signature of the callable should be:
 *
 * ```php
 * function ($model, $field) {
 * // return field value
 * }
 * ```
 *
 * For example, the following code declares four fields:
 *
 * - `email`: the field name is the same as the property name `email`;
 * - `firstName` and `lastName`: the field names are `firstName` and `lastName`, and their
 * values are obtained from the `first_name` and `last_name` properties;
 * - `fullName`: the field name is `fullName`. Its value is obtained by concatenating `first_name`
 * and `last_name`.
 *
 * ```php
 * return [
 * 'email',
 * 'firstName' => 'first_name',
 * 'lastName' => 'last_name',
 * 'fullName' => function () {
 * return $this->first_name . ' ' . $this->last_name;
 * },
 * ];
 * ```
 *
 * In this method, you may also want to return different lists of fields based on some context
 * information. For example, depending on the privilege of the current application user,
 * you may return different sets of visible fields or filter out some fields.
 *
 * The default implementation of this method returns the public object member variables indexed by themselves.
 *
 * @return array the list of field names or field definitions.
 * @see toArray()
 */
 public function fields()
 {
 $fields = array_keys(Yii::getObjectVars($this));
 return array_combine($fields, $fields);
 }

 /**
 * Returns the list of fields that can be expanded further and returned by [[toArray()]].
 *
 * This method is similar to [[fields()]] except that the list of fields returned
 * by this method are not returned by default by [[toArray()]]. Only when field names
 * to be expanded are explicitly specified when calling [[toArray()]], will their values
 * be exported.
 *
 * The default implementation returns an empty array.
 *
 * You may override this method to return a list of expandable fields based on some context information
 * (e.g. the current application user).
 *
 * @return array the list of expandable field names or field definitions. Please refer
 * to [[fields()]] on the format of the return value.
 * @see toArray()
 * @see fields()
 */
 public function extraFields()
 {
 return [];
 }

 /**
 * Converts the model into an array.
 *
 * This method will first identify which fields to be included in the resulting array by calling [[resolveFields()]].
 * It will then turn the model into an array with these fields. If `$recursive` is true,
 * any embedded objects will also be converted into arrays.
 *
 * If the model implements the [[Linkable]] interface, the resulting array will also have a `_link` element
 * which refers to a list of links as specified by the interface.
 *
 * @param array $fields the fields being requested. If empty, all fields as specified by [[fields()]] will be returned.
 * @param array $expand the additional fields being requested for exporting. Only fields declared in [[extraFields()]]
 * will be considered.
 * @param boolean $recursive whether to recursively return array representation of embedded objects.
 * @return array the array representation of the object
 */
 public function toArray(array $fields = [], array $expand = [], $recursive = true)
 {
 $data = [];
 foreach ($this->resolveFields($fields, $expand) as $field => $definition) {
 $data[$field] = is_string($definition) ? $this->$definition : call_user_func($definition, $this, $field);
 }

 if ($this instanceof Linkable) {
 $data['_links'] = Link::serialize($this->getLinks());
 }

 return $recursive ? ArrayHelper::toArray($data) : $data;
 }

 /**
 * Determines which fields can be returned by [[toArray()]].
 * This method will check the requested fields against those declared in [[fields()]] and [[extraFields()]]
 * to determine which fields can be returned.
 * @param array $fields the fields being requested for exporting
 * @param array $expand the additional fields being requested for exporting
 * @return array the list of fields to be exported. The array keys are the field names, and the array values
 * are the corresponding object property names or PHP callables returning the field values.
 */
 protected function resolveFields(array $fields, array $expand)
 {
 $result = [];

 foreach ($this->fields() as $field => $definition) {
 if (is_integer($field)) {
 $field = $definition;
 }
 if (empty($fields) || in_array($field, $fields, true)) {
 $result[$field] = $definition;
 }
 }

 if (empty($expand)) {
 return $result;
 }

 foreach ($this->extraFields() as $field => $definition) {
 if (is_integer($field)) {
 $field = $definition;
 }
 if (in_array($field, $expand, true)) {
 $result[$field] = $definition;
 }
 }

 return $result;
 }
}