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<?php
/**
* Copyright 2017 Google Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
namespace Google\Cloud\Core\Iterator;
use Google\Cloud\Core\ArrayTrait;
/**
* This trait fulfills the
* [\Iterator](http://php.net/manual/en/class.iterator.php) interface and
* returns results as a page of items.
*/
trait PageIteratorTrait
{
use ArrayTrait;
/**
* @var array|null
*/
private $page;
/**
* @var callable
*/
private $resultMapper;
/**
* @var callable
*/
private $call;
/**
* @var array
*/
private $callOptions;
/**
* @var array
*/
private $config;
/**
* @var int
*/
private $position = 0;
/**
* @var int
*/
private $itemCount = 0;
/**
* @var array
*/
private $resultTokenPath;
/**
* @var array
*/
private $nextResultTokenPath;
/**
* @var array
*/
private $itemsPath;
/**
* @var string|null
*/
private $initialResultToken;
/**
* @param callable $resultMapper Maps a result.
* @param callable $call The call to execute.
* @param array $callOptions Options to use with the call.
* @param array $config [optional] {
* Configuration options.
*
* @type string $itemsKey The key for the items to iterate over from the
* response. **Defaults to** `"items"`.
* @type string $nextResultTokenKey The key for the next result token in
* the response. **Defaults to** `"nextPageToken"`.
* @type string $resultTokenKey The key for the results token set in the
* request. **Defaults too** `"pageToken"`.
* @type array $firstPage The first page of results. If set, this data
* will be used for the first page of results instead of making
* a network request.
* @type callable $setNextResultTokenCondition If this condition passes
* then it should be considered safe to set the token to get the
* next set of results.
* @type int $resultLimit Limit the number of results returned in total.
* **Defaults to** `0` (return all results).
* }
*/
public function __construct(
callable $resultMapper,
callable $call,
array $callOptions,
array $config = []
) {
$this->resultMapper = $resultMapper;
$this->call = $call;
$this->config = $config + [
'itemsKey' => 'items',
'nextResultTokenKey' => 'nextPageToken',
'resultTokenKey' => 'pageToken',
'firstPage' => null,
'resultLimit' => 0,
'setNextResultTokenCondition' => function () {
return true;
}
];
$this->callOptions = $callOptions;
$this->resultTokenPath = explode('.', $this->config['resultTokenKey']);
$this->nextResultTokenPath = explode('.', $this->config['nextResultTokenKey']);
$this->itemsPath = explode('.', $this->config['itemsKey']);
$this->initialResultToken = $this->nextResultToken();
}
/**
* Fetch the token used to get the next set of results.
*
* @return string|null
*/
public function nextResultToken()
{
return $this->get($this->resultTokenPath, $this->callOptions);
}
/**
* Rewind the iterator.
*
* @return null
*/
#[\ReturnTypeWillChange]
public function rewind()
{
$this->itemCount = 0;
$this->position = 0;
if ($this->config['firstPage']) {
list($this->page, $shouldContinue) = $this->mapResults($this->config['firstPage']);
$nextResultToken = $this->determineNextResultToken($this->page, $shouldContinue);
} else {
$this->page = null;
$nextResultToken = $this->initialResultToken;
}
if ($nextResultToken) {
$this->set($this->resultTokenPath, $this->callOptions, $nextResultToken);
}
}
/**
* Get the current page.
*
* @return array|null
*/
#[\ReturnTypeWillChange]
public function current()
{
if ($this->page === null) {
$this->page = $this->executeCall();
}
$page = $this->get($this->itemsPath, $this->page);
if ($this->nextResultToken()) {
return $page ?: [];
}
return $page;
}
/**
* Get the key current page's key.
*
* @return int
*/
#[\ReturnTypeWillChange]
public function key()
{
return $this->position;
}
/**
* Advances to the next page.
*
* @return null
*/
#[\ReturnTypeWillChange]
public function next()
{
$this->position++;
$this->page = $this->nextResultToken()
? $this->executeCall()
: null;
}
/**
* Determines if the current position is valid.
*
* @return bool
*/
#[\ReturnTypeWillChange]
public function valid()
{
if (!$this->page && $this->position) {
return false;
}
return true;
}
/**
* Executes the provided call to get a set of results.
*
* @return array
*/
private function executeCall()
{
$call = $this->call;
list($results, $shouldContinue) = $this->mapResults(
$call($this->callOptions)
);
$this->set(
$this->resultTokenPath,
$this->callOptions,
$this->determineNextResultToken($results, $shouldContinue)
);
return $results;
}
/**
* @param array $results
* @return array
*/
private function mapResults(array $results)
{
$items = $this->get($this->itemsPath, $results);
$resultMapper = $this->resultMapper;
$shouldContinue = true;
if ($items) {
foreach ($items as $key => $item) {
$items[$key] = $resultMapper($item);
$this->itemCount++;
if ($this->config['resultLimit'] && $this->config['resultLimit'] <= $this->itemCount) {
$items = array_slice($items, 0, $key + 1);
$shouldContinue = false;
break;
}
}
$this->set($this->itemsPath, $results, $items);
}
return [$results, $shouldContinue];
}
/**
* @param array $results
* @param bool $shouldContinue
* @return null
*/
private function determineNextResultToken(array $results, $shouldContinue = true)
{
return $shouldContinue && $this->config['setNextResultTokenCondition']($results)
? $this->get($this->nextResultTokenPath, $results)
: null;
}
/**
* @param array $path
* @param array $array
* @return mixed
*/
private function get(array $path, array $array)
{
$result = $array;
foreach ($path as $key) {
if (!isset($result[$key])) {
return null;
}
$result = $result[$key];
}
return $result;
}
/**
* @param array $path
* @param array $array
* @param mixed $value
* @return null
*/
private function set(array $path, array &$array, $value)
{
$temp = &$array;
foreach ($path as $key) {
$temp = &$temp[$key];
}
$temp = $value;
}
}
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