/**
* This method iterates over a collection of resources. It sends the operation's request to the API,
* parses the response, converts each element into {@see self} and - if pagination is supported - continues
* to send requests until an empty collection is received back.
*
* For paginated collections, it sends subsequent requests according to a marker URL query. The value
* of the marker will depend on the last element returned in the previous response. If a limit is
* provided, the loop will continue up until that point.
*
* @param Operation $operation The operation responsible for retrieving a new collection
* @param callable $mapFn An optional callback that will be executed on every resource iteration.
*/
public function enumerate(Operation $operation, callable $mapFn = null)
{
$limit = $operation->getValue('limit') ?: false;
$supportsPagination = $operation->hasParam('marker');
$markerKey = $this->markerKey ?: self::DEFAULT_MARKER_KEY;
$count = 0;
$moreRequestsRequired = true;
$totalReached = function ($count) use($limit) {
return $limit && $count >= $limit;
};
while ($moreRequestsRequired && $count < 20) {
$response = $operation->send();
$body = $response->json();
$json = $this->flatten($body, $this->resourcesKey);
foreach ($json as $resourceData) {
if ($totalReached($count)) {
break;
}
$count++;
$resource = $this->newInstance();
$resource->populateFromArray($resourceData);
if ($mapFn) {
call_user_func_array($mapFn, [$resource]);
}
if ($supportsPagination) {
$operation->setValue('marker', $resource->{$markerKey});
}
(yield $resource);
}
if ($totalReached($count) || !$supportsPagination || empty($json)) {
$moreRequestsRequired = false;
}
}
}
