--- /dev/null
+<?php
+namespace GuzzleHttp\Promise;
+
+/**
+ * Represents a promise that iterates over many promises and invokes
+ * side-effect functions in the process.
+ */
+class EachPromise implements PromisorInterface
+{
+ private $pending = [];
+
+ /** @var \Iterator */
+ private $iterable;
+
+ /** @var callable|int */
+ private $concurrency;
+
+ /** @var callable */
+ private $onFulfilled;
+
+ /** @var callable */
+ private $onRejected;
+
+ /** @var Promise */
+ private $aggregate;
+
+ /** @var bool */
+ private $mutex;
+
+ /**
+ * Configuration hash can include the following key value pairs:
+ *
+ * - fulfilled: (callable) Invoked when a promise fulfills. The function
+ * is invoked with three arguments: the fulfillment value, the index
+ * position from the iterable list of the promise, and the aggregate
+ * promise that manages all of the promises. The aggregate promise may
+ * be resolved from within the callback to short-circuit the promise.
+ * - rejected: (callable) Invoked when a promise is rejected. The
+ * function is invoked with three arguments: the rejection reason, the
+ * index position from the iterable list of the promise, and the
+ * aggregate promise that manages all of the promises. The aggregate
+ * promise may be resolved from within the callback to short-circuit
+ * the promise.
+ * - concurrency: (integer) Pass this configuration option to limit the
+ * allowed number of outstanding concurrently executing promises,
+ * creating a capped pool of promises. There is no limit by default.
+ *
+ * @param mixed $iterable Promises or values to iterate.
+ * @param array $config Configuration options
+ */
+ public function __construct($iterable, array $config = [])
+ {
+ $this->iterable = iter_for($iterable);
+
+ if (isset($config['concurrency'])) {
+ $this->concurrency = $config['concurrency'];
+ }
+
+ if (isset($config['fulfilled'])) {
+ $this->onFulfilled = $config['fulfilled'];
+ }
+
+ if (isset($config['rejected'])) {
+ $this->onRejected = $config['rejected'];
+ }
+ }
+
+ public function promise()
+ {
+ if ($this->aggregate) {
+ return $this->aggregate;
+ }
+
+ try {
+ $this->createPromise();
+ $this->iterable->rewind();
+ $this->refillPending();
+ } catch (\Throwable $e) {
+ $this->aggregate->reject($e);
+ } catch (\Exception $e) {
+ $this->aggregate->reject($e);
+ }
+
+ return $this->aggregate;
+ }
+
+ private function createPromise()
+ {
+ $this->mutex = false;
+ $this->aggregate = new Promise(function () {
+ reset($this->pending);
+ if (empty($this->pending) && !$this->iterable->valid()) {
+ $this->aggregate->resolve(null);
+ return;
+ }
+
+ // Consume a potentially fluctuating list of promises while
+ // ensuring that indexes are maintained (precluding array_shift).
+ while ($promise = current($this->pending)) {
+ next($this->pending);
+ $promise->wait();
+ if ($this->aggregate->getState() !== PromiseInterface::PENDING) {
+ return;
+ }
+ }
+ });
+
+ // Clear the references when the promise is resolved.
+ $clearFn = function () {
+ $this->iterable = $this->concurrency = $this->pending = null;
+ $this->onFulfilled = $this->onRejected = null;
+ };
+
+ $this->aggregate->then($clearFn, $clearFn);
+ }
+
+ private function refillPending()
+ {
+ if (!$this->concurrency) {
+ // Add all pending promises.
+ while ($this->addPending() && $this->advanceIterator());
+ return;
+ }
+
+ // Add only up to N pending promises.
+ $concurrency = is_callable($this->concurrency)
+ ? call_user_func($this->concurrency, count($this->pending))
+ : $this->concurrency;
+ $concurrency = max($concurrency - count($this->pending), 0);
+ // Concurrency may be set to 0 to disallow new promises.
+ if (!$concurrency) {
+ return;
+ }
+ // Add the first pending promise.
+ $this->addPending();
+ // Note this is special handling for concurrency=1 so that we do
+ // not advance the iterator after adding the first promise. This
+ // helps work around issues with generators that might not have the
+ // next value to yield until promise callbacks are called.
+ while (--$concurrency
+ && $this->advanceIterator()
+ && $this->addPending());
+ }
+
+ private function addPending()
+ {
+ if (!$this->iterable || !$this->iterable->valid()) {
+ return false;
+ }
+
+ $promise = promise_for($this->iterable->current());
+ $idx = $this->iterable->key();
+
+ $this->pending[$idx] = $promise->then(
+ function ($value) use ($idx) {
+ if ($this->onFulfilled) {
+ call_user_func(
+ $this->onFulfilled, $value, $idx, $this->aggregate
+ );
+ }
+ $this->step($idx);
+ },
+ function ($reason) use ($idx) {
+ if ($this->onRejected) {
+ call_user_func(
+ $this->onRejected, $reason, $idx, $this->aggregate
+ );
+ }
+ $this->step($idx);
+ }
+ );
+
+ return true;
+ }
+
+ private function advanceIterator()
+ {
+ // Place a lock on the iterator so that we ensure to not recurse,
+ // preventing fatal generator errors.
+ if ($this->mutex) {
+ return false;
+ }
+
+ $this->mutex = true;
+
+ try {
+ $this->iterable->next();
+ $this->mutex = false;
+ return true;
+ } catch (\Throwable $e) {
+ $this->aggregate->reject($e);
+ $this->mutex = false;
+ return false;
+ } catch (\Exception $e) {
+ $this->aggregate->reject($e);
+ $this->mutex = false;
+ return false;
+ }
+ }
+
+ private function step($idx)
+ {
+ // If the promise was already resolved, then ignore this step.
+ if ($this->aggregate->getState() !== PromiseInterface::PENDING) {
+ return;
+ }
+
+ unset($this->pending[$idx]);
+
+ // Only refill pending promises if we are not locked, preventing the
+ // EachPromise to recursively invoke the provided iterator, which
+ // cause a fatal error: "Cannot resume an already running generator"
+ if ($this->advanceIterator() && !$this->checkIfFinished()) {
+ // Add more pending promises if possible.
+ $this->refillPending();
+ }
+ }
+
+ private function checkIfFinished()
+ {
+ if (!$this->pending && !$this->iterable->valid()) {
+ // Resolve the promise if there's nothing left to do.
+ $this->aggregate->resolve(null);
+ return true;
+ }
+
+ return false;
+ }
+}
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