feat(io): add streaming function

Signed-off-by: azjezz <azjezz@protonmail.com>

docs/component/io.md

@@ -16,6 +16,7 @@
 - [input_handle](./../../src/Psl/IO/input_handle.php#L20)
 - [output_handle](./../../src/Psl/IO/output_handle.php#L20)
 - [pipe](./../../src/Psl/IO/pipe.php#L24)
+- [streaming](./../../src/Psl/IO/streaming.php#L37)
 - [write](./../../src/Psl/IO/write.php#L21)
 - [write_error](./../../src/Psl/IO/write_error.php#L23)
 - [write_error_line](./../../src/Psl/IO/write_error_line.php#L23)

src/Psl/IO/streaming.php

@@ -0,0 +1,105 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\IO;
+
+use Generator;
+use Psl\Async;
+use Psl\Channel;
+use Psl\Result;
+use Psl\Str;
+use Psl;
+
+/**
+ * Streaming the output of the given read stream handles using a generator.
+ *
+ * Example:
+ *
+ *  $handles = [
+ *    'foo' => get_read_stream('foo'),
+ *    'bar' => get_read_stream('bar'),
+ *  ];
+ *
+ *  foreach(IO\streaming($handles) as $type => $chunk) {
+ *    IO\write_line('received chunk "%s" from "%s" stream', $chunk, $type);
+ *  }
+ *
+ * @template T of array-key
+ *
+ * @param iterable<T, ReadStreamHandleInterface> $handles
+ *
+ * @throws Exception\AlreadyClosedException If one of the handles has been already closed.
+ * @throws Exception\RuntimeException If an error occurred during the operation.
+ * @throws Exception\TimeoutException If $timeout is reached before being able to read all the handles until the end.
+ *
+ * @return Generator<T, string, mixed, void>
+ */
+function streaming(iterable $handles, ?float $timeout = null): Generator
+{
+    /**
+     * @psalm-suppress UnnecessaryVarAnnotation
+     * @var Channel\ReceiverInterface<array{T|null, Result\ResultInterface<string>}> $receiver
+     * @psalm-suppress UnnecessaryVarAnnotation
+     * @var Channel\SenderInterface<array{T|null, Result\ResultInterface<string>}> $sender
+     */
+    [$receiver, $sender] = Channel\unbounded();
+
+    /** @var Psl\Ref<array<T, string>> $watchers */
+    $watchers = new Psl\Ref([]);
+    foreach ($handles as $k => $handle) {
+        $stream = $handle->getStream();
+        if ($stream === null) {
+            throw new Exception\AlreadyClosedException(Str\format('Handle "%s" is already closed.', (string) $k));
+        }
+
+        $watchers->value[$k] = Async\Scheduler::onReadable($stream, static function (string $watcher) use ($k, $handle, $sender, $watchers): void {
+            $result = Result\wrap($handle->tryRead(...));
+            if ($result->isFailed() || ($result->isSucceeded() && $result->getResult() === '')) {
+                Async\Scheduler::cancel($watcher);
+                unset($watchers->value[$k]);
+                if ($watchers->value === []) {
+                    $sender->close();
+                }
+
+                return;
+            }
+
+            $sender->send([$k, $result]);
+        });
+    }
+
+    $timeout_watcher = null;
+    if ($timeout !== null) {
+        $timeout_watcher = Async\Scheduler::delay($timeout, static function () use ($sender): void {
+            /** @var Result\ResultInterface<string> $failure */
+            $failure = new Result\Failure(
+                new Exception\TimeoutException('Reached timeout before being able to read all the handles until the end.')
+            );
+
+            $sender->send([null, $failure]);
+        });
+    }
+
+    try {
+        while (true) {
+            [$k, $result] = $receiver->receive();
+            if (null === $k || $result->isFailed()) {
+                throw $result->getThrowable();
+            }
+
+            yield $k => $result->getResult();
+        }
+    } catch (Channel\Exception\ClosedChannelException) {
+        // completed.
+        return;
+    } finally {
+        if ($timeout_watcher !== null) {
+            Async\Scheduler::cancel($timeout_watcher);
+        }
+
+        foreach ($watchers->value as $watcher) {
+            Async\Scheduler::cancel($watcher);
+        }
+    }
+}

src/Psl/Internal/Loader.php

@@ -468,6 +468,7 @@ final class Loader
         'Psl\Unix\connect',
         'Psl\Channel\bounded',
         'Psl\Channel\unbounded',
+        'Psl\IO\streaming',
         'Psl\IO\write',
         'Psl\IO\write_line',
         'Psl\IO\write_error',