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Merge pull request #4 from clue-labs/unwrap-writable
Add unwrapWritable() function
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‎README.md

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@@ -10,6 +10,7 @@ built on top of [React PHP](http://reactphp.org/).
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* [first()](#first)
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* [all()](#all)
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* [unwrapReadable()](#unwrapreadable)
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* [unwrapWritable()](#unwrapwritable)
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* [Install](#install)
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* [License](#license)
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instance of `ReadableStreamInterface`, then you will not be able to receive
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the `error` event.
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### unwrapWritable()
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The `unwrapWritable(PromiseInterface $promise)` function can be used to unwrap
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a `Promise` which resolves with a `WritableStreamInterface`.
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This function returns a writable stream instance (implementing `WritableStreamInterface`)
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right away which acts as a proxy for the future promise resolution.
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Once the given Promise resolves with a `WritableStreamInterface`, any data you
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wrote to the proxy will be piped to the inner stream.
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```php
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//$promise = someFunctionWhichResolvesWithAStream();
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$promise = startUploadStream($uri);
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$stream = Stream\unwrapWritable($promise);
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$stream->write('hello');
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$stream->end('world');
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$stream->on('close', function () {
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echo 'DONE';
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});
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```
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If the given promise is either rejected or fulfilled with anything but an
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instance of `WritableStreamInterface`, then the output stream will emit
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an `error` event and close:
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```php
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$promise = startUploadStream($invalidUri);
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$stream = Stream\unwrapWritable($promise);
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$stream->on('error', function (Exception $error) {
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echo 'Error: ' . $error->getMessage();
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});
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```
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The given `$promise` SHOULD be pending, i.e. it SHOULD NOT be fulfilled or rejected
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at the time of invoking this function.
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If the given promise is already settled and does not resolve with an
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instance of `WritableStreamInterface`, then you will not be able to receive
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the `error` event.
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## Install
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The recommended way to install this library is [through Composer](https://getcomposer.org).

‎src/UnwrapWritableStream.php

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<?php
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namespace Clue\React\Promise\Stream;
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use Evenement\EventEmitter;
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use React\Promise\PromiseInterface;
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use React\Stream\WritableStreamInterface;
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use React\Stream\Util;
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use React\Promise\CancellablePromiseInterface;
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use InvalidArgumentException;
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/**
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* @internal
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* @see unwrapWritable() instead
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*/
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class UnwrapWritableStream extends EventEmitter implements WritableStreamInterface
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{
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private $promise;
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private $stream;
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private $buffer = '';
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private $closed = false;
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private $ending = false;
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/**
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* Instantiate new unwrapped writable stream for given `Promise` which resolves with a `WritableStreamInterface`.
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*
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* @param PromiseInterface $promise Promise<WritableStreamInterface, Exception>
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*/
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public function __construct(PromiseInterface $promise)
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{
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$out = $this;
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$store =& $this->stream;
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$buffer =& $this->buffer;
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$ending =& $this->ending;
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$closed =& $this->closed;
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$this->promise = $promise->then(
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function ($stream) {
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if (!($stream instanceof WritableStreamInterface)) {
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throw new InvalidArgumentException('Not a writable stream');
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}
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return $stream;
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}
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)->then(
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function (WritableStreamInterface $stream) use ($out, &$store, &$buffer, &$ending, &$closed) {
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// stream is already closed, make sure to close output stream
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if (!$stream->isWritable()) {
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$out->close();
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return $stream;
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}
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// resolves but output is already closed, make sure to close stream silently
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if ($closed) {
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$stream->close();
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return $stream;
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}
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// forward drain events for back pressure
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$stream->on('drain', function () use ($out) {
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$out->emit('drain', array($out));
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});
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// error events cancel output stream
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$stream->on('error', function ($error) use ($out) {
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$out->emit('error', array($error, $out));
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$out->close();
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});
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// close both streams once either side closes
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$stream->on('close', array($out, 'close'));
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$out->on('close', array($stream, 'close'));
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if ($buffer !== '') {
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// flush buffer to stream and check if its buffer is not exceeded
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$drained = $stream->write($buffer) !== false;
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$buffer = '';
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if ($drained) {
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// signal drain event, because the output stream previous signalled a full buffer
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$out->emit('drain', array($out));
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}
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}
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if ($ending) {
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$stream->end();
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} else {
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$store = $stream;
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}
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return $stream;
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},
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function ($e) use ($out) {
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$out->emit('error', array($e, $out));
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$out->close();
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}
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);
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}
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public function write($data)
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{
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if ($this->ending) {
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return;
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}
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// forward to inner stream if possible
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if ($this->stream !== null) {
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return $this->stream->write($data);
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}
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// append to buffer and signal the buffer is full
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$this->buffer .= $data;
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return false;
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}
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public function end($data = null)
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{
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if ($this->ending) {
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return;
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}
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$this->ending = true;
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// forward to inner stream if possible
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if ($this->stream !== null) {
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return $this->stream->end($data);
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}
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// append to buffer
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if ($data !== null) {
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$this->buffer .= $data;
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}
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}
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public function isWritable()
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{
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return !$this->ending;
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}
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public function close()
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{
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if ($this->closed) {
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return;
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}
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$this->buffer = '';
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$this->ending = true;
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$this->closed = true;
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// try to cancel promise once the stream closes
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if ($this->promise instanceof CancellablePromiseInterface) {
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$this->promise->cancel();
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}
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$this->emit('close', array($this));
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}
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}

‎src/functions.php

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{
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return new UnwrapReadableStream($promise);
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}
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/**
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* unwrap a `Promise` which resolves with a `WritableStreamInterface`.
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*
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* @param PromiseInterface $promise Promise<WritableStreamInterface, Exception>
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* @return WritableStreamInterface
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*/
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function unwrapWritable(PromiseInterface $promise)
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{
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return new UnwrapWritableStream($promise);
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}

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