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chore: Basic backend y.js message decoder
Signed-off-by: Julius Härtl <jus@bitgrid.net>
1 parent 3dfaa7f commit b98ff8b

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6 files changed

+143
-7
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6 files changed

+143
-7
lines changed

‎composer/composer/autoload_classmap.php‎

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@@ -61,4 +61,5 @@
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'OCA\\Text\\Service\\SessionService' => $baseDir . '/../lib/Service/SessionService.php',
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'OCA\\Text\\Service\\WorkspaceService' => $baseDir . '/../lib/Service/WorkspaceService.php',
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'OCA\\Text\\TextFile' => $baseDir . '/../lib/TextFile.php',
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'OCA\\Text\\YjsMessage' => $baseDir . '/../lib/YjsMessage.php',
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);

‎composer/composer/autoload_static.php‎

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@@ -76,6 +76,7 @@ class ComposerStaticInitText
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'OCA\\Text\\Service\\SessionService' => __DIR__ . '/..' . '/../lib/Service/SessionService.php',
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'OCA\\Text\\Service\\WorkspaceService' => __DIR__ . '/..' . '/../lib/Service/WorkspaceService.php',
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'OCA\\Text\\TextFile' => __DIR__ . '/..' . '/../lib/TextFile.php',
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'OCA\\Text\\YjsMessage' => __DIR__ . '/..' . '/../lib/YjsMessage.php',
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);
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public static function getInitializer(ClassLoader $loader)

‎lib/Service/DocumentService.php‎

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@@ -36,6 +36,7 @@
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use OCA\Text\Db\StepMapper;
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use OCA\Text\Exception\DocumentHasUnsavedChangesException;
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use OCA\Text\Exception\DocumentSaveConflictException;
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use OCA\Text\YjsMessage;
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use OCP\AppFramework\Db\DoesNotExistException;
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use OCP\AppFramework\Db\Entity;
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use OCP\Constants;
@@ -227,11 +228,9 @@ public function addStep($documentId, $sessionId, $steps, $version): array {
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$getStepsSinceVersion = null;
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$newVersion = $version;
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foreach ($steps as $step) {
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// Steps are base64 encoded messages of the yjs protocols
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// https://github.com/yjs/y-protocols
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// Base64 encoded values smaller than "AAE" belong to sync step 1 messages.
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// These messages query other participants for their current state.
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if ($step < "AAE") {
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$message = YjsMessage::fromBase64($step);
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// Filter out query steps as they would just trigger clients to send their steps again
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if ($message->getYjsMessageType() === YjsMessage::YJS_MESSAGE_SYNC && $message->getYjsSyncType() === YjsMessage::YJS_MESSAGE_SYNC_STEP1) {
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array_push($querySteps, $step);
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} else {
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array_push($stepsToInsert, $step);
@@ -245,8 +244,9 @@ public function addStep($documentId, $sessionId, $steps, $version): array {
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$allSteps = $this->getSteps($documentId, $getStepsSinceVersion);
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$stepsToReturn = [];
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foreach ($allSteps as $step) {
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if ($step < "AAQ") {
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array_push($stepsToReturn, $step);
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$message = YjsMessage::fromBase64($step);
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if ($message->getYjsMessageType() === YjsMessage::YJS_MESSAGE_SYNC) {
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$stepsToReturn[] = $step;
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}
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}
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return [

‎lib/Service/SessionService.php‎

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@@ -28,6 +28,7 @@
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use OCA\Text\Db\Session;
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use OCA\Text\Db\SessionMapper;
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use OCA\Text\YjsMessage;
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use OCP\AppFramework\Db\DoesNotExistException;
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use OCP\AppFramework\Utility\ITimeFactory;
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use OCP\DirectEditing\IManager;
@@ -240,6 +241,12 @@ public function updateSessionAwareness(int $documentId, int $sessionId, string $
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if (empty($message)) {
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return $session;
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}
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$decoded = YjsMessage::fromBase64($message);
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if ($decoded->getYjsMessageType() !== YjsMessage::YJS_MESSAGE_AWARENESS) {
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throw new \ValueError('Message passed was not an awareness message');
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}
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$session->setLastAwarenessMessage($message);
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return $this->sessionMapper->update($session);
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}

‎lib/YjsMessage.php‎

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@@ -0,0 +1,85 @@
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<?php
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namespace OCA\Text;
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use InvalidArgumentException;
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/**
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* Steps are base64 encoded messages of the yjs protocols
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* https://github.com/yjs/y-protocols
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*
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* This class is a simple representation of a message containing some methods
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* to decode parts of it for what we need on the backend
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*
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* Relevant resources:
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* https://github.com/yjs/y-protocols/blob/master/PROTOCOL.md
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* https://github.com/yjs/y-websocket/blob/master/src/y-websocket.js#L19-L22
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* https://github.com/yjs/y-protocols/blob/master/sync.js#L38-L40
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* https://github.com/dmonad/lib0/blob/master/decoding.js
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*/
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class YjsMessage {
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public const YJS_MESSAGE_SYNC = 0;
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public const YJS_MESSAGE_AWARENESS = 1;
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public const YJS_MESSAGE_AWARENESS_QUERY = 3;
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public const YJS_MESSAGE_SYNC_STEP1 = 0;
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public const YJS_MESSAGE_SYNC_STEP2 = 1;
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public const YJS_MESSAGE_SYNC_UPDATE = 2;
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private int $pos = 0;
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public function __construct(
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private string $data = ''
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) {
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}
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public static function fromBase64(string $data = ''): self {
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return new self(base64_decode($data));
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}
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public function readVarUint(): int {
42+
$bytes = unpack('C*', substr($this->data, $this->pos, 4));
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$segments = [];
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$offset = 0;
45+
foreach ($bytes as $byte) {
46+
$offset++;
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$segments[] = (0x7f & $byte);
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49+
if (($byte & 0x80) === 0) {
50+
$integer = 0;
51+
foreach($segments as $segment) {
52+
$integer <<= 7;
53+
$integer |= (0x7f & $segment);
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}
55+
$this->pos += $offset;
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return $integer;
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}
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}
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if (($byte & 0x80) !== 0) {
60+
throw new InvalidArgumentException('Incomplete byte sequence.');
61+
}
62+
throw new InvalidArgumentException('Incomplete byte sequence.');
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}
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public function getYjsMessageType(): int {
66+
$oldPos = $this->pos;
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$this->pos = 0;
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$messageType = $this->readVarUint();
69+
$this->pos = $oldPos;
70+
return $messageType;
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}
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public function getYjsSyncType(): int {
74+
$oldPos = $this->pos;
75+
$this->pos = 0;
76+
$messageType = $this->readVarUint();
77+
if ($messageType !== self::YJS_MESSAGE_SYNC) {
78+
throw new \ValueError('Message is not a sync message');
79+
}
80+
$syncType = $this->readVarUint();
81+
$this->pos = $oldPos;
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return $syncType;
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}
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}

‎tests/unit/YjsMessageTest.php‎

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<?php
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namespace OCA\Text;
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use Test\TestCase;
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class YjsMessageTest extends TestCase {
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protected function setUp(): void {
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parent::setUp();
10+
}
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// https://github.com/yjs/y-dat/blob/745d25f9690fceae5901d1225575fe8b6bcafdd7/src/y-dat.js#LL207C59-L210C1
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public function dataMessageTypes() {
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return [
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//
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['AAABAA==', 0, 0],
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// messageSync messageYjsSyncStep1
18+
['AAAyCIqghaQNBvrS2LoMB8L10I8KrQPD+t3RB2DcrYL4A40Ema2O4AMHz9bk8AIOtbm0PAE=', 0, 0],
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// messageAwareness
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['AQoBkZWK7gMAAnt9', 1, null],
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['AUIBwvXQjwqWAzl7InVzZXIiOnsibmFtZSI6ImFkbWluIiwiY29sb3IiOiIjZDA5ZTZkIn0sImN1cnNvciI6bnVsbH0=', 1, null],
22+
['AegBAcP63dEHtwHeAXsidXNlciI6eyJuYW1lIjoiR3Vlc3QiLCJjb2xvciI6IiM5M2IyN2IifSwiY3Vyc29yIjp7ImFuY2hvciI6eyJ0eXBlIjp7ImNsaWVudCI6MjcxNzEzNzYwMiwiY2xvY2siOjl9LCJ0bmFtZSI6bnVsbCwiaXRlbSI6bnVsbCwiYXNzb2MiOjB9LCJoZWFkIjp7InR5cGUiOnsiY2xpZW50IjoyNzE3MTM3NjAyLCJjbG9jayI6OX0sInRuYW1lIjpudWxsLCJpdGVtIjpudWxsLCJhc3NvYyI6MH19fQ==', 1, null],
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['AbsBAZGViu4DArIBeyJ1c2VyIjp7Im5hbWUiOiJHdWVzdCIsImNvbG9yIjoiI2I4YmU2OCJ9LCJjdXJzb3IiOnsiYW5jaG9yIjp7InR5cGUiOm51bGwsInRuYW1lIjoiZGVmYXVsdCIsIml0ZW0iOm51bGwsImFzc29jIjowfSwiaGVhZCI6eyJ0eXBlIjpudWxsLCJ0bmFtZSI6ImRlZmF1bHQiLCJpdGVtIjpudWxsLCJhc3NvYyI6MH19fQ==', 1, null],
24+
// messageSync messageYjsUpdate
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['AAISAQHD+t3RB2CEwvXQjwpHAWEA', 0, 2],
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['AAI0AQOKoIWkDQAHAQdkZWZhdWx0AwlwYXJhZ3JhcGgHAIqghaQNAAYEAIqghaQNAQR0ZXN0AA==', 0, 2],
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['AAIdAQGRlYruAx2okZWK7gMbAXcCaC0BkZWK7gMBGwE=', 0, 2],
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['AAIKAAGRlYruAwEVBA==', 0, 2],
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];
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}
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/** @dataProvider dataMessageTypes */
33+
public function testMessageTypes($data, $type, $subtype) {
34+
$buffer = YjsMessage::fromBase64($data);
35+
$unpack1 = $buffer->getYjsMessageType();
36+
self::assertEquals($type, $unpack1, 'type');
37+
if ($subtype !== null) {
38+
$unpack2 = $buffer->getYjsSyncType();
39+
self::assertEquals($subtype, $unpack2);
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}
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}
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}

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