From b9a1ef1357e6b784f5f2de15e5a0b7bc31e296a5 Mon Sep 17 00:00:00 2001
From: "Dylan K. Taylor" <dktapps@pmmp.io>
Date: Fri, 1 Mar 2024 17:07:19 +0000
Subject: [PATCH] Throttle resource pack sending using ack receipts this isn't
 the best solution, as it limits the download speed somewhat, but it's
 relatively simple and works quite well. closes #3127

---
 .../handler/ResourcePacksPacketHandler.php    | 49 +++++++++++++++++--
 1 file changed, 46 insertions(+), 3 deletions(-)

diff --git a/src/network/mcpe/handler/ResourcePacksPacketHandler.php b/src/network/mcpe/handler/ResourcePacksPacketHandler.php
index 3d413ee5a..b9089d146 100644
--- a/src/network/mcpe/handler/ResourcePacksPacketHandler.php
+++ b/src/network/mcpe/handler/ResourcePacksPacketHandler.php
@@ -50,11 +50,22 @@ use function substr;
  * packs to the client.
  */
 class ResourcePacksPacketHandler extends PacketHandler{
-	private const PACK_CHUNK_SIZE = 128 * 1024; //128KB
+	private const PACK_CHUNK_SIZE = 256 * 1024; //256KB
+
+	/**
+	 * Larger values allow downloading more chunks at the same time, increasing download speed, but the client may choke
+	 * and cause the download speed to drop (due to ACKs taking too long to arrive).
+	 */
+	private const MAX_CONCURRENT_CHUNK_REQUESTS = 1;
 
 	/** @var bool[][] uuid => [chunk index => hasSent] */
 	private array $downloadedChunks = [];
 
+	/** @phpstan-var \SplQueue<array{ResourcePack, int}> */
+	private \SplQueue $requestQueue;
+
+	private int $activeRequests = 0;
+
 	/**
 	 * @phpstan-param \Closure() : void $completionCallback
 	 */
@@ -62,7 +73,9 @@ class ResourcePacksPacketHandler extends PacketHandler{
 		private NetworkSession $session,
 		private ResourcePackManager $resourcePackManager,
 		private \Closure $completionCallback
-	){}
+	){
+		$this->requestQueue = new \SplQueue();
+	}
 
 	public function setUp() : void{
 		$resourcePackEntries = array_map(function(ResourcePack $pack) : ResourcePackInfoEntry{
@@ -176,8 +189,38 @@ class ResourcePacksPacketHandler extends PacketHandler{
 			$this->downloadedChunks[$packId][$packet->chunkIndex] = true;
 		}
 
-		$this->session->sendDataPacket(ResourcePackChunkDataPacket::create($packId, $packet->chunkIndex, $offset, $pack->getPackChunk($offset, self::PACK_CHUNK_SIZE)));
+		$this->requestQueue->enqueue([$pack, $packet->chunkIndex]);
+		$this->processChunkRequestQueue();
 
 		return true;
 	}
+
+	private function processChunkRequestQueue() : void{
+		if($this->activeRequests >= self::MAX_CONCURRENT_CHUNK_REQUESTS || $this->requestQueue->isEmpty()){
+			return;
+		}
+		/**
+		 * @var ResourcePack $pack
+		 * @var int          $chunkIndex
+		 */
+		[$pack, $chunkIndex] = $this->requestQueue->dequeue();
+
+		$packId = $pack->getPackId();
+		$offset = $chunkIndex * self::PACK_CHUNK_SIZE;
+		$chunkData = $pack->getPackChunk($offset, self::PACK_CHUNK_SIZE);
+		$this->activeRequests++;
+		$this->session
+			->sendDataPacketWithReceipt(ResourcePackChunkDataPacket::create($packId, $chunkIndex, $offset, $chunkData))
+			->onCompletion(
+				function() use ($packId, $chunkIndex) : void{
+					$this->activeRequests--;
+					$this->processChunkRequestQueue();
+				},
+				function() : void{
+					//this may have been rejected because of a disconnection - this will do nothing in that case
+					$this->disconnectWithError("Plugin interrupted sending of resource packs");
+				}
+			);
+		$this->session->getLogger()->debug("Sent resource pack $packId chunk $chunkIndex");
+	}
 }