From 91f58eb220ea8e6d26ca0fc01476ce95a1b33afe Mon Sep 17 00:00:00 2001
From: Kenneth Myhra <kennethmyhra@gmail.com>
Date: Fri, 7 Jul 2023 16:09:27 +0200
Subject: [PATCH] LibWeb: Add AO transform_stream_set_backpressure()

---
 .../LibWeb/Streams/AbstractOperations.cpp     | 22 +++++++++++++++++++
 .../LibWeb/Streams/AbstractOperations.h       |  1 +
 2 files changed, 23 insertions(+)

diff --git a/Userland/Libraries/LibWeb/Streams/AbstractOperations.cpp b/Userland/Libraries/LibWeb/Streams/AbstractOperations.cpp
index 40f5bb17d6..8f299db1cc 100644
--- a/Userland/Libraries/LibWeb/Streams/AbstractOperations.cpp
+++ b/Userland/Libraries/LibWeb/Streams/AbstractOperations.cpp
@@ -21,6 +21,7 @@
 #include <LibWeb/Streams/ReadableStreamDefaultController.h>
 #include <LibWeb/Streams/ReadableStreamDefaultReader.h>
 #include <LibWeb/Streams/ReadableStreamGenericReader.h>
+#include <LibWeb/Streams/TransformStream.h>
 #include <LibWeb/Streams/TransformStreamDefaultController.h>
 #include <LibWeb/Streams/UnderlyingSink.h>
 #include <LibWeb/Streams/UnderlyingSource.h>
@@ -2733,6 +2734,27 @@ void transform_stream_default_controller_clear_algorithms(TransformStreamDefault
     controller.set_flush_algorithm({});
 }
 
+//  https://streams.spec.whatwg.org/#transform-stream-set-backpressure
+WebIDL::ExceptionOr<void> transform_stream_set_backpressure(TransformStream& stream, bool backpressure)
+{
+    auto& realm = stream.realm();
+
+    // 1. Assert: stream.[[backpressure]] is not backpressure.
+    VERIFY(stream.backpressure() != backpressure);
+
+    // 2. If stream.[[backpressureChangePromise]] is not undefined, resolve stream.[[backpressureChangePromise]] with undefined.
+    if (stream.backpressure_change_promise())
+        WebIDL::resolve_promise(realm, *stream.backpressure_change_promise(), JS::js_undefined());
+
+    // 3. Set stream.[[backpressureChangePromise]] to a new promise.
+    stream.set_backpressure_change_promise(WebIDL::create_promise(realm));
+
+    // 4. Set stream.[[backpressure]] to backpressure.
+    stream.set_backpressure(backpressure);
+
+    return {};
+}
+
 // https://streams.spec.whatwg.org/#is-non-negative-number
 bool is_non_negative_number(JS::Value value)
 {
diff --git a/Userland/Libraries/LibWeb/Streams/AbstractOperations.h b/Userland/Libraries/LibWeb/Streams/AbstractOperations.h
index 2ff9e92f79..b01581b433 100644
--- a/Userland/Libraries/LibWeb/Streams/AbstractOperations.h
+++ b/Userland/Libraries/LibWeb/Streams/AbstractOperations.h
@@ -133,6 +133,7 @@ WebIDL::ExceptionOr<void> writable_stream_default_controller_process_write(Writa
 WebIDL::ExceptionOr<void> writable_stream_default_controller_write(WritableStreamDefaultController&, JS::Value chunk, JS::Value chunk_size);
 
 void transform_stream_default_controller_clear_algorithms(TransformStreamDefaultController&);
+WebIDL::ExceptionOr<void> transform_stream_set_backpressure(TransformStream&, bool backpressure);
 
 bool is_non_negative_number(JS::Value);