LibWeb: Add the ReadableStreamGenericReader mixin interface

Userland/Libraries/LibWeb/Streams/ReadableStreamGenericReader.h

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2023, Matthew Olsson <mattco@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <LibJS/Forward.h>
+#include <LibWeb/Bindings/PlatformObject.h>
+#include <LibWeb/Forward.h>
+#include <LibWeb/WebIDL/Promise.h>
+
+namespace Web::Streams {
+
+// https://streams.spec.whatwg.org/#readablestreamgenericreader
+class ReadableStreamGenericReaderMixin {
+public:
+    WebIDL::ExceptionOr<JS::GCPtr<JS::Promise>> closed();
+
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<JS::Promise>> cancel(JS::Value reason);
+
+    JS::GCPtr<ReadableStream> stream() const { return m_stream; }
+    void set_stream(JS::GCPtr<ReadableStream> stream) { m_stream = stream; }
+
+    JS::GCPtr<WebIDL::Promise> closed_promise_capability() { return m_closed_promise; }
+    void set_closed_promise_capability(JS::GCPtr<WebIDL::Promise> promise) { m_closed_promise = promise; }
+
+protected:
+    void visit_edges(JS::Cell::Visitor&);
+
+    // https://streams.spec.whatwg.org/#readablestreamgenericreader-closedpromise
+    // A promise returned by the reader's closed getter
+    JS::GCPtr<WebIDL::Promise> m_closed_promise;
+
+    // https://streams.spec.whatwg.org/#readablestreamgenericreader-stream
+    // A ReadableStream instance that owns this reader
+    JS::GCPtr<ReadableStream> m_stream;
+};
+
+}