serenity/Userland/Libraries/LibWeb/Streams/ReadableStreamBYOBReader.cpp

/*
 * Copyright (c) 2023, Matthew Olsson <mattco@serenityos.org>
 * Copyright (c) 2023, Shannon Booth <shannon@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibJS/Runtime/PromiseCapability.h>
#include <LibJS/Runtime/TypedArray.h>
#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/Streams/AbstractOperations.h>
#include <LibWeb/Streams/ReadableStream.h>
#include <LibWeb/Streams/ReadableStreamBYOBReader.h>
#include <LibWeb/WebIDL/ExceptionOr.h>

namespace Web::Streams {

JS_DEFINE_ALLOCATOR(ReadableStreamBYOBReader);

ReadableStreamBYOBReader::ReadableStreamBYOBReader(JS::Realm& realm)
    : Bindings::PlatformObject(realm)
    , ReadableStreamGenericReaderMixin(realm)
{
}

void ReadableStreamBYOBReader::initialize(JS::Realm& realm)
{
    Base::initialize(realm);
    set_prototype(&Bindings::ensure_web_prototype<Bindings::ReadableStreamBYOBReaderPrototype>(realm, "ReadableStreamBYOBReader"));
}

// https://streams.spec.whatwg.org/#byob-reader-constructor
WebIDL::ExceptionOr<JS::NonnullGCPtr<ReadableStreamBYOBReader>> ReadableStreamBYOBReader::construct_impl(JS::Realm& realm, JS::NonnullGCPtr<ReadableStream> stream)
{
    auto reader = realm.heap().allocate<ReadableStreamBYOBReader>(realm, realm);

    // 1. Perform ? SetUpReadableStreamBYOBReader(this, stream).
    TRY(set_up_readable_stream_byob_reader(reader, *stream));

    return reader;
}

// https://streams.spec.whatwg.org/#byob-reader-release-lock
void ReadableStreamBYOBReader::release_lock()
{
    // 1. If this.[[stream]] is undefined, return.
    if (!m_stream)
        return;

    // 2. Perform ! ReadableStreamBYOBReaderRelease(this).
    readable_stream_byob_reader_release(*this);
}

void ReadableStreamBYOBReader::visit_edges(Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    ReadableStreamGenericReaderMixin::visit_edges(visitor);
    for (auto& request : m_read_into_requests)
        visitor.visit(request);
}

class BYOBReaderReadIntoRequest : public ReadIntoRequest {
    JS_CELL(BYOBReaderReadIntoRequest, ReadIntoRequest);

public:
    BYOBReaderReadIntoRequest(JS::Realm& realm, WebIDL::Promise& promise)
        : m_realm(realm)
        , m_promise(promise)
    {
    }

    // chunk steps, given chunk
    virtual void on_chunk(JS::Value chunk) override
    {
        // 1. Resolve promise with «[ "value" → chunk, "done" → false ]».
        WebIDL::resolve_promise(m_realm, m_promise, JS::create_iterator_result_object(m_realm.vm(), chunk, false));
    }

    // close steps, given chunk
    virtual void on_close(JS::Value chunk) override
    {
        // 1. Resolve promise with «[ "value" → chunk, "done" → true ]».
        WebIDL::resolve_promise(m_realm, m_promise, JS::create_iterator_result_object(m_realm.vm(), chunk, true));
    }

    // error steps, given e
    virtual void on_error(JS::Value error) override
    {
        // 1. Reject promise with e.
        WebIDL::reject_promise(m_realm, m_promise, error);
    }

private:
    virtual void visit_edges(Visitor& visitor) override
    {
        Base::visit_edges(visitor);
        visitor.visit(m_realm);
        visitor.visit(m_promise);
    }

    JS::Realm& m_realm;
    WebIDL::Promise& m_promise;
};

// https://streams.spec.whatwg.org/#byob-reader-read
WebIDL::ExceptionOr<JS::NonnullGCPtr<JS::Promise>> ReadableStreamBYOBReader::read(JS::Value view_value)
{
    auto& realm = this->realm();

    // FIXME: Support DataViews
    auto& view = verify_cast<JS::TypedArrayBase>(view_value.as_object());

    // 1. If view.[[ByteLength]] is 0, return a promise rejected with a TypeError exception.
    if (view.byte_length() == 0) {
        auto exception = JS::TypeError::create(realm, "Cannot read in an empty buffer"sv);
        auto promise_capability = WebIDL::create_rejected_promise(realm, exception);
        return JS::NonnullGCPtr { verify_cast<JS::Promise>(*promise_capability->promise()) };
    }

    // 2. If view.[[ViewedArrayBuffer]].[[ArrayBufferByteLength]] is 0, return a promise rejected with a TypeError exception.
    if (view.viewed_array_buffer()->byte_length() == 0) {
        auto exception = JS::TypeError::create(realm, "Cannot read in an empty buffer"sv);
        auto promise_capability = WebIDL::create_rejected_promise(realm, exception);
        return JS::NonnullGCPtr { verify_cast<JS::Promise>(*promise_capability->promise()) };
    }

    // 3. If ! IsDetachedBuffer(view.[[ViewedArrayBuffer]]) is true, return a promise rejected with a TypeError exception.
    if (view.viewed_array_buffer()->is_detached()) {
        auto exception = JS::TypeError::create(realm, "Cannot read in a detached buffer"sv);
        auto promise_capability = WebIDL::create_rejected_promise(realm, exception);
        return JS::NonnullGCPtr { verify_cast<JS::Promise>(*promise_capability->promise()) };
    }

    // 4. If this.[[stream]] is undefined, return a promise rejected with a TypeError exception.
    if (!m_stream) {
        auto exception = JS::TypeError::create(realm, "Cannot read from an empty stream"sv);
        auto promise_capability = WebIDL::create_rejected_promise(realm, exception);
        return JS::NonnullGCPtr { verify_cast<JS::Promise>(*promise_capability->promise()) };
    }

    // 5. Let promise be a new promise.
    auto promise_capability = WebIDL::create_promise(realm);

    // 6. Let readIntoRequest be a new read-into request with the following items:
    //    chunk steps, given chunk
    //        Resolve promise with «[ "value" → chunk, "done" → false ]».
    //    close steps, given chunk
    //        Resolve promise with «[ "value" → chunk, "done" → true ]».
    //    error steps, given e
    //        Reject promise with e.
    auto read_into_request = heap().allocate_without_realm<BYOBReaderReadIntoRequest>(realm, promise_capability);

    // 7. Perform ! ReadableStreamBYOBReaderRead(this, view, readIntoRequest).
    readable_stream_byob_reader_read(*this, view_value, *read_into_request);

    // 8. Return promise.
    return JS::NonnullGCPtr { verify_cast<JS::Promise>(*promise_capability->promise()) };
}
}