ladybird/Userland/Libraries/LibWeb/Streams/ReadableStream.h

/*
 * Copyright (c) 2022, Linus Groh <linusg@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>

namespace Web::Streams {

// FIXME: Variant<DefaultReader, ByteStreamReader>
// https://streams.spec.whatwg.org/#typedefdef-readablestreamreader
using ReadableStreamReader = JS::GCPtr<ReadableStreamDefaultReader>;

// https://streams.spec.whatwg.org/#typedefdef-readablestreamcontroller
using ReadableStreamController = Variant<JS::NonnullGCPtr<ReadableStreamDefaultController>, JS::NonnullGCPtr<ReadableByteStreamController>>;

// https://streams.spec.whatwg.org/#readablestream
class ReadableStream final : public Bindings::PlatformObject {
    WEB_PLATFORM_OBJECT(ReadableStream, Bindings::PlatformObject);

public:
    enum class State {
        Readable,
        Closed,
        Errored,
    };

    static WebIDL::ExceptionOr<JS::NonnullGCPtr<ReadableStream>> construct_impl(JS::Realm&, Optional<JS::Handle<JS::Object>> const& underlying_source);

    virtual ~ReadableStream() override;

    bool locked();
    WebIDL::ExceptionOr<JS::GCPtr<JS::Object>> cancel(JS::Value view);
    WebIDL::ExceptionOr<ReadableStreamReader> get_reader();

    Optional<ReadableStreamController>& controller() { return m_controller; }
    void set_controller(Optional<ReadableStreamController> value) { m_controller = move(value); }

    JS::Value stored_error() const { return m_stored_error; }
    void set_stored_error(JS::Value value) { m_stored_error = value; }

    ReadableStreamReader reader() const { return m_reader; }
    void set_reader(ReadableStreamReader value) { m_reader = value; }

    bool is_disturbed() const;
    void set_disturbed(bool value) { m_disturbed = value; }

    bool is_readable() const;
    bool is_closed() const;
    bool is_errored() const;
    bool is_locked() const;

    State state() const { return m_state; }
    void set_state(State value) { m_state = value; }

private:
    explicit ReadableStream(JS::Realm&);

    virtual JS::ThrowCompletionOr<void> initialize(JS::Realm&) override;
    virtual void visit_edges(Cell::Visitor&) override;

    // https://streams.spec.whatwg.org/#readablestream-controller
    // A ReadableStreamDefaultController or ReadableByteStreamController created with the ability to control the state and queue of this stream
    Optional<ReadableStreamController> m_controller;

    // https://streams.spec.whatwg.org/#readablestream-detached
    // A boolean flag set to true when the stream is transferred
    bool m_detached { false };

    // https://streams.spec.whatwg.org/#readablestream-disturbed
    // A boolean flag set to true when the stream has been read from or canceled
    bool m_disturbed { false };

    // https://streams.spec.whatwg.org/#readablestream-reader
    // A ReadableStreamDefaultReader or ReadableStreamBYOBReader instance, if the stream is locked to a reader, or undefined if it is not
    ReadableStreamReader m_reader;

    // https://streams.spec.whatwg.org/#readablestream-state
    // A string containing the stream’s current state, used internally; one of "readable", "closed", or "errored"
    State m_state { State::Readable };

    // https://streams.spec.whatwg.org/#readablestream-storederror
    // A value indicating how the stream failed, to be given as a failure reason or exception when trying to operate on an errored stream
    JS::Value m_stored_error { JS::js_undefined() };
};

}