/*

 * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>

 * Copyright (c) 2024, Kenneth Myhra <kennethmyhra@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/Bindings/ReadableStreamPrototype.h>

#include <LibWeb/Forward.h>

#include <LibWeb/Streams/QueuingStrategy.h>

namespace Web::Streams {

// https://streams.spec.whatwg.org/#typedefdef-readablestreamreader

using ReadableStreamReader = Variant<JS::NonnullGCPtr<ReadableStreamDefaultReader>, JS::NonnullGCPtr<ReadableStreamBYOBReader>>;

// https://streams.spec.whatwg.org/#typedefdef-readablestreamcontroller

using ReadableStreamController = Variant<JS::NonnullGCPtr<ReadableStreamDefaultController>, JS::NonnullGCPtr<ReadableByteStreamController>>;

// https://streams.spec.whatwg.org/#dictdef-readablestreamgetreaderoptions

struct ReadableStreamGetReaderOptions {

    Optional<Bindings::ReadableStreamReaderMode> mode;

};

struct ReadableWritablePair {

    JS::GCPtr<ReadableStream> readable;

    JS::GCPtr<WritableStream> writable;

};

struct StreamPipeOptions {

    bool prevent_close { false };

    bool prevent_abort { false };

    bool prevent_cancel { false };

    JS::GCPtr<DOM::AbortSignal> signal;

};

struct ReadableStreamPair {

    // Define a couple container-like methods so this type may be used as the return type of the IDL `tee` implementation.

    size_t size() const { return 2; }

    JS::NonnullGCPtr<ReadableStream>& at(size_t index)

    {

        if (index == 0)

            return first;

        if (index == 1)

            return second;

        VERIFY_NOT_REACHED();

    }

    JS::NonnullGCPtr<ReadableStream> first;

    JS::NonnullGCPtr<ReadableStream> second;

};

// https://streams.spec.whatwg.org/#readablestream

class ReadableStream final : public Bindings::PlatformObject {

    WEB_PLATFORM_OBJECT(ReadableStream, Bindings::PlatformObject);

    JS_DECLARE_ALLOCATOR(ReadableStream);

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, QueuingStrategy const& = {});

    static WebIDL::ExceptionOr<JS::NonnullGCPtr<ReadableStream>> from(JS::VM& vm, JS::Value async_iterable);

    virtual ~ReadableStream() override;

    bool locked() const;

    JS::NonnullGCPtr<JS::Object> cancel(JS::Value reason);

    WebIDL::ExceptionOr<ReadableStreamReader> get_reader(ReadableStreamGetReaderOptions const& = {});

    WebIDL::ExceptionOr<JS::NonnullGCPtr<ReadableStream>> pipe_through(ReadableWritablePair transform, StreamPipeOptions const& = {});

    JS::NonnullGCPtr<JS::Object> pipe_to(WritableStream& destination, StreamPipeOptions const& = {});

    WebIDL::ExceptionOr<ReadableStreamPair> tee();

    void close();

    void error(JS::Value);

    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; }

    Optional<ReadableStreamReader> const& reader() const { return m_reader; }

    void set_reader(Optional<ReadableStreamReader> value) { m_reader = move(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 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

    Optional<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() };

};

}