script/dom/stream/

writablestreamdefaultcontroller.rs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

use std::cell::{Cell, RefCell};
use std::ptr;
use std::rc::Rc;

use dom_struct::dom_struct;
use js::context::JSContext;
use js::jsapi::{Heap, JSObject};
use js::jsval::{JSVal, UndefinedValue};
use js::realm::CurrentRealm;
use js::rust::{HandleObject as SafeHandleObject, HandleValue as SafeHandleValue};
use script_bindings::reflector::{Reflector, reflect_dom_object_with_cx};

use crate::dom::bindings::callback::ExceptionHandling;
use crate::dom::bindings::codegen::Bindings::QueuingStrategyBinding::QueuingStrategySize;
use crate::dom::bindings::codegen::Bindings::UnderlyingSinkBinding::{
    UnderlyingSinkAbortCallback, UnderlyingSinkCloseCallback, UnderlyingSinkStartCallback,
    UnderlyingSinkWriteCallback,
};
use crate::dom::bindings::codegen::Bindings::WritableStreamDefaultControllerBinding::WritableStreamDefaultControllerMethods;
use crate::dom::bindings::error::{Error, ErrorToJsval, Fallible};
use crate::dom::bindings::reflector::DomGlobal;
use crate::dom::bindings::root::{Dom, DomRoot, MutNullableDom};
use crate::dom::globalscope::GlobalScope;
use crate::dom::messageport::MessagePort;
use crate::dom::promise::{Promise, RootedPromise, TracedPromise};
use crate::dom::promisenativehandler::{Callback, PromiseNativeHandler};
use crate::dom::readablestreamdefaultcontroller::{EnqueuedValue, QueueWithSizes, ValueWithSize};
use crate::dom::stream::writablestream::WritableStream;
use crate::dom::types::{AbortController, AbortSignal, TransformStream};
use crate::realms::enter_auto_realm;

impl js::gc::Rootable for CloseAlgorithmFulfillmentHandler {}

/// The fulfillment handler for
/// <https://streams.spec.whatwg.org/#writable-stream-default-controller-process-close>
#[derive(Clone, JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
struct CloseAlgorithmFulfillmentHandler {
    stream: Dom<WritableStream>,
}

impl Callback for CloseAlgorithmFulfillmentHandler {
    fn callback(&self, cx: &mut CurrentRealm, _v: SafeHandleValue) {
        let stream = self.stream.as_rooted();

        // Perform ! WritableStreamFinishInFlightClose(stream).
        stream.finish_in_flight_close(cx);
    }
}

impl js::gc::Rootable for CloseAlgorithmRejectionHandler {}

/// The rejection handler for
/// <https://streams.spec.whatwg.org/#writable-stream-default-controller-process-close>
#[derive(Clone, JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
struct CloseAlgorithmRejectionHandler {
    stream: Dom<WritableStream>,
}

impl Callback for CloseAlgorithmRejectionHandler {
    fn callback(&self, cx: &mut CurrentRealm, v: SafeHandleValue) {
        let stream = self.stream.as_rooted();

        let global = GlobalScope::from_current_realm(cx);

        // Perform ! WritableStreamFinishInFlightCloseWithError(stream, reason).
        stream.finish_in_flight_close_with_error(cx, &global, v);
    }
}

impl js::gc::Rootable for StartAlgorithmFulfillmentHandler {}

/// The fulfillment handler for
/// <https://streams.spec.whatwg.org/#set-up-writable-stream-default-controller>
#[derive(Clone, JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
struct StartAlgorithmFulfillmentHandler {
    controller: Dom<WritableStreamDefaultController>,
}

impl Callback for StartAlgorithmFulfillmentHandler {
    /// Continuation of <https://streams.spec.whatwg.org/#set-up-writable-stream-default-controller>
    /// Upon fulfillment of startPromise,
    fn callback(&self, cx: &mut CurrentRealm, _v: SafeHandleValue) {
        let controller = self.controller.as_rooted();
        let stream = controller
            .stream
            .get()
            .expect("Controller should have a stream.");

        // Assert: stream.[[state]] is "writable" or "erroring".
        assert!(stream.is_erroring() || stream.is_writable());

        // Set controller.[[started]] to true.
        controller.started.set(true);

        let global = GlobalScope::from_current_realm(cx);

        // Perform ! WritableStreamDefaultControllerAdvanceQueueIfNeeded(controller).
        controller.advance_queue_if_needed(cx, &global)
    }
}

impl js::gc::Rootable for StartAlgorithmRejectionHandler {}

/// The rejection handler for
/// <https://streams.spec.whatwg.org/#set-up-writable-stream-default-controller>
#[derive(Clone, JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
struct StartAlgorithmRejectionHandler {
    controller: Dom<WritableStreamDefaultController>,
}

impl Callback for StartAlgorithmRejectionHandler {
    /// Continuation of <https://streams.spec.whatwg.org/#set-up-writable-stream-default-controller>
    /// Upon rejection of startPromise with reason r,
    fn callback(&self, cx: &mut CurrentRealm, v: SafeHandleValue) {
        let controller = self.controller.as_rooted();
        let stream = controller
            .stream
            .get()
            .expect("Controller should have a stream.");

        // Assert: stream.[[state]] is "writable" or "erroring".
        assert!(stream.is_erroring() || stream.is_writable());

        // Set controller.[[started]] to true.
        controller.started.set(true);

        let global = GlobalScope::from_current_realm(cx);

        // Perform ! WritableStreamDealWithRejection(stream, r).
        stream.deal_with_rejection(cx, &global, v);
    }
}

impl js::gc::Rootable for TransferBackPressurePromiseReaction {}

/// Reacting to backpressurePromise as part of the `writeAlgorithm` of
/// <https://streams.spec.whatwg.org/#abstract-opdef-setupcrossrealmtransformwritable>
#[derive(JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
struct TransferBackPressurePromiseReaction {
    /// The result of reacting to backpressurePromise.
    result_promise: TracedPromise,

    /// The backpressurePromise.
    #[ignore_malloc_size_of = "nested Rc"]
    backpressure_promise: Rc<RefCell<Option<TracedPromise>>>,

    /// The chunk received by the `writeAlgorithm`.
    #[ignore_malloc_size_of = "mozjs"]
    chunk: Box<Heap<JSVal>>,

    /// The port used in the algorithm.
    port: Dom<MessagePort>,
}

impl Callback for TransferBackPressurePromiseReaction {
    /// Reacting to backpressurePromise with the following fulfillment steps:
    fn callback(&self, cx: &mut CurrentRealm, _v: SafeHandleValue) {
        let global = self.result_promise.global();
        // Set backpressurePromise to a new promise.
        let promise = Promise::new_rooted(cx, &global);
        *self.backpressure_promise.borrow_mut() = Some(promise.to_traced());

        // Let result be PackAndPostMessageHandlingError(port, "chunk", chunk).
        rooted!(&in(cx) let mut chunk = UndefinedValue());
        chunk.set(self.chunk.get());
        let result = self
            .port
            .pack_and_post_message_handling_error(cx, "chunk", chunk.handle());

        // If result is an abrupt completion,
        if let Err(error) = result {
            // Disentangle port.
            global.disentangle_port(cx, &self.port);

            // Return a promise rejected with result.[[Value]].
            self.result_promise.reject_error(cx, error);
        } else {
            // Otherwise, return a promise resolved with undefined.
            self.result_promise.resolve_native(cx, &());
        }
    }
}

impl js::gc::Rootable for WriteAlgorithmFulfillmentHandler {}

/// The fulfillment handler for
/// <https://streams.spec.whatwg.org/#writable-stream-default-controller-process-write>
#[derive(Clone, JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
struct WriteAlgorithmFulfillmentHandler {
    controller: Dom<WritableStreamDefaultController>,
}

impl Callback for WriteAlgorithmFulfillmentHandler {
    fn callback(&self, cx: &mut CurrentRealm, _v: SafeHandleValue) {
        let controller = self.controller.as_rooted();
        let stream = controller
            .stream
            .get()
            .expect("Controller should have a stream.");

        // Perform ! WritableStreamFinishInFlightWrite(stream).
        stream.finish_in_flight_write(cx);

        // Let state be stream.[[state]].
        // Assert: state is "writable" or "erroring".
        assert!(stream.is_erroring() || stream.is_writable());

        // Perform ! DequeueValue(controller).
        rooted!(&in(cx) let mut rval = UndefinedValue());
        controller.queue.dequeue_value(cx, Some(rval.handle_mut()));

        let global = GlobalScope::from_current_realm(cx);

        // If ! WritableStreamCloseQueuedOrInFlight(stream) is false and state is "writable",
        if !stream.close_queued_or_in_flight() && stream.is_writable() {
            // Let backpressure be ! WritableStreamDefaultControllerGetBackpressure(controller).
            let backpressure = controller.get_backpressure();

            // Perform ! WritableStreamUpdateBackpressure(stream, backpressure).
            stream.update_backpressure(cx, backpressure, &global);
        }

        // Perform ! WritableStreamDefaultControllerAdvanceQueueIfNeeded(controller).
        controller.advance_queue_if_needed(cx, &global)
    }
}

impl js::gc::Rootable for WriteAlgorithmRejectionHandler {}

/// The rejection handler for
/// <https://streams.spec.whatwg.org/#writable-stream-default-controller-process-write>
#[derive(Clone, JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
struct WriteAlgorithmRejectionHandler {
    controller: Dom<WritableStreamDefaultController>,
}

impl Callback for WriteAlgorithmRejectionHandler {
    fn callback(&self, cx: &mut CurrentRealm, v: SafeHandleValue) {
        let controller = self.controller.as_rooted();
        let stream = controller
            .stream
            .get()
            .expect("Controller should have a stream.");

        // If stream.[[state]] is "writable",
        if stream.is_writable() {
            // perform ! WritableStreamDefaultControllerClearAlgorithms(controller).
            controller.clear_algorithms();
        }

        let global = GlobalScope::from_current_realm(cx);

        // Perform ! WritableStreamFinishInFlightWriteWithError(stream, reason).
        stream.finish_in_flight_write_with_error(cx, &global, v);
    }
}

/// The type of sink algorithms we are using.
#[derive(JSTraceable, PartialEq)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
pub enum UnderlyingSinkType {
    /// Algorithms are provided by Js callbacks.
    Js {
        /// <https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-abortalgorithm>
        abort: RefCell<Option<Rc<UnderlyingSinkAbortCallback>>>,

        start: RefCell<Option<Rc<UnderlyingSinkStartCallback>>>,

        /// <https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-closealgorithm>
        close: RefCell<Option<Rc<UnderlyingSinkCloseCallback>>>,

        /// <https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-writealgorithm>
        write: RefCell<Option<Rc<UnderlyingSinkWriteCallback>>>,
    },
    /// Algorithms supporting streams transfer are implemented in Rust.
    /// The promise and port used in those algorithms are stored here.
    Transfer {
        backpressure_promise: Rc<RefCell<Option<TracedPromise>>>,
        port: Dom<MessagePort>,
    },
    /// Algorithms supporting transform streams are implemented in Rust.
    Transform(Dom<TransformStream>, TracedPromise),
}

impl UnderlyingSinkType {
    pub(crate) fn new_js(
        abort: Option<Rc<UnderlyingSinkAbortCallback>>,
        start: Option<Rc<UnderlyingSinkStartCallback>>,
        close: Option<Rc<UnderlyingSinkCloseCallback>>,
        write: Option<Rc<UnderlyingSinkWriteCallback>>,
    ) -> Self {
        UnderlyingSinkType::Js {
            abort: RefCell::new(abort),
            start: RefCell::new(start),
            close: RefCell::new(close),
            write: RefCell::new(write),
        }
    }
}

/// <https://streams.spec.whatwg.org/#ws-default-controller-class>
#[dom_struct]
pub struct WritableStreamDefaultController {
    reflector_: Reflector,

    /// The type of underlying sink used. Besides the default JS one,
    /// there will be others for stream transfer, and for transform stream.
    #[ignore_malloc_size_of = "underlying_sink_type"]
    underlying_sink_type: UnderlyingSinkType,

    /// The JS object used as `this` when invoking sink algorithms.
    #[ignore_malloc_size_of = "mozjs"]
    underlying_sink_obj: Heap<*mut JSObject>,

    /// <https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-queue>
    queue: QueueWithSizes,

    /// <https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-started>
    started: Cell<bool>,

    /// <https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-strategyhwm>
    strategy_hwm: f64,

    /// <https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-strategysizealgorithm>
    #[ignore_malloc_size_of = "QueuingStrategySize"]
    strategy_size: RefCell<Option<Rc<QueuingStrategySize>>>,

    /// <https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-stream>
    stream: MutNullableDom<WritableStream>,

    /// <https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-abortcontroller>
    abort_controller: Dom<AbortController>,
}

impl WritableStreamDefaultController {
    /// <https://streams.spec.whatwg.org/#set-up-writable-stream-default-controller-from-underlying-sink>
    #[cfg_attr(crown, expect(crown::unrooted_must_root))]
    fn new_inherited(
        cx: &mut JSContext,
        global: &GlobalScope,
        underlying_sink_type: UnderlyingSinkType,
        strategy_hwm: f64,
        strategy_size: Rc<QueuingStrategySize>,
    ) -> WritableStreamDefaultController {
        WritableStreamDefaultController {
            reflector_: Reflector::new(),
            underlying_sink_type,
            queue: Default::default(),
            stream: Default::default(),
            underlying_sink_obj: Default::default(),
            strategy_hwm,
            strategy_size: RefCell::new(Some(strategy_size)),
            started: Default::default(),
            abort_controller: Dom::from_ref(&AbortController::new_with_proto(cx, global, None)),
        }
    }

    #[cfg_attr(crown, expect(crown::unrooted_must_root))]
    pub(crate) fn new(
        cx: &mut JSContext,
        global: &GlobalScope,
        underlying_sink_type: UnderlyingSinkType,
        strategy_hwm: f64,
        strategy_size: Rc<QueuingStrategySize>,
    ) -> DomRoot<WritableStreamDefaultController> {
        reflect_dom_object_with_cx(
            Box::new(WritableStreamDefaultController::new_inherited(
                cx,
                global,
                underlying_sink_type,
                strategy_hwm,
                strategy_size,
            )),
            global,
            cx,
        )
    }

    pub(crate) fn started(&self) -> bool {
        self.started.get()
    }

    /// Setting the JS object after the heap has settled down.
    pub(crate) fn set_underlying_sink_this_object(&self, this_object: SafeHandleObject) {
        self.underlying_sink_obj.set(*this_object);
    }

    /// "Signal abort" call from <https://streams.spec.whatwg.org/#writable-stream-abort>
    pub(crate) fn signal_abort(&self, cx: &mut CurrentRealm, reason: SafeHandleValue) {
        self.abort_controller.signal_abort(cx, reason);
    }

    /// <https://streams.spec.whatwg.org/#writable-stream-default-controller-clear-algorithms>
    fn clear_algorithms(&self) {
        match &self.underlying_sink_type {
            UnderlyingSinkType::Js {
                abort,
                start: _,
                close,
                write,
            } => {
                // Set controller.[[writeAlgorithm]] to undefined.
                write.borrow_mut().take();

                // Set controller.[[closeAlgorithm]] to undefined.
                close.borrow_mut().take();

                // Set controller.[[abortAlgorithm]] to undefined.
                abort.borrow_mut().take();
            },
            UnderlyingSinkType::Transfer {
                backpressure_promise,
                ..
            } => {
                backpressure_promise.borrow_mut().take();
            },
            UnderlyingSinkType::Transform(_, _) => {
                return;
            },
        }

        // Set controller.[[strategySizeAlgorithm]] to undefined.
        self.strategy_size.borrow_mut().take();
    }

    /// <https://streams.spec.whatwg.org/#set-up-writable-stream-default-controller>
    pub(crate) fn setup(
        &self,
        cx: &mut JSContext,
        global: &GlobalScope,
        stream: &WritableStream,
    ) -> Result<(), Error> {
        // Assert: stream implements WritableStream.
        // Implied by stream type.

        // Assert: stream.[[controller]] is undefined.
        stream.assert_no_controller();

        // Set controller.[[stream]] to stream.
        self.stream.set(Some(stream));

        // Set stream.[[controller]] to controller.
        stream.set_default_controller(self);

        // Perform ! ResetQueue(controller).

        // Set controller.[[abortController]] to a new AbortController.

        // Set controller.[[started]] to false.

        // Set controller.[[strategySizeAlgorithm]] to sizeAlgorithm.

        // Set controller.[[strategyHWM]] to highWaterMark.

        // Set controller.[[writeAlgorithm]] to writeAlgorithm.

        // Set controller.[[closeAlgorithm]] to closeAlgorithm.

        // Set controller.[[abortAlgorithm]] to abortAlgorithm.

        // Note: above steps are done in `new_inherited`.

        // Let backpressure be ! WritableStreamDefaultControllerGetBackpressure(controller).
        let backpressure = self.get_backpressure();

        // Perform ! WritableStreamUpdateBackpressure(stream, backpressure).
        stream.update_backpressure(cx, backpressure, global);

        // Let startResult be the result of performing startAlgorithm. (This may throw an exception.)
        // Let startPromise be a promise resolved with startResult.
        let start_promise = self.start_algorithm(cx, global)?;

        let rooted_default_controller = DomRoot::from_ref(self);

        // Upon fulfillment of startPromise,
        rooted!(&in(cx) let mut fulfillment_handler = Some(StartAlgorithmFulfillmentHandler {
            controller: Dom::from_ref(&rooted_default_controller),
        }));

        // Upon rejection of startPromise with reason r,
        rooted!(&in(cx) let mut rejection_handler = Some(StartAlgorithmRejectionHandler {
            controller: Dom::from_ref(&rooted_default_controller),
        }));

        let handler = PromiseNativeHandler::new(
            cx,
            global,
            fulfillment_handler.take().map(|h| Box::new(h) as Box<_>),
            rejection_handler.take().map(|h| Box::new(h) as Box<_>),
        );
        let mut realm = enter_auto_realm(cx, global);
        let cx = &mut realm.current_realm();
        start_promise.append_native_handler(cx, &handler);

        Ok(())
    }

    /// <https://streams.spec.whatwg.org/#writable-stream-default-controller-close>
    pub(crate) fn close(&self, cx: &mut JSContext, global: &GlobalScope) {
        // Perform ! EnqueueValueWithSize(controller, close sentinel, 0).
        self.queue
            .enqueue_value_with_size(EnqueuedValue::CloseSentinel)
            .expect("Enqueuing the close sentinel should not fail.");
        // Perform ! WritableStreamDefaultControllerAdvanceQueueIfNeeded(controller).
        self.advance_queue_if_needed(cx, global);
    }

    fn start_algorithm(&self, cx: &mut JSContext, global: &GlobalScope) -> Fallible<RootedPromise> {
        match &self.underlying_sink_type {
            UnderlyingSinkType::Js {
                start,
                abort: _,
                close: _,
                write: _,
            } => {
                let algo = start.borrow().clone();
                let start_promise = if let Some(start) = algo {
                    rooted!(&in(cx) let mut result: JSVal);
                    rooted!(&in(cx) let this_object = self.underlying_sink_obj.get());
                    start.Call_(
                        cx,
                        &this_object.handle(),
                        self,
                        result.handle_mut(),
                        ExceptionHandling::Rethrow,
                    )?;
                    Promise::resolve_or_wrap_promise(cx, result.handle(), global)
                } else {
                    // Let startAlgorithm be an algorithm that returns undefined.
                    Promise::new_resolved_rooted(cx, global, ())
                };

                Ok(start_promise)
            },
            UnderlyingSinkType::Transfer { .. } => {
                // Let startAlgorithm be an algorithm that returns undefined.
                Ok(Promise::new_resolved_rooted(cx, global, ()))
            },
            UnderlyingSinkType::Transform(_, start_promise) => {
                // Let startAlgorithm be an algorithm that returns startPromise.
                Ok(start_promise.root(cx))
            },
        }
    }

    /// <https://streams.spec.whatwg.org/#ref-for-abstract-opdef-writablestreamcontroller-abortsteps>
    pub(crate) fn abort_steps(
        &self,
        cx: &mut JSContext,
        global: &GlobalScope,
        reason: SafeHandleValue,
    ) -> RootedPromise {
        let result = match &self.underlying_sink_type {
            UnderlyingSinkType::Js {
                abort,
                start: _,
                close: _,
                write: _,
            } => {
                rooted!(&in(cx) let this_object = self.underlying_sink_obj.get());
                let algo = abort.borrow().clone();
                // Let result be the result of performing this.[[abortAlgorithm]], passing reason.
                let result = if let Some(algo) = algo {
                    algo.Call_(
                        cx,
                        &this_object.handle(),
                        Some(reason),
                        ExceptionHandling::Rethrow,
                    )
                } else {
                    Ok(Promise::new_resolved_rooted(cx, global, ()))
                };
                result.unwrap_or_else(|e| {
                    let promise = Promise::new_rooted(cx, global);
                    promise.reject_error(cx, e);
                    promise
                })
            },
            UnderlyingSinkType::Transfer { port, .. } => {
                // The steps from the `abortAlgorithm` at
                // <https://streams.spec.whatwg.org/#abstract-opdef-setupcrossrealmtransformwritable>

                // Let result be PackAndPostMessageHandlingError(port, "error", reason).
                let result = port.pack_and_post_message_handling_error(cx, "error", reason);

                // Disentangle port.
                global.disentangle_port(cx, port);

                let promise = Promise::new_rooted(cx, global);

                // If result is an abrupt completion, return a promise rejected with result.[[Value]]
                if let Err(error) = result {
                    promise.reject_error(cx, error);
                } else {
                    // Otherwise, return a promise resolved with undefined.
                    promise.resolve_native(cx, &());
                }
                promise
            },
            UnderlyingSinkType::Transform(stream, _) => {
                // Return ! TransformStreamDefaultSinkAbortAlgorithm(stream, reason).
                stream
                    .transform_stream_default_sink_abort_algorithm(cx, global, reason)
                    .expect("Transform stream default sink abort algorithm should not fail.")
            },
        };

        // Perform ! WritableStreamDefaultControllerClearAlgorithms(controller).
        self.clear_algorithms();

        result
    }

    /// <https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-writealgorithm>
    fn call_write_algorithm(
        &self,
        cx: &mut JSContext,
        chunk: SafeHandleValue,
        global: &GlobalScope,
    ) -> RootedPromise {
        match &self.underlying_sink_type {
            UnderlyingSinkType::Js {
                abort: _,
                start: _,
                close: _,
                write,
            } => {
                rooted!(&in(cx) let this_object = self.underlying_sink_obj.get());
                let algo = write.borrow().clone();
                let result = if let Some(algo) = algo {
                    algo.Call_(
                        cx,
                        &this_object.handle(),
                        chunk,
                        self,
                        ExceptionHandling::Rethrow,
                    )
                } else {
                    Ok(Promise::new_resolved_rooted(cx, global, ()))
                };
                result.unwrap_or_else(|e| {
                    let promise = Promise::new_rooted(cx, global);
                    promise.reject_error(cx, e);
                    promise
                })
            },
            UnderlyingSinkType::Transfer {
                backpressure_promise,
                port,
            } => {
                // The steps from the `writeAlgorithm` at
                // <https://streams.spec.whatwg.org/#abstract-opdef-setupcrossrealmtransformwritable>

                // If backpressurePromise is undefined,
                // set backpressurePromise to a promise resolved with undefined.
                if backpressure_promise.borrow().is_none() {
                    let promise = Promise::new_resolved_rooted(cx, global, ());
                    *backpressure_promise.borrow_mut() = Some(promise.to_traced());
                }

                // Return the result of reacting to backpressurePromise with the following fulfillment steps:
                let result_promise = Promise::new_rooted(cx, global);
                rooted!(&in(cx) let mut fulfillment_handler = Some(TransferBackPressurePromiseReaction {
                    port: port.clone(),
                    backpressure_promise: backpressure_promise.clone(),
                    chunk: Heap::boxed(chunk.get()),
                    result_promise: result_promise.to_traced(),
                }));
                let handler = PromiseNativeHandler::new(
                    cx,
                    global,
                    fulfillment_handler.take().map(|h| Box::new(h) as Box<_>),
                    None,
                );
                let mut realm = enter_auto_realm(cx, global);
                let realm = &mut realm.current_realm();
                backpressure_promise
                    .borrow()
                    .as_ref()
                    .expect("Promise must be some by now.")
                    .append_native_handler(realm, &handler);
                result_promise
            },
            UnderlyingSinkType::Transform(stream, _) => {
                // Return ! TransformStreamDefaultSinkWriteAlgorithm(stream, chunk).
                stream
                    .transform_stream_default_sink_write_algorithm(cx, global, chunk)
                    .expect("Transform stream default sink write algorithm should not fail.")
            },
        }
    }

    /// <https://streams.spec.whatwg.org/#writablestreamdefaultcontroller-closealgorithm>
    fn call_close_algorithm(&self, cx: &mut JSContext, global: &GlobalScope) -> RootedPromise {
        match &self.underlying_sink_type {
            UnderlyingSinkType::Js {
                abort: _,
                start: _,
                close,
                write: _,
            } => {
                rooted!(&in(cx) let mut this_object = ptr::null_mut::<JSObject>());
                this_object.set(self.underlying_sink_obj.get());
                let algo = close.borrow().clone();
                let result = if let Some(algo) = algo {
                    algo.Call_(cx, &this_object.handle(), ExceptionHandling::Rethrow)
                } else {
                    Ok(Promise::new_resolved_rooted(cx, global, ()))
                };
                result.unwrap_or_else(|e| {
                    let promise = Promise::new_rooted(cx, global);
                    promise.reject_error(cx, e);
                    promise
                })
            },
            UnderlyingSinkType::Transfer { port, .. } => {
                // The steps from the `closeAlgorithm` at
                // <https://streams.spec.whatwg.org/#abstract-opdef-setupcrossrealmtransformwritable>

                // Perform ! PackAndPostMessage(port, "close", undefined).
                rooted!(&in(cx) let mut value = UndefinedValue());
                port.pack_and_post_message(cx, "close", value.handle())
                    .expect("Sending close should not fail.");

                // Disentangle port.
                global.disentangle_port(cx, port);

                // Return a promise resolved with undefined.
                Promise::new_resolved_rooted(cx, global, ())
            },
            UnderlyingSinkType::Transform(stream, _) => {
                // Return ! TransformStreamDefaultSinkCloseAlgorithm(stream).
                stream
                    .transform_stream_default_sink_close_algorithm(cx, global)
                    .expect("Transform stream default sink close algorithm should not fail.")
            },
        }
    }

    /// <https://streams.spec.whatwg.org/#writable-stream-default-controller-process-close>
    pub(crate) fn process_close(&self, cx: &mut JSContext, global: &GlobalScope) {
        // Let stream be controller.[[stream]].
        let Some(stream) = self.stream.get() else {
            unreachable!("Controller should have a stream");
        };

        // Perform ! WritableStreamMarkCloseRequestInFlight(stream).
        stream.mark_close_request_in_flight();

        // Perform ! DequeueValue(controller).
        self.queue.dequeue_value(cx, None);

        // Assert: controller.[[queue]] is empty.
        assert!(self.queue.is_empty());

        // Let sinkClosePromise be the result of performing controller.[[closeAlgorithm]].
        let sink_close_promise = self.call_close_algorithm(cx, global);

        // Perform ! WritableStreamDefaultControllerClearAlgorithms(controller).
        self.clear_algorithms();

        // Upon fulfillment of sinkClosePromise,
        rooted!(&in(cx) let mut fulfillment_handler = Some(CloseAlgorithmFulfillmentHandler {
            stream: Dom::from_ref(&stream),
        }));

        // Upon rejection of sinkClosePromise with reason reason,
        rooted!(&in(cx) let mut rejection_handler = Some(CloseAlgorithmRejectionHandler {
            stream: Dom::from_ref(&stream),
        }));

        // Attach handlers to the promise.
        let handler = PromiseNativeHandler::new(
            cx,
            global,
            fulfillment_handler.take().map(|h| Box::new(h) as Box<_>),
            rejection_handler.take().map(|h| Box::new(h) as Box<_>),
        );
        let mut realm = enter_auto_realm(cx, global);
        let realm = &mut realm.current_realm();
        sink_close_promise.append_native_handler(realm, &handler);
    }

    /// <https://streams.spec.whatwg.org/#writable-stream-default-controller-advance-queue-if-needed>
    fn advance_queue_if_needed(&self, cx: &mut JSContext, global: &GlobalScope) {
        // Let stream be controller.[[stream]].
        let Some(stream) = self.stream.get() else {
            unreachable!("Controller should have a stream");
        };

        // If controller.[[started]] is false, return.
        if !self.started.get() {
            return;
        }

        // If stream.[[inFlightWriteRequest]] is not undefined, return.
        if stream.has_in_flight_write_request() {
            return;
        }

        // Let state be stream.[[state]].

        // Assert: state is not "closed" or "errored".
        assert!(!(stream.is_errored() || stream.is_closed()));

        // If state is "erroring",
        if stream.is_erroring() {
            // Perform ! WritableStreamFinishErroring(stream).
            stream.finish_erroring(cx, global);

            // Return.
            return;
        }

        // Let value be ! PeekQueueValue(controller).
        rooted!(&in(cx) let mut value = UndefinedValue());
        let is_closed = {
            // If controller.[[queue]] is empty, return.
            if self.queue.is_empty() {
                return;
            }
            self.queue.peek_queue_value(cx, value.handle_mut())
        };

        if is_closed {
            // If value is the close sentinel, perform ! WritableStreamDefaultControllerProcessClose(controller).
            self.process_close(cx, global);
        } else {
            // Otherwise, perform ! WritableStreamDefaultControllerProcessWrite(controller, value).
            self.process_write(cx, value.handle(), global);
        };
    }

    /// <https://streams.spec.whatwg.org/#ws-default-controller-private-error>
    pub(crate) fn perform_error_steps(&self) {
        // Perform ! ResetQueue(this).
        self.queue.reset();
    }

    /// <https://streams.spec.whatwg.org/#writable-stream-default-controller-process-write>
    fn process_write(&self, cx: &mut JSContext, chunk: SafeHandleValue, global: &GlobalScope) {
        // Let stream be controller.[[stream]].
        let Some(stream) = self.stream.get() else {
            unreachable!("Controller should have a stream");
        };

        // Perform ! WritableStreamMarkFirstWriteRequestInFlight(stream).
        stream.mark_first_write_request_in_flight();

        // Let sinkWritePromise be the result of performing controller.[[writeAlgorithm]], passing in chunk.
        let sink_write_promise = self.call_write_algorithm(cx, chunk, global);

        // Upon fulfillment of sinkWritePromise,
        rooted!(&in(cx) let mut fulfillment_handler = Some(WriteAlgorithmFulfillmentHandler {
            controller: Dom::from_ref(self),
        }));

        // Upon rejection of sinkWritePromise with reason,
        rooted!(&in(cx) let mut rejection_handler = Some(WriteAlgorithmRejectionHandler {
            controller: Dom::from_ref(self),
        }));

        // Attach handlers to the promise.
        let handler = PromiseNativeHandler::new(
            cx,
            global,
            fulfillment_handler.take().map(|h| Box::new(h) as Box<_>),
            rejection_handler.take().map(|h| Box::new(h) as Box<_>),
        );
        let mut realm = enter_auto_realm(cx, global);
        let realm = &mut realm.current_realm();
        sink_write_promise.append_native_handler(realm, &handler);
    }

    /// <https://streams.spec.whatwg.org/#writable-stream-default-controller-get-desired-size>
    pub(crate) fn get_desired_size(&self) -> f64 {
        // Return controller.[[strategyHWM]] − controller.[[queueTotalSize]].
        let desired_size = self.strategy_hwm - self.queue.total_size.get().clamp(0.0, f64::MAX);
        desired_size.clamp(desired_size, self.strategy_hwm)
    }

    /// <https://streams.spec.whatwg.org/#writable-stream-default-controller-get-backpressure>
    fn get_backpressure(&self) -> bool {
        // Let desiredSize be ! WritableStreamDefaultControllerGetDesiredSize(controller).
        let desired_size = self.get_desired_size();

        // Return true if desiredSize ≤ 0, or false otherwise.
        desired_size == 0.0 || desired_size.is_sign_negative()
    }

    /// <https://streams.spec.whatwg.org/#writable-stream-default-controller-get-chunk-size>
    pub(crate) fn get_chunk_size(
        &self,
        cx: &mut JSContext,
        global: &GlobalScope,
        chunk: SafeHandleValue,
    ) -> f64 {
        // If controller.[[strategySizeAlgorithm]] is undefined, then:
        let Some(strategy_size) = self.strategy_size.borrow().clone() else {
            // Assert: controller.[[stream]].[[state]] is not "writable".
            let Some(stream) = self.stream.get() else {
                unreachable!("Controller should have a stream");
            };
            assert!(!stream.is_writable());

            // Return 1.
            return 1.0;
        };

        // Let returnValue be the result of performing controller.[[strategySizeAlgorithm]],
        // passing in chunk, and interpreting the result as a completion record.
        let result = strategy_size.Call__(cx, chunk, ExceptionHandling::Rethrow);

        match result {
            // Let chunkSize be result.[[Value]].
            Ok(size) => size,
            Err(error) => {
                // If result is an abrupt completion,

                // Perform ! WritableStreamDefaultControllerErrorIfNeeded(controller, returnValue.[[Value]]).
                // Create a rooted value for the error.
                rooted!(&in(cx) let mut rooted_error = UndefinedValue());
                error.to_jsval(cx, global, rooted_error.handle_mut());
                self.error_if_needed(cx, rooted_error.handle(), global);

                // Return 1.
                1.0
            },
        }
    }

    /// <https://streams.spec.whatwg.org/#writable-stream-default-controller-write>
    pub(crate) fn write(
        &self,
        cx: &mut JSContext,
        global: &GlobalScope,
        chunk: SafeHandleValue,
        chunk_size: f64,
    ) {
        // Let enqueueResult be EnqueueValueWithSize(controller, chunk, chunkSize).
        let enqueue_result = self
            .queue
            .enqueue_value_with_size(EnqueuedValue::Js(ValueWithSize {
                value: Heap::boxed(chunk.get()),
                size: chunk_size,
            }));

        // If enqueueResult is an abrupt completion,
        if let Err(error) = enqueue_result {
            // Perform ! WritableStreamDefaultControllerErrorIfNeeded(controller, enqueueResult.[[Value]]).
            // Create a rooted value for the error.
            rooted!(&in(cx) let mut rooted_error = UndefinedValue());
            error.to_jsval(cx, global, rooted_error.handle_mut());
            self.error_if_needed(cx, rooted_error.handle(), global);

            // Return.
            return;
        }

        // Let stream be controller.[[stream]].
        let Some(stream) = self.stream.get() else {
            unreachable!("Controller should have a stream");
        };

        // If ! WritableStreamCloseQueuedOrInFlight(stream) is false and stream.[[state]] is "writable",
        if !stream.close_queued_or_in_flight() && stream.is_writable() {
            // Let backpressure be ! WritableStreamDefaultControllerGetBackpressure(controller).
            let backpressure = self.get_backpressure();

            // Perform ! WritableStreamUpdateBackpressure(stream, backpressure).
            stream.update_backpressure(cx, backpressure, global);
        }

        // Perform ! WritableStreamDefaultControllerAdvanceQueueIfNeeded(controller).
        self.advance_queue_if_needed(cx, global);
    }

    /// <https://streams.spec.whatwg.org/#writable-stream-default-controller-error-if-needed>
    pub(crate) fn error_if_needed(
        &self,
        cx: &mut JSContext,
        error: SafeHandleValue,
        global: &GlobalScope,
    ) {
        // Let stream be controller.[[stream]].
        let Some(stream) = self.stream.get() else {
            unreachable!("Controller should have a stream");
        };

        // If stream.[[state]] is "writable",
        if stream.is_writable() {
            // Perform ! WritableStreamDefaultControllerError(controller, e).
            self.error(cx, &stream, error, global);
        }
    }

    /// <https://streams.spec.whatwg.org/#writable-stream-default-controller-error>
    fn error(
        &self,
        cx: &mut JSContext,
        stream: &WritableStream,
        e: SafeHandleValue,
        global: &GlobalScope,
    ) {
        // Let stream be controller.[[stream]].
        // Done above with the argument.

        // Assert: stream.[[state]] is "writable".
        assert!(stream.is_writable());

        // Perform ! WritableStreamDefaultControllerClearAlgorithms(controller).
        self.clear_algorithms();

        // Perform ! WritableStreamStartErroring(stream, error).
        stream.start_erroring(cx, global, e);
    }
}

impl WritableStreamDefaultControllerMethods<crate::DomTypeHolder>
    for WritableStreamDefaultController
{
    /// <https://streams.spec.whatwg.org/#ws-default-controller-error>
    fn Error(&self, cx: &mut CurrentRealm, e: SafeHandleValue) {
        // Let state be this.[[stream]].[[state]].
        let Some(stream) = self.stream.get() else {
            unreachable!("Controller should have a stream");
        };

        // If state is not "writable", return.
        if !stream.is_writable() {
            return;
        }

        let global = GlobalScope::from_current_realm(cx);

        // Perform ! WritableStreamDefaultControllerError(this, e).
        self.error(cx, &stream, e, &global);
    }

    /// <https://streams.spec.whatwg.org/#ws-default-controller-signal>
    fn Signal(&self) -> DomRoot<AbortSignal> {
        // Return this.[[abortController]]’s signal.
        self.abort_controller.signal()
    }
}