script/dom/audio/

baseaudiocontext.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;
use std::collections::hash_map::Entry;
use std::collections::{HashMap, VecDeque};
use std::sync::{Arc, Mutex};

use dom_struct::dom_struct;
use js::context::JSContext;
use js::realm::CurrentRealm;
use js::rust::CustomAutoRooterGuard;
use js::typedarray::{ArrayBuffer, ArrayBufferU8};
use script_bindings::cell::DomRefCell;
use script_bindings::cformat;
use script_bindings::codegen::GenericBindings::AnalyserNodeBinding::AnalyserNodeMethods;
use script_bindings::codegen::GenericBindings::AudioBufferSourceNodeBinding::AudioBufferSourceNodeMethods;
use script_bindings::codegen::GenericBindings::BiquadFilterNodeBinding::BiquadFilterNodeMethods;
use script_bindings::codegen::GenericBindings::ChannelMergerNodeBinding::ChannelMergerNodeMethods;
use script_bindings::codegen::GenericBindings::ChannelSplitterNodeBinding::ChannelSplitterNodeMethods;
use script_bindings::codegen::GenericBindings::ConstantSourceNodeBinding::ConstantSourceNodeMethods;
use script_bindings::codegen::GenericBindings::ConvolverNodeBinding::{
    ConvolverNodeMethods, ConvolverOptions,
};
use script_bindings::codegen::GenericBindings::DelayNodeBinding::{DelayNodeMethods, DelayOptions};
use script_bindings::codegen::GenericBindings::GainNodeBinding::GainNodeMethods;
use script_bindings::codegen::GenericBindings::IIRFilterNodeBinding::IIRFilterNodeMethods;
use script_bindings::codegen::GenericBindings::OscillatorNodeBinding::OscillatorNodeMethods;
use script_bindings::codegen::GenericBindings::PannerNodeBinding::PannerNodeMethods;
use script_bindings::codegen::GenericBindings::PeriodicWaveBinding::PeriodicWaveMethods;
use script_bindings::codegen::GenericBindings::StereoPannerNodeBinding::StereoPannerNodeMethods;
use servo_base::id::PipelineId;
use servo_media::audio::context::{
    AudioContext, AudioContextOptions, OfflineAudioContextOptions, ProcessingState,
    RealTimeAudioContextOptions,
};
use servo_media::audio::decoder::AudioDecoderCallbacksBuilder;
use servo_media::audio::graph::NodeId;
use servo_media::{ClientContextId, ServoMedia};
use uuid::Uuid;

use crate::conversions::Convert;
use crate::dom::audio::analysernode::AnalyserNode;
use crate::dom::audio::audiobuffer::AudioBuffer;
use crate::dom::audio::audiobuffersourcenode::AudioBufferSourceNode;
use crate::dom::audio::audiodestinationnode::AudioDestinationNode;
use crate::dom::audio::audiolistener::AudioListener;
use crate::dom::audio::audionode::MAX_CHANNEL_COUNT;
use crate::dom::audio::biquadfilternode::BiquadFilterNode;
use crate::dom::audio::channelmergernode::ChannelMergerNode;
use crate::dom::audio::channelsplitternode::ChannelSplitterNode;
use crate::dom::audio::constantsourcenode::ConstantSourceNode;
use crate::dom::audio::convolvernode::ConvolverNode;
use crate::dom::audio::delaynode::DelayNode;
use crate::dom::audio::gainnode::GainNode;
use crate::dom::audio::iirfilternode::IIRFilterNode;
use crate::dom::audio::oscillatornode::OscillatorNode;
use crate::dom::audio::pannernode::PannerNode;
use crate::dom::audio::periodicwave::PeriodicWave;
use crate::dom::audio::stereopannernode::StereoPannerNode;
use crate::dom::bindings::buffer_source::HeapBufferSource;
use crate::dom::bindings::callback::{ExceptionHandling, RootedCallback, TracedCallback};
use crate::dom::bindings::codegen::Bindings::AnalyserNodeBinding::AnalyserOptions;
use crate::dom::bindings::codegen::Bindings::AudioBufferSourceNodeBinding::AudioBufferSourceOptions;
use crate::dom::bindings::codegen::Bindings::AudioNodeBinding::{
    AudioNodeOptions, ChannelCountMode, ChannelInterpretation,
};
use crate::dom::bindings::codegen::Bindings::BaseAudioContextBinding::{
    AudioContextState, BaseAudioContextMethods, DecodeErrorCallback, DecodeSuccessCallback,
};
use crate::dom::bindings::codegen::Bindings::BiquadFilterNodeBinding::BiquadFilterOptions;
use crate::dom::bindings::codegen::Bindings::ChannelMergerNodeBinding::ChannelMergerOptions;
use crate::dom::bindings::codegen::Bindings::ChannelSplitterNodeBinding::ChannelSplitterOptions;
use crate::dom::bindings::codegen::Bindings::ConstantSourceNodeBinding::ConstantSourceOptions;
use crate::dom::bindings::codegen::Bindings::GainNodeBinding::GainOptions;
use crate::dom::bindings::codegen::Bindings::IIRFilterNodeBinding::IIRFilterOptions;
use crate::dom::bindings::codegen::Bindings::OscillatorNodeBinding::OscillatorOptions;
use crate::dom::bindings::codegen::Bindings::PannerNodeBinding::PannerOptions;
use crate::dom::bindings::codegen::Bindings::PeriodicWaveBinding::{
    PeriodicWaveConstraints, PeriodicWaveOptions,
};
use crate::dom::bindings::codegen::Bindings::StereoPannerNodeBinding::StereoPannerOptions;
use crate::dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
use crate::dom::bindings::error::{Error, ErrorResult, Fallible};
use crate::dom::bindings::inheritance::Castable;
use crate::dom::bindings::num::Finite;
use crate::dom::bindings::refcounted::Trusted;
use crate::dom::bindings::reflector::DomGlobal;
use crate::dom::bindings::root::{DomRoot, MutNullableDom};
use crate::dom::domexception::{DOMErrorName, DOMException};
use crate::dom::eventtarget::EventTarget;
use crate::dom::promise::{Promise, RootedPromise, TracedPromise};

pub(crate) enum BaseAudioContextOptions {
    AudioContext(RealTimeAudioContextOptions),
    OfflineAudioContext(OfflineAudioContextOptions),
}

#[derive(JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
struct DecodeResolver {
    pub(crate) promise: TracedPromise,
    pub(crate) success_callback: Option<TracedCallback<DecodeSuccessCallback>>,
    pub(crate) error_callback: Option<TracedCallback<DecodeErrorCallback>>,
}

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

type BoxedSliceOfPromises = Box<[TracedPromise]>;

#[dom_struct]
pub(crate) struct BaseAudioContext {
    eventtarget: EventTarget,
    #[no_trace]
    #[conditional_malloc_size_of]
    audio_context_impl: Arc<Mutex<AudioContext>>,
    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-destination>
    destination: MutNullableDom<AudioDestinationNode>,
    listener: MutNullableDom<AudioListener>,
    /// Resume promises which are soon to be fulfilled by a queued task.
    in_flight_resume_promises_queue: DomRefCell<VecDeque<(BoxedSliceOfPromises, ErrorResult)>>,
    /// <https://webaudio.github.io/web-audio-api/#pendingresumepromises>
    pending_resume_promises: DomRefCell<Vec<TracedPromise>>,
    decode_resolvers: DomRefCell<HashMap<String, DecodeResolver>>,
    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-samplerate>
    sample_rate: f32,
    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-state>
    /// Although servo-media already keeps track of the control thread state,
    /// we keep a state flag here as well. This is so that we can synchronously
    /// throw when trying to do things on the context when the context has just
    /// been "closed()".
    state: Cell<AudioContextState>,
    channel_count: u32,
}

impl BaseAudioContext {
    pub(crate) fn new_inherited(
        options: BaseAudioContextOptions,
        pipeline_id: PipelineId,
    ) -> Fallible<BaseAudioContext> {
        let (sample_rate, channel_count) = match options {
            BaseAudioContextOptions::AudioContext(ref opt) => (opt.sample_rate, 2),
            BaseAudioContextOptions::OfflineAudioContext(ref opt) => {
                (opt.sample_rate, opt.channels)
            },
        };

        let client_context_id =
            ClientContextId::build(pipeline_id.namespace_id.0, pipeline_id.index.0.get());
        let audio_context_impl = ServoMedia::get()
            .create_audio_context(&client_context_id, options.convert())
            .map_err(|_| Error::NotSupported(Some("Failed to create audio context".into())))?;

        Ok(BaseAudioContext {
            eventtarget: EventTarget::new_inherited(),
            audio_context_impl,
            destination: Default::default(),
            listener: Default::default(),
            in_flight_resume_promises_queue: Default::default(),
            pending_resume_promises: Default::default(),
            decode_resolvers: Default::default(),
            sample_rate,
            state: Cell::new(AudioContextState::Suspended),
            channel_count: channel_count.into(),
        })
    }

    /// Tells whether this is an OfflineAudioContext or not.
    pub(crate) fn is_offline(&self) -> bool {
        false
    }

    pub(crate) fn audio_context_impl(&self) -> Arc<Mutex<AudioContext>> {
        self.audio_context_impl.clone()
    }

    pub(crate) fn destination_node(&self) -> NodeId {
        self.audio_context_impl.lock().unwrap().dest_node()
    }

    pub(crate) fn listener(&self) -> NodeId {
        self.audio_context_impl.lock().unwrap().listener()
    }

    // https://webaudio.github.io/web-audio-api/#allowed-to-start
    pub(crate) fn is_allowed_to_start(&self) -> bool {
        self.state.get() == AudioContextState::Suspended
    }

    fn push_pending_resume_promise(&self, promise: &RootedPromise) {
        self.pending_resume_promises
            .borrow_mut()
            .push(promise.to_traced());
    }

    /// Takes the pending resume promises.
    ///
    /// The result with which these promises will be fulfilled is passed here
    /// and this method returns nothing because we actually just move the
    /// current list of pending resume promises to the
    /// `in_flight_resume_promises_queue` field.
    ///
    /// Each call to this method must be followed by a call to
    /// `fulfill_in_flight_resume_promises`, to actually fulfill the promises
    /// which were taken and moved to the in-flight queue.
    fn take_pending_resume_promises(&self, result: ErrorResult) {
        self.in_flight_resume_promises_queue
            .borrow_mut()
            .push_back((
                std::mem::take(&mut *self.pending_resume_promises.borrow_mut()).into(),
                result,
            ));
    }

    /// Fulfills the next in-flight resume promises queue after running a closure.
    ///
    /// See the comment on `take_pending_resume_promises` for why this method
    /// does not take a list of promises to fulfill. Callers cannot just pop
    /// the front list off of `in_flight_resume_promises_queue` and later fulfill
    /// the promises because that would mean putting
    /// `#[cfg_attr(crown, expect(crown::unrooted_must_root))]` on even more functions, potentially
    /// hiding actual safety bugs.
    fn fulfill_in_flight_resume_promises<F>(&self, cx: &mut JSContext, f: F)
    where
        F: FnOnce(),
    {
        let (promises, result) = self
            .in_flight_resume_promises_queue
            .borrow_mut()
            .pop_front()
            .map(|(promises, result)| {
                let promises: Vec<RootedPromise> =
                    promises.iter().map(|promise| promise.root(cx)).collect();
                (promises, result)
            })
            .expect("there should be at least one list of in flight resume promises");
        f();
        for promise in &promises {
            match result {
                Ok(ref value) => promise.resolve_native(cx, value),
                Err(ref error) => promise.reject_error(cx, error.clone()),
            }
        }
    }

    /// Control thread processing state
    pub(crate) fn control_thread_state(&self) -> ProcessingState {
        self.audio_context_impl.lock().unwrap().state()
    }

    /// Set audio context state
    pub(crate) fn set_state_attribute(&self, state: AudioContextState) {
        self.state.set(state);
    }

    pub(crate) fn resume(&self) {
        let this = Trusted::new(self);
        // Set the rendering thread state to 'running' and start
        // rendering the audio graph.
        match self.audio_context_impl.lock().unwrap().resume() {
            Some(()) => {
                self.take_pending_resume_promises(Ok(()));
                self.global().task_manager().dom_manipulation_task_source().queue(
                    task!(resume_success: move |cx| {
                        let this = this.root();
                        this.fulfill_in_flight_resume_promises(cx, || {
                            if this.state.get() != AudioContextState::Running {
                                this.state.set(AudioContextState::Running);
                                this.global().task_manager().dom_manipulation_task_source().queue_simple_event(
                                    this.upcast(),
                                    atom!("statechange"),
                                    );
                            }
                        });
                    })
                );
            },
            None => {
                self.take_pending_resume_promises(Err(Error::Type(
                    c"Something went wrong".to_owned(),
                )));
                self.global()
                    .task_manager()
                    .dom_manipulation_task_source()
                    .queue(task!(resume_error: move |cx| {
                        this.root().fulfill_in_flight_resume_promises(cx, || {})
                    }));
            },
        }
    }

    pub(crate) fn channel_count(&self) -> u32 {
        self.channel_count
    }
}

impl BaseAudioContextMethods<crate::DomTypeHolder> for BaseAudioContext {
    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-samplerate>
    fn SampleRate(&self) -> Finite<f32> {
        Finite::wrap(self.sample_rate)
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-currenttime>
    fn CurrentTime(&self) -> Finite<f64> {
        let current_time = self.audio_context_impl.lock().unwrap().current_time();
        Finite::wrap(current_time)
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-state>
    fn State(&self) -> AudioContextState {
        self.state.get()
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-resume>
    fn Resume(&self, cx: &mut CurrentRealm) -> RootedPromise {
        // Step 1.
        let promise = Promise::new_in_realm(cx);

        // Step 2.
        if self.audio_context_impl.lock().unwrap().state() == ProcessingState::Closed {
            promise.reject_error(
                cx,
                Error::InvalidState(Some("Cannot resume a closed AudioContext".into())),
            );
            return promise;
        }

        // Step 3.
        if self.state.get() == AudioContextState::Running {
            promise.resolve_native(cx, &());
            return promise;
        }

        self.push_pending_resume_promise(&promise);

        // Step 4.
        if !self.is_allowed_to_start() {
            return promise;
        }

        // Steps 5 and 6.
        self.resume();

        // Step 7.
        promise
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-destination>
    fn Destination(&self, cx: &mut JSContext) -> DomRoot<AudioDestinationNode> {
        let global = self.global();
        self.destination.or_init(|| {
            let mut options = AudioNodeOptions::empty();
            options.channelCount = Some(self.channel_count);
            options.channelCountMode = Some(ChannelCountMode::Explicit);
            options.channelInterpretation = Some(ChannelInterpretation::Speakers);
            AudioDestinationNode::new(cx, &global, self, &options)
        })
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-listener>
    fn Listener(&self, cx: &mut JSContext) -> DomRoot<AudioListener> {
        let global = self.global();
        let window = global.as_window();
        self.listener
            .or_init(|| AudioListener::new(cx, window, self))
    }

    // https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-onstatechange
    event_handler!(statechange, GetOnstatechange, SetOnstatechange);

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createconvolver>
    fn CreateConvolver(&self, cx: &mut JSContext) -> Fallible<DomRoot<ConvolverNode>> {
        ConvolverNode::Constructor(
            cx,
            self.global().as_window(),
            None,
            self,
            &ConvolverOptions::empty(),
        )
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createoscillator>
    fn CreateOscillator(&self, cx: &mut JSContext) -> Fallible<DomRoot<OscillatorNode>> {
        OscillatorNode::Constructor(
            cx,
            self.global().as_window(),
            None,
            self,
            &OscillatorOptions::empty(),
        )
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-creategain>
    fn CreateGain(&self, cx: &mut JSContext) -> Fallible<DomRoot<GainNode>> {
        GainNode::Constructor(
            cx,
            self.global().as_window(),
            None,
            self,
            &GainOptions::empty(),
        )
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createdelay>
    fn CreateDelay(
        &self,
        cx: &mut JSContext,
        max_delay_time: Finite<f64>,
    ) -> Fallible<DomRoot<DelayNode>> {
        // <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createdelay-maxdelaytime-maxdelaytime>
        // Specifies the maximum delay time in seconds allowed for the delay line.
        // If specified, this value MUST be greater than zero and less than three minutes.
        if *max_delay_time <= 0. || *max_delay_time >= 180. {
            return Err(Error::NotSupported(Some(String::from(
                "maxDelayTime is not within 0 - 3 minutes",
            ))));
        }
        let mut options = DelayOptions::empty();
        options.maxDelayTime = max_delay_time;
        DelayNode::Constructor(cx, self.global().as_window(), None, self, &options)
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createpanner>
    fn CreatePanner(&self, cx: &mut JSContext) -> Fallible<DomRoot<PannerNode>> {
        PannerNode::Constructor(
            cx,
            self.global().as_window(),
            None,
            self,
            &PannerOptions::empty(),
        )
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createperiodicwave>
    fn CreatePeriodicWave(
        &self,
        cx: &mut JSContext,
        real: Vec<Finite<f32>>,
        imag: Vec<Finite<f32>>,
        constraints: &PeriodicWaveConstraints,
    ) -> Fallible<DomRoot<PeriodicWave>> {
        // options is a new object of type PeriodicWaveOptions.
        let mut options = PeriodicWaveOptions::empty();
        let mut constraints_copy = PeriodicWaveConstraints::empty();
        // Set the disableNormalization attribute on options to the value of the
        // disableNormalization attribute of the constraints attribute passed to the factory method.
        constraints_copy.disableNormalization = constraints.disableNormalization;
        // Respectively set the real and imag parameters passed to this factory method to the attributes
        // of the same name on options.
        options.real = Some(real);
        options.imag = Some(imag);
        options.parent = constraints_copy;
        PeriodicWave::Constructor(cx, self.global().as_window(), None, self, &options)
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createanalyser>
    fn CreateAnalyser(&self, cx: &mut JSContext) -> Fallible<DomRoot<AnalyserNode>> {
        AnalyserNode::Constructor(
            cx,
            self.global().as_window(),
            None,
            self,
            &AnalyserOptions::empty(),
        )
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createbiquadfilter>
    fn CreateBiquadFilter(&self, cx: &mut JSContext) -> Fallible<DomRoot<BiquadFilterNode>> {
        BiquadFilterNode::Constructor(
            cx,
            self.global().as_window(),
            None,
            self,
            &BiquadFilterOptions::empty(),
        )
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createstereopanner>
    fn CreateStereoPanner(&self, cx: &mut JSContext) -> Fallible<DomRoot<StereoPannerNode>> {
        StereoPannerNode::Constructor(
            cx,
            self.global().as_window(),
            None,
            self,
            &StereoPannerOptions::empty(),
        )
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createconstantsource>
    fn CreateConstantSource(&self, cx: &mut JSContext) -> Fallible<DomRoot<ConstantSourceNode>> {
        ConstantSourceNode::Constructor(
            cx,
            self.global().as_window(),
            None,
            self,
            &ConstantSourceOptions::empty(),
        )
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createchannelmerger>
    fn CreateChannelMerger(
        &self,
        cx: &mut JSContext,
        count: u32,
    ) -> Fallible<DomRoot<ChannelMergerNode>> {
        let mut opts = ChannelMergerOptions::empty();
        opts.numberOfInputs = count;
        ChannelMergerNode::Constructor(cx, self.global().as_window(), None, self, &opts)
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createchannelsplitter>
    fn CreateChannelSplitter(
        &self,
        cx: &mut JSContext,
        count: u32,
    ) -> Fallible<DomRoot<ChannelSplitterNode>> {
        let mut opts = ChannelSplitterOptions::empty();
        opts.numberOfOutputs = count;
        ChannelSplitterNode::Constructor(cx, self.global().as_window(), None, self, &opts)
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createbuffer>
    fn CreateBuffer(
        &self,
        cx: &mut JSContext,
        number_of_channels: u32,
        length: u32,
        sample_rate: Finite<f32>,
    ) -> Fallible<DomRoot<AudioBuffer>> {
        if number_of_channels == 0 ||
            number_of_channels > MAX_CHANNEL_COUNT ||
            length == 0 ||
            *sample_rate <= 0.
        {
            return Err(Error::NotSupported(Some(
                "Invalid number of channels, length or sample rate".into(),
            )));
        }
        Ok(AudioBuffer::new(
            cx,
            self.global().as_window(),
            number_of_channels,
            length,
            *sample_rate,
            None,
        ))
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createbuffersource>
    fn CreateBufferSource(&self, cx: &mut JSContext) -> Fallible<DomRoot<AudioBufferSourceNode>> {
        AudioBufferSourceNode::Constructor(
            cx,
            self.global().as_window(),
            None,
            self,
            &AudioBufferSourceOptions::empty(),
        )
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-decodeaudiodata>
    fn DecodeAudioData(
        &self,
        cx: &mut CurrentRealm,
        audio_data: CustomAutoRooterGuard<ArrayBuffer>,
        decode_success_callback: Option<Option<RootedCallback<DecodeSuccessCallback>>>,
        decode_error_callback: Option<Option<RootedCallback<DecodeErrorCallback>>>,
    ) -> RootedPromise {
        // Step 1. If this's relevant global object's associated Document is NOT fully active,
        // return a promise rejected with "InvalidStateError".
        if !self.global().as_window().Document().is_fully_active() {
            let promise = Promise::new_in_realm(cx);
            promise.reject_error(
                cx,
                Error::InvalidState(Some("Audio context's document is not fully active.".into())),
            );
            return promise;
        }

        // Step 2. Let promise be a new promise.
        let promise = Promise::new_in_realm(cx);

        // flatten the optionally nullable callbacks
        let decode_success_callback = decode_success_callback.flatten();
        let decode_error_callback = decode_error_callback.flatten();

        let audio_data = HeapBufferSource::<ArrayBufferU8>::from_view(cx, audio_data);

        // Step 3. If audio_data is NOT detached, execute the following steps:
        // - Append promise to [[pending promises]].
        // - Detach the audio_data ArrayBuffer. If this operation throws, jump to step 4.1.
        // - Queue a decoding operation to be performed on another thread.
        let audio_data = if !audio_data.is_detached_buffer(cx) {
            audio_data
                .get_typed_array()
                .ok()
                .and_then(|buffer| buffer.to_vec())
                .filter(|_| audio_data.detach_buffer(cx))
        } else {
            None
        };

        if let Some(audio_data) = audio_data {
            let uuid = Uuid::new_v4().simple().to_string();
            let uuid_ = uuid.clone();
            self.decode_resolvers.safe_borrow_mut(cx.no_gc()).insert(
                uuid.clone(),
                DecodeResolver {
                    promise: promise.to_traced(),
                    success_callback: decode_success_callback.map(|callback| callback.to_traced()),
                    error_callback: decode_error_callback.map(|callback| callback.to_traced()),
                },
            );
            let decoded_audio = Arc::new(Mutex::new(Vec::new()));
            let decoded_audio_ = decoded_audio.clone();
            let decoded_audio__ = decoded_audio.clone();
            // servo-media returns an audio channel position along
            // with the AudioDecoderCallback progress callback, which
            // may not be the same as the index of the decoded_audio
            // Vec.
            let channels = Arc::new(Mutex::new(HashMap::new()));
            let this = Trusted::new(self);
            let this_ = this.clone();
            let task_source = self
                .global()
                .task_manager()
                .dom_manipulation_task_source()
                .to_sendable();
            let task_source_clone = task_source.clone();
            let callbacks = AudioDecoderCallbacksBuilder::default()
                .ready(move |channel_count| {
                    decoded_audio
                        .lock()
                        .unwrap()
                        .resize(channel_count as usize, Vec::new());
                })
                .progress(move |buffer, channel_pos_mask| {
                    let mut decoded_audio = decoded_audio_.lock().unwrap();
                    let mut channels = channels.lock().unwrap();
                    let channel = match channels.entry(channel_pos_mask) {
                        Entry::Occupied(entry) => *entry.get(),
                        Entry::Vacant(entry) => {
                            let x = (channel_pos_mask as f32).log2() as usize;
                            *entry.insert(x)
                        },
                    };
                    decoded_audio[channel].extend_from_slice((*buffer).as_ref());
                })
                .eos(move || {
                    let mut decoded_audio = std::mem::take(&mut *decoded_audio__.lock().unwrap());
                    for channel in &mut decoded_audio {
                        channel.shrink_to_fit();
                    }
                    task_source.queue(task!(audio_decode_eos: move |cx| {
                        let this = this.root();
                        let length = if !decoded_audio.is_empty() {
                            decoded_audio[0].len()
                        } else {
                            0
                        };
                        let buffer = AudioBuffer::new_with_channel_data(
                            cx,
                            this.global().as_window(),
                            length as u32,
                            this.sample_rate,
                            decoded_audio,
                        );
                        rooted!(&in(cx) let resolver = this
                            .decode_resolvers
                            .safe_borrow_mut(cx.no_gc())
                            .remove(&uuid_)
                            .expect("resolver should exist"));
                        let promise = resolver.promise.root(cx);

                        if let Some(callback) = &resolver.success_callback {
                            let _ = callback.Call__(cx, &buffer, ExceptionHandling::Report);
                        }
                        promise.resolve_native(cx, &buffer);
                    }));
                })
                .error(move |error| {
                    task_source_clone.queue(task!(audio_decode_eos: move |cx| {
                        let this = this_.root();
                        rooted!(&in(cx) let resolver = this
                            .decode_resolvers
                            .safe_borrow_mut(cx.no_gc())
                            .remove(&uuid)
                            .expect("resolver should exist"));
                        let promise = resolver.promise.root(cx);

                        if let Some(callback) = &resolver.error_callback {
                            let exception = DOMException::new(
                                cx,
                                &this.global(),
                                DOMErrorName::DataCloneError,
                            );
                            let _ =
                                callback.Call__(cx, &exception, ExceptionHandling::Report);
                        }
                        let error = cformat!("Audio decode error {:?}", error);
                        promise.reject_error(cx, Error::Type(error));
                    }));
                })
                .build();
            self.audio_context_impl
                .lock()
                .unwrap()
                .decode_audio_data(audio_data, callbacks);
        } else {
            // Step 4.
            // Else, execute the following error steps:
            // - Let error be a DataCloneError.
            // - Reject promise with error, and remove it from [[pending promises]].
            // - Queue a media element task to invoke errorCallback with error.
            let exception = DOMException::new(cx, &self.global(), DOMErrorName::DataCloneError);
            promise.reject_native(cx, &exception);

            if let Some(callback) = decode_error_callback {
                // Build the Task object using a unique uuid as a key to remove the callback resolver entry.
                // Stash the callback with clone of uuid in the decode_resolvers map.
                // Enqueue the task after the callback is stashed.
                let uuid = Uuid::new_v4().simple().to_string();
                let uuid_ = uuid.clone();
                let this = Trusted::new(self);
                let exception = Trusted::new(&*exception);
                let task = task!(decode_audio_data_detached_buffer: move |cx| {
                    let this = this.root();
                    let exception = exception.root();
                    rooted!(&in(cx) let resolver = this
                        .decode_resolvers
                        .safe_borrow_mut(cx.no_gc())
                        .remove(&uuid)
                        .expect("resolver should exist"));

                    if let Some(callback) = &resolver.error_callback {
                        let _ = callback.Call__(
                            cx,
                            &exception,
                            ExceptionHandling::Report
                        );
                    }
                });
                self.decode_resolvers.safe_borrow_mut(cx.no_gc()).insert(
                    uuid_,
                    DecodeResolver {
                        promise: promise.to_traced(),
                        success_callback: None,
                        error_callback: Some(callback.to_traced()),
                    },
                );
                self.global()
                    .task_manager()
                    .media_element_task_source()
                    .queue(task);
            }
        }

        // Step 5. Return promise.
        promise
    }

    /// <https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createiirfilter>
    fn CreateIIRFilter(
        &self,
        cx: &mut JSContext,
        feedforward: Vec<Finite<f64>>,
        feedback: Vec<Finite<f64>>,
    ) -> Fallible<DomRoot<IIRFilterNode>> {
        let opts = IIRFilterOptions {
            parent: AudioNodeOptions::empty(),
            feedback,
            feedforward,
        };
        IIRFilterNode::Constructor(cx, self.global().as_window(), None, self, &opts)
    }
}

impl Convert<AudioContextOptions> for BaseAudioContextOptions {
    fn convert(self) -> AudioContextOptions {
        match self {
            BaseAudioContextOptions::AudioContext(options) => {
                AudioContextOptions::RealTimeAudioContext(options)
            },
            BaseAudioContextOptions::OfflineAudioContext(options) => {
                AudioContextOptions::OfflineAudioContext(options)
            },
        }
    }
}

impl Convert<AudioContextState> for ProcessingState {
    fn convert(self) -> AudioContextState {
        match self {
            ProcessingState::Suspended => AudioContextState::Suspended,
            ProcessingState::Running => AudioContextState::Running,
            ProcessingState::Closed => AudioContextState::Closed,
        }
    }
}