use std::f32::consts::PI;
use std::sync::atomic::{AtomicU8, Ordering};
use std::sync::Arc;

use crate::context::{AudioContextRegistration, AudioParamId, BaseAudioContext};
use crate::param::{AudioParam, AudioParamDescriptor};
use crate::render::{AudioParamValues, AudioProcessor, AudioRenderQuantum, RenderScope};
use crate::{AtomicF64, RENDER_QUANTUM_SIZE};

use super::{
    AudioNode, ChannelConfig, ChannelConfigOptions, ChannelCountMode, ChannelInterpretation,
};

use crossbeam_channel::{Receiver, Sender};
use float_eq::float_eq;
use hrtf::{HrirSphere, HrtfContext, HrtfProcessor, Vec3};

/// Spatialization algorithm used to position the audio in 3D space
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum PanningModelType {
    EqualPower,
    HRTF,
}

impl From<u8> for PanningModelType {
    fn from(i: u8) -> Self {
        match i {
            0 => PanningModelType::EqualPower,
            1 => PanningModelType::HRTF,
            _ => unreachable!(),
        }
    }
}

impl Default for PanningModelType {
    fn default() -> Self {
        PanningModelType::EqualPower
    }
}

/// Algorithm to reduce the volume of an audio source as it moves away from the listener
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum DistanceModelType {
    Linear,
    Inverse,
    Exponential,
}

impl From<u8> for DistanceModelType {
    fn from(i: u8) -> Self {
        match i {
            0 => DistanceModelType::Linear,
            1 => DistanceModelType::Inverse,
            2 => DistanceModelType::Exponential,
            _ => unreachable!(),
        }
    }
}

impl Default for DistanceModelType {
    fn default() -> Self {
        DistanceModelType::Inverse
    }
}

/// Options for constructing a [`PannerNode`]
// dictionary PannerOptions : AudioNodeOptions {
//   PanningModelType panningModel = "equalpower";
//   DistanceModelType distanceModel = "inverse";
//   float positionX = 0;
//   float positionY = 0;
//   float positionZ = 0;
//   float orientationX = 1;
//   float orientationY = 0;
//   float orientationZ = 0;
//   double refDistance = 1;
//   double maxDistance = 10000;
//   double rolloffFactor = 1;
//   double coneInnerAngle = 360;
//   double coneOuterAngle = 360;
//   double coneOuterGain = 0;
// };
#[derive(Clone, Debug)]
pub struct PannerOptions {
    pub panning_model: PanningModelType,
    pub distance_model: DistanceModelType,
    pub position_x: f32,
    pub position_y: f32,
    pub position_z: f32,
    pub orientation_x: f32,
    pub orientation_y: f32,
    pub orientation_z: f32,
    pub ref_distance: f64,
    pub max_distance: f64,
    pub rolloff_factor: f64,
    pub cone_inner_angle: f64,
    pub cone_outer_angle: f64,
    pub cone_outer_gain: f64,
    pub channel_config: ChannelConfigOptions,
}

impl Default for PannerOptions {
    fn default() -> Self {
        PannerOptions {
            panning_model: PanningModelType::default(),
            distance_model: DistanceModelType::default(),
            position_x: 0.,
            position_y: 0.,
            position_z: 0.,
            orientation_x: 1.,
            orientation_y: 0.,
            orientation_z: 0.,
            ref_distance: 1.,
            max_distance: 10000.,
            rolloff_factor: 1.,
            cone_inner_angle: 360.,
            cone_outer_angle: 360.,
            cone_outer_gain: 0.,
            channel_config: ChannelConfigOptions {
                count: 2,
                count_mode: ChannelCountMode::ClampedMax,
                interpretation: ChannelInterpretation::Speakers,
            },
        }
    }
}

/// Assert that the channel count is valid for the PannerNode
/// see <https://webaudio.github.io/web-audio-api/#audionode-channelcount-constraints>
///
/// # Panics
///
/// This function panics if given count is greater than 2
///
#[track_caller]
#[inline(always)]
fn assert_valid_channel_count(count: usize) {
    if count > 2 {
        panic!("NotSupportedError: PannerNode channel count cannot be greater than two");
    }
}

/// Assert that the channel count is valid for the PannerNode
/// see <https://webaudio.github.io/web-audio-api/#audionode-channelcountmode-constraints>
///
/// # Panics
///
/// This function panics if given count mode is [`ChannelCountMode::Max`]
///
#[track_caller]
#[inline(always)]
fn assert_valid_channel_count_mode(mode: ChannelCountMode) {
    if mode == ChannelCountMode::Max {
        panic!("NotSupportedError: PannerNode channel count mode cannot be set to max");
    }
}

/// Internal state of the HRTF renderer
struct HrtfState {
    len: usize,
    processor: HrtfProcessor,
    output_interleaved: Vec<(f32, f32)>,
    prev_sample_vector: Vec3,
    prev_left_samples: Vec<f32>,
    prev_right_samples: Vec<f32>,
    prev_distance_gain: f32,
}

impl HrtfState {
    fn new(hrir_sphere: HrirSphere) -> Self {
        let len = hrir_sphere.len();

        let interpolation_steps = 1;
        let samples_per_step = RENDER_QUANTUM_SIZE / interpolation_steps;

        let processor = HrtfProcessor::new(hrir_sphere, interpolation_steps, samples_per_step);

        Self {
            len,
            processor,
            output_interleaved: vec![(0., 0.); RENDER_QUANTUM_SIZE],
            prev_sample_vector: Vec3::new(0., 0., 1.),
            prev_left_samples: vec![],  // will resize accordingly
            prev_right_samples: vec![], // will resize accordingly
            prev_distance_gain: 0.,
        }
    }

    fn process(
        &mut self,
        source: &[f32],
        new_distance_gain: f32,
        projected_source: [f32; 3],
    ) -> &[(f32, f32)] {
        // reset state of output buffer
        self.output_interleaved.fill((0., 0.));

        let new_sample_vector = Vec3 {
            x: projected_source[0],
            z: projected_source[1],
            y: projected_source[2],
        };

        let context = HrtfContext {
            source,
            output: &mut self.output_interleaved,
            new_sample_vector,
            prev_sample_vector: self.prev_sample_vector,
            prev_left_samples: &mut self.prev_left_samples,
            prev_right_samples: &mut self.prev_right_samples,
            new_distance_gain,
            prev_distance_gain: self.prev_distance_gain,
        };

        self.processor.process_samples(context);

        self.prev_sample_vector = new_sample_vector;
        self.prev_distance_gain = new_distance_gain;

        &self.output_interleaved
    }

    fn tail_time_samples(&self) -> usize {
        self.len
    }
}

/// `PannerNode` positions / spatializes an incoming audio stream in three-dimensional space.
///
/// - MDN documentation: <https://developer.mozilla.org/en-US/docs/Web/API/PannerNode>
/// - specification: <https://www.w3.org/TR/webaudio/#pannernode> and
/// <https://www.w3.org/TR/webaudio/#Spatialization>
/// - see also:
/// [`BaseAudioContext::create_panner`](crate::context::BaseAudioContext::create_panner)
///
/// # Usage
/// ```no_run
/// use web_audio_api::context::{BaseAudioContext, AudioContext};
/// use web_audio_api::node::AudioNode;
/// use web_audio_api::node::AudioScheduledSourceNode;
///
/// // Setup a new audio context
/// let context = AudioContext::default();
///
/// // Create a friendly tone
/// let tone = context.create_oscillator();
/// tone.frequency().set_value_at_time(300.0f32, 0.);
/// tone.start();
///
/// // Connect tone > panner node > destination node
/// let panner = context.create_panner();
/// tone.connect(&panner);
/// panner.connect(&context.destination());
///
/// // The panner node is 1 unit in front of listener
/// panner.position_z().set_value_at_time(1., 0.);
///
/// // And sweeps 10 units left to right, every second
/// let moving = context.create_oscillator();
/// moving.start();
/// moving.frequency().set_value_at_time(1., 0.);
/// let gain = context.create_gain();
/// gain.gain().set_value_at_time(10., 0.);
/// moving.connect(&gain);
/// gain.connect(panner.position_x());
///
/// // enjoy listening
/// std::thread::sleep(std::time::Duration::from_secs(4));
/// ```
///
/// # Examples
///
/// - `cargo run --release --example spatial`
/// - `cargo run --release --example panner_cone`
pub struct PannerNode {
    registration: AudioContextRegistration,
    channel_config: ChannelConfig,
    position_x: AudioParam,
    position_y: AudioParam,
    position_z: AudioParam,
    orientation_x: AudioParam,
    orientation_y: AudioParam,
    orientation_z: AudioParam,
    cone_inner_angle: Arc<AtomicF64>,
    cone_outer_angle: Arc<AtomicF64>,
    cone_outer_gain: Arc<AtomicF64>,
    distance_model: Arc<AtomicU8>,
    ref_distance: Arc<AtomicF64>,
    max_distance: Arc<AtomicF64>,
    rolloff_factor: Arc<AtomicF64>,
    panning_model: AtomicU8,
    /// HRTF message bus to the renderer
    sender: Sender<Option<HrtfState>>,
}

impl AudioNode for PannerNode {
    fn registration(&self) -> &AudioContextRegistration {
        &self.registration
    }

    fn channel_config(&self) -> &ChannelConfig {
        &self.channel_config
    }

    fn number_of_inputs(&self) -> usize {
        1
    }

    fn number_of_outputs(&self) -> usize {
        1
    }

    // same limitations as for the StereoPannerNode
    // see: https://webaudio.github.io/web-audio-api/#panner-channel-limitations
    fn set_channel_count(&self, count: usize) {
        assert_valid_channel_count(count);
        self.channel_config.set_count(count);
    }

    fn set_channel_count_mode(&self, mode: ChannelCountMode) {
        assert_valid_channel_count_mode(mode);
        self.channel_config.set_count_mode(mode);
    }
}

impl PannerNode {
    /// returns a `PannerNode` instance
    ///
    /// # Arguments
    ///
    /// * `context` - audio context in which the audio node will live.
    /// * `options` - stereo panner options
    ///
    /// # Panics
    ///
    /// Will panic if:
    ///
    /// * `options.channel_config.count` is greater than 2
    /// * `options.channel_config.mode` is `ChannelCountMode::Max`
    ///
    /// Can panic when loading HRIR-sphere
    #[allow(clippy::missing_panics_doc)]
    pub fn new<C: BaseAudioContext>(context: &C, options: PannerOptions) -> Self {
        let node = context.register(move |registration| {
            use crate::spatial::PARAM_OPTS;
            // position params
            let (position_x, render_px) = context.create_audio_param(PARAM_OPTS, &registration);
            let (position_y, render_py) = context.create_audio_param(PARAM_OPTS, &registration);
            let (position_z, render_pz) = context.create_audio_param(PARAM_OPTS, &registration);
            position_x.set_value_at_time(options.position_x, 0.);
            position_y.set_value_at_time(options.position_y, 0.);
            position_z.set_value_at_time(options.position_z, 0.);

            // orientation params
            let orientation_x_opts = AudioParamDescriptor {
                default_value: 1.0,
                ..PARAM_OPTS
            };
            let (orientation_x, render_ox) =
                context.create_audio_param(orientation_x_opts, &registration);
            let (orientation_y, render_oy) = context.create_audio_param(PARAM_OPTS, &registration);
            let (orientation_z, render_oz) = context.create_audio_param(PARAM_OPTS, &registration);
            orientation_x.set_value_at_time(options.orientation_x, 0.);
            orientation_y.set_value_at_time(options.orientation_y, 0.);
            orientation_z.set_value_at_time(options.orientation_z, 0.);

            // distance attributes
            let distance_model = Arc::new(AtomicU8::new(options.distance_model as u8));
            let ref_distance = Arc::new(AtomicF64::new(options.ref_distance));
            let max_distance = Arc::new(AtomicF64::new(options.max_distance));
            let rolloff_factor = Arc::new(AtomicF64::new(options.rolloff_factor));

            // cone attributes
            let cone_inner_angle = Arc::new(AtomicF64::new(options.cone_inner_angle));
            let cone_outer_angle = Arc::new(AtomicF64::new(options.cone_outer_angle));
            let cone_outer_gain = Arc::new(AtomicF64::new(options.cone_outer_gain));

            // Channel to send a HRTF processor to the renderer.  A capacity of 1 suffices, it will
            // simply block the control thread when used concurrently
            let (sender, receiver) = crossbeam_channel::bounded(1);

            let render = PannerRenderer {
                position_x: render_px,
                position_y: render_py,
                position_z: render_pz,
                orientation_x: render_ox,
                orientation_y: render_oy,
                orientation_z: render_oz,
                distance_model: distance_model.clone(),
                ref_distance: ref_distance.clone(),
                max_distance: max_distance.clone(),
                rolloff_factor: rolloff_factor.clone(),
                cone_inner_angle: cone_inner_angle.clone(),
                cone_outer_angle: cone_outer_angle.clone(),
                cone_outer_gain: cone_outer_gain.clone(),
                hrtf_state: None,
                receiver,
                tail_time_counter: 0,
            };

            let node = PannerNode {
                registration,
                channel_config: ChannelConfigOptions {
                    count: 2,
                    count_mode: ChannelCountMode::ClampedMax,
                    interpretation: ChannelInterpretation::Speakers,
                }
                .into(),
                position_x,
                position_y,
                position_z,
                orientation_x,
                orientation_y,
                orientation_z,
                distance_model,
                ref_distance,
                max_distance,
                rolloff_factor,
                cone_inner_angle,
                cone_outer_angle,
                cone_outer_gain,
                sender,
                panning_model: AtomicU8::new(0),
            };

            node.set_panning_model(options.panning_model);

            // instruct to BaseContext to add the AudioListener if it has not already
            context.base().ensure_audio_listener_present();

            (node, Box::new(render))
        });

        // after the node is registered, connect the AudioListener
        context
            .base()
            .connect_listener_to_panner(node.registration().id());

        node
    }

    pub fn position_x(&self) -> &AudioParam {
        &self.position_x
    }

    pub fn position_y(&self) -> &AudioParam {
        &self.position_y
    }

    pub fn position_z(&self) -> &AudioParam {
        &self.position_z
    }

    pub fn orientation_x(&self) -> &AudioParam {
        &self.orientation_x
    }

    pub fn orientation_y(&self) -> &AudioParam {
        &self.orientation_y
    }

    pub fn orientation_z(&self) -> &AudioParam {
        &self.orientation_z
    }

    pub fn distance_model(&self) -> DistanceModelType {
        self.distance_model.load(Ordering::SeqCst).into()
    }

    pub fn set_distance_model(&self, value: DistanceModelType) {
        self.distance_model.store(value as u8, Ordering::SeqCst);
    }

    pub fn ref_distance(&self) -> f64 {
        self.ref_distance.load()
    }

    pub fn set_ref_distance(&self, value: f64) {
        self.ref_distance.store(value);
    }

    pub fn max_distance(&self) -> f64 {
        self.max_distance.load()
    }

    pub fn set_max_distance(&self, value: f64) {
        self.max_distance.store(value);
    }

    pub fn rolloff_factor(&self) -> f64 {
        self.rolloff_factor.load()
    }

    pub fn set_rolloff_factor(&self, value: f64) {
        self.rolloff_factor.store(value);
    }

    pub fn cone_inner_angle(&self) -> f64 {
        self.cone_inner_angle.load()
    }

    pub fn set_cone_inner_angle(&self, value: f64) {
        self.cone_inner_angle.store(value);
    }

    pub fn cone_outer_angle(&self) -> f64 {
        self.cone_outer_angle.load()
    }

    pub fn set_cone_outer_angle(&self, value: f64) {
        self.cone_outer_angle.store(value);
    }

    pub fn cone_outer_gain(&self) -> f64 {
        self.cone_outer_gain.load()
    }

    pub fn set_cone_outer_gain(&self, value: f64) {
        self.cone_outer_gain.store(value);
    }

    pub fn panning_model(&self) -> PanningModelType {
        self.panning_model.load(Ordering::SeqCst).into()
    }

    // can panic when loading HRIR-sphere
    #[allow(clippy::missing_panics_doc)]
    pub fn set_panning_model(&self, value: PanningModelType) {
        let hrtf_option = match value {
            PanningModelType::EqualPower => None,
            PanningModelType::HRTF => {
                let resource = include_bytes!("../../resources/IRC_1003_C.bin");
                let sample_rate = self.context().sample_rate() as u32;
                let hrir_sphere = HrirSphere::new(&resource[..], sample_rate).unwrap();
                Some(HrtfState::new(hrir_sphere))
            }
        };

        let _ = self.sender.send(hrtf_option); // can fail when render thread shut down
        self.panning_model.store(value as u8, Ordering::SeqCst);
    }
}

#[derive(Copy, Clone)]
struct SpatialParams {
    dist_gain: f32,
    cone_gain: f32,
    azimuth: f32,
    elevation: f32,
}

struct PannerRenderer {
    position_x: AudioParamId,
    position_y: AudioParamId,
    position_z: AudioParamId,
    orientation_x: AudioParamId,
    orientation_y: AudioParamId,
    orientation_z: AudioParamId,
    distance_model: Arc<AtomicU8>,
    ref_distance: Arc<AtomicF64>,
    max_distance: Arc<AtomicF64>,
    rolloff_factor: Arc<AtomicF64>,
    cone_inner_angle: Arc<AtomicF64>,
    cone_outer_angle: Arc<AtomicF64>,
    cone_outer_gain: Arc<AtomicF64>,
    receiver: Receiver<Option<HrtfState>>,
    hrtf_state: Option<HrtfState>,
    tail_time_counter: usize,
}

impl AudioProcessor for PannerRenderer {
    fn process(
        &mut self,
        inputs: &[AudioRenderQuantum],
        outputs: &mut [AudioRenderQuantum],
        params: AudioParamValues,
        _scope: &RenderScope,
    ) -> bool {
        // single input/output node
        let input = &inputs[0];
        let output = &mut outputs[0];

        // pass through input
        *output = input.clone();

        // only handle mono for now (todo issue #44)
        output.mix(1, ChannelInterpretation::Speakers);

        // early exit for silence
        if input.is_silent() {
            // HRTF panner has tail time equal to the max length of the impulse response buffers
            // (12 ms)
            let tail_time = match &self.hrtf_state {
                None => false,
                Some(hrtf_state) => hrtf_state.tail_time_samples() > self.tail_time_counter,
            };
            if !tail_time {
                return false;
            }
            self.tail_time_counter += RENDER_QUANTUM_SIZE;
        }

        // convert mono to identical stereo
        output.mix(2, ChannelInterpretation::Speakers);

        // handle changes in panning_model_type mandated from control thread
        if let Ok(hrtf_state) = self.receiver.try_recv() {
            self.hrtf_state = hrtf_state;
        }
        // for borrow reasons, take the hrtf_state out of self
        let mut hrtf_state = self.hrtf_state.take();

        // source parameters (Panner)
        let source_position_x = params.get(&self.position_x);
        let source_position_y = params.get(&self.position_y);
        let source_position_z = params.get(&self.position_z);
        let source_orientation_x = params.get(&self.orientation_x);
        let source_orientation_y = params.get(&self.orientation_y);
        let source_orientation_z = params.get(&self.orientation_z);

        // listener parameters (AudioListener)
        let [listener_position_x, listener_position_y, listener_position_z, listener_forward_x, listener_forward_y, listener_forward_z, listener_up_x, listener_up_y, listener_up_z] =
            params.listener_params();

        // build up the a-rate iterator for spatial variables
        let mut a_rate_params = source_position_x
            .iter()
            .cycle()
            .zip(source_position_y.iter().cycle())
            .zip(source_position_z.iter().cycle())
            .zip(source_orientation_x.iter().cycle())
            .zip(source_orientation_y.iter().cycle())
            .zip(source_orientation_z.iter().cycle())
            .zip(listener_position_x.iter().cycle())
            .zip(listener_position_y.iter().cycle())
            .zip(listener_position_z.iter().cycle())
            .zip(listener_forward_x.iter().cycle())
            .zip(listener_forward_y.iter().cycle())
            .zip(listener_forward_z.iter().cycle())
            .zip(listener_up_x.iter().cycle())
            .zip(listener_up_y.iter().cycle())
            .zip(listener_up_z.iter().cycle())
            .map(|tuple| {
                // unpack giant tuple
                let ((((((sp_so_lp, lfx), lfy), lfz), lux), luy), luz) = tuple;
                let (((sp_so, lpx), lpy), lpz) = sp_so_lp;
                let (((sp, sox), soy), soz) = sp_so;
                let ((spx, spy), spz) = sp;

                // define base vectors in 3D
                let source_position = [*spx, *spy, *spz];
                let source_orientation = [*sox, *soy, *soz];
                let listener_position = [*lpx, *lpy, *lpz];
                let listener_forward = [*lfx, *lfy, *lfz];
                let listener_up = [*lux, *luy, *luz];

                // determine distance and cone gain
                let dist_gain = self.dist_gain(source_position, listener_position);
                let cone_gain =
                    self.cone_gain(source_position, source_orientation, listener_position);

                // azimuth and elevation of the panner in frame of reference of the listener
                let (azimuth, elevation) = crate::spatial::azimuth_and_elevation(
                    source_position,
                    listener_position,
                    listener_forward,
                    listener_up,
                );

                SpatialParams {
                    dist_gain,
                    cone_gain,
                    azimuth,
                    elevation,
                }
            });

        if let Some(hrtf_state) = &mut hrtf_state {
            // HRTF panning - always k-rate so take a single value from the a-rate iter
            let SpatialParams {
                dist_gain,
                cone_gain,
                azimuth,
                elevation,
            } = a_rate_params.next().unwrap();
            let new_distance_gain = cone_gain * dist_gain;

            // convert az/el to carthesian coordinates to determine unit direction
            let az_rad = azimuth * PI / 180.;
            let el_rad = elevation * PI / 180.;
            let x = az_rad.sin() * el_rad.cos();
            let z = az_rad.cos() * el_rad.cos();
            let y = el_rad.sin();
            let mut projected_source = [x, y, z];

            if float_eq!(&projected_source[..], &[0.; 3][..], abs_all <= 1E-6) {
                projected_source = [0., 0., 1.];
            }

            let output_interleaved =
                hrtf_state.process(output.channel_data(0), new_distance_gain, projected_source);

            let [left, right] = output.stereo_mut();
            output_interleaved
                .iter()
                .zip(&mut left[..])
                .zip(&mut right[..])
                .for_each(|((p, l), r)| {
                    *l = p.0;
                    *r = p.1;
                });
        } else {
            // EqualPower panning
            let [left, right] = output.stereo_mut();

            // Closure to apply gain per stereo channel
            let apply_stereo_gain =
                |((spatial_params, l), r): ((SpatialParams, &mut f32), &mut f32)| {
                    let SpatialParams {
                        dist_gain,
                        cone_gain,
                        azimuth,
                        ..
                    } = spatial_params;

                    // Determine left/right ear gain. Clamp azimuth to range of [-180, 180].
                    let mut azimuth = azimuth.clamp(-180., 180.);

                    // Then wrap to range [-90, 90].
                    if azimuth < -90. {
                        azimuth = -180. - azimuth;
                    } else if azimuth > 90. {
                        azimuth = 180. - azimuth;
                    }

                    // x is the horizontal plane orientation of the sound
                    let x = (azimuth + 90.) / 180.;
                    let gain_l = (x * PI / 2.).cos();
                    let gain_r = (x * PI / 2.).sin();

                    // multiply signal with gain per ear
                    *l *= gain_l * dist_gain * cone_gain;
                    *r *= gain_r * dist_gain * cone_gain;
                };

            // Optimize for static Panner & Listener
            let single_valued = listener_position_x.len() == 1
                && listener_position_y.len() == 1
                && listener_position_z.len() == 1
                && listener_forward_x.len() == 1
                && listener_forward_y.len() == 1
                && listener_forward_z.len() == 1
                && listener_up_x.len() == 1
                && listener_up_y.len() == 1
                && listener_up_z.len() == 1;
            if single_valued {
                std::iter::repeat(a_rate_params.next().unwrap())
                    .zip(&mut left[..])
                    .zip(&mut right[..])
                    .for_each(apply_stereo_gain);
            } else {
                a_rate_params
                    .zip(&mut left[..])
                    .zip(&mut right[..])
                    .for_each(apply_stereo_gain);
            }
        }

        // put the hrtf_state back into self (borrow reasons)
        self.hrtf_state = hrtf_state;

        // tail time only for HRTF panning
        self.hrtf_state.is_some()
    }
}

impl PannerRenderer {
    fn cone_gain(
        &self,
        source_position: [f32; 3],
        source_orientation: [f32; 3],
        listener_position: [f32; 3],
    ) -> f32 {
        let abs_inner_angle = self.cone_inner_angle.load().abs() as f32 / 2.;
        let abs_outer_angle = self.cone_outer_angle.load().abs() as f32 / 2.;
        if abs_inner_angle >= 180. && abs_outer_angle >= 180. {
            1. // no cone specified
        } else {
            let cone_outer_gain = self.cone_outer_gain.load() as f32;

            let abs_angle =
                crate::spatial::angle(source_position, source_orientation, listener_position);

            if abs_angle < abs_inner_angle {
                1. // No attenuation
            } else if abs_angle >= abs_outer_angle {
                cone_outer_gain // Max attenuation
            } else {
                // Between inner and outer cones: inner -> outer, x goes from 0 -> 1
                let x = (abs_angle - abs_inner_angle) / (abs_outer_angle - abs_inner_angle);
                (1. - x) + cone_outer_gain * x
            }
        }
    }

    fn dist_gain(&self, source_position: [f32; 3], listener_position: [f32; 3]) -> f32 {
        let distance_model = self.distance_model.load(Ordering::SeqCst).into();
        let ref_distance = self.ref_distance.load();
        let rolloff_factor = self.rolloff_factor.load();
        let distance = crate::spatial::distance(source_position, listener_position) as f64;

        let dist_gain = match distance_model {
            DistanceModelType::Linear => {
                let max_distance = self.max_distance.load();
                let d2ref = ref_distance.min(max_distance);
                let d2max = ref_distance.max(max_distance);
                let d_clamped = distance.clamp(d2ref, d2max);
                1. - rolloff_factor * (d_clamped - d2ref) / (d2max - d2ref)
            }
            DistanceModelType::Inverse => {
                if distance > 0. {
                    ref_distance
                        / (ref_distance
                            + rolloff_factor * (ref_distance.max(distance) - ref_distance))
                } else {
                    1.
                }
            }
            DistanceModelType::Exponential => {
                (distance.max(ref_distance) / ref_distance).powf(-rolloff_factor)
            }
        };
        dist_gain as f32
    }
}

#[cfg(test)]
mod tests {
    use float_eq::{assert_float_eq, assert_float_ne};

    use crate::context::{BaseAudioContext, OfflineAudioContext};
    use crate::node::{AudioBufferSourceNode, AudioBufferSourceOptions, AudioScheduledSourceNode};
    use crate::AudioBuffer;

    use super::*;

    #[test]
    fn test_equal_power() {
        let sample_rate = 44100.;
        let length = RENDER_QUANTUM_SIZE * 4;
        let context = OfflineAudioContext::new(2, length, sample_rate);

        // 128 input samples of value 1.
        let input = AudioBuffer::from(vec![vec![1.; RENDER_QUANTUM_SIZE]], sample_rate);
        let src = AudioBufferSourceNode::new(&context, AudioBufferSourceOptions::default());
        src.set_buffer(input);
        src.start();

        let options = PannerOptions {
            panning_model: PanningModelType::EqualPower,
            ..PannerOptions::default()
        };
        let panner = PannerNode::new(&context, options);
        assert_eq!(panner.panning_model(), PanningModelType::EqualPower);
        panner.position_x().set_value(1.); // sound comes from the right

        src.connect(&panner);
        panner.connect(&context.destination());

        let output = context.start_rendering_sync();
        let original = vec![1.; RENDER_QUANTUM_SIZE];
        let zero = vec![0.; RENDER_QUANTUM_SIZE];

        // assert first quantum fully panned to the right
        assert_float_eq!(
            output.get_channel_data(0)[..128],
            &zero[..],
            abs_all <= 1E-6
        );
        assert_float_eq!(
            output.get_channel_data(1)[..128],
            &original[..],
            abs_all <= 1E-6
        );

        // assert no tail-time
        assert_float_eq!(
            output.get_channel_data(0)[128..256],
            &zero[..],
            abs_all <= 1E-6
        );
        assert_float_eq!(
            output.get_channel_data(1)[128..256],
            &zero[..],
            abs_all <= 1E-6
        );
    }

    #[test]
    fn test_hrtf() {
        let sample_rate = 44100.;
        let length = RENDER_QUANTUM_SIZE * 4;
        let context = OfflineAudioContext::new(2, length, sample_rate);

        // 128 input samples of value 1.
        let input = AudioBuffer::from(vec![vec![1.; RENDER_QUANTUM_SIZE]], sample_rate);
        let src = AudioBufferSourceNode::new(&context, AudioBufferSourceOptions::default());
        src.set_buffer(input);
        src.start();

        let options = PannerOptions {
            panning_model: PanningModelType::HRTF,
            ..PannerOptions::default()
        };
        let panner = PannerNode::new(&context, options);
        assert_eq!(panner.panning_model(), PanningModelType::HRTF);
        panner.position_x().set_value(1.); // sound comes from the right

        src.connect(&panner);
        panner.connect(&context.destination());

        let output = context.start_rendering_sync();
        let original = vec![1.; RENDER_QUANTUM_SIZE];

        // assert first quantum not equal to input buffer (both left and right)
        assert_float_ne!(
            output.get_channel_data(0)[..128],
            &original[..],
            abs_all <= 1E-6
        );
        assert_float_ne!(
            output.get_channel_data(1)[..128],
            &original[..],
            abs_all <= 1E-6
        );

        // assert some samples non-zero in the tail time
        let left = output.channel_data(0).as_slice();
        assert!(left[128..256].iter().any(|v| *v >= 1E-6));

        let right = output.channel_data(1).as_slice();
        assert!(right[128..256].iter().any(|v| *v >= 1E-6));
    }
}