TinyChan

var PI=Math.PI,TAU=PI*2,
    mod=(n,m)=>(n%m+m)%m;

class Delay{
	constructor(maximumDelayInSamples=0){
		this.sampleRate=44100; //Default sample rate
		this.totalSize=Math.max(4,maximumDelayInSamples+1);
		this.bufferData=new Float32Array(this.totalSize);
		this.writePos=0;
		this.readPos=0;
		this.delay=0;
		this.delayInt=0;
		this.delayFrac=0;
		this.v=new Float32Array(this.totalSize);
		this.feedback=0; //Feedback factor
	}
	setDelay(newDelayInSamples){
		const upperLimit=this.getMaximumDelayInSamples();
		if(newDelayInSamples<0||newDelayInSamples>upperLimit)
			throw new Error("Delay out of bounds");
		this.delay=newDelayInSamples;
		this.delayInt=Math.floor(this.delay);
		this.delayFrac=this.delay-this.delayInt;
	}
	getDelay(){
		return this.delay;
	}
	setFeedback(feedback){
		this.feedback=feedback; //Set feedback factor (0 to 1)
	}
	prepare(numChannels,sampleRate){
		this.sampleRate=sampleRate;
		this.bufferData=new Float32Array(numChannels*this.totalSize);
		this.writePos=new Array(numChannels).fill(0);
		this.readPos=new Array(numChannels).fill(0);
		this.v=new Float32Array(numChannels);
		this.reset();
	}
	setMaximumDelayInSamples(maxDelayInSamples){
		this.totalSize=Math.max(4,maxDelayInSamples+1);
		this.bufferData=new Float32Array(this.totalSize);
		this.reset();
	}
	reset(){
		this.writePos.fill(0);
		this.readPos.fill(0);
		this.v.fill(0);
		this.bufferData.fill(0);
	}
	pushSample(channel,sample){
		const index=(this.writePos[channel]+this.totalSize-1)%this.totalSize;
		this.bufferData[index]=sample;
		this.writePos[channel]=index;
	}
	popSample(channel,delayInSamples=-1,updateReadPointer=true){
		if(delayInSamples>=0)
			this.setDelay(delayInSamples);
		const result=this.interpolateSample(channel);
		if(updateReadPointer)
			this.readPos[channel]=(this.readPos[channel]+this.totalSize-1)%this.totalSize;
		return result;
	}
	interpolateSample(channel){
		const index=(this.readPos[channel]+this.delayInt)%this.totalSize,
		      value1=this.bufferData[index],
		      value2=this.bufferData[(index+1)%this.totalSize];
		return value1+this.delayFrac*(value2-value1);
	}
	processSample(channel,inputSample){
		//Get the delayed sample
		const delayedSample=this.popSample(channel);
		//Calculate the output sample with feedback
		const outputSample=inputSample+delayedSample*this.feedback;
		//Push the new sample into the delay line
		this.pushSample(channel,outputSample);
		return outputSample;
	}
	getMaximumDelayInSamples(){return this.totalSize-1;}
}

let d=new Delay(32000);
d.prepare(1,32000); //Prepare the delay line
d.setFeedback(.85); //Set the feedback factor (0 to 1)
//d.setDelay(2000);
return function dsp(time){
	let o=sin(time*2e3*TAU)*(1-mod(time,.5))**40;
	//d.setDelay((.05+(time%.1))*8000);
	d.setDelay(500+(((1+sin(time*20))/2)*100));
	o=d.processSample(0,o);
	return o*.5;
};