// #17 Portamento. DittyToy 2022.
// The MIT License.
//
// https://dittytoy.net/ditty/220e9dcde7
//
// Forked from "How do I create a mono synth?" by athibaul - https://dittytoy.net/ditty/662d460791
//
// Every time Dittytoy starts a new iteration of a loop, the entire body of the loop is evaluated instantaneously. 
// All play-calls are collected and sorted based on the intervening sleep times and put on a timeline before playback starts.
//
// A side effect of having the body of a loop evaluated in its entirety is that if you assign a value to a variable within
// a loop at different times, it thus has the last assigned value after the evaluation. 
//
// One possible solution to this problem is not to use a separate variable but to create an additional property in the 
// options object. When setting an options property value, it tracks the time of the setter within the loop. The actual 
// assignment of the value is then, like the play calls, put on a timeline and executed later at the appropriate time.
//
// https://dittytoy.net/syntax#portamento
// https://dittytoy.net/syntax#options
//

ditty.bpm = 60;

// To create a mono synth with portamento, we need to glide between notes, so I'm creating
// a "pitch smoother" to do that

class Smoother {
    // We feed values to this object, and it smoothes them out
    constructor(v, dur) {
        this.v = v;
        this.a0 = clamp01(ditty.dt / dur);
    }
    update(target) { // should be called once per sample
        return this.v += this.a0 * (target - this.v);
    }
}

// Melody
const melody = [c4,d4,e4,b3,e4,a3,a4,e4];

loop( () => {
    const note_smoother = new Smoother(c4, 0.1);
    
    // Use the smoothed values as the note number
    const s = sine.play( (tick, options) => note_smoother.update(options.target), { duration: melody.length, target: c4 } );

    melody.forEach( note => { // We now communicate notes via the option object
        s.options.target = note;
        sleep(1);
    });
});