var dittyTime = 0;


var myNotes = [[0, c4], [0, e4], [0, g4], [1, e3], [2, g3], [3.5, c4]];
var loopCount = 4;

synth.def(
    class {
        constructor() {
            this.playingNotes = []
        }
        process() {
            dittyTime += ditty.dt;
            
            let playedNotes = getNotes(dittyTime, myNotes, loopCount);
            this.playingNotes = this.playingNotes.concat(playedNotes);
            let doneNotes = []
            
            let result = 0;
            for (let i in this.playingNotes) {
                let playingNote = this.playingNotes[i];
                let freq = midi_to_hz(playingNote.pitch);
                
                let ampEnv = basicEnv(dittyTime, playingNote.startTime, 0.01, 0.5);
                
                if (ampEnv.done) {
                    doneNotes.push(i)
                    continue;
                }
                
                result += osc(dittyTime, freq) * ampEnv.value * 0.75;
            }
            
            for (let i of doneNotes) this.playingNotes.splice(i, 1);
            
            return result; 
        }
    }, {}
).play(0, { env: one });

function basicEnv(time, startTime, attack, release) {
    let noteTime = time - startTime;
    if (noteTime > attack + release) return { "done": true, "value" : 0 }
    return { "done": false, "value" : noteTime < attack ? noteTime / attack : 1 - Math.min((noteTime - attack) / release, 1) }
}

function osc(time, freq) {
    return Math.sin(time * freq * Math.PI * 2)
}

// -- utilities -- 

var prevSeqTime = -1;
function getNotes(time, notes, loopCount) {
    let noteNum = null;
    let seqTime = (time + ditty.dt) % loopCount;
    let playedNotes = [];
    notes.forEach(note => {
        if (note[0] > prevSeqTime && note[0] <= seqTime) {
            playedNotes.push({ "startTime" : time, "pitch" : note[1] });
        }
    });
    prevSeqTime = prevSeqTime > seqTime ? -1 : seqTime;    
    return playedNotes;
}