// one of the reference
// https://p5js.org/reference/#/p5.Envelope/triggerAttack
// This adds slider to control sound and experiments with
// envelope.
let attackLevel = 1.0;
let releaseLevel = 0;
let attackTime = 0.001;
let decayTime = 0.3;
let releaseTime = 0.5;
let osc, envelope;
let display = " ";
let vol;

function setup() { 
  var canvas = createCanvas(200, 200);
  canvas.parent("sketch-holder");
  // set up volume slider
  para = createP("Volume");
  para.parent("sketch-holder");
  volSlider = createSlider(0, 100, 40);
  volSlider.parent("sketch-holder");
  vol = volSlider.value()/100;

  // Instantiate the envelope
  envelope = new p5.Env();
  envelope.setADSR(attackTime, decayTime, vol, releaseTime); 
  envelope.setRange(attackLevel, releaseLevel);
  
  // set up oscillator 
  osc = new p5.Oscillator('Triangle');
  osc.start();
  osc.amp(envelope);
   
  // declare variables
  midi = 0; 
} // setup

function draw() {
  background(200 - midi, midi, 3 * midi);
  vol = volSlider.value()/100;
  


  if (midi > 0) {
  text("Note: " +display + "\nMidi value: " + midi + "\nFrequency: "
      + (round(1000* midiToFreq(midi))/1000) + "Hz", 
       30, height/2 - 25 );
  } else {
    text("Type a note key:\nc, C, d, D, e, f, F, g, G, a, A, b"
        + "\nor `, 1, 2, ...9, 0, -, =", 20, height/2 - 25);
  }
  text("Vol: " + vol, 20, 160);
}  // draw

// when a key is typed, interpret key, determine midi, and change frequency
function keyTyped() {
  midi = interpretCh(key);   // midi value associated with key pressed
  osc.freq(midiToFreq(midi));
  envelope.setADSR(attackTime, decayTime, vol, releaseTime); 
  envelope.triggerAttack();
}

// when a key is released, turn of the key and clear the display
function keyReleased() {
  midi = 0;
  envelope.triggerRelease();
  interpretCh("");  ////
  return false;
}

function interpretCh(aCh) {
  // display is global
  
  let midi;
  switch(aCh) {
    case 'c': case '`': display = "Middle C"; midi = 60; break;
    case 'C': case '1': display = "C#"; midi = 61; break;
    case 'd': case '2': display = "D"; midi = 62; break;
    case 'D': case '3': display = "D#"; midi = 63; break;
    case 'e': case '4': display = "E"; midi = 64; break;
    case 'f': case '5': display = "F"; midi = 65; break;
    case 'F': case '6': display = "F#"; midi = 66; break;
    case 'g': case '7': display = "G"; midi = 67; break;
    case 'G': case '8': display = "G#"; midi = 68; break;
    case 'a': case '9': display = "A"; midi = 69; break;
    case 'A': case '0': display = "A#"; midi = 70; break;
    case 'b': case '-': display = "B"; midi = 71; break;
    case '=': display = "C above middle C"; midi = 72; break;
    default:  display = "rest"; midi = 0;
  }
  return midi;
}  // interpretCh