let sketch = function(p) {
  let bgCol = hexToRgb('#222233');
  let starCol = [hexToRgb('#ffcdff'), hexToRgb('#804442'), hexToRgb('#ffff7d')]

  let starDensity = 0.0005; //0.0005 is safe. Above 0.01 is absurd

  let currentWidth;
  let currentHeight;

  let nbStars;
  let stars;
  let bg;

  let time = 0;


  p.setup = function(){
    p.frameRate(24);
    currentWidth = p.windowWidth;
    currentHeight = p.windowHeight;
    p.createCanvas(currentWidth, currentHeight);

    bgInit();



    // p.noLoop();
  }

  p.draw = function(){
    p.background(bgCol);
    p.image(bg, 0, 0);

    // p.circle(30, time*1.5, 10);



    // for (let i=0; i<nbStars; i++) {
    //   let x = p.random(p.windowWidth);
    //   let y = p.random(p.windowHeight);
    //   let d = 1 + p.random(2);
    //   let c = p.random(starCol);
    //   let a = p.random(230);
    //   c.setAlpha(a);
    //   // console.log(c);
    //
    //   p.stroke(c);
    //   // p.point(x, y);
    //   p.circle(x, y, d);
    // }
    time += 1;
  } //End of draw()

  class Stars {
    //Inspired by https://www.youtube.com/watch?v=NJjEGoqTn1Y
    constructor(nb) {
      this.nb = nb;
      this.x = [];
      this.y = [];
      this.color = [];
      this.size = [];
    }

    make() {
      for (let i = 0; i < this.nb; i++) {
        this.x[i] = p.random(0,p.width);
        this.y[i] = p.random(0,p.height);
        this.color[i] = p.random(starCol);
        this.color[i].setAlpha(p.random(100,230));
        this.size[i] = 1 + p.random(2);
      }
    }

    draw() {
      for (let i = 0; i < this.nb; i++) {
        bg.strokeWeight(this.size[i]);
        bg.stroke(this.color[i]);
        bg.point(this.x[i], this.y[i]);
      }
    }
  }

  p.windowResized = function() {
    //Redraw only if new size if bigger than previously
    let newWidth = p.windowWidth;
    let newHeight = p.windowHeight;
    if (newWidth > currentWidth || newHeight > currentHeight) {
      currentWidth = newWidth;
      currentHeight = newHeight;

      p.resizeCanvas(currentWidth, currentHeight);
      bgInit();
    }

  }

  function bgInit() {
    nbStars = calcNumberOfStars();
    bg = p.createGraphics(p.width, p.height);
    bg.background(bgCol);
    setGradient(0, 0, p.width, p.height, bgCol, starCol[1]);

    stars = new Stars(nbStars);
    stars.make();
    stars.draw();
  }

  function calcNumberOfStars() {
    //Helps to get a consistent number of starts regardless the window size
    if (starDensity > 0.01) {
      console.log('starDensity is too high! going back to the maximum (0.01) in order to prevent too much CPU load when starting the patch');
      starDensity = 0.01;
    }
    let nb = p.round(starDensity * currentWidth * currentHeight)
    console.log('nbStars: ' + nb);
    return nb;
  }

  function hexToRgb(hex) {
      hex = hex.replace('#', '');

      var bigint = parseInt(hex, 16);

      var r = (bigint >> 16) & 255;
      var g = (bigint >> 8) & 255;
      var b = bigint & 255;

      return p.color(r, g, b);
  }
  function setGradient(x, y, w, h, c1, c2) {
    bg.noFill();
      // Top to bottom gradient
    for (let i = y; i <= y + h; i++) {
      let inter = p.pow(p.map(i, y, y + h, 0, 1),6);
      let c = bg.lerpColor(c1, c2, inter);
      bg.stroke(c);
      bg.line(x, i, x + w, i);
    }

  }
};

new p5(sketch, 'bg');