import {
  setFillColor: FillType,
  fillRect: FillType,
  getCanvasWidth: GetSizeType,
  getCanvasHeight: GetSizeType,
  log: LogType
} from 'env';
type FillType = (i32, i32, i32, i32) => void;
type LogType = (f32) => void;
type GetSizeType = () => i32;
type ParticleType = {
  x: f32,
  y: f32,
  vx: f32,
  vy: f32
};

const memory: Memory<{ initial: 1 }>;
const particleByteSize: i32 = 16;

let total: i32 = 0;
let width: i32 = 0;
let height: i32 = 0;
export function onInit(totalParticles: i32) {
  width = getCanvasWidth();
  height = getCanvasHeight();
  total = totalParticles;

  let particle: ParticleType = 0;
  let i: i32 = 0;

  for (i = 0; i < total; i += 1) {
    particle = i * particleByteSize;
    particle = {
      x: width / 2.0,
      y: height / 2.0,
      vx: ((i * 7 % 200) - 100) / 100.0,
      vy: ((i * 19 % 200) - 100) / 100.0
    };
  }
}

function bounce(particle: ParticleType, min: f32) {
  const maxHeight: f32 = height - min;
  const maxWidth: f32 = width - min;
  // destructuring assignment is WIP
  let y: f32 = particle.y;
  let vy: f32 = particle.vy;
  let x: f32 = particle.x;
  let vx: f32 = particle.vx;

  if (y > maxHeight) {
    y -= y - maxHeight;
    vy = -vy;
  } else if (y < min) {
    y = min + (min - y);
    vy = -vy;
  }

  if (x > maxWidth) {
    x -= x - maxWidth;
    vx = -vx;
  } else if (x < min) {
    x = min + (min - x);
    vx = -vx;
  }

  // Object assign syntax sugar, NOTE: this does not create a new object
  particle = { y, vy, x, vx };
}

let previous: i32 = 0;
export function onAnimationFrame(timestamp: i32): i32 {
  const delta: i32 = previous ? timestamp - previous : 0;
  previous = timestamp;

  setFillColor(64, 64, 64, 255);
  fillRect(0, 0, width, height);

  let particle: ParticleType = 0;

  setFillColor(255, 0, 0, 255);

  let i: i32 = 0;
  for (i = 0; i < total; i += 1) {
    particle = i * particleByteSize;
    particle.vy += 0.001 * delta;
    particle.vx += 0.001 * delta;
    particle.x += particle.vx * delta;
    particle.y += particle.vy * delta;

    bounce(particle, 10.0);

    fillRect((particle.x + 0.5) : i32, (particle.y + 0.5): i32, 10, 10);
  }

  return 42;
}