// deno run --allow-write mandelbrot.ts
import { createCanvas } from "https://deno.land/x/canvas@v1.4.2/mod.ts";

const WIDTH = 1024*2;
const HEIGHT = 1024*2;
const MAX_ITER = 1000;
const ZOOM = 0.8;
const X_CENTER = -0.75;
const Y_CENTER = 0.0;

// Converts HSV to RGB [0..1] input/output
function hsvToRgb(h: number, s: number, v: number): [number, number, number] {
  let c = v * s;
  let x = c * (1 - Math.abs(((h / 60) % 2) - 1));
  let m = v - c;
  let r = 0, g = 0, b = 0;
  if (0 <= h && h < 60) [r, g, b] = [c, x, 0];
  else if (60 <= h && h < 120) [r, g, b] = [x, c, 0];
  else if (120 <= h && h < 180) [r, g, b] = [0, c, x];
  else if (180 <= h && h < 240) [r, g, b] = [0, x, c];
  else if (240 <= h && h < 300) [r, g, b] = [x, 0, c];
  else if (300 <= h && h < 360) [r, g, b] = [c, 0, x];
  return [
    Math.round((r + m) * 255),
    Math.round((g + m) * 255),
    Math.round((b + m) * 255),
  ];
}

// Learn more at https://docs.deno.com/runtime/manual/examples/module_metadata#concepts
if (import.meta.main) {
  const canvas = createCanvas(WIDTH, HEIGHT);
  const ctx = canvas.getContext("2d");

  /* deno-canvas has broader compatibility with putImageData than node-canvas, so we can use it as below. */
  const imageData = ctx.createImageData(WIDTH, HEIGHT);
  const data = imageData.data;

  const start = new Date();

  for (let y = 0; y < HEIGHT; y++) {
    for (let x = 0; x < WIDTH; x++) {
      const cx = (x - WIDTH / 2) * (4 / WIDTH) * ZOOM + X_CENTER;
      const cy = (y - HEIGHT / 2) * (4 / HEIGHT) * ZOOM + Y_CENTER;
      let zx = 0, zy = 0;
      let iter = 0;
      while (zx * zx + zy * zy < 4 && iter < MAX_ITER) {
        const tmp = zx * zx - zy * zy + cx;
        zy = 2 * zx * zy + cy;
        zx = tmp;
        iter++;
      }
      let pixelIndex = 4 * (y * WIDTH + x);
      if (iter === MAX_ITER) {
        data[pixelIndex + 0] = 0;
        data[pixelIndex + 1] = 0;
        data[pixelIndex + 2] = 0;
        data[pixelIndex + 3] = 255;
      } else {
        let zn = Math.sqrt(zx * zx + zy * zy);
        let nu = Math.log(Math.log(zn)) / Math.log(2);
        let smoothIter = iter + 1 - nu;
        let hue = 360 * smoothIter * smoothIter / MAX_ITER;
        let rgb = hsvToRgb(hue, 1, 1);
        data[pixelIndex + 0] = rgb[0];
        data[pixelIndex + 1] = rgb[1];
        data[pixelIndex + 2] = rgb[2];
        data[pixelIndex + 3] = 255;
      }
    }
  }
  const stop = new Date();
  ctx.putImageData(imageData, 0, 0);

  // Save PNG
  await Deno.writeFile("mandelbrot.png", canvas.toBuffer("image/png"));
  const doneSecs = (stop.getTime()-start.getTime())/1000;
  console.log(`Done! in ${doneSecs} sec`);
}