import { canvas2d, h } from "../lib/html";
import { Cancel } from "../lib/source";
import { tick } from "../lib/tick";

export function TickDebug() {
  const output = h("pre", {});

  const tickSource = tick(30);
  let cancel: Cancel;

  const begin = () => {
    // reset / init
    cancel?.();
    output.innerHTML = "";
    // subscribe to source, stash cancellation func
    cancel = tickSource((tick) => {
      switch (tick[0]) {
        case "physics":
          output.append(`${new Date().toISOString()}: Physics\n`);
          break;
        case "render":
          output.append(
            `${new Date().toISOString()}: Render (dt=${tick[1]})\n`
          );
          break;
      }
    });
  };

  const end = () => cancel?.();

  const start = h("button", { onclick: begin }, "Begin");
  const stop = h("button", { onclick: end }, "Cease");

  return [h("h1", {}, "Tick Event Demo"), start, stop, output, h("hr")];
}

export function OrbitDemo() {
  const [canvas, cx] = canvas2d({
    width: 512,
    height: 512,
  });
  cx.scale(1 / 2, 1 / 2);
  cx.translate(512, 512);

  const G = 8000;
  const PHYSICS_TICKS = 30;
  const masses: {
    x: number;
    y: number;
    vx: number;
    vy: number;
    r: number;
    m: number;
    c: string;
  }[] = [];

  const tickSource = tick(PHYSICS_TICKS);
  let cancel: Cancel;

  const begin = () => {
    // reset / init
    cancel?.();
    masses.length = 0;
    masses.push(
      { x: 0, y: 0, vx: -1, vy: -2, r: 10, m: 1000, c: "yellow" },
      { x: -150, y: 150, vx: 130, vy: 130, r: 9, m: 10, c: "red" },
      { x: -450, y: 0, vx: 0, vy: 120, r: 4, m: 5, c: "#0f8" }
    );
    // subscribe to source, stash cancellation func
    cancel = tickSource((tick) => {
      switch (tick[0]) {
        case "physics":
          // apply velocities
          masses.forEach((mass) => {
            mass.x += mass.vx * (1 / PHYSICS_TICKS);
            mass.y += mass.vy * (1 / PHYSICS_TICKS);
          });
          // apply accelerations
          masses.forEach((mass) => {
            masses.forEach((other) => {
              if (mass != other) {
                const dx = other.x - mass.x;
                const dy = other.y - mass.y;

                const rSquared = dx ** 2 + dy ** 2;
                const f = (G * other.m) / rSquared;
                const d = Math.sqrt(rSquared);
                const fx = (f * dx) / d;
                const fy = (f * dy) / d;

                mass.vx += fx / PHYSICS_TICKS;
                mass.vy += fy / PHYSICS_TICKS;
              }
            });
          });
          break;
        case "render":
          const [, dt] = tick;
          cx.fillStyle = "black";
          cx.fillRect(-512, -512, 1024, 1024);
          masses.forEach(({ x, y, vx, vy, r, c }) => {
            cx.fillStyle = c;
            cx.beginPath();
            cx.arc(x + vx * dt, y + vy * dt, r, 0, Math.PI * 2);
            cx.fill();
          });
          break;
      }
    });
  };

  const end = () => cancel?.();

  const start = h("button", { onclick: begin }, "Begin");
  const stop = h("button", { onclick: end }, "Cease");

  return [h("h1", {}, "Orbit Demo"), h("p", {}, start, stop), canvas, h("hr")];
}