import * as Color from './color.js';

export const WIDTH = 1000;
export const HEIGHT = 673;


export type Layer = 'static' | 'eyeshine' | Color.Layer;

// in compositing order
export const allLayers: Layer[] =
  ['static', 'outer', 'spines', 'stripes', 'cuffs', 'fins1', 'fins2', 'fins3',
   'belly1', 'belly2', 'masks', 'claws', 'vitiligo1', 'vitiligo2', 'vitiligo3',
   'vitiligo4', 'eyes', 'eyeshine', 'lines'];

export function makeLayerInfo<A>(f: (l: Layer) => A): Record<Layer, A> {
  return Object.fromEntries(allLayers.map(l => [l, f(l)])) as Record<Layer, A>;
}

export type Position = [x: number, y: number];
export type Positions = Record<Layer, Position>;

export async function loadPos(side: SideName): Promise<Positions> {
  let req = new Request(`./${side}/pos.json`);
  return fetch(req).then(resp => resp.json());
}

export type LayerInfo1 = {data: ImageData, pos: Position};

export type LayerInfo = {
  layers: Record<Layer, LayerInfo1>,
  comp?:  ImageData,
};


type Rgb = [number, number, number];
type Rgbs = Record<Color.Layer, Rgb>;

let rgbBuf = new OffscreenCanvas(1, 1).getContext('2d')!;

function toRgb(col: Color.Oklch): Rgb {
  // :)
  rgbBuf.fillStyle = col.css();
  rgbBuf.fillRect(0, 0, 1, 1);
  const rgb = rgbBuf.getImageData(0, 0, 1, 1).data;
  return [rgb[0]!, rgb[1]!, rgb[2]!];
}

function toRgbs(col: Color.Colors): Rgbs {
  return Color.makeColorInfo(l => toRgb(col[l]));
}


function setImageDataRgb({ data }: ImageData, [r, g, b]: Rgb, a: number = -1) {
  for (let i = 0; i < data.length; i += 4) {
    data[i] = r; data[i+1] = g; data[i+2] = b;
    if (a >= 0) data[i+3]! *= a;
  }
}


async function loadImage(url: string): Promise<ImageBitmap> {
  const img0 = new Image; img0.src = url;
  const img: ImageBitmapSource = img0.complete ? img0 :
    await new Promise(r => img0.addEventListener('load', () => r(img0)));
  return createImageBitmap(img);
}

async function load(buf: OffscreenCanvasRenderingContext2D,
                    side: SideName, layer: Layer): Promise<ImageData> {
  if (layer == 'eyeshine') layer = 'eyes';
  let bmp = await loadImage(`./${side}/${layer}.webp`);
  return navigator.locks.request('buf', async () => {
    buf.clearRect(0, 0, WIDTH, HEIGHT); // ?
    buf.drawImage(bmp, 0, 0);
    return buf.getImageData(0, 0, WIDTH, HEIGHT)
  });
}

async function loadSide(buf: OffscreenCanvasRenderingContext2D,
                        side: SideName): Promise<LayerInfo> {
  const layers: Partial<Record<Layer, LayerInfo1>> = { };
  const pos = await loadPos(side);
  const images = Object.fromEntries(
    await Promise.all(
      allLayers.map(l => load(buf, side, l).then(res => [l, res])))
    ) as Record<Layer, ImageData>;
  console.log(images);
  for (const l of allLayers) {
    layers[l] = { data: images[l], pos: pos[l] };
  }
  return { layers: layers as Record<Layer, LayerInfo1> };
}

function setColors(cols: Rgbs, info: LayerInfo): void {
  for (const l of allLayers) {
    if (l == 'static' || l == 'eyeshine') continue;
    setImageDataRgb(info.layers[l].data, cols[l]);
  }
  delete info.comp;
}

async function compose(buf: OffscreenCanvasRenderingContext2D,
                       { layers }: LayerInfo): Promise<ImageData> {
  return navigator.locks.request('buf', async () => {
    buf.save();
    buf.clearRect(0, 0, WIDTH, HEIGHT);

    for (const l of allLayers) {
      const [x, y] = layers[l].pos;
      buf.globalCompositeOperation =
        l == 'eyeshine' ? 'luminosity' : 'source-over';
      buf.drawImage(await createImageBitmap(layers[l].data), x, y);
    }

    buf.restore();
    return buf.getImageData(0, 0, WIDTH, HEIGHT);
  });
}


async function redraw(ctx: CanvasRenderingContext2D,
                      buf: OffscreenCanvasRenderingContext2D,
                      info: LayerInfo) {
  let data = info.comp ??= await compose(buf, info);
  ctx.putImageData(data, 0, 0);
}


function message(msg: string, ctx: CanvasRenderingContext2D) {
  ctx.save();
  ctx.clearRect(0, 0, WIDTH, HEIGHT);
  ctx.font = 'bold 100px Muller, sans-serif';
  ctx.textAlign = 'center';
  ctx.fillText(msg, WIDTH/2, HEIGHT/2);
  ctx.restore();
}


function startAnim(name: string) {
  document.documentElement.dataset.running = name;
}

function isRunning(): boolean {
  return !!document.documentElement.dataset.running;
}

function finishAnim() {
  delete document.documentElement.dataset.running;
}

type SideName = 'front' | 'back';

class Side {
  cur:    SideName = 'front';
  fronts: LayerInfo;
  backs:  LayerInfo;

  private constructor(fronts: LayerInfo, backs: LayerInfo) {
    this.fronts = fronts; this.backs = backs;
  }

  static async init(buf: OffscreenCanvasRenderingContext2D) {
    return new Side(await loadSide(buf, 'front'), await loadSide(buf, 'back'));
  }

  flip() { this.cur = (this.cur == 'front' ? 'back' : 'front'); }
  layers() { return this.cur == 'front' ? this.fronts : this.backs; }

  async recolorOn(ctx: CanvasRenderingContext2D,
                  buf: OffscreenCanvasRenderingContext2D) {
    const cols = Color.colors();
    const rgbs = toRgbs(cols);
    setColors(rgbs, this.fronts);
    setColors(rgbs, this.backs);
    await redraw(ctx, buf, this.layers());
    return cols.outer.h;
  }

  async ensureComposed(buf: OffscreenCanvasRenderingContext2D) {
    this.fronts.comp ??= await compose(buf, this.fronts);
    this.backs.comp  ??= await compose(buf, this.backs);
  }
}

function setBg(hue: number) {
  document.documentElement.style.setProperty('--hue', `${hue}`);
}


async function animateReroll(ctx1: CanvasRenderingContext2D,
                             ctx2: CanvasRenderingContext2D,
                             buf: OffscreenCanvasRenderingContext2D,
                             side: Side,
                             done: () => void) {
  const duration = 200;
  const hue = await side.recolorOn(ctx2, buf);
  ctx2.canvas.style.animation = `${duration}ms ease fade-in`;
  setBg(hue);
  setTimeout(finish, duration);

  async function finish() {
    await redraw(ctx1, buf, side.layers()).then(() => {
      ctx2.canvas.style.removeProperty('animation');
      ctx2.canvas.style.removeProperty('opacity');
      done();
    });
  }
}


async function animateSwap(picCtx: CanvasRenderingContext2D,
                           pic2Ctx: CanvasRenderingContext2D,
                           side: Side,
                           buf: OffscreenCanvasRenderingContext2D,
                           done: () => void) {
  const duration = 400;

  side.flip();
  await Promise.all([
    side.ensureComposed(buf),
    redraw(pic2Ctx, buf, side.layers()),
  ]);

  picCtx.canvas.style.animation  = `${duration}ms ease swap1`;
  pic2Ctx.canvas.style.animation = `${duration}ms ease swap2`;
  setTimeout(swap, duration/2);
  setTimeout(finish, duration);

  function swap() {
    let data = pic2Ctx.getImageData(0, 0, WIDTH, HEIGHT);
    picCtx.putImageData(data, 0, 0);
  }

  function finish() {
    picCtx.canvas.style.removeProperty('animation');
    pic2Ctx.canvas.style.removeProperty('animation');
    done();
  }
}


document.addEventListener('DOMContentLoaded', async function() {
  let pic = document.getElementById('pic') as HTMLCanvasElement;
  let picCtx = pic.getContext('2d')!;

  let pic2 = document.getElementById('pic2') as HTMLCanvasElement;
  let pic2Ctx = pic2.getContext('2d')!;

  let buf = new OffscreenCanvas(WIDTH, HEIGHT).getContext('2d')!;

  message('loading layers…', picCtx);

  let side: Side = await Side.init(buf).catch(err => {
    message(err, picCtx);
    throw err;
  });

  let hue = await side.recolorOn(picCtx, buf);
  setBg(hue);
  await redraw(picCtx, buf, side.layers());

  const reroll = document.getElementById('reroll')!;
  const swap   = document.getElementById('swap')!;

  addListeners();

  function addListeners() {
    reroll.addEventListener('click', handleReroll);
    swap.addEventListener('click', handleSwap);
  }

  function removeListeners() {
    reroll.removeEventListener('click', handleReroll);
    swap.removeEventListener('click', handleSwap);
  }

  function handleReroll(e: Event) {
    wrap(reroll, done => animateReroll(picCtx, pic2Ctx, buf, side, done),
         'reroll', e);
  }

  function handleSwap(e: Event) {
    wrap(swap, done => animateSwap(picCtx, pic2Ctx, side, buf, done),
         'swap', e);
  }

  type Handler = (finish: () => void) => void;

  function wrap(elem: Element, f: Handler, name: string, e: Event) {
    if (elem != e.target) return;
    e.stopPropagation();
    if (isRunning()) return;
    removeListeners();
    startAnim(name);
    f(() => { finishAnim(); addListeners(); });
  }
});

export { load, loadSide };