'use strict';
const DATA = JSON.parse(document.getElementById('data').textContent);
const cv = document.getElementById('view');
const ctx = cv.getContext('2d');

// ---------------------------------------------------------------- state
const S = {
  track: 0,
  cx: 0, cz: 0,          // view centre, world units
  mpp: 10,               // meters per pixel - the engine's own scale term
  gps: false,            // false = NavDisplay (LOD follows zoom), true = GPS
  stats: {},
};

// Seen from above with +Z up the page the engine's +X runs to the LEFT.
// The console's own picture of Brewer's Bane is what settles the
// handedness; drawn the other way every plan comes out mirrored.
function toScreen(x, z, w, h) {
  return [w / 2 - (x - S.cx) / S.mpp, h / 2 - (z - S.cz) / S.mpp];
}

// Quaternion (x,y,z,w) applied to a point - MUNGA's own convention.
function rotate(q, p) {
  const [qx, qy, qz, qw] = q, [x, y, z] = p;
  const tx = 2 * (qy * z - qz * y);
  const ty = 2 * (qz * x - qx * z);
  const tz = 2 * (qx * y - qy * x);
  return [x + qw * tx + qy * tz - qz * ty,
          y + qw * ty + qz * tx - qx * tz,
          z + qw * tz + qx * ty - qy * tx];
}

// The map screen is not a phosphor display. Primitives carry palette
// indices and the palette is the one the port was configured with -
// secpal.pcc for the pod's secondary screen, where the nav display lives.
// Walls (index 51) are grey. L4GaugeImage::Draw only overrides the colour
// when it is non-zero, so 0 means "keep what is set", which is the
// display's own staticColor (0x3C).
function ink(c) {
  return DATA.palette[c ? c : DATA.staticColor] || '#535353';
}

// ------------------------------------------------------------- bounds
function bounds(list) {
  let x0 = Infinity, x1 = -Infinity, z0 = Infinity, z1 = -Infinity;
  for (const r of list) {
    if (r[1] < x0) x0 = r[1];
    if (r[1] > x1) x1 = r[1];
    if (r[3] < z0) z0 = r[3];
    if (r[3] > z1) z1 = r[3];
  }
  return list.length ? {x0, x1, z0, z1} : {x0: -1, x1: 1, z0: -1, z1: 1};
}

// Fourteen tracks park a single piece far off the course; fitting to
// everything squeezes the track into a sliver, so "fit" ignores loners
// and "fit all" (A) is there when you want the literal extent.
function course(t) {
  if (t._course) return t._course;
  const keep = t.i.filter(a =>
    t.i.some(b => b !== a && (b[1] - a[1]) ** 2 + (b[3] - a[3]) ** 2 < 200 * 200));
  return (t._course = keep.length ? keep : t.i);
}

function fit(all) {
  const t = DATA.tracks[S.track];
  const b = bounds(all ? t.i : course(t));
  S.cx = (b.x0 + b.x1) / 2;
  S.cz = (b.z0 + b.z1) / 2;
  const w = cv.clientWidth || 800, h = cv.clientHeight || 600;
  // The GPS gauge allows 1.2x "for large objects at edges of map"
  // (RPL4GAUG.cpp:2060); same here so nothing clips at the border.
  S.mpp = Math.max((b.x1 - b.x0) / w, (b.z1 - b.z0) / h, 1e-4) * 1.2;
  draw();
}

// -------------------------------------------------------------- render
function draw() {
  const dpr = window.devicePixelRatio || 1;
  const w = cv.clientWidth, h = cv.clientHeight;
  if (cv.width !== Math.round(w * dpr) || cv.height !== Math.round(h * dpr)) {
    cv.width = Math.round(w * dpr);
    cv.height = Math.round(h * dpr);
  }
  ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
  ctx.clearRect(0, 0, w, h);

  const t = DATA.tracks[S.track];
  // NavDisplay sets LODIndex = metersPerPixel every time it recalculates
  // bounds. The GPS gauge takes its LOD from the config and never moves it.
  const lodValue = S.gps ? 1.0 : S.mpp;
  let drawn = 0, culled = 0, prims = 0;

  ctx.lineWidth = 1;
  ctx.lineJoin = 'round';
  for (const r of t.i) {
    const img = DATA.images[r[0]];
    if (!img) { culled++; continue; }

    // L4GaugeImage::Draw - scales ascend, so index 0 is the FINEST, and
    // running past the largest means the object is not drawn at all.
    let k = 0;
    while (k < img.l.length && lodValue > img.l[k].s) k++;
    if (k >= img.l.length) { culled++; continue; }
    drawn++;

    const q = [r[4], r[5], r[6], r[7]];
    for (const p of img.l[k].p) {
      ctx.strokeStyle = ink(p.c);
      ctx.beginPath();
      for (let n = 0; n < p.i.length; n++) {
        let v = img.v[p.i[n]];
        if (!v) continue;
        // attributeUnscaled: pre-multiply by the scale factor so the
        // primitive keeps a constant size on screen (L4GAUIMA.cpp:1599).
        if (p.a & 1) v = [v[0] * S.mpp, v[1] * S.mpp, v[2] * S.mpp];
        const g = rotate(q, v);
        const [sx, sy] = toScreen(g[0] + r[1], g[2] + r[3], w, h);
        n ? ctx.lineTo(sx, sy) : ctx.moveTo(sx, sy);
      }
      ctx.stroke();
      prims++;
    }
  }
  S.stats = {drawn, culled, prims, lodValue};
  hud();
}

// ----------------------------------------------------------------- hud
function hud() {
  const t = DATA.tracks[S.track];
  const s = S.stats;
  const px = 1 / S.mpp;
  document.getElementById('name').textContent = t.name;
  document.getElementById('key').textContent =
    t.key + '   ' + (S.track + 1) + '/' + DATA.tracks.length;
  const rows = [
    ['mode', S.gps ? 'GPS  (LOD pinned 1.0)' : 'NavDisplay  (LOD = m/px)'],
    ['metersPerPixel', S.mpp.toFixed(3)],
    ['pixelsPerMeter', px.toFixed(4)],
    ['LOD value', s.lodValue.toFixed(3)],
    ['centre X / Z', S.cx.toFixed(0) + '  /  ' + S.cz.toFixed(0)],
    ['objects drawn', s.drawn],
    ['dropped by LOD', s.culled],
    ['primitives', s.prims],
    ['no map art', t.noart],
  ];
  document.getElementById('stats').innerHTML = rows.map(
    r => '<dt>' + r[0] + '</dt><dd>' + r[1] + '</dd>').join('');

  // Scale bar: a round number of meters, whatever fits under 160px.
  let m = Math.pow(10, Math.floor(Math.log10(160 * S.mpp)));
  for (const f of [5, 2, 1]) if (m * f <= 160 * S.mpp) { m *= f; break; }
  document.getElementById('barline').style.width = (m / S.mpp) + 'px';
  document.getElementById('bartext').textContent = m + ' m';
}

// ------------------------------------------------------------ controls
function pan(dx, dz) {
  const step = 0.1 * Math.min(cv.clientWidth, cv.clientHeight) * S.mpp;
  S.cx += dx * step;
  S.cz += dz * step;
  draw();
}

function zoom(f) {
  S.mpp = Math.max(0.02, Math.min(4000, S.mpp * f));
  draw();
}

function pick(n) {
  S.track = (n + DATA.tracks.length) % DATA.tracks.length;
  document.getElementById('track').value = S.track;
  fit(false);
}

addEventListener('keydown', e => {
  if (e.target.tagName === 'SELECT') return;
  const k = e.key;
  // Right on screen is -X, up is +Z: north/south/east/west as drawn.
  if (k === 'ArrowUp') pan(0, 1);
  else if (k === 'ArrowDown') pan(0, -1);
  else if (k === 'ArrowLeft') pan(1, 0);
  else if (k === 'ArrowRight') pan(-1, 0);
  else if (k === '+' || k === '=') zoom(1 / 1.25);
  else if (k === '-' || k === '_') zoom(1.25);
  else if (k === '[') pick(S.track - 1);
  else if (k === ']') pick(S.track + 1);
  else if (k === 'f' || k === 'F') fit(false);
  else if (k === 'a' || k === 'A') fit(true);
  else if (k === 'g' || k === 'G') { S.gps = !S.gps; draw(); }
  else return;
  e.preventDefault();
});

let drag = null;
cv.addEventListener('pointerdown', e => {
  drag = {x: e.clientX, y: e.clientY};
  cv.setPointerCapture(e.pointerId);
});
cv.addEventListener('pointermove', e => {
  if (!drag) return;
  S.cx -= (e.clientX - drag.x) * S.mpp;
  S.cz += (e.clientY - drag.y) * S.mpp;
  drag = {x: e.clientX, y: e.clientY};
  draw();
});
cv.addEventListener('pointerup', () => { drag = null; });
cv.addEventListener('wheel', e => {
  e.preventDefault();
  zoom(e.deltaY > 0 ? 1.1 : 1 / 1.1);
}, {passive: false});

const sel = document.getElementById('track');
sel.innerHTML = DATA.tracks.map(
  (t, i) => '<option value="' + i + '">' + t.name + '</option>').join('');
sel.addEventListener('change', () => pick(+sel.value));
addEventListener('resize', draw);
pick(0);