// Bars and other loose objects (ents), and the bag: adding, taking, costs and refunds.
// ---------- Bars (loose objects) ----------
// A bar is 4x2 grains. It falls, rests on things, rides belts, and melts back
// into molten metal if it gets hot enough. While it sits somewhere, grains treat
// its cells as solid (occ).
const BAR_W = 4, BAR_H = 2;
let entCurM = 0; // the bar being moved, so a filter can let its own kind of bar through
function entSolidCell(j) { const m = mat[j], p = part[j]; return occ[j] || PH[m] === PH_SOLID || PH[m] === PH_POWDER || (p !== 0 && (p <= P_GRATE || (p === P_FILTER && !filterPassAt(entCurM, j)))); }
function entFreeAt(x, y) {
  if (x < 0 || y < 0 || x + BAR_W > W || y + BAR_H > H) return false;
  for (let dy = 0; dy < BAR_H; dy++) for (let dx = 0; dx < BAR_W; dx++) if (entSolidCell((y + dy) * W + x + dx)) return false;
  return true;
}
function entMark(e, on) {
  const x = e.ix, y = e.iy;
  for (let dy = 0; dy < BAR_H; dy++) for (let dx = 0; dx < BAR_W; dx++) {
    const xx = x + dx, yy = y + dy;
    if (xx < 0 || yy < 0 || xx >= W || yy >= H) continue;
    occ[yy * W + xx] = on ? 1 : 0;
    if (!on) wakeXY(xx, yy);
  }
}
function spawnBar(m, x, y, vx, vy, T) {
  if (ents.length >= 4000 || !m) return null;
  let ix = Math.round(x), iy = Math.round(y);
  // find a free spot near the requested one
  let ok = entFreeAt(ix, iy);
  for (let k = 1; !ok && k < 12; k++) { if (entFreeAt(ix, iy - k)) { iy -= k; ok = true; } }
  if (!ok) return null;
  const e = { m, x: ix, y: iy, ix, iy, vx: vx || 0, vy: vy || 0, T: T === undefined ? AMB[Math.max(0, Math.min(H - 1, iy))] : T, rest: 0 };
  ents.push(e); entMark(e, 1);
  return e;
}
function removeEnt(e) { entMark(e, 0); const k = ents.indexOf(e); if (k >= 0) ents.splice(k, 1); }
// No transient tube state: even a loaded bar derives its ride from its eight cells.
function entTubeAt(x, y) {
  if (x < 0 || y < 0 || x + BAR_W > W || y + BAR_H > H) return 0;
  for (let yy = y; yy < y + BAR_H; yy++) for (let xx = x; xx < x + BAR_W; xx++) {
    const p = part[yy * W + xx]; if (p < P_TU || p > P_TR) return 0;
  }
  return part[(y + 1) * W + x + 1];
}
function entTubeFree(x, y, tubeOnly = false) {
  if (x < 0 || y < 0 || x + BAR_W > W || y + BAR_H > H) return false;
  for (let yy = y; yy < y + BAR_H; yy++) for (let xx = x; xx < x + BAR_W; xx++) {
    const j = yy * W + xx, p = part[j], tube = p >= P_TU && p <= P_TR;
    // gas and liquid don't stop a bar, in a tube or in the open
    if (occ[j] || (mat[j] !== EMPTY && PH[mat[j]] !== PH_GAS && PH[mat[j]] !== PH_LIQUID) || (tubeOnly ? !tube : !tube && entSolidCell(j))) return false;
  }
  return true;
}
// Check the swept rectangle too: a snap must never jump through a grain or another bar.
function entTubeMove(e, x, y, tubeOnly = false) {
  if (!entTubeFree(x, y, tubeOnly)) return false;
  for (let yy = Math.min(e.iy, y); yy <= Math.max(e.iy, y); yy++)
    for (let xx = Math.min(e.ix, x); xx <= Math.max(e.ix, x); xx++) if (!entTubeFree(xx, yy)) return false;
  e.x = e.ix = x; e.y = e.iy = y; e.vx = e.vy = 0; return true;
}
function entTubeEnter(e, dx, dy) {
  for (let k = 0; k < (dx ? BAR_H : BAR_W); k++) {
    const xx = e.ix + (dx > 0 ? BAR_W : dx < 0 ? -1 : k), yy = e.iy + (dy > 0 ? BAR_H : dy < 0 ? -1 : k);
    if (xx < 0 || yy < 0 || xx >= W || yy >= H) continue;
    const p = part[yy * W + xx]; if (p < P_TU || p > P_TR || (!dx && TDX[p]) || dx * TDX[p] + dy * TDY[p] < 0) continue;
    // Vertical screws require the full width; horizontal screws use the nearest two-row lane.
    const x = (xx & ~3), y = Math.max(yy & ~3, Math.min((yy & ~3) + 2, e.iy));
    if (entTubeMove(e, x, TDX[p] || dy ? y : e.iy, true)) return true;
  }
  return false;
}
function entTubeTick(e, p) {
  e.vx = e.vy = 0; e.x = e.ix; e.y = e.iy;
  const ci = (e.iy + 1) * W + e.ix + 1;
  if ((tick & 1) || netSat(ci) <= 0 || rnd() > netSat(ci)) return;
  const dx = TDX[p], dy = TDY[p];
  let x = e.ix + dx, y = e.iy + dy, next = 0, ax = 0, ay = 0;
  for (let k = 0; k < (dx ? BAR_H : BAR_W); k++) {
    const xx = e.ix + (dx > 0 ? BAR_W : dx < 0 ? -1 : k), yy = e.iy + (dy > 0 ? BAR_H : dy < 0 ? -1 : k);
    if (xx < 0 || yy < 0 || xx >= W || yy >= H) return;
    const q = part[yy * W + xx];
    if (q >= P_TU && q <= P_TR && q !== p) { next = q; ax = xx; ay = yy; break; }
  }
  if (next) {
    if (TDX[next] === -dx && TDY[next] === -dy) return;
    x = ax & ~3; y = Math.max(ay & ~3, Math.min((ay & ~3) + 2, e.iy));
    if (entTubeMove(e, x, y, true)) stats.moved++;
    return;
  }
  if (entTubeAt(x, y)) { if (entTubeMove(e, x, y, true)) stats.moved++; return; }
  // Clear the mouth in one move so the next tick can derive ordinary falling from position.
  x = e.ix + dx * BAR_W; y = e.iy + dy * BAR_H;
  if (!entTubeFree(x, y) || entTubeAt(x, y)) return;
  for (let yy = y; yy < y + BAR_H; yy++) for (let xx = x; xx < x + BAR_W; xx++) if (part[yy * W + xx]) return;
  if (entTubeMove(e, x, y)) { e.vx = dx ? dx * 0.5 : (rnd() - 0.5) * 0.4; e.vy = dy * 0.6; stats.moved++; }
}
function entTick() {
  for (let k = ents.length - 1; k >= 0; k--) {
    const e = ents[k];
    entMark(e, 0);
    entCurM = e.m;
    const ix = e.ix, iy = e.iy;
    const tube = entTubeAt(ix, iy);
    if (tube) entTubeTick(e, tube);
    else {
      // what is underneath?
      let belt = 0, bsat = 0, support = iy + BAR_H >= H;
      if (!support) {
        const yb = iy + BAR_H;
        for (let dx = 0; dx < BAR_W; dx++) {
          const x = ix + dx; if (x < 0 || x >= W) continue;
          const j = yb * W + x, m = mat[j];
          if (m === BELTL || m === BELTR) { const s = netSat(j); if (s > bsat) { bsat = s; belt = m === BELTR ? 1 : -1; } }
          else if (part[j] === P_FILTER && !filterPassAt(e.m, j) && (yb & 3) === 0) { bsat = 1; belt = blockV[(yb >> 2) * BW + (x >> 2)] & 128 ? 1 : -1; }
          if (entSolidCell(j)) support = true;
        }
      }
      const ci = Math.min(H - 1, iy + 1) * W + Math.min(W - 1, ix + 1);
      const inLiq = PH[mat[ci]] === PH_LIQUID;
      if (support) { if (e.vy > 0) e.vy = 0; e.vx = belt ? belt * 0.5 * bsat : e.vx * 0.55; }
      else { e.vy = Math.min(inLiq ? 0.35 : 1.3, e.vy + 0.07); e.vx *= inLiq ? 0.8 : 0.985; }
      if (belt && bsat > 0) stats.moved += 0.05;
      e.x += e.vx; e.y += e.vy;
      // step toward the new rounded position one cell at a time
      let tx = Math.round(e.x), ty = Math.round(e.y), cx = ix, cy = iy;
      while (cx !== tx) { const s = Math.sign(tx - cx); if (entFreeAt(cx + s, cy)) cx += s; else if (belt && entTubeEnter(e, s, 0)) { cx = e.ix; cy = e.iy; e.x = cx; e.y = cy; break; } else { e.vx = 0; e.x = cx; break; } }
      while (cy !== ty) { const s = Math.sign(ty - cy); if (entTubeAt(cx, cy)) break; if (entFreeAt(cx, cy + s)) cy += s; else if (entTubeEnter(e, 0, s)) { cx = e.ix; cy = e.iy; break; } else { e.vy = 0; e.y = cy; break; } }
      if (support && !belt && entTubeEnter(e, 0, 1)) { cx = e.ix; cy = e.iy; }
      if (!entTubeAt(cx, cy) && !entFreeAt(cx, cy)) {
        // something moved into us (a grain fell in): try to step up out of it
        let freed = false;
        for (let u = 1; u < 6; u++) if (entFreeAt(cx, cy - u)) { cy -= u; e.y = cy; freed = true; break; }
        if (!freed) e.y = cy;
      }
      e.ix = cx; e.iy = cy;
    }
    const cx = e.ix, cy = e.iy;
    // heat: the bar tends toward the temperature around it
    const T = temp[Math.min(H - 1, cy + 1) * W + Math.min(W - 1, cx + 1)];
    e.T += (T - e.T) * 0.04;
    if (FIRETO[e.m] && e.T >= 880 && rnd() < 0.004 + (e.T - 880) * 0.00012) {
      e.m = FIRETO[e.m]; discover(e.m, e.ix, e.iy, GREENB, 'fire', 880);
    }
    if (e.T >= MELT[e.m]) {
      // melts back into 8 grains of molten metal if they fit here
      let fits = true;
      for (let dy = 0; dy < BAR_H && fits; dy++) for (let dx = 0; dx < BAR_W; dx++) { const j = (cy + dy) * W + cx + dx; if (PH[mat[j]] === PH_SOLID || PH[mat[j]] === PH_POWDER) { fits = false; break; } }
      if (fits) {
        for (let dy = 0; dy < BAR_H; dy++) for (let dx = 0; dx < BAR_W; dx++) setCell((cy + dy) * W + cx + dx, MELTTO[e.m], e.T, 0);
        ents.splice(k, 1);
        discover(MELTTO[e.m], cx, cy);
        continue;
      }
    }
    entMark(e, 1);
  }
  entCurM = 0;
}
function entsInCircle(cx, cy, r) {
  const out = [];
  for (const e of ents) {
    const ex = e.ix + BAR_W / 2, ey = e.iy + BAR_H / 2;
    if ((ex - cx) * (ex - cx) + (ey - cy) * (ey - cy) <= (r + 2.5) * (r + 2.5)) out.push(e);
  }
  return out;
}

// ---------- Bag ----------
function bagAdd(m, n, force) {
  const room = force ? n : Math.max(0, bagCap() - bagTotal);
  const k = Math.min(n, room);
  bag[m] += k; bagTotal += k;
  if (k > 0 && m < NMAT) discover(m, undefined, undefined, 0, 'pickup');
  return k;
}
function bagTake(m, n) { const k = Math.min(n, bag[m]); bag[m] -= k; bagTotal -= k; return k; }
// Give back what fits in the bag; the rest drops into the world near (x, y):
// grains as loose material, bars as bar objects. Counts what dropped.
let droppedLast = 0;
function giveOrDrop(m, n, x, y) {
  if (n <= 0) return;
  if (m === CASH) { money += n; return; }
  const k = bagAdd(m, n, false);
  let rest = n - k;
  if (!rest) return;
  droppedLast += rest;
  if (PH[m] === PH_ITEM) {
    for (let j = 0; j < rest; j++) if (!spawnBar(m, x - 2 + (j % 3) * 2, y - 2 - j, (rnd() - 0.5) * 0.4, -0.3)) bagAdd(m, 1, true);
    return;
  }
  for (let r = 0; r <= 12 && rest > 0; r++) for (let dy = -r; dy <= r && rest > 0; dy++) for (let dx = -r; dx <= r && rest > 0; dx++) {
    if (Math.max(Math.abs(dx), Math.abs(dy)) !== r) continue;
    const xx = Math.round(x) + dx, yy = Math.round(y) + dy;
    if (xx < 0 || yy < 0 || xx >= W || yy >= H) continue;
    const j = yy * W + xx;
    if (mat[j] === EMPTY && !occ[j] && !part[j] && !mach[j]) { setCell(j, m, AMB[yy], 0); rest--; }
  }
  if (rest > 0) bagAdd(m, rest, true);
}
function refundAt(cost, mult, x, y) { for (const [m, n] of cost) giveOrDrop(m, n * mult, x, y); }
function canAfford(cost, mult) { for (const [m, n] of cost) if ((m === CASH ? money : bag[m]) < n * mult) return false; return true; }
function payCost(cost, mult) { for (const [m, n] of cost) { if (m === CASH) money -= n * mult; else bagTake(m, n * mult); } }
function fmtMoney(v) { return '$' + Math.round(v).toLocaleString('en-US'); }
function costText(cost, mult) { return cost.map(([m, n]) => { const k = n * (mult || 1); return m === CASH ? fmtMoney(k) : `${k} ${MD[m].name.toLowerCase()}${PH[m] === PH_ITEM && k !== 1 ? 's' : ''}`; }).join(' + '); }
function needText(cost, mult) { const c = cost.find(([m, n]) => (m === CASH ? money : bag[m]) < n * (mult || 1)); return c && c[0] === CASH ? `Costs ${fmtMoney(c[1] * (mult || 1))}; you have ${fmtMoney(money)}.` : 'Not enough ' + costText(c ? [c] : cost, mult) + '.'; }