// Each rack block owns its bars; only the bottom of a column releases them.
const RACK_CAP = 50;
let rackState = new Map();
function newRack() { return { q: [], n: 0, open: false, wait: 0 }; }
function rackTop(b) { while (b >= BW && blockP[b - BW] === BP_RACK) b -= BW; return b; }
function rackBottom(b) { while (b + BW < NB && blockP[b + BW] === BP_RACK) b += BW; return b; }
function rackPush(s, m, n) {
  const last = s.q[s.q.length - 1];
  if (last && last[0] === m) last[1] += n; else s.q.push([m, n]);
  s.n += n;
}
function rackShift(s, n) {
  s.q[0][1] -= n; s.n -= n;
  if (!s.q[0][1]) s.q.shift();
}
// Called with the moving bar unmarked, after its ordinary collision handling.
function rackIntake(e) {
  const y = e.iy + BAR_H;
  if (e.vy !== 0 || Math.abs(e.vx) >= 0.05 || y >= H || y % BS) return false;
  for (let x = Math.max(0, e.ix); x < Math.min(W, e.ix + BAR_W); x += BS - x % BS) {
    const b = (y / BS) * BW + Math.floor(x / BS), left = (b % BW) * BS;
    if (blockP[b] !== BP_RACK || b >= BW && blockP[b - BW] === BP_RACK || Math.min(e.ix + BAR_W, left + BS) - Math.max(e.ix, left) < BAR_W / 2) continue;
    for (let q = rackBottom(b); q >= b; q -= BW) {
      const s = rackState.get(q);
      if (s.n < RACK_CAP) { rackPush(s, e.m, 1); return true; }
    }
  }
  return false;
}
function rackRefill(b) {
  const top = rackTop(b);
  for (let q = b; q > top; q -= BW) {
    const lower = rackState.get(q);
    for (let above = q - BW; above >= top && lower.n < RACK_CAP; above -= BW) {
      const upper = rackState.get(above);
      while (lower.n < RACK_CAP && upper.n) {
        const n = Math.min(RACK_CAP - lower.n, upper.q[0][1]);
        rackPush(lower, upper.q[0][0], n); rackShift(upper, n);
      }
    }
  }
}
function rackTick() {
  for (const [b, s] of rackState) {
    if (b + BW < NB && blockP[b + BW] === BP_RACK) continue;
    if (!s.open) continue;
    if (!s.n) rackRefill(b);
    if (!s.n) continue;
    if (s.wait < 20) s.wait++;
    if (s.wait < 20) continue;
    const x = (b % BW) * BS, y = (((b / BW) | 0) + 1) * BS;
    if (!entFreeAt(x, y) || !spawnBar(s.q[0][0], x, y, 0, 0)) continue;
    rackShift(s, 1); s.wait = 0;
    rackRefill(b);
  }
}