// Bounded scheduler for best-effort stream prewarming. Requests beyond the
// active limit wait in a short FIFO instead of being silently discarded.
export function createWarmQueue({ concurrency = 2, maxQueued = 8, run }) {
  const queued = [];
  const known = new Set();
  let active = 0;

  function pump() {
    while (active < concurrency && queued.length) {
      const id = queued.shift();
      active++;
      Promise.resolve().then(() => run(id)).catch(() => {}).finally(() => {
        active--;
        known.delete(id);
        pump();
      });
    }
  }

  function enqueue(id) {
    if (known.has(id)) return true;
    if (active >= concurrency && queued.length >= maxQueued) return false;
    known.add(id);
    queued.push(id);
    pump();
    return true;
  }

  return { enqueue, get pending() { return queued.length + active; } };
}