/**
 * Per-actuator leading+trailing debounce so a dragged slider doesn't fire a
 * device command on every pointermove - devices don't need mouse-move-rate
 * updates, and most BLE stacks choke on a command flood.
 */
const THROTTLE_MS = 75;

interface ThrottleEntry {
  timer: ReturnType<typeof setTimeout> | null;
  pendingValue: number | null;
  pendingDuration: number | undefined;
  lastSentAt: number;
}

const entries = new Map<string, ThrottleEntry>();

export function throttledSend(
  key: string,
  send: (value: number, durationMs?: number) => void | Promise<void>,
  value: number,
  durationMs?: number,
): void {
  let entry = entries.get(key);
  if (!entry) {
    entry = { timer: null, pendingValue: null, pendingDuration: undefined, lastSentAt: 0 };
    entries.set(key, entry);
  }

  entry.pendingValue = value;
  entry.pendingDuration = durationMs;

  const flush = (): void => {
    const v = entry!.pendingValue;
    entry!.pendingValue = null;
    entry!.timer = null;
    entry!.lastSentAt = Date.now();
    if (v !== null) void send(v, entry!.pendingDuration);
  };

  const elapsed = Date.now() - entry.lastSentAt;
  if (elapsed >= THROTTLE_MS) {
    if (entry.timer) clearTimeout(entry.timer);
    flush();
  } else if (!entry.timer) {
    entry.timer = setTimeout(flush, THROTTLE_MS - elapsed);
  }
}

export function clearThrottle(key: string): void {
  const entry = entries.get(key);
  if (entry?.timer) clearTimeout(entry.timer);
  entries.delete(key);
}