import { useEffect, useState } from "react";

type Listener = () => void;

const activeByProject = new Map<string, Set<string>>();
const listeners = new Set<Listener>();

function emit(): void {
  for (const listener of listeners) listener();
}

function activeSet(projectId: string): Set<string> {
  let set = activeByProject.get(projectId);
  if (!set) {
    set = new Set();
    activeByProject.set(projectId, set);
  }
  return set;
}

export function markProjectCliInteractionStarted(
  projectId: string,
  interactionId: string,
): void {
  const set = activeSet(projectId);
  const before = set.size;
  set.add(interactionId);
  if (set.size !== before) emit();
}

export function markProjectCliInteractionFinished(
  projectId: string,
  interactionId: string,
): void {
  const set = activeByProject.get(projectId);
  if (!set?.delete(interactionId)) return;
  if (set.size === 0) activeByProject.delete(projectId);
  emit();
}

export function markProjectCliInteractionStopped(
  projectId: string,
  interactionId: string,
): void {
  markProjectCliInteractionFinished(projectId, interactionId);
}

export function hasProjectCliInteraction(projectId: string): boolean {
  return (activeByProject.get(projectId)?.size ?? 0) > 0;
}

/**
 * Drops optimistic interaction markers once the authoritative project snapshot
 * confirms that no work remains. This is intentionally project-scoped: a
 * terminal event received while another project is displayed must never leave
 * the originating project's LED busy, nor clear activity in another project.
 */
export function reconcileProjectCliInteractionActivity(
  projectId: string,
  hasActiveWork: boolean,
): void {
  if (hasActiveWork || !activeByProject.delete(projectId)) return;
  emit();
}

export function subscribeProjectCliInteractionActivity(
  listener: Listener,
): () => void {
  listeners.add(listener);
  return () => listeners.delete(listener);
}

export function useProjectCliInteractionActivityVersion(): number {
  const [version, setVersion] = useState(0);
  useEffect(
    () => subscribeProjectCliInteractionActivity(() => setVersion((v) => v + 1)),
    [],
  );
  return version;
}

export function __resetProjectCliInteractionActivityForTests(): void {
  activeByProject.clear();
  emit();
}