export type BannerSeverity = "error" | "warning" | "notice" | "success";

export interface BannerEntry {
  id: number;
  severity: BannerSeverity;
  message: string;
}

const DISMISS_AFTER_MS = 8000;

let banners: BannerEntry[] = [];
let nextId = 1;
const listeners = new Set<() => void>();

function notify() {
  for (const listener of listeners) listener();
}

function show(severity: BannerSeverity, message: string): void {
  const isDuplicate = banners.some(
    (b) => b.severity === severity && b.message === message,
  );
  if (isDuplicate) return;

  const id = nextId++;
  banners = [{ id, severity, message }, ...banners];
  notify();
  setTimeout(() => dismiss(id), DISMISS_AFTER_MS);
}

export function showError(message: string): void {
  show("error", message);
}

export function showWarning(message: string): void {
  show("warning", message);
}

export function showNotice(message: string): void {
  show("notice", message);
}

export function showSuccess(message: string): void {
  show("success", message);
}

export function dismiss(id: number): void {
  banners = banners.filter((b) => b.id !== id);
  notify();
}

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

export function getSnapshot(): BannerEntry[] {
  return banners;
}