/**
 * @file toast.ts
 * @description App-wide toast queue: `toast.success(msg)` / `toast.error(msg)`
 * from anywhere, rendered once by `components/Toaster.tsx` inside live regions.
 * A success fades after a few seconds; an error stays until dismissed, because
 * a message that vanishes before it is read is no message at all (WCAG 2.2.1).
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

export type ToastKind = "success" | "error" | "info";

export interface ToastItem {
  id: number;
  kind: ToastKind;
  message: string;
}

const SUCCESS_MS = 4000;
let items: ToastItem[] = [];
let nextId = 1;
const listeners = new Set<(items: ToastItem[]) => void>();

function emit() {
  for (const l of listeners) l(items);
}

/** Remove one toast. */
export function dismissToast(id: number): void {
  items = items.filter((t) => t.id !== id);
  emit();
}

function push(kind: ToastKind, message: string): number {
  const id = nextId++;
  // Same text twice in a row (a double click, a retry) shows once.
  items = [...items.filter((t) => t.message !== message), { id, kind, message }].slice(-4);
  emit();
  if (kind !== "error") window.setTimeout(() => dismissToast(id), SUCCESS_MS);
  return id;
}

/** Subscribe to the queue; returns the unsubscribe. */
export function subscribeToasts(fn: (items: ToastItem[]) => void): () => void {
  listeners.add(fn);
  fn(items);
  return () => {
    listeners.delete(fn);
  };
}

export const toast = {
  success: (message: string) => push("success", message),
  info: (message: string) => push("info", message),
  error: (message: unknown) =>
    push("error", message instanceof Error ? message.message : String(message)),
};