// App-wide store of open floating chat windows (the Messenger-style dock, bottom-right).
// A window can be opened from anywhere (e.g. a conversation's "pop out" button) and stays
// open across page navigation. Plain external store so any component can read/drive it.
import { useSyncExternalStore } from "react";

export interface DockChat {
  partnerId: number;
  name: string;
  avatar: string | null;
  minimized: boolean;
}

const MAX_OPEN = 3; // keep the dock from overflowing the corner
let chats: DockChat[] = [];
const subs = new Set<() => void>();

function emit(next: DockChat[]): void {
  chats = next;
  for (const s of subs) s();
}

export function openChat(partner: { id: number; name: string; avatar_url: string | null }): void {
  const existing = chats.find((c) => c.partnerId === partner.id);
  if (existing) {
    // Re-opening focuses it: ensure expanded and move to the front.
    emit([
      { ...existing, minimized: false },
      ...chats.filter((c) => c.partnerId !== partner.id),
    ]);
    return;
  }
  const next = [
    { partnerId: partner.id, name: partner.name, avatar: partner.avatar_url, minimized: false },
    ...chats,
  ].slice(0, MAX_OPEN);
  emit(next);
}

export function closeChat(partnerId: number): void {
  emit(chats.filter((c) => c.partnerId !== partnerId));
}

export function toggleMinimize(partnerId: number): void {
  emit(chats.map((c) => (c.partnerId === partnerId ? { ...c, minimized: !c.minimized } : c)));
}

export function useDockChats(): DockChat[] {
  return useSyncExternalStore(
    (cb) => {
      subs.add(cb);
      return () => subs.delete(cb);
    },
    () => chats,
    () => chats
  );
}