// Minimal pub/sub for ephemeral UI events that don't belong on the sessionEvents
// bus (sessionEvents is for DB-state changes; this file is for UI-only signals
// like "user clicked send-to-terminal on selected text").
//
// Also exposes a tiny registry of currently-mounted terminal panes so the
// MessageBubble context menu can list them. TerminalPane registers on mount,
// unregisters on unmount.

type Listener<T> = (payload: T) => void;

interface EventBus<T> {
  emit(payload: T): void;
  subscribe(listener: Listener<T>): () => void;
}

function createEvent<T>(): EventBus<T> {
  const listeners = new Set<Listener<T>>();
  return {
    emit(payload) {
      for (const l of listeners) {
        try {
          l(payload);
        } catch {
          /* one bad listener shouldn't break others */
        }
      }
    },
    subscribe(listener) {
      listeners.add(listener);
      return () => {
        listeners.delete(listener);
      };
    },
  };
}

export interface SendToTerminalPayload {
  pane_id: string;
  text: string;
}

export const sendToTerminal = createEvent<SendToTerminalPayload>();

export interface TerminalRegistration {
  paneId: string;
  label: string;
  // v1.10.3 kbd-shortcuts: Cmd+` needs to focus the active terminal's xterm
  // input layer. TerminalPane binds this to term.focus().
  focus: () => void;
}

const terminalRegistry = new Map<string, TerminalRegistration>();
const registryListeners = new Set<Listener<void>>();

function notifyRegistry(): void {
  for (const l of registryListeners) {
    try {
      l();
    } catch {
      /* ignore */
    }
  }
}

export const terminalsRegistry = {
  register(paneId: string, label: string, focus: () => void): () => void {
    terminalRegistry.set(paneId, { paneId, label, focus });
    notifyRegistry();
    return () => {
      terminalRegistry.delete(paneId);
      notifyRegistry();
    };
  },
  list(): TerminalRegistration[] {
    return Array.from(terminalRegistry.values());
  },
  get(paneId: string): TerminalRegistration | undefined {
    return terminalRegistry.get(paneId);
  },
  subscribe(listener: Listener<void>): () => void {
    registryListeners.add(listener);
    return () => {
      registryListeners.delete(listener);
    };
  },
};