export interface ComradePresence {
  user: string;
  page: string;
  online: boolean;
  ts: number;
}

export interface NotesTyping {
  user: string;
  active: boolean;
  ts: number;
}

export interface PresenceState {
  comrades: Record<string, ComradePresence>;
  notesTyping: NotesTyping | null;
  selfUser: string | null;
}

export const initialPresenceState: PresenceState = {
  comrades: {},
  notesTyping: null,
  selfUser: null,
};

export type PresenceAction =
  | { type: 'set_self'; user: string | null }
  | { type: 'presence_snapshot'; comrades: ComradePresence[] }
  | { type: 'presence_update'; user: string; page: string; online: boolean; ts: number }
  | { type: 'notes_typing'; user: string; active: boolean; ts: number }
  | { type: 'clear_notes_typing' };

export function reducePresence(state: PresenceState, action: PresenceAction): PresenceState {
  switch (action.type) {
    case 'set_self':
      return { ...state, selfUser: action.user };
    case 'presence_snapshot': {
      const comrades: Record<string, ComradePresence> = {};
      for (const c of action.comrades) {
        if (!c.user || !c.online) continue;
        if (state.selfUser && c.user === state.selfUser) continue;
        comrades[c.user] = { ...c, online: true };
      }
      return { ...state, comrades };
    }
    case 'presence_update': {
      const next = { ...state.comrades };
      if (!action.online || (state.selfUser && action.user === state.selfUser)) {
        delete next[action.user];
        return { ...state, comrades: next };
      }
      next[action.user] = {
        user: action.user,
        page: action.page || '/dashboard',
        online: true,
        ts: action.ts,
      };
      return { ...state, comrades: next };
    }
    case 'notes_typing': {
      if (state.selfUser && action.user === state.selfUser) {
        return state;
      }
      if (!action.active) {
        if (state.notesTyping?.user === action.user) {
          return { ...state, notesTyping: null };
        }
        return state;
      }
      return {
        ...state,
        notesTyping: { user: action.user, active: true, ts: action.ts },
      };
    }
    case 'clear_notes_typing':
      return { ...state, notesTyping: null };
    default:
      return state;
  }
}

export function onlineComrades(state: PresenceState): ComradePresence[] {
  return Object.values(state.comrades).filter((c) => c.online);
}

export function comradesOnPage(state: PresenceState, page: string): ComradePresence[] {
  const normalized = page.startsWith('/') ? page : `/${page}`;
  return onlineComrades(state).filter((c) => {
    const p = c.page.startsWith('/') ? c.page : `/${c.page}`;
    return p === normalized;
  });
}