import type { AuthMode, Reply } from "../api/types";

/*
 * Session persistence behind one small interface. Web uses localStorage; the mobile shell swaps the backend for
 * secure device storage (e.g. Capacitor Preferences / Keychain) without touching screens.
 */

export interface Session {
  token: string;
  mode: AuthMode;
  displayName: string | null;
}

export type ChatEntry =
  | { id: string; from: "assistant"; reply: Reply }
  | { id: string; from: "patient"; text: string };

/** Dialog snapshot per token: full history + the latest unanswered batch of engine replies. */
export interface DialogSnapshot {
  entries: ChatEntry[];
  pending: Reply[];
  unread: number;
}

interface KeyValue {
  get(key: string): string | null;
  set(key: string, value: string): void;
  remove(key: string): void;
}

const browserStorage: KeyValue = {
  get: (k) => {
    try {
      return window.localStorage.getItem(k);
    } catch {
      return null;
    }
  },
  set: (k, v) => {
    try {
      window.localStorage.setItem(k, v);
    } catch {
      /* private mode / quota: the session simply is not remembered */
    }
  },
  remove: (k) => {
    try {
      window.localStorage.removeItem(k);
    } catch {
      /* ignore */
    }
  },
};

const SESSION_KEY = "ptsr.session.v1";
const dialogKey = (token: string) => `ptsr.dialog.v2.${token}`;
const EMPTY: DialogSnapshot = { entries: [], pending: [], unread: 0 };

function read<T>(storage: KeyValue, key: string): T | null {
  const raw = storage.get(key);
  if (!raw) return null;
  try {
    return JSON.parse(raw) as T;
  } catch {
    return null;
  }
}

export function createSessionStore(storage: KeyValue = browserStorage) {
  return {
    load: () => read<Session>(storage, SESSION_KEY),
    save: (s: Session) => storage.set(SESSION_KEY, JSON.stringify(s)),
    clear: (s: Session | null, wipeDialog = true) => {
      storage.remove(SESSION_KEY);
      if (s && wipeDialog) storage.remove(dialogKey(s.token));
    },
    loadDialog: (token: string): DialogSnapshot => ({ ...EMPTY, ...read<DialogSnapshot>(storage, dialogKey(token)) }),
    saveDialog: (token: string, snap: DialogSnapshot) => storage.set(dialogKey(token), JSON.stringify(snap)),
  };
}

export const sessionStore = createSessionStore();