import type { AuthUser, Product } from "@/lib/types";

/**
 * The last confirmed session and catalogue, so the terminal can start and
 * keep selling with no network. Only a snapshot for display and for
 * labelling queued sales: the server still authenticates every sync with
 * the httpOnly cookies and re-prices every line.
 */

const KEY = "aquaflow_terminal_session";

/** The branch's stock as the server last reported it. */
export interface StockSnapshot {
  byProduct: Record<string, number>;
  fetchedAt: string;
}

export interface SessionSnapshot {
  user: AuthUser;
  features: { mpesa: boolean };
  products: Product[];
  stock?: StockSnapshot;
  savedAt: string;
}

export function loadSession(): SessionSnapshot | null {
  try {
    const raw = localStorage.getItem(KEY);
    return raw ? (JSON.parse(raw) as SessionSnapshot) : null;
  } catch {
    return null;
  }
}

export function saveSession(update: Partial<SessionSnapshot> & { user: AuthUser }): void {
  try {
    const prev = loadSession();
    const sameUser = prev?.user.id === update.user.id;
    const next: SessionSnapshot = {
      features: update.features ?? (sameUser ? prev!.features : { mpesa: false }),
      products: update.products ?? (sameUser ? prev!.products : []),
      stock: update.stock ?? (sameUser ? prev!.stock : undefined),
      user: update.user,
      savedAt: new Date().toISOString(),
    };
    localStorage.setItem(KEY, JSON.stringify(next));
  } catch {
    // Storage full or blocked: the terminal still works online.
  }
}

export function clearSession(): void {
  try {
    localStorage.removeItem(KEY);
  } catch {
    // ignore
  }
}