/**
 * PB-26-203: the session-key escrow is only as trustworthy as the boundary
 * around chrome.storage.session. This initializer positively establishes
 * trusted-only access on both storage areas before any session restore runs.
 * Where the browser cannot prove that state, the caller must disable the
 * escrow (fail closed) instead of trusting an unproven boundary.
 */
export type StorageHardening = {
  localHardened: boolean;
  sessionHardened: boolean;
  sessionEscrowAvailable: boolean;
};

type AccessLevelArea = {
  setAccessLevel?: (options: { accessLevel: "TRUSTED_CONTEXTS" }) => Promise<void>;
};

async function setTrustedContexts(area: unknown): Promise<boolean> {
  const typed = area as AccessLevelArea | undefined;
  if (typeof typed?.setAccessLevel !== "function") return false;
  try {
    await typed.setAccessLevel({ accessLevel: "TRUSTED_CONTEXTS" });
    return true;
  } catch {
    // Optional browser hardening must never prevent the extension from
    // starting; the message policy remains the primary security boundary.
    return false;
  }
}

export async function hardenExtensionStorage(): Promise<StorageHardening> {
  const localHardened = await setTrustedContexts(chrome.storage?.local);
  const session = chrome.storage?.session;
  // No session area (older Firefox): no escrow exists to protect, so there
  // is nothing to harden — but escrow is still reported unavailable.
  const sessionHardened = session ? await setTrustedContexts(session) : false;
  return { localHardened, sessionHardened, sessionEscrowAvailable: sessionHardened };
}