// Shared pairing primitives used by the live relay-adoption path.

import type { DeviceType } from "./sync-types";

export interface PairingTransport {
  send(msg: Uint8Array): Promise<void>;
  receive(): Promise<Uint8Array>;
}

export interface LocalIdentity {
  deviceId: string;
  deviceName: string;
  deviceType: DeviceType;
  longTermPublicKeyHex: string;
  signingPublicKeyHex?: string;
  /** Server-only field — Android/iOS sync hosts announce their port. */
  wsPort?: number;
  /** Stable per-vault id, omitted while the vault is locked. */
  vaultId?: string;
  /** Signed Pro license blob advertised after SAS confirmation. */
  license?: string;
  relayUrl?: string;
}

/** Derive the cross-platform 8-digit SAS from a Noise handshake hash. */
export function derivePairingSAS(handshakeHash: Uint8Array): string {
  if (handshakeHash.length < 8) {
    throw new Error("handshake hash too short for SAS");
  }
  // The big-endian rule is pinned by the Android cross-platform KATs.
  let value = 0n;
  for (const byte of handshakeHash.subarray(0, 8)) {
    value = (value << 8n) | BigInt(byte);
  }
  return String(value % 100_000_000n).padStart(8, "0");
}