import { CONSENSUS, MAX_TARGET, NETWORK } from './testnet.ts';
import { NETWORK_GENESIS_TIME } from './network.ts';

export type ChainIdentity = { chainId: string; genesis: string };
let identity: Promise<ChainIdentity> | undefined;

/** Derive the same public manifest as the node from this immutable browser build. */
export function expectedChainIdentity(): Promise<ChainIdentity> {
  if (!identity) identity = (async () => {
    const digestHex = async (value: string) => Array.from(new Uint8Array(await crypto.subtle.digest(
      'SHA-256', new TextEncoder().encode(value))), byte => byte.toString(16).padStart(2, '0')).join('');
    const chainId = await digestHex(JSON.stringify([NETWORK, CONSENSUS, NETWORK_GENESIS_TIME, MAX_TARGET]));
    return { chainId, genesis: await digestHex(`${NETWORK}:genesis:${chainId}`) };
  })();
  return identity;
}