/**
 * Script to generate IBFT 2.0 genesis extraData.
 *
 * Usage (Node.js ≥18):
 *   node generate-genesis.mjs <validator-pubkey-hex> [<validator-pubkey-hex> ...]
 *
 * Example:
 *   node generate-genesis.mjs 09b... 12a...
 *
 * Prints the full genesis JSON to stdout with extraData populated.
 */
import fs from "fs";
import path from "path";
import { fileURLToPath } from "url";

const __dirname = path.dirname(fileURLToPath(import.meta.url));

const VANITY = "0x".padEnd(66, "0");          // 32 bytes of zeros
const ROUND = "0x0000000000000000";           // 8 bytes round (big-endian uint64)
const SEAL = "0x".padEnd(194, "0");           // 96 bytes proposer seal (empty)

function encodeRlpListOfAddresses(pubkeys) {
  // RLP list of 64-byte addresses (we use pubkey as address placeholder for IBFT 2.0 extraData)
  // For Besu IBFT 2.0 the extraData is: vanity (32) | RLP([validators...]) | round (8) | seal (0 or 96)
  // The addresses inside RLP are 20-byte Ethereum addresses derived from pubkeys.
  // For simplicity, we require 20-byte hex addresses as input here.
  const items = pubkeys.map((pk) => {
    const hex = pk.startsWith("0x") ? pk : "0x" + pk;
    if (hex.length !== 42) {
      throw new Error(`Expected 20-byte address (42 hex chars), got ${hex.length} for ${pk}`);
    }
    // RLP encode: 0x80 + len for short strings
    const buf = Buffer.from(hex.slice(2), "hex");
    if (buf.length <= 55) {
      return Buffer.from([0x80 + buf.length, ...buf]);
    }
    throw new Error("RLP long string not implemented");
  });

  const payload = Buffer.concat(items);
  if (payload.length <= 55) {
    return Buffer.concat([Buffer.from([0xc0 + payload.length]), payload]);
  }
  throw new Error("RLP long list not implemented");
}

function encodeExtraData(addresses) {
  const vanity = Buffer.from(VANITY.slice(2), "hex");
  const validators = encodeRlpListOfAddresses(addresses);
  const round = Buffer.from(ROUND.slice(2), "hex");
  const seal = Buffer.from(SEAL.slice(2), "hex");
  const full = Buffer.concat([vanity, validators, round, seal]);
  return "0x" + full.toString("hex");
}

const addresses = process.argv.slice(2);
if (addresses.length < 4) {
  console.error("Usage: node generate-genesis.mjs <20-byte-address> ... (provide at least 4 for IBFT)");
  process.exit(1);
}

const templatePath = path.join(__dirname, "besu-config", "ibftGenesisTemplate.json");
const template = JSON.parse(fs.readFileSync(templatePath, "utf8"));

template.extraData = encodeExtraData(addresses);

// Add alloc for a faucet / deployer account if needed (placeholder)
template.alloc = {};

console.log(JSON.stringify(template, null, 2));