import crypto from 'crypto';
import { getRealIP } from './network.js';

export function generateChallenge(checkpointConfig) {
  const challenge = crypto.randomBytes(16).toString('hex');
  const salt = crypto.randomBytes(checkpointConfig.SaltLength).toString('hex');
  return { challenge, salt };
}

export function calculateHash(input) {
  return crypto.createHash('sha256').update(input).digest('hex');
}

export function verifyPoW(challenge, salt, nonce, difficulty) {
  const hash = calculateHash(challenge + salt + nonce);
  return hash.startsWith('0'.repeat(difficulty));
}

export function checkPoSTimes(times, enableCheck, ratio) {
  if (!Array.isArray(times) || times.length !== 3) {
    throw new Error('Invalid PoS run times length');
  }
  const minT = Math.min(...times);
  const maxT = Math.max(...times);
  if (enableCheck && maxT > minT * ratio) {
    throw new Error(`PoS run times inconsistent (ratio ${maxT / minT} > ${ratio})`);
  }
}

export const challengeStore = new Map();

export function generateRequestID(request, checkpointConfig) {
  const { challenge, salt } = generateChallenge(checkpointConfig);
  const posSeed = crypto.randomBytes(32).toString('hex');
  const requestID = crypto.randomBytes(16).toString('hex');
  const params = {
    Challenge: challenge,
    Salt: salt,
    Difficulty: checkpointConfig.Difficulty,
    ExpiresAt: Date.now() + checkpointConfig.ChallengeExpiration,
    CreatedAt: Date.now(),
    ClientIP: getRealIP(request),
    PoSSeed: posSeed,
  };
  challengeStore.set(requestID, params);
  return requestID;
}

export function getChallengeParams(requestID) {
  return challengeStore.get(requestID);
}

export function deleteChallenge(requestID) {
  challengeStore.delete(requestID);
}

export function verifyPoS(hashes, times, checkpointConfig) {
  if (!Array.isArray(hashes) || hashes.length !== 3) {
    throw new Error('Invalid PoS hashes length');
  }
  if (!Array.isArray(times) || times.length !== 3) {
    throw new Error('Invalid PoS run times length');
  }
  if (hashes[0] !== hashes[1] || hashes[1] !== hashes[2]) {
    throw new Error('PoS hashes do not match');
  }
  if (hashes[0].length !== 64) {
    throw new Error('Invalid PoS hash length');
  }

  checkPoSTimes(times, checkpointConfig.CheckPoSTimes, checkpointConfig.PoSTimeConsistencyRatio);
}