A fairness checker.
No verifiable game.

// Select the result display element
const resultDiv = document.getElementById('result');

const RISK_LEVELS = {
  LOW: {
    maxMultiplier: 10,
    minMultiplier: 0.3,
    riskFactor: 1.2,
  },
  MEDIUM: {
    maxMultiplier: 33,
    minMultiplier: 0.3,
    riskFactor: 1.5,
  },
  HIGH: {
    maxMultiplier: 1000,
    minMultiplier: 0.2,
    riskFactor: 9.5,
  },
};

const error = message => {
  resultDiv.innerHTML = `<div class="text-red-500 text-center">${message}</div>`;
};

const generateRandomNumber = (seed) => {
  const hash = CryptoJS.SHA256(seed).toString();
  const decimal = parseInt(hash.slice(0, 8), 16);
  return decimal / 0xffffffff;
};

function calculatePositionProbabilities(nbRows) {
  const nbBuckets = nbRows + 1;
  const probabilities = new Array(nbBuckets).fill(0);
  const totalPaths = Math.pow(2, nbRows);

  for (let path = 0; path < totalPaths; path++) {
    let position = 0;
    for (let row = 0; row < nbRows; row++) {
      if ((path & (1 << row)) !== 0) {
        position++;
      }
    }
    probabilities[position]++;
  }

  return probabilities.map((p) => p / totalPaths);
}

function generateMultipliers(riskLevel, nbRows) {
  const config = RISK_LEVELS[riskLevel];
  const nbBuckets = nbRows + 1;
  const multipliers = new Array(nbBuckets);
  const probabilities = calculatePositionProbabilities(nbRows);

  const centerPosition = nbBuckets % 2 === 0
    ? Math.floor((nbBuckets - 1) / 2)
    : Math.floor(nbBuckets / 2);

  for (let i = 0; i <= centerPosition; i++) {
    const distanceFromCenter = Math.abs(i - centerPosition);
    const normalizedDistance = distanceFromCenter / centerPosition;

    if (i === centerPosition) {
      multipliers[i] = config.minMultiplier;
    } else {
      const progressionFactor = Math.pow(normalizedDistance, config.riskFactor);
      multipliers[i] = config.minMultiplier + (config.maxMultiplier - config.minMultiplier) * progressionFactor;
    }
  }

  for (let i = centerPosition + 1; i < nbBuckets; i++) {
    multipliers[i] = multipliers[nbBuckets - i - 1];
  }

  const expectedValue = multipliers.reduce((sum, mult, i) => sum + mult * probabilities[i], 0);
  const targetExpectedValue = 0.95;
  const adjustmentFactor = targetExpectedValue / expectedValue;

  return multipliers.map(mult => Math.round(mult * adjustmentFactor * 100) / 100);
}

function calculateResult(seed, riskLevel, nbRows) {
  let position = 0;
  const path = [];

  for (let i = 0; i < nbRows; i++) {
    const random = generateRandomNumber(seed + i.toString());
    if (random < 0.5) {
      position += 1;
      path.push(1);
    } else {
      path.push(0);
    }
  }

  const multipliers = generateMultipliers(riskLevel, nbRows);
  return {
    multiplier: multipliers[position],
    position: position,
    path: path
  };
}

document.getElementById('verify').onclick = () => {
  const serverSeed = document.getElementById('serverSeed').value;
  const clientSeed = document.getElementById('clientSeed').value;
  const numRows = parseInt(document.getElementById('numRows').value);
  const riskLevel = document.getElementById('riskLevel').value;

  if (!serverSeed) return error('Server seed is required');
  if (!clientSeed) return error('Client seed is required');
  if (!numRows || numRows < 8 || numRows > 16) return error('Number of rows must be between 8 and 16');
  if (!RISK_LEVELS[riskLevel]) return error('Invalid risk level');

  try {
    const combinedSeed = clientSeed + serverSeed;
    const gameResult = calculateResult(combinedSeed, riskLevel, numRows);
    
    resultDiv.innerHTML = `
      <div class="text-center">
        <table class="w-full border-collapse border border-gray-600">
          <thead>
            <tr>
              <th class="border border-gray-600 p-2">Position</th>
              <th class="border border-gray-600 p-2">Multiplier</th>
              <th class="border border-gray-600 p-2">Path</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td class="border border-gray-600 p-2">${gameResult.position}/${numRows}</td>
              <td class="border border-gray-600 p-2">${gameResult.multiplier}x</td>
              <td class="border border-gray-600 p-2">${gameResult.path.join(" → ")}</td>
            </tr>
          </tbody>
        </table>
      </div>`;
  } catch (e) {
    console.error('Error:', e);
    error('An error occurred while generating the results.');
  }
};