/// <summary>
/// Calculates the difficulty for the next block given a previous blocks header, the timestamp of the new block, and the configuration.
/// </summary>
/// <param name="parentBlockHeader">The previous block header from which we derive difficulty.</param>
/// <param name="timestamp">The timestamp of the new block.</param>
/// <param name="configuration">The configuration under which we calculate difficulty.</param>
/// <returns>Returns the difficulty for the supposed new block.</returns>
public static BigInteger CalculateDifficulty(BlockHeader parentBlockHeader, BigInteger timestamp, Configuration.Configuration configuration)
{
// Handle the special case of difficulty for test chains (difficulty 1 keeps difficulty at 1).
if (parentBlockHeader.Difficulty == 1)
{
return(1);
}
// Check our versioning
BigInteger newBlockNumber = parentBlockHeader.BlockNumber + 1;
bool isByzantium = newBlockNumber >= configuration.GetReleaseStartBlockNumber(Configuration.EthereumRelease.Byzantium);
bool isHomestead = newBlockNumber >= configuration.GetReleaseStartBlockNumber(Configuration.EthereumRelease.Homestead);
// TODO: Revisit the rest of this. Currently a poor implementation. Use following as source: https://dltlabs.com/how-difficulty-adjustment-algorithm-works-in-ethereum/
BigInteger offset = parentBlockHeader.Difficulty / configuration.DifficultyFactor;
BigInteger sign = 0;
BigInteger deltaTime = timestamp - parentBlockHeader.Timestamp;
if (isByzantium)
{
BigInteger x = 2;
if (parentBlockHeader.UnclesHash.ValuesEqual(BLANK_UNCLES_HASH))
{
x = 1;
}
sign = BigInteger.Max(-99, x - (deltaTime / configuration.DifficultyAdjustmentCutOffByzantium));
}
else if (isHomestead)
{
sign = BigInteger.Max(-99, 1 - (deltaTime / configuration.DifficultyAdjustmentCutOffHomestead));
}
else
{
if (deltaTime < configuration.DifficultyAdjustmentCutOff)
{
sign = 1;
}
else
{
sign = -1;
}
}
BigInteger minDifficulty = BigInteger.Min(configuration.MinDifficulty, parentBlockHeader.Difficulty);
BigInteger difficulty = BigInteger.Max(minDifficulty, parentBlockHeader.Difficulty + (offset * sign));
BigInteger periods = newBlockNumber / configuration.DifficultyExponentialPeriod;
if (isByzantium)
{
periods -= configuration.DifficultyExponentialFreePeriodsByzantium;
}
if (periods >= configuration.DifficultyExponentialFreePeriods)
{
BigInteger exponent = periods - configuration.DifficultyExponentialFreePeriods;
return(BigInteger.Max(difficulty + BigInteger.Pow(2, (int)exponent), configuration.MinDifficulty));
}
return(difficulty);
}
