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using System;
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using Libplanet.Action;
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using Libplanet.Blocks;
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using Libplanet.Tx;
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namespace Libplanet.Blockchain.Policies
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{
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/// <summary>
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/// A default implementation of <see cref="IBlockPolicy{T}"/> interface.
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/// </summary>
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/// <typeparam name="T">An <see cref="IAction"/> type. It should match
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/// to <see cref="Block{T}"/>'s type parameter.</typeparam>
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public class BlockPolicy<T> : IBlockPolicy<T>
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where T : IAction, new()
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{
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private readonly Func<Transaction<T>, BlockChain<T>, bool> _doesTransactionFollowPolicy;
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/// <summary>
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/// Creates a <see cref="BlockPolicy{T}"/> with configuring
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/// <see cref="BlockInterval"/> in milliseconds,
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/// <see cref="MinimumDifficulty"/> and
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/// <see cref="DifficultyBoundDivisor"/>.
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/// </summary>
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/// <param name="blockAction">A block action to execute and be rendered for every block.
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/// </param>
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/// <param name="blockIntervalMilliseconds">Configures
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/// <see cref="BlockInterval"/> in milliseconds.
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/// 5000 milliseconds by default.
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/// </param>
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/// <param name="minimumDifficulty">Configures
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/// <see cref="MinimumDifficulty"/>. 1024 by default.</param>
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/// <param name="difficultyBoundDivisor">Configures
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/// <see cref="DifficultyBoundDivisor"/>. 128 by default.</param>
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/// <param name="doesTransactionFollowPolicy">
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/// A predicate that determines if the transaction follows the block policy.
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/// </param>
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public BlockPolicy(
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IAction blockAction = null,
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int blockIntervalMilliseconds = 5000,
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long minimumDifficulty = 1024,
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int difficultyBoundDivisor = 128,
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Func<Transaction<T>, BlockChain<T>, bool> doesTransactionFollowPolicy = null)
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: this(
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blockAction,
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TimeSpan.FromMilliseconds(blockIntervalMilliseconds),
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minimumDifficulty,
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difficultyBoundDivisor,
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doesTransactionFollowPolicy)
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{
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}
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/// <summary>
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/// Creates a <see cref="BlockPolicy{T}"/> with configuring
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/// <see cref="BlockInterval"/>, <see cref="MinimumDifficulty"/> and
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/// <see cref="DifficultyBoundDivisor"/>.
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/// </summary>
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/// <param name="blockAction">A block action to execute and be rendered for every block.
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/// </param>
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/// <param name="blockInterval">Configures <see cref="BlockInterval"/>.
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/// </param>
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/// <param name="minimumDifficulty">Configures
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/// <see cref="MinimumDifficulty"/>.</param>
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/// <param name="difficultyBoundDivisor">Configures
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/// <see cref="DifficultyBoundDivisor"/>.</param>
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/// <param name="doesTransactionFollowPolicy">
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/// A predicate that determines if the transaction follows the block policy.
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/// </param>
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public BlockPolicy(
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IAction blockAction,
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TimeSpan blockInterval,
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long minimumDifficulty,
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int difficultyBoundDivisor,
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Func<Transaction<T>, BlockChain<T>, bool> doesTransactionFollowPolicy = null)
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{
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if (blockInterval < TimeSpan.Zero)
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{
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throw new ArgumentOutOfRangeException(
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nameof(blockInterval),
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"Interval between blocks cannot be negative.");
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}
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1
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if (minimumDifficulty < 0)
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{
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throw new ArgumentOutOfRangeException(
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nameof(minimumDifficulty),
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"Minimum difficulty must be greater than 0.");
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}
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if (minimumDifficulty <= difficultyBoundDivisor)
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{
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const string message =
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"Difficulty bound divisor must be less than " +
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"the minimum difficulty.";
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throw new ArgumentOutOfRangeException(
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nameof(difficultyBoundDivisor),
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message);
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}
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BlockAction = blockAction;
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BlockInterval = blockInterval;
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MinimumDifficulty = minimumDifficulty;
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DifficultyBoundDivisor = difficultyBoundDivisor;
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_doesTransactionFollowPolicy = doesTransactionFollowPolicy ?? ((_, __) => true);
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}
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/// <inheritdoc/>
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public IAction BlockAction { get; }
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109
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/// <summary>
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/// An appropriate interval between consecutive <see cref="Block{T}"/>s.
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/// It is usually from 20 to 30 seconds.
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/// <para>If a previous interval took longer than this
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/// <see cref="GetNextBlockDifficulty(BlockChain{T})"/> method
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/// raises the <see cref="Block{T}.Difficulty"/>. If it took shorter
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/// than this <see cref="Block{T}.Difficulty"/> is dropped.</para>
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/// </summary>
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1
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public TimeSpan BlockInterval { get; }
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private long MinimumDifficulty { get; }
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private int DifficultyBoundDivisor { get; }
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/// <inheritdoc
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/// cref="IBlockPolicy{T}.DoesTransactionFollowsPolicy(Transaction{T}, BlockChain{T})"/>
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public virtual bool DoesTransactionFollowsPolicy(
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Transaction<T> transaction,
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BlockChain<T> blockChain)
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{
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return _doesTransactionFollowPolicy(transaction, blockChain);
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1
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}
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/// <inheritdoc/>
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/// <exception cref="InvalidBlockStateRootHashException">It will be thrown when the
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/// given block has incorrect <see cref="Block{T}.StateRootHash"/>.</exception>
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public virtual InvalidBlockException ValidateNextBlock(
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BlockChain<T> blocks,
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Block<T> nextBlock)
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{
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return null;
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1
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}
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/// <inheritdoc />
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public virtual long GetNextBlockDifficulty(BlockChain<T> blocks)
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{
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long index = blocks.Count;
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if (index < 0)
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{
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throw new InvalidBlockIndexException(
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$"index must be 0 or more, but its index is {index}.");
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}
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if (index <= 1)
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{
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return index == 0 ? 0 : MinimumDifficulty;
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}
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158
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var prevBlock = blocks[index - 1];
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DateTimeOffset prevPrevTimestamp = blocks[index - 2].Timestamp;
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DateTimeOffset prevTimestamp = prevBlock.Timestamp;
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TimeSpan timeDiff = prevTimestamp - prevPrevTimestamp;
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long timeDiffMilliseconds = (long)timeDiff.TotalMilliseconds;
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const long minimumMultiplier = -99;
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long multiplier = 1 - (timeDiffMilliseconds /
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(long)BlockInterval.TotalMilliseconds);
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multiplier = Math.Max(multiplier, minimumMultiplier);
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var prevDifficulty = prevBlock.Difficulty;
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var offset = prevDifficulty / DifficultyBoundDivisor;
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long nextDifficulty = prevDifficulty + (offset * multiplier);
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return Math.Max(nextDifficulty, MinimumDifficulty);
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1
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}
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}
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}
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longfin