Expose txPriority parameter for customized transaction selection

- Added `txPriority` as an argument in the public constructor API.
- This allows external callers to specify the priority for including
  transactions in the block to propose.

Libplanet.Net/Consensus/ConsensusContext.cs

@@ -7,6 +7,8 @@
 using Libplanet.Crypto;
 using Libplanet.Net.Messages;
 using Libplanet.Types.Blocks;
+using Libplanet.Types.Consensus;
+using Libplanet.Types.Tx;
 using Serilog;
 
 namespace Libplanet.Net.Consensus
@@ -26,9 +28,11 @@ public partial class ConsensusContext : IDisposable
         private readonly TimeSpan _newHeightDelay;
         private readonly ILogger _logger;
         private readonly Dictionary<long, Context> _contexts;
+        private readonly IComparer<Transaction>? _txPriority;
 
         private CancellationTokenSource? _newHeightCts;
 
+#pragma warning disable MEN002
         /// <summary>
         /// Initializes a new instance of the <see cref="ConsensusContext"/> class.
         /// </summary>
@@ -44,18 +48,25 @@ public partial class ConsensusContext : IDisposable
         /// </param>
         /// <param name="contextTimeoutOption">A <see cref="ContextTimeoutOption"/> for
         /// configuring a timeout for each <see cref="Step"/>.</param>
+        /// <param name="txPriority">An optional comparer for give certain transactions to
+        /// priority to belong to the block.  It will be passed as
+        /// <see cref="Context(IConsensusMessageCommunicator,BlockChain,long,PrivateKey,ValidatorSet,ContextTimeoutOption,IComparer{Transaction})"/>
+        /// 's parameter.</param>
+#pragma warning restore MEN002
         public ConsensusContext(
             IConsensusMessageCommunicator consensusMessageCommunicator,
             BlockChain blockChain,
             PrivateKey privateKey,
             TimeSpan newHeightDelay,
-            ContextTimeoutOption contextTimeoutOption)
+            ContextTimeoutOption contextTimeoutOption,
+            IComparer<Transaction>? txPriority = null)
         {
             _consensusMessageCommunicator = consensusMessageCommunicator;
             _blockChain = blockChain;
             _privateKey = privateKey;
             Height = -1;
             _newHeightDelay = newHeightDelay;
+            _txPriority = txPriority;
 
             _contextTimeoutOption = contextTimeoutOption;
 
@@ -439,7 +450,8 @@ private Context CreateContext(long height)
                 height,
                 _privateKey,
                 _blockChain.GetValidatorSet(_blockChain[Height - 1].Hash),
-                contextTimeoutOptions: _contextTimeoutOption);
+                contextTimeoutOptions: _contextTimeoutOption,
+                txPriority: _txPriority);
             AttachEventHandlers(context);
             return context;
         }

Libplanet.Net/Consensus/Context.cs

@@ -84,6 +84,7 @@ public partial class Context : IDisposable
         private readonly BlockChain _blockChain;
         private readonly Codec _codec;
         private readonly ValidatorSet _validatorSet;
+        private readonly IComparer<Transaction>? _txPriority;
         private readonly Channel<ConsensusMsg> _messageRequests;
         private readonly Channel<System.Action> _mutationRequests;
         private readonly HeightVoteSet _heightVoteSet;
@@ -128,13 +129,18 @@ private readonly
         /// given <paramref name="height"/>.</param>
         /// <param name="contextTimeoutOptions">A <see cref="ContextTimeoutOption"/> for
         /// configuring a timeout for each <see cref="ConsensusStep"/>.</param>
+        /// <param name="txPriority">An optional comparer for give certain transactions to
+        /// priority to belong to the block.  It will be passed as
+        /// <see cref="BlockChain.GatherTransactionsToPropose(long,IComparer{Transaction})"/>'s
+        /// parameter.</param>
         public Context(
             IConsensusMessageCommunicator consensusMessageCommunicator,
             BlockChain blockChain,
             long height,
             PrivateKey privateKey,
             ValidatorSet validators,
-            ContextTimeoutOption contextTimeoutOptions)
+            ContextTimeoutOption contextTimeoutOptions,
+            IComparer<Transaction>? txPriority = null)
             : this(
                 consensusMessageCommunicator,
                 blockChain,
@@ -144,7 +150,8 @@ public Context(
                 ConsensusStep.Default,
                 -1,
                 128,
-                contextTimeoutOptions)
+                contextTimeoutOptions,
+                txPriority)
         {
         }
 
@@ -157,7 +164,8 @@ private Context(
             ConsensusStep consensusStep,
             int round = -1,
             int cacheSize = 128,
-            ContextTimeoutOption? contextTimeoutOptions = null)
+            ContextTimeoutOption? contextTimeoutOptions = null,
+            IComparer<Transaction>? txPriority = null)
         {
             if (height < 1)
             {
@@ -191,6 +199,7 @@ private Context(
             _hasTwoThirdsPreVoteFlags = new HashSet<int>();
             _preCommitTimeoutFlags = new HashSet<int>();
             _validatorSet = validators;
+            _txPriority = txPriority;
             _cancellationTokenSource = new CancellationTokenSource();
             _blockValidationCache =
                 new LRUCache<BlockHash, (bool, IReadOnlyList<ICommittedActionEvaluation>)>(
@@ -418,7 +427,7 @@ private TimeSpan TimeoutPropose(long round)
         {
             try
             {
-                Block block = _blockChain.ProposeBlock(_privateKey, _lastCommit);
+                Block block = _blockChain.ProposeBlock(_privateKey, _lastCommit, _txPriority);
                 _blockChain.Store.PutBlock(block);
                 return block;
             }