feat: Add begin/end block actions.

Libplanet.Action/ActionEvaluator.cs

@@ -26,27 +26,34 @@ namespace Libplanet.Action
     public class ActionEvaluator : IActionEvaluator
     {
         private readonly ILogger _logger;
-        private readonly PolicyBlockActionGetter _policyBlockActionGetter;
+        private readonly PolicyBlockActionGetter _policyBeginBlockActionGetter;
+        private readonly PolicyBlockActionGetter _policyEndBlockActionGetter;
         private readonly IStateStore _stateStore;
         private readonly IActionLoader _actionLoader;
 
         /// <summary>
         /// Creates a new <see cref="ActionEvaluator"/>.
         /// </summary>
-        /// <param name="policyBlockActionGetter">A delegator to get policy block action to evaluate
-        /// at the end for each <see cref="IPreEvaluationBlock"/> that gets evaluated.</param>
+        /// <param name="policyBeginBlockActionGetter">A delegator to get policy block actions to
+        /// evaluate at the beginning for each <see cref="IPreEvaluationBlock"/>
+        /// that gets evaluated.</param>
+        /// <param name="policyEndBlockActionGetter">A delegator to get policy block actions to
+        /// evaluate at the end for each <see cref="IPreEvaluationBlock"/> that gets evaluated.
+        /// </param>
         /// <param name="stateStore">The <see cref="IStateStore"/> to use to retrieve
         /// the states for a provided <see cref="HashDigest{SHA256}"/>.</param>
         /// <param name="actionTypeLoader"> A <see cref="IActionLoader"/> implementation using
         /// action type lookup.</param>
         public ActionEvaluator(
-            PolicyBlockActionGetter policyBlockActionGetter,
+            PolicyBlockActionGetter policyBeginBlockActionGetter,
+            PolicyBlockActionGetter policyEndBlockActionGetter,
             IStateStore stateStore,
             IActionLoader actionTypeLoader)
         {
             _logger = Log.ForContext<ActionEvaluator>()
                 .ForContext("Source", nameof(ActionEvaluator));
-            _policyBlockActionGetter = policyBlockActionGetter;
+            _policyBeginBlockActionGetter = policyBeginBlockActionGetter;
+            _policyEndBlockActionGetter = policyEndBlockActionGetter;
             _stateStore = stateStore;
             _actionLoader = actionTypeLoader;
         }
@@ -123,16 +130,29 @@ public IReadOnlyList<ICommittedActionEvaluation> Evaluate(
                     throw new ApplicationException("World cannot be mutated from modern to legacy");
                 }
 
-                ImmutableList<ActionEvaluation> evaluations =
-                    EvaluateBlock(block, previousState).ToImmutableList();
+                var evaluations = ImmutableList<ActionEvaluation>.Empty;
+                if (_policyBeginBlockActionGetter(block) is { } beginBlockActions &&
+                    beginBlockActions.Length > 0)
+                {
+                    evaluations = evaluations.AddRange(EvaluatePolicyBeginBlockActions(
+                        block, previousState
+                    ));
+                    previousState = evaluations.Last().OutputState;
+                }
+
+                evaluations = evaluations.AddRange(
+                    EvaluateBlock(block, previousState).ToImmutableList()
+                );
 
-                var policyBlockAction = _policyBlockActionGetter(block);
-                if (policyBlockAction is { } blockAction)
+                if (_policyEndBlockActionGetter(block) is { } endBlockActions &&
+                    endBlockActions.Length > 0)
                 {
                     previousState = evaluations.Count > 0
                         ? evaluations.Last().OutputState
                         : previousState;
-                    evaluations = evaluations.Add(EvaluatePolicyBlockAction(block, previousState));
+                    evaluations = evaluations.AddRange(EvaluatePolicyEndBlockActions(
+                        block, previousState
+                    ));
                 }
 
                 var committed = ToCommittedEvaluation(block, evaluations, baseStateRootHash);
@@ -491,30 +511,50 @@ internal IEnumerable<ActionEvaluation> EvaluateTx(
         /// the <see cref="IBlockPolicy.BlockAction"/> held by the instance
         /// for the <paramref name="blockHeader"/>.</returns>
         [Pure]
-        internal ActionEvaluation EvaluatePolicyBlockAction(
+        internal ActionEvaluation[] EvaluatePolicyBeginBlockActions(
             IPreEvaluationBlockHeader blockHeader,
             IWorld previousState)
         {
-            var policyBlockAction = _policyBlockActionGetter(blockHeader);
-            if (policyBlockAction is null)
-            {
-                var message =
-                    "To evaluate policy block action, " +
-                    "policyBlockAction must not be null.";
-                throw new InvalidOperationException(message);
-            }
+            _logger.Information(
+                $"Evaluating policy begin block actions for block #{blockHeader.Index} " +
+                $"{ByteUtil.Hex(blockHeader.PreEvaluationHash.ByteArray)}");
+
+            return EvaluateActions(
+                blockHeader: blockHeader,
+                tx: null,
+                previousState: previousState,
+                actions: _policyBeginBlockActionGetter(blockHeader),
+                stateStore: _stateStore,
+                logger: _logger).ToArray();
+        }
 
+        /// <summary>
+        /// Evaluates the <see cref="IBlockPolicy.BlockAction"/> set by the policy when
+        /// this <see cref="ActionEvaluator"/> was instantiated for a given
+        /// <see cref="IPreEvaluationBlockHeader"/>.
+        /// </summary>
+        /// <param name="blockHeader">The header of the block to evaluate.</param>
+        /// <param name="previousState">The states immediately before the evaluation of
+        /// the <see cref="IBlockPolicy.BlockAction"/> held by the instance.</param>
+        /// <returns>The <see cref="ActionEvaluation"/> of evaluating
+        /// the <see cref="IBlockPolicy.BlockAction"/> held by the instance
+        /// for the <paramref name="blockHeader"/>.</returns>
+        [Pure]
+        internal ActionEvaluation[] EvaluatePolicyEndBlockActions(
+            IPreEvaluationBlockHeader blockHeader,
+            IWorld previousState)
+        {
             _logger.Information(
-                $"Evaluating policy block action for block #{blockHeader.Index} " +
+                $"Evaluating policy end block actions for block #{blockHeader.Index} " +
                 $"{ByteUtil.Hex(blockHeader.PreEvaluationHash.ByteArray)}");
 
             return EvaluateActions(
                 blockHeader: blockHeader,
                 tx: null,
                 previousState: previousState,
-                actions: new[] { policyBlockAction }.ToImmutableList(),
+                actions: _policyEndBlockActionGetter(blockHeader),
                 stateStore: _stateStore,
-                logger: _logger).Single();
+                logger: _logger).ToArray();
         }
 
         internal IWorld PrepareInitialDelta(HashDigest<SHA256>? stateRootHash)

Libplanet.Action/PolicyBlockActionGetter.cs

@@ -1,6 +1,9 @@
+using System.Collections.Immutable;
 using Libplanet.Types.Blocks;
 
 namespace Libplanet.Action
 {
-    public delegate IAction? PolicyBlockActionGetter(IPreEvaluationBlockHeader blockHeader);
+    public delegate ImmutableArray<IAction> PolicyBlockActionGetter(
+        IPreEvaluationBlockHeader blockHeader
+    );
 }

Libplanet/Blockchain/BlockChain.Evaluate.cs

@@ -147,7 +147,8 @@ public IReadOnlyList<ICommittedActionEvaluation> EvaluateBlock(IPreEvaluationBlo
 
         /// <summary>
         /// Evaluates all actions in the <see cref="PreEvaluationBlock.Transactions"/> and
-        /// an optional <see cref="Blockchain.Policies.IBlockPolicy.BlockAction"/>, and returns
+        /// optional <see cref="Policies.IBlockPolicy.BeginBlockActions"/>,
+        /// <see cref="Policies.IBlockPolicy.EndBlockActions"/>, and returns
         /// a <see cref="Block"/> instance combined with the <see cref="Block.StateRootHash"/>
         /// The returned <see cref="Block"/> is signed by the given <paramref name="privateKey"/>.
         /// </summary>

Libplanet/Blockchain/Policies/BlockPolicy.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Immutable;
 using System.Diagnostics.Contracts;
 using System.Linq;
 using Libplanet.Action;
@@ -34,7 +35,11 @@ public class BlockPolicy : IBlockPolicy
         /// description for more detail.
         /// </para>
         /// </summary>
-        /// <param name="blockAction">A <see cref="IAction"/> to executed for
+        /// <param name="beginBlockActions">Array of <see cref="IAction"/> to executed for
+        /// every <see cref="Block"/>.  Set to <see langword="null"/> by default, which results
+        /// in no additional execution other than those included in <see cref="Transaction"/>s.
+        /// </param>
+        /// <param name="endBlockActions">A <see cref="IAction"/> to executed for
         /// every <see cref="Block"/>.  Set to <see langword="null"/> by default, which results
         /// in no additional execution other than those included in <see cref="Transaction"/>s.
         /// </param>
@@ -66,7 +71,8 @@ public class BlockPolicy : IBlockPolicy
         /// Goes to <see cref="GetMaxTransactionsPerSignerPerBlock"/>.  Set to
         /// <see cref="GetMaxTransactionsPerBlock"/> by default.</param>
         public BlockPolicy(
-            IAction? blockAction = null,
+            ImmutableArray<IAction>? beginBlockActions = null,
+            ImmutableArray<IAction>? endBlockActions = null,
             TimeSpan? blockInterval = null,
             Func<BlockChain, Transaction, TxPolicyViolationException?>?
                 validateNextBlockTx = null,
@@ -77,7 +83,8 @@ public BlockPolicy(
             Func<long, int>? getMaxTransactionsPerBlock = null,
             Func<long, int>? getMaxTransactionsPerSignerPerBlock = null)
         {
-            BlockAction = blockAction;
+            BeginBlockActions = beginBlockActions ?? ImmutableArray<IAction>.Empty;
+            EndBlockActions = endBlockActions ?? ImmutableArray<IAction>.Empty;
             BlockInterval = blockInterval ?? DefaultTargetBlockInterval;
             _getMaxTransactionsBytes = getMaxTransactionsBytes ?? (_ => 100L * 1024L);
             _getMinTransactionsPerBlock = getMinTransactionsPerBlock ?? (_ => 0);
@@ -152,7 +159,10 @@ public BlockPolicy(
         }
 
         /// <inheritdoc/>
-        public IAction? BlockAction { get; }
+        public ImmutableArray<IAction> BeginBlockActions { get; }
+
+        /// <inheritdoc/>
+        public ImmutableArray<IAction> EndBlockActions { get; }
 
         /// <summary>
         /// Targeted time interval between two consecutive <see cref="Block"/>s.

Libplanet/Blockchain/Policies/IBlockPolicy.cs

@@ -1,3 +1,4 @@
+using System.Collections.Immutable;
 using System.Diagnostics.Contracts;
 using Libplanet.Action;
 using Libplanet.Types.Blocks;
@@ -21,9 +22,14 @@ namespace Libplanet.Blockchain.Policies
     public interface IBlockPolicy
     {
         /// <summary>
-        /// An <see cref="IAction"/> to execute and be rendered for every block, if any.
-        /// </summary>
-        IAction? BlockAction { get; }
+        /// An array of <see cref="IAction"/> to execute and be rendered at the beginning
+        /// for every block, if any.</summary>
+        ImmutableArray<IAction> BeginBlockActions { get; }
+
+        /// <summary>
+        /// An array of <see cref="IAction"/> to execute and be rendered at the end for every block,
+        /// if any.</summary>
+        ImmutableArray<IAction> EndBlockActions { get; }
 
         /// <summary>
         /// Checks if a <see cref="Transaction"/> can be included in a yet to be mined

Libplanet/Blockchain/Policies/NullBlockPolicy.cs

@@ -1,5 +1,6 @@
 #nullable disable
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using Libplanet.Action;
 using Libplanet.Crypto;
 using Libplanet.Types.Blocks;
@@ -22,7 +23,9 @@ public NullBlockPolicy(
 
         public ISet<Address> BlockedMiners { get; } = new HashSet<Address>();
 
-        public IAction BlockAction => null;
+        public ImmutableArray<IAction> BeginBlockActions => ImmutableArray<IAction>.Empty;
+
+        public ImmutableArray<IAction> EndBlockActions => ImmutableArray<IAction>.Empty;
 
         public int GetMinTransactionsPerBlock(long index) => 0;