From b7d7ecb3bf6b454fc11d6cd23ee36390576aa3d4 Mon Sep 17 00:00:00 2001
From: scooletz <scooletz@gmail.com>
Date: Fri, 16 Jun 2023 17:45:44 +0200
Subject: [PATCH] Merkle foundations with pre-commit hook

---
 src/Paprika.Runner/Program.cs           |  2 +-
 src/Paprika/Chain/Blockchain.cs         | 15 ++++-
 src/Paprika/Chain/IPreCommitBehavior.cs | 74 +++++++++++++++++++++++++
 3 files changed, 87 insertions(+), 4 deletions(-)
 create mode 100644 src/Paprika/Chain/IPreCommitBehavior.cs

diff --git a/src/Paprika.Runner/Program.cs b/src/Paprika.Runner/Program.cs
index 414812a0..b9c8e502 100644
--- a/src/Paprika.Runner/Program.cs
+++ b/src/Paprika.Runner/Program.cs
@@ -130,7 +130,7 @@ public static async Task Main(String[] args)
                     ctx.Refresh();
                 }));
 
-            await using (var blockchain = new Blockchain(db, FlushEvery, 1000, reporter.Observe))
+            await using (var blockchain = new Blockchain(db, null, FlushEvery, 1000, reporter.Observe))
             {
                 counter = Writer(blockchain, bigStorageAccount, random, layout[writing]);
             }
diff --git a/src/Paprika/Chain/Blockchain.cs b/src/Paprika/Chain/Blockchain.cs
index d156b141..af3c5e7e 100644
--- a/src/Paprika/Chain/Blockchain.cs
+++ b/src/Paprika/Chain/Blockchain.cs
@@ -44,6 +44,7 @@ public class Blockchain : IAsyncDisposable
     private readonly MetricsExtensions.IAtomicIntGauge _flusherQueueCount;
 
     private readonly PagedDb _db;
+    private readonly IPreCommitBehavior? _preCommit;
     private readonly TimeSpan _minFlushDelay;
     private readonly Action? _beforeMetricsDisposed;
     private readonly Task _flusher;
@@ -52,9 +53,10 @@ public class Blockchain : IAsyncDisposable
 
     private static readonly TimeSpan DefaultFlushDelay = TimeSpan.FromSeconds(1);
 
-    public Blockchain(PagedDb db, TimeSpan? minFlushDelay = null, int? finalizationQueueLimit = null, Action? beforeMetricsDisposed = null)
+    public Blockchain(PagedDb db, IPreCommitBehavior? preCommit = null, TimeSpan? minFlushDelay = null, int? finalizationQueueLimit = null, Action? beforeMetricsDisposed = null)
     {
         _db = db;
+        _preCommit = preCommit;
         _minFlushDelay = minFlushDelay ?? DefaultFlushDelay;
         _beforeMetricsDisposed = beforeMetricsDisposed;
 
@@ -270,7 +272,7 @@ public bool TryGet(in Key key, out ReadOnlySpan<byte> result)
     /// <summary>
     /// Represents a block that is a result of ExecutionPayload, storing it in a in-memory trie
     /// </summary>
-    private class Block : RefCountingDisposable, IWorldState
+    private class Block : RefCountingDisposable, IWorldState, ICommit
     {
         public Keccak Hash { get; }
         public Keccak ParentHash { get; }
@@ -316,6 +318,9 @@ public void Commit()
             // acquires one more lease for this block as it is stored in the blockchain
             AcquireLease();
 
+            // run pre-commit
+            _blockchain._preCommit?.BeforeCommit(this);
+
             // set to blocks in number and in blocks by hash
             _blockchain._blocksByNumber.AddOrUpdate(BlockNumber,
                 static (_, block) => new[] { block },
@@ -391,7 +396,9 @@ public void SetStorage(in Keccak key, in Keccak address, UInt256 value)
             Set(Key.StorageCell(path, address), payload);
         }
 
-        private void Set(in Key key, in ReadOnlySpan<byte> payload)
+        public bool TryGet(in Key key, out ReadOnlySpanOwner<byte> result) => throw new NotImplementedException("Not implemented yet");
+
+        public void Set(in Key key, in ReadOnlySpan<byte> payload)
         {
             RawFixedMap map;
 
@@ -417,6 +424,8 @@ private void Set(in Key key, in ReadOnlySpan<byte> payload)
             map.TrySet(key, payload);
         }
 
+        public IKeyEnumerator GetEnumerator() => throw new NotImplementedException("Not implemented yet");
+
         private ReadOnlySpanOwner<byte> Get(int bloom, in Key key)
         {
             if (TryAcquireLease() == false)
diff --git a/src/Paprika/Chain/IPreCommitBehavior.cs b/src/Paprika/Chain/IPreCommitBehavior.cs
new file mode 100644
index 00000000..b44fe142
--- /dev/null
+++ b/src/Paprika/Chain/IPreCommitBehavior.cs
@@ -0,0 +1,74 @@
+using Paprika.Data;
+using Paprika.Utils;
+
+namespace Paprika.Chain;
+
+/// <summary>
+/// A pre-commit behavior run by <see cref="Blockchain"/> component just before commiting a <see cref="IWorldState"/>
+/// with <see cref="IWorldState.Commit"/>. Useful to provide concerns, like the Merkle construct and others.
+/// </summary>
+public interface IPreCommitBehavior
+{
+    /// <summary>
+    /// Executed just before commit.
+    /// </summary>
+    /// <param name="commit">The object representing the commit.</param>
+    public void BeforeCommit(ICommit commit);
+}
+
+/// <summary>
+/// The set of changes applied by <see cref="IWorldState"/>.
+/// Allows for additional modifications of the data just before the commit.
+/// </summary>
+/// <remarks>
+/// To access all the keys use the enumerator:
+///
+/// public static void Foreach(this ICommit commit)
+/// {
+///     foreach (var key in commit)
+///     {
+///         key.
+///     }
+///  }
+/// </remarks>
+public interface ICommit
+{
+    /// <summary>
+    /// Tries to retrieve the result stored under the given key.
+    /// </summary>
+    /// <returns>
+    /// Whether the retrieval was successful.
+    /// </returns>
+    /// <remarks>
+    /// If successful, returns a result as an owner. Must be disposed properly.
+    /// </remarks>
+    public bool TryGet(in Key key, out ReadOnlySpanOwner<byte> result);
+
+    /// <summary>
+    /// Sets the value under the given key.
+    /// </summary>
+    void Set(in Key key, in ReadOnlySpan<byte> payload);
+
+    /// <summary>
+    /// Gets the enumerator for the keys in the given commit.
+    /// </summary>
+    /// <returns></returns>
+    IKeyEnumerator GetEnumerator();
+}
+
+/// <summary>
+/// The <see cref="Key"/> enumerator.
+/// </summary>
+public interface IKeyEnumerator : IDisposable
+{
+    /// <summary>
+    /// The current key.
+    /// </summary>
+    ref readonly Key Current { get; }
+
+    /// <summary>
+    /// Moves to the next.
+    /// </summary>
+    public bool MoveNext();
+}
+