From 405d514e5eb851c9cbcacfb4c8ab0469a0c5c56c Mon Sep 17 00:00:00 2001
From: Hong Minhee <hong.minhee@gmail.com>
Date: Wed, 28 Aug 2019 21:09:53 +0900
Subject: [PATCH] Fix https://github.com/planetarium/libplanet/issues/465

---
 CHANGES.md                         |  9 +++++++++
 Libplanet.Tests/Store/StoreTest.cs | 32 ++++++++++++++++++++++++++++++
 Libplanet/Store/LiteDBStore.cs     |  7 ++++---
 3 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/CHANGES.md b/CHANGES.md
index d5c0fb9865e..3a27636ff4a 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -8,6 +8,15 @@ To be released.
 
 ### Bug fixes
 
+ -  Fixed a bug that `Swarm<T>.PreloadAsync()` method had thrown `LiteException`
+    (or other exception depending on `IStore`), which indicates a state
+    reference is duplicate, where `trustedStateValidators` is present and
+    a miner tries to download precalculated states from a trusted peer.
+    [[#465], [#474]]
+
+[#465]: https://github.com/planetarium/libplanet/issues/465
+[#474]: https://github.com/planetarium/libplanet/pull/474
+
 
 Version 0.5.1
 -------------
diff --git a/Libplanet.Tests/Store/StoreTest.cs b/Libplanet.Tests/Store/StoreTest.cs
index fb4c8f95f84..39c7545342c 100644
--- a/Libplanet.Tests/Store/StoreTest.cs
+++ b/Libplanet.Tests/Store/StoreTest.cs
@@ -360,6 +360,38 @@ public void IterateStateReferences()
             );
         }
 
+        [Fact]
+        public void StoreStateReferenceAllowsDuplication()
+        {
+            Address address3 = new PrivateKey().PublicKey.ToAddress();
+            Fx.Store.StoreStateReference(
+                Fx.StoreNamespace,
+                new[] { Fx.Address1, Fx.Address2 }.ToImmutableHashSet(),
+                Fx.Block1
+            );
+            Fx.Store.StoreStateReference(
+                Fx.StoreNamespace,
+                new[] { Fx.Address2, address3 }.ToImmutableHashSet(),
+                Fx.Block1
+            );
+            var expectedStateRefs = new[]
+            {
+                new Tuple<HashDigest<SHA256>, long>(Fx.Block1.Hash, Fx.Block1.Index),
+            };
+            Assert.Equal(
+                expectedStateRefs,
+                Fx.Store.IterateStateReferences(Fx.StoreNamespace, Fx.Address1)
+            );
+            Assert.Equal(
+                expectedStateRefs,
+                Fx.Store.IterateStateReferences(Fx.StoreNamespace, Fx.Address2)
+            );
+            Assert.Equal(
+                expectedStateRefs,
+                Fx.Store.IterateStateReferences(Fx.StoreNamespace, address3)
+            );
+        }
+
         [InlineData(0)]
         [InlineData(1)]
         [InlineData(2)]
diff --git a/Libplanet/Store/LiteDBStore.cs b/Libplanet/Store/LiteDBStore.cs
index 92e4d54d4d6..2ad6a75593c 100644
--- a/Libplanet/Store/LiteDBStore.cs
+++ b/Libplanet/Store/LiteDBStore.cs
@@ -439,14 +439,15 @@ public override void StoreStateReference<T>(
         {
             string collId = StateRefId(@namespace);
             LiteCollection<StateRefDoc> coll = _db.GetCollection<StateRefDoc>(collId);
-            coll.InsertBulk(
-                addresses.Select(addr => new StateRefDoc
+            IEnumerable<StateRefDoc> stateRefDocs = addresses
+                .Select(addr => new StateRefDoc
                 {
                     Address = addr,
                     BlockIndex = block.Index,
                     BlockHash = block.Hash,
                 })
-            );
+                .Where(doc => !coll.Exists(d => d.Id == doc.Id));
+            coll.InsertBulk(stateRefDocs);
             coll.EnsureIndex("AddressString");
             coll.EnsureIndex("BlockIndex");
         }