From e8e751c44e2bfe71f01505c8cf7412e22e777c87 Mon Sep 17 00:00:00 2001
From: samliok <samliok@stanford.edu>
Date: Thu, 13 Aug 2026 19:10:44 -0400
Subject: [PATCH] Extract BlockDeserializer interface from VM

---
 adapters.go      | 10 +++++-----
 config.go        |  5 ++---
 instance.go      | 18 ++++++++++--------
 instance_test.go |  4 +++-
 4 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/adapters.go b/adapters.go
index 1f8512be..4d6b2153 100644
--- a/adapters.go
+++ b/adapters.go
@@ -229,17 +229,17 @@ func (bw *BlockBuilderWaiter) BuildBlock(ctx context.Context, metadata common.Pr
 }
 
 type blockDeserializer struct {
-	vm  VM
-	msm *metadata.StateMachine
+	deserializer BlockDeserializer
+	msm          *metadata.StateMachine
 }
 
-func (bp *blockDeserializer) DeserializeBlock(ctx context.Context, bytes []byte) (common.Block, error) {
+func (bd *blockDeserializer) DeserializeBlock(ctx context.Context, bytes []byte) (common.Block, error) {
 	var rawBlock metadata.RawBlock
 	if err := rawBlock.UnmarshalCanoto(bytes); err != nil {
 		return nil, err
 	}
 
-	block, err := bp.vm.ParseBlock(ctx, rawBlock.InnerBlockBytes)
+	block, err := bd.deserializer.ParseBlock(ctx, rawBlock.InnerBlockBytes)
 	if err != nil {
 		return nil, err
 	}
@@ -248,6 +248,6 @@ func (bp *blockDeserializer) DeserializeBlock(ctx context.Context, bytes []byte)
 			InnerBlock: block,
 			Metadata:   rawBlock.Metadata,
 		},
-		msm: bp.msm,
+		msm: bd.msm,
 	}, nil
 }
diff --git a/config.go b/config.go
index a47474f5..1aba21aa 100644
--- a/config.go
+++ b/config.go
@@ -53,12 +53,11 @@ type VM interface {
 	// WaitForPendingBlock returns when either the given context is cancelled,
 	// or when the VM signals that a block should be built.
 	WaitForPendingBlock(ctx context.Context)
+}
 
+type BlockDeserializer interface {
 	// ParseBlock parses the given block bytes into a VMBlock.
 	ParseBlock(context.Context, []byte) (avalanchego.VMBlock, error)
-
-	// ComputeICMEpoch computes the ICM epoch transition given the input parameters.
-	ComputeICMEpoch(input metadata.ICMEpochInput) metadata.ICMEpochInfo
 }
 
 type Storage interface {
diff --git a/instance.go b/instance.go
index 7dc61abe..848e14b2 100644
--- a/instance.go
+++ b/instance.go
@@ -39,12 +39,14 @@ type Config struct {
 	// WalCreator is the interface to create new write-ahead logs for the simplex instance.
 	WalCreator wal.Creator
 	// Storage is the interface to the block storage layer for the simplex instance.
-	Storage Storage
-	Logger  common.Logger
-	Sender  Sender
-	WALs    []wal.DeletableWAL
-	VM      VM
-	ID      common.NodeID
+	Storage           Storage
+	Logger            common.Logger
+	Sender            Sender
+	WALs              []wal.DeletableWAL
+	VM                VM
+	ICMETransition    metadata.ICMEpochTransition
+	BlockDeserializer BlockDeserializer
+	ID                common.NodeID
 }
 
 type nodeRole byte
@@ -461,7 +463,7 @@ func (i *Instance) createEpochConfig() (simplex.EpochConfig, error) {
 		GetPChainHeightForProposing:     i.Config.PlatformChain.GetMinimumHeight,
 		GetPChainHeightForVerifying:     i.Config.PlatformChain.GetCurrentHeight,
 		AuxiliaryInfoApp:                &NoopAuxiliaryInfoApp{},
-		ComputeICMEpoch:                 i.Config.VM.ComputeICMEpoch,
+		ComputeICMEpoch:                 i.Config.ICMETransition,
 		GetBlock:                        i.cs.RetrieveBlock,
 	})
 	if err != nil {
@@ -513,7 +515,7 @@ func (i *Instance) createEpochConfig() (simplex.EpochConfig, error) {
 		Storage:                    epochAwareStorage,
 		Comm:                       comm,
 		BlockBuilder:               blockBuilder,
-		BlockDeserializer:          &blockDeserializer{vm: i.Config.VM, msm: msm},
+		BlockDeserializer:          &blockDeserializer{deserializer: i.Config.BlockDeserializer, msm: msm},
 	}
 	return epochConfig, nil
 }
diff --git a/instance_test.go b/instance_test.go
index a6092468..e271fcd9 100644
--- a/instance_test.go
+++ b/instance_test.go
@@ -873,12 +873,14 @@ func newInstance(t *testing.T, nodeID common.NodeID, storage *MockStorage, net *
 
 // newInstanceWithVM is like newInstance but uses a caller-supplied VM, so a test
 // can share one controllable VM across restarts of the same node.
-func newInstanceWithVM(t *testing.T, nodeID common.NodeID, storage *MockStorage, net *inMemNetwork, pChain *testPlatformChain, cops *testCryptoOps, genesisBlock *testInnerBlock, vm VM) *Instance {
+func newInstanceWithVM(t *testing.T, nodeID common.NodeID, storage *MockStorage, net *inMemNetwork, pChain *testPlatformChain, cops *testCryptoOps, genesisBlock *testInnerBlock, vm *testVM) *Instance {
 	comm := &networkSender{net: net, self: nodeID}
 	config := Config{
 		Logger:                   testutil.MakeLogger(t, int(nodeID[0])),
 		ID:                       nodeID,
 		VM:                       vm,
+		BlockDeserializer:        vm,
+		ICMETransition:           vm.ComputeICMEpoch,
 		Storage:                  storage,
 		Sender:                   comm,
 		Broadcaster:              comm,