Add missing interfaces for EVM compatibility

- Add AppSender interface to engine/core for VM plugin communication
- Add AppHandler interface with message handling methods
- Add Fx struct for feature extensions
- Add AppSender interface to engine/chain/block for node integration
- Fix GetValidatorState to return typed ValidatorState instead of interface{}
- Add appsender package in core for consensus-level app messaging

These interfaces are required by the EVM package to build successfully
with the consensus package.

context/context.go

@@ -121,9 +121,11 @@ func GetNetworkID(ctx context.Context) uint32 {
 }
 
 // GetValidatorState gets the validator state from context
-func GetValidatorState(ctx context.Context) interface{} {
+func GetValidatorState(ctx context.Context) ValidatorState {
 	if c, ok := ctx.Value(contextKey).(*Context); ok {
-		return c.ValidatorState
+		if vs, ok := c.ValidatorState.(ValidatorState); ok {
+			return vs
+		}
 	}
 	return nil
 }

core/appsender/appsender.go

@@ -0,0 +1,30 @@
+// Copyright (C) 2019-2025, Lux Industries Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+// Package appsender provides application-level message sending interfaces
+package appsender
+
+import (
+	"context"
+
+	"github.com/luxfi/ids"
+	"github.com/luxfi/math/set"
+)
+
+// AppSender sends application-level messages.
+type AppSender interface {
+	// SendAppRequest sends an application-level request to the given nodes.
+	SendAppRequest(ctx context.Context, nodeIDs set.Set[ids.NodeID], requestID uint32, appRequestBytes []byte) error
+
+	// SendAppResponse sends an application-level response to the given node.
+	SendAppResponse(ctx context.Context, nodeID ids.NodeID, requestID uint32, appResponseBytes []byte) error
+
+	// SendAppError sends an application-level error to the given node.
+	SendAppError(ctx context.Context, nodeID ids.NodeID, requestID uint32, errorCode int32, errorMessage string) error
+
+	// SendAppGossip sends an application-level gossip to all connected nodes.
+	SendAppGossip(ctx context.Context, nodeIDs set.Set[ids.NodeID], appGossipBytes []byte) error
+
+	// SendAppGossipSpecific sends an application-level gossip to specific nodes.
+	SendAppGossipSpecific(ctx context.Context, nodeIDs set.Set[ids.NodeID], appGossipBytes []byte) error
+}

engine/chain/block/vm.go

@@ -57,3 +57,21 @@ const (
 	PendingTxs    = core.PendingTxs
 	StateSyncDone = core.StateSyncDone
 )
+
+// AppSender sends application-level messages
+type AppSender interface {
+	// SendAppRequest sends an application-level request to the given nodes
+	SendAppRequest(ctx context.Context, nodeIDs []ids.NodeID, requestID uint32, appRequestBytes []byte) error
+
+	// SendAppResponse sends an application-level response to the given node
+	SendAppResponse(ctx context.Context, nodeID ids.NodeID, requestID uint32, appResponseBytes []byte) error
+
+	// SendAppError sends an application-level error to the given node
+	SendAppError(ctx context.Context, nodeID ids.NodeID, requestID uint32, errorCode int32, errorMessage string) error
+
+	// SendAppGossip sends an application-level gossip to peers
+	SendAppGossip(ctx context.Context, nodeIDs []ids.NodeID, appGossipBytes []byte) error
+
+	// SendAppGossipSpecific sends an application-level gossip to specific peers
+	SendAppGossipSpecific(ctx context.Context, nodeIDs []ids.NodeID, appGossipBytes []byte) error
+}

engine/core/interfaces.go

@@ -0,0 +1,73 @@
+// Copyright (C) 2019-2025, Lux Industries Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+// Package core provides core interfaces for the Lux consensus engine
+package core
+
+import (
+	"context"
+	"time"
+
+	"github.com/luxfi/ids"
+	"github.com/luxfi/math/set"
+)
+
+// AppError represents an application-level error
+type AppError struct {
+	Code    int32
+	Message string
+}
+
+// Error implements error interface
+func (e *AppError) Error() string {
+	return e.Message
+}
+
+// AppSender sends application-level messages.
+type AppSender interface {
+	// SendAppRequest sends an application-level request to the given nodes.
+	SendAppRequest(ctx context.Context, nodeIDs set.Set[ids.NodeID], requestID uint32, appRequestBytes []byte) error
+
+	// SendAppResponse sends an application-level response to the given node.
+	SendAppResponse(ctx context.Context, nodeID ids.NodeID, requestID uint32, appResponseBytes []byte) error
+
+	// SendAppError sends an application-level error to the given node.
+	SendAppError(ctx context.Context, nodeID ids.NodeID, requestID uint32, errorCode int32, errorMessage string) error
+
+	// SendAppGossip sends an application-level gossip to all connected nodes.
+	SendAppGossip(ctx context.Context, nodeIDs set.Set[ids.NodeID], appGossipBytes []byte) error
+
+	// SendAppGossipSpecific sends an application-level gossip to specific nodes.
+	SendAppGossipSpecific(ctx context.Context, nodeIDs set.Set[ids.NodeID], appGossipBytes []byte) error
+}
+
+// AppHandler handles application-level messages from nodes.
+type AppHandler interface {
+	// AppRequest handles an application-level request from a node.
+	AppRequest(ctx context.Context, nodeID ids.NodeID, requestID uint32, deadline time.Time, request []byte) error
+
+	// AppRequestFailed handles a failed application-level request.
+	AppRequestFailed(ctx context.Context, nodeID ids.NodeID, requestID uint32, appErr *AppError) error
+
+	// AppResponse handles an application-level response from a node.
+	AppResponse(ctx context.Context, nodeID ids.NodeID, requestID uint32, response []byte) error
+
+	// AppGossip handles an application-level gossip from a node.
+	AppGossip(ctx context.Context, nodeID ids.NodeID, msg []byte) error
+}
+
+// FxInterface is a feature extension interface
+type FxInterface interface {
+	// Initialize initializes the Fx
+	Initialize(vm interface{}) error
+	// Bootstrapping is called when the chain is bootstrapping
+	Bootstrapping() error
+	// Bootstrapped is called when the chain is done bootstrapping
+	Bootstrapped() error
+}
+
+// Fx is a feature extension wrapper with ID
+type Fx struct {
+	ID ids.ID
+	Fx FxInterface
+}