From 71182306390990e5ef9726e73924bc5a9f070282 Mon Sep 17 00:00:00 2001
From: Paul Buetow <paul@buetow.org>
Date: Thu, 26 Mar 2026 23:32:34 +0200
Subject: Implement Raft vote handling for 04c78b3c-2267-495b-9aca-84b544a1882f

---
 .../protocols/implementations/VSRaftProtocol.java  | 120 ++++++++++++++++++++-
 1 file changed, 119 insertions(+), 1 deletion(-)

(limited to 'src/main/java/protocols/implementations/VSRaftProtocol.java')

diff --git a/src/main/java/protocols/implementations/VSRaftProtocol.java b/src/main/java/protocols/implementations/VSRaftProtocol.java
index 6257538..597c1e0 100644
--- a/src/main/java/protocols/implementations/VSRaftProtocol.java
+++ b/src/main/java/protocols/implementations/VSRaftProtocol.java
@@ -3,6 +3,7 @@ package protocols.implementations;
 import java.util.ArrayList;
 import java.util.Vector;
 
+import core.VSInternalProcess;
 import core.VSMessage;
 import protocols.VSAbstractProtocol;
 
@@ -87,12 +88,14 @@ public class VSRaftProtocol extends VSAbstractProtocol {
      * @see protocols.VSAbstractProtocol#onServerRecv(core.VSMessage)
      */
     public void onServerRecv(VSMessage recvMessage) {
+        handleMessage(recvMessage);
     }
 
     /* (non-Javadoc)
      * @see protocols.VSAbstractProtocol#onClientRecv(core.VSMessage)
      */
     public void onClientRecv(VSMessage recvMessage) {
+        handleMessage(recvMessage);
     }
 
     /* (non-Javadoc)
@@ -157,10 +160,23 @@ public class VSRaftProtocol extends VSAbstractProtocol {
     private void becomeLeader() {
         isLeader = true;
         isCandidate = false;
-        removeSchedules();
+        votesReceived = 0;
         leaderId = process.getProcessID();
         lastHeartbeatTime = process.getTime();
+        isServer(true);
+
+        if (!getLongKeySet().contains("heartbeatInterval")) {
+            onServerInit();
+        }
+
+        boolean previousContextIsServer = currentContextIsServer();
+
+        currentContextIsServer(false);
+        removeSchedules();
+
+        currentContextIsServer(true);
         sendHeartbeat();
+        currentContextIsServer(previousContextIsServer);
     }
 
     /**
@@ -218,6 +234,7 @@ public class VSRaftProtocol extends VSAbstractProtocol {
         isCandidate = true;
         leaderId = -1;
         lastHeartbeatTime = process.getTime();
+        isServer(true);
 
         VSMessage voteRequest = new VSMessage();
         voteRequest.setString("type", "voteRequest");
@@ -241,4 +258,105 @@ public class VSRaftProtocol extends VSAbstractProtocol {
         lastHeartbeatTime = process.getTime();
         scheduleAt(process.getTime() + getLong("heartbeatInterval"));
     }
+
+    /**
+     * Dispatches Raft messages to the relevant handlers.
+     *
+     * @param recvMessage the received message
+     */
+    private void handleMessage(VSMessage recvMessage) {
+        String messageType = recvMessage.getString("type");
+
+        if ("voteRequest".equals(messageType)) {
+            handleVoteRequest(recvMessage);
+        } else if ("voteResponse".equals(messageType)) {
+            handleVoteResponse(recvMessage);
+        }
+    }
+
+    /**
+     * Handles an incoming vote request from a candidate.
+     *
+     * @param recvMessage the vote request
+     */
+    private void handleVoteRequest(VSMessage recvMessage) {
+        int messageTerm = recvMessage.getInteger("term");
+        int candidateId = recvMessage.getInteger("candidateId");
+        boolean voteGranted = false;
+
+        if (messageTerm >= currentTerm &&
+                (votedFor == -1 || votedFor == candidateId)) {
+            becomeFollower(messageTerm, -1);
+            votedFor = candidateId;
+            voteGranted = true;
+        }
+
+        VSMessage voteResponse = new VSMessage();
+        voteResponse.setString("type", "voteResponse");
+        voteResponse.setInteger("term", currentTerm);
+        voteResponse.setInteger("pid", process.getProcessID());
+        voteResponse.setBoolean("voteGranted", voteGranted);
+        voteResponse.setInteger("targetPid", candidateId);
+        sendMessage(voteResponse);
+    }
+
+    /**
+     * Handles an incoming vote response for an active election.
+     *
+     * @param recvMessage the vote response
+     */
+    private void handleVoteResponse(VSMessage recvMessage) {
+        int messageTerm = recvMessage.getInteger("term");
+
+        if (messageTerm > currentTerm) {
+            becomeFollower(messageTerm, -1);
+            return;
+        }
+
+        if (!isCandidate || !isForMe(recvMessage) ||
+                !recvMessage.getBoolean("voteGranted") ||
+                messageTerm != currentTerm) {
+            return;
+        }
+
+        votesReceived++;
+
+        if (votesReceived > getClusterSize() / 2) {
+            becomeLeader();
+        }
+    }
+
+    /**
+     * Checks whether a directed response is meant for this process.
+     *
+     * @param recvMessage the received message
+     * @return true if the message targets this process or has no target field
+     */
+    private boolean isForMe(VSMessage recvMessage) {
+        if (!recvMessage.getIntegerKeySet().contains("targetPid")) {
+            return true;
+        }
+
+        return recvMessage.getInteger("targetPid") == process.getProcessID();
+    }
+
+    /**
+     * Determines the cluster size used for majority calculations.
+     *
+     * @return the number of processes participating in the election
+     */
+    private int getClusterSize() {
+        VSInternalProcess internalProcess = (VSInternalProcess) process;
+        int numProcesses = internalProcess.getSimulatorCanvas().getNumProcesses();
+
+        if (numProcesses > 0) {
+            return numProcesses;
+        }
+
+        if (getVectorKeySet().contains("pids")) {
+            return getVector("pids").size() + 1;
+        }
+
+        return 1;
+    }
 }
-- 
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