volpe/simulations/hyperloglog-tombstone/simulation.ts

type HLLRegisters = Uint8Array;

interface HLL {
  registers: HLLRegisters;
  m: number;
  alphaMM: number;
}

const createHLL = (precision: number = 10): HLL => {
  const m = 1 << precision;
  const alphaMM = m === 16 ? 0.673 * m * m
    : m === 32 ? 0.697 * m * m
    : m === 64 ? 0.709 * m * m
    : (0.7213 / (1 + 1.079 / m)) * m * m;
  
  return { registers: new Uint8Array(m), m, alphaMM };
};

const hashString = (value: string): number => {
  let hash = 0;
  for (let i = 0; i < value.length; i++) {
    hash = ((hash << 5) - hash) + value.charCodeAt(i);
    hash = hash & hash;
  }
  hash ^= hash >>> 16;
  hash = Math.imul(hash, 0x85ebca6b);
  hash ^= hash >>> 13;
  hash = Math.imul(hash, 0xc2b2ae35);
  hash ^= hash >>> 16;
  return hash >>> 0;
};

const rho = (value: number): number => {
  if (value === 0) return 32;
  let count = 1;
  while ((value & 0x80000000) === 0) {
    count++;
    value <<= 1;
  }
  return count;
};

const hllAdd = (hll: HLL, value: string): HLL => {
  const hash = hashString(value);
  const index = hash >>> (32 - Math.log2(hll.m));
  const w = hash << Math.log2(hll.m);
  const rank = rho(w);
  const newRegisters = new Uint8Array(hll.registers);
  newRegisters[index] = Math.max(newRegisters[index], rank);
  return { ...hll, registers: newRegisters };
};

const hllEstimate = (hll: HLL): number => {
  let sum = 0;
  let zeros = 0;
  for (let i = 0; i < hll.m; i++) {
    sum += Math.pow(2, -hll.registers[i]);
    if (hll.registers[i] === 0) zeros++;
  }
  let estimate = hll.alphaMM / sum;
  if (estimate <= 2.5 * hll.m && zeros > 0) {
    estimate = hll.m * Math.log(hll.m / zeros);
  }
  return Math.round(estimate);
};

const hllMerge = (a: HLL, b: HLL): HLL => {
  const newRegisters = new Uint8Array(a.m);
  for (let i = 0; i < a.m; i++) {
    newRegisters[i] = Math.max(a.registers[i], b.registers[i]);
  }
  return { ...a, registers: newRegisters };
};

const hllClone = (hll: HLL): HLL => ({
  ...hll,
  registers: new Uint8Array(hll.registers),
});

interface DataRecord<Data> {
  readonly id: string;
  readonly data: Data;
  readonly recordHLL: HLL;
}

interface Tombstone {
  readonly id: string;
  readonly recordHLL: HLL;
  readonly tombstoneHLL: HLL;
}

interface NodeState<Data> {
  readonly id: string;
  readonly records: ReadonlyMap<string, DataRecord<Data>>;
  readonly tombstones: ReadonlyMap<string, Tombstone>;
  readonly isOnline: boolean;
  readonly partitionId: string; // Nodes in the same partition can communicate
  readonly stats: {
    readonly messagesReceived: number;
    readonly tombstonesGarbageCollected: number;
    readonly resurrections: number;
  };
}

interface NetworkState<Data> {
  readonly nodes: ReadonlyMap<string, NodeState<Data>>;
}

const createRecord = <Data>(id: string, data: Data, nodeId: string): DataRecord<Data> => ({
  id,
  data,
  recordHLL: hllAdd(createHLL(), nodeId),
});

const createTombstone = <Data>(record: DataRecord<Data>, nodeId: string): Tombstone => ({
  id: record.id,
  recordHLL: hllClone(record.recordHLL),
  tombstoneHLL: hllAdd(createHLL(), nodeId),
});

const createNode = <Data>(id: string, partitionId: string = "main"): NodeState<Data> => ({
  id,
  records: new Map(),
  tombstones: new Map(),
  isOnline: true,
  partitionId,
  stats: { messagesReceived: 0, tombstonesGarbageCollected: 0, resurrections: 0 },
});

const checkGCStatus = (
  tombstone: Tombstone,
  incomingTombstoneEstimate: number | null,
  myTombstoneEstimateBeforeMerge: number,
  myNodeId: string,
  senderNodeId: string | null
): { shouldGC: boolean; stepDownAsKeeper: boolean } => {
  const targetCount = hllEstimate(tombstone.recordHLL);

  const isKeeper = myTombstoneEstimateBeforeMerge >= targetCount;

  if (isKeeper) {
    if (incomingTombstoneEstimate !== null && incomingTombstoneEstimate >= targetCount) {
      if (myTombstoneEstimateBeforeMerge < incomingTombstoneEstimate) {
        return { shouldGC: true, stepDownAsKeeper: true };
      }
      if (myTombstoneEstimateBeforeMerge === incomingTombstoneEstimate && 
          senderNodeId !== null && myNodeId > senderNodeId) {
        return { shouldGC: true, stepDownAsKeeper: true };
      }
    }
    return { shouldGC: false, stepDownAsKeeper: false };
  }

  return { shouldGC: false, stepDownAsKeeper: false };
};

const receiveRecord = <Data>(
  node: NodeState<Data>,
  incoming: DataRecord<Data>
): NodeState<Data> => {
  const newStats = { ...node.stats, messagesReceived: node.stats.messagesReceived + 1 };
  
  if (node.tombstones.has(incoming.id)) {
    return { ...node, stats: { ...newStats, resurrections: newStats.resurrections + 1 } };
  }

  const existing = node.records.get(incoming.id);
  const updatedRecord: DataRecord<Data> = existing
    ? { ...existing, recordHLL: hllAdd(hllMerge(existing.recordHLL, incoming.recordHLL), node.id) }
    : { ...incoming, recordHLL: hllAdd(hllClone(incoming.recordHLL), node.id) };

  const newRecords = new Map(node.records);
  newRecords.set(incoming.id, updatedRecord);
  return { ...node, records: newRecords, stats: newStats };
};

const receiveTombstone = <Data>(
  node: NodeState<Data>,
  incoming: Tombstone,
  senderNodeId: string
): NodeState<Data> => {
  let newStats = { ...node.stats, messagesReceived: node.stats.messagesReceived + 1 };

  const record = node.records.get(incoming.id);
  if (!record) {
    return { ...node, stats: newStats };
  }

  const existing = node.tombstones.get(incoming.id);

  const mergedTombstoneHLL = existing
    ? hllAdd(hllMerge(existing.tombstoneHLL, incoming.tombstoneHLL), node.id)
    : hllAdd(hllClone(incoming.tombstoneHLL), node.id);

  let bestFrozenHLL = incoming.recordHLL;
  if (existing?.recordHLL) {
    bestFrozenHLL = hllEstimate(existing.recordHLL) > hllEstimate(bestFrozenHLL)
      ? existing.recordHLL
      : bestFrozenHLL;
  }
  if (hllEstimate(record.recordHLL) > hllEstimate(bestFrozenHLL)) {
    bestFrozenHLL = hllClone(record.recordHLL);
  }

  const updatedTombstone: Tombstone = {
    id: incoming.id,
    tombstoneHLL: mergedTombstoneHLL,
    recordHLL: bestFrozenHLL,
  };

  const myEstimateBeforeMerge = existing ? hllEstimate(existing.tombstoneHLL) : 0;
  
  const gcStatus = checkGCStatus(
    updatedTombstone,
    hllEstimate(incoming.tombstoneHLL),
    myEstimateBeforeMerge,
    node.id,
    senderNodeId
  );

  const newRecords = new Map(node.records);
  newRecords.delete(incoming.id);

  if (gcStatus.stepDownAsKeeper) {
    const newTombstones = new Map(node.tombstones);
    newTombstones.delete(incoming.id);
    newStats = { ...newStats, tombstonesGarbageCollected: newStats.tombstonesGarbageCollected + 1 };
    return { ...node, records: newRecords, tombstones: newTombstones, stats: newStats };
  }

  const newTombstones = new Map(node.tombstones);
  newTombstones.set(incoming.id, updatedTombstone);
  return { ...node, records: newRecords, tombstones: newTombstones, stats: newStats };
};

// Create a fully connected network (all nodes can talk to all other online nodes in same partition)
const createNetwork = <Data>(nodeCount: number, partitionId: string = "main"): NetworkState<Data> => {
  const nodes = new Map<string, NodeState<Data>>();
  
  for (let i = 0; i < nodeCount; i++) {
    nodes.set(`node-${i}`, createNode<Data>(`node-${i}`, partitionId));
  }
  
  return { nodes };
};

// Get all reachable nodes (online and in same partition)
const getReachableNodes = <Data>(
  network: NetworkState<Data>,
  fromNodeId: string
): string[] => {
  const fromNode = network.nodes.get(fromNodeId);
  if (!fromNode || !fromNode.isOnline) return [];
  
  const reachable: string[] = [];
  for (const [nodeId, node] of network.nodes) {
    if (nodeId !== fromNodeId && 
        node.isOnline && 
        node.partitionId === fromNode.partitionId) {
      reachable.push(nodeId);
    }
  }
  return reachable;
};

const forwardTombstoneToAllReachable = <Data>(
  network: NetworkState<Data>,
  forwardingNodeId: string,
  tombstone: Tombstone,
  excludeNodeId?: string
): NetworkState<Data> => {
  const forwardingNode = network.nodes.get(forwardingNodeId);
  if (!forwardingNode || !forwardingNode.isOnline) return network;
  
  let newNodes = new Map(network.nodes);
  const reachable = getReachableNodes({ nodes: newNodes }, forwardingNodeId);
  
  for (const peerId of reachable) {
    if (peerId === excludeNodeId) continue;
    
    const peer = newNodes.get(peerId);
    if (!peer || !peer.records.has(tombstone.id)) continue;
    
    const updatedPeer = receiveTombstone(peer, tombstone, forwardingNodeId);
    newNodes.set(peerId, updatedPeer);
    
    // If this peer also stepped down, recursively forward
    if (!updatedPeer.tombstones.has(tombstone.id) && peer.tombstones.has(tombstone.id)) {
      const result = forwardTombstoneToAllReachable({ nodes: newNodes }, peerId, tombstone, forwardingNodeId);
      newNodes = new Map(result.nodes);
    }
  }
  
  return { nodes: newNodes };
};

const gossipOnce = <Data>(network: NetworkState<Data>, senderNodeId: string, recordId: string): NetworkState<Data> => {
  const sender = network.nodes.get(senderNodeId);
  if (!sender || !sender.isOnline) return network;

  const record = sender.records.get(recordId);
  const tombstone = sender.tombstones.get(recordId);
  if (!record && !tombstone) return network;

  const reachable = getReachableNodes(network, senderNodeId);
  if (reachable.length === 0) return network;

  const peerId = reachable[Math.floor(Math.random() * reachable.length)];
  const peer = network.nodes.get(peerId);
  if (!peer) return network;

  let newNodes = new Map(network.nodes);

  if (record && !tombstone) {
    const updatedPeer = receiveRecord(peer, record);
    newNodes.set(peerId, updatedPeer);
  }

  if (tombstone) {
    if (record && !peer.records.has(recordId)) {
      const peerWithRecord = receiveRecord(peer, record);
      newNodes.set(peerId, peerWithRecord);
    }
    const currentPeer = newNodes.get(peerId)!;
    const peerHadTombstone = currentPeer.tombstones.has(recordId);
    const updatedPeer = receiveTombstone(currentPeer, tombstone, senderNodeId);
    newNodes.set(peerId, updatedPeer);
    
    if (peerHadTombstone && !updatedPeer.tombstones.has(recordId)) {
      const result = forwardTombstoneToAllReachable({ nodes: newNodes }, peerId, tombstone, senderNodeId);
      newNodes = new Map(result.nodes);
    }

    if (updatedPeer.tombstones.has(recordId)) {
      const peerTombstone = updatedPeer.tombstones.get(recordId)!;
      const senderEstimateBeforeMerge = hllEstimate(tombstone.tombstoneHLL);
      
      const mergedTombstoneHLL = hllMerge(tombstone.tombstoneHLL, peerTombstone.tombstoneHLL);
      const bestFrozenHLL = hllEstimate(peerTombstone.recordHLL) > hllEstimate(tombstone.recordHLL)
        ? peerTombstone.recordHLL
        : tombstone.recordHLL;
      
      const updatedSenderTombstone: Tombstone = {
        ...tombstone,
        tombstoneHLL: mergedTombstoneHLL,
        recordHLL: bestFrozenHLL,
      };
      
      const gcStatus = checkGCStatus(
        updatedSenderTombstone,
        hllEstimate(peerTombstone.tombstoneHLL),
        senderEstimateBeforeMerge,
        senderNodeId,
        peerId
      );
      
      if (gcStatus.stepDownAsKeeper) {
        const currentSender = newNodes.get(senderNodeId)!;
        const newSenderTombstones = new Map(currentSender.tombstones);
        newSenderTombstones.delete(recordId);
        const newSenderStats = { ...currentSender.stats, tombstonesGarbageCollected: currentSender.stats.tombstonesGarbageCollected + 1 };
        newNodes.set(senderNodeId, { ...currentSender, tombstones: newSenderTombstones, stats: newSenderStats });
        
        const result = forwardTombstoneToAllReachable({ nodes: newNodes }, senderNodeId, peerTombstone, peerId);
        newNodes = new Map(result.nodes);
      } else {
        const currentSender = newNodes.get(senderNodeId)!;
        const newSenderTombstones = new Map(currentSender.tombstones);
        newSenderTombstones.set(recordId, updatedSenderTombstone);
        newNodes.set(senderNodeId, { ...currentSender, tombstones: newSenderTombstones });
      }
    }
  }

  return { nodes: newNodes };
};

const gossipRounds = <Data>(network: NetworkState<Data>, recordId: string, rounds: number): NetworkState<Data> => {
  let state = network;
  for (let round = 0; round < rounds; round++) {
    for (const [nodeId, node] of state.nodes) {
      if (node.isOnline && (node.records.has(recordId) || node.tombstones.has(recordId))) {
        state = gossipOnce(state, nodeId, recordId);
      }
    }
  }
  return state;
};

interface ClusterStats {
  name: string;
  nodeCount: number;
  recordCount: number;
  tombstoneCount: number;
  onlineCount: number;
}

interface SimulationResult {
  testName: string;
  recordsDeleted: boolean;
  roundsToDeleteRecords: number;
  totalRounds: number;
  clusters: ClusterStats[];
}

const getClusterStats = <Data>(
  network: NetworkState<Data>,
  recordId: string,
  partitionFilter?: string
): ClusterStats => {
  let recordCount = 0;
  let tombstoneCount = 0;
  let nodeCount = 0;
  let onlineCount = 0;

  for (const [, node] of network.nodes) {
    if (partitionFilter && node.partitionId !== partitionFilter) continue;
    nodeCount++;
    if (node.isOnline) onlineCount++;
    if (node.records.has(recordId)) recordCount++;
    if (node.tombstones.has(recordId)) tombstoneCount++;
  }

  return {
    name: partitionFilter ?? 'all',
    nodeCount,
    recordCount,
    tombstoneCount,
    onlineCount,
  };
};

const printSimulationResult = (result: SimulationResult): void => {
  console.log(`\n== ${result.testName} ==`);
  
  if (result.recordsDeleted) {
    console.log(`  Records deleted: YES (${result.roundsToDeleteRecords} rounds)`);
  } else {
    console.log(`  Records deleted: NO`);
  }
  console.log(`  Total rounds run: ${result.totalRounds}`);
  
  console.log(`  Final State:`);
  
  for (const cluster of result.clusters) {
    const clusterLabel = cluster.name === 'all' ? 'Network' : `Partition ${cluster.name}`;
    console.log(`    ${clusterLabel} (${cluster.nodeCount} nodes, ${cluster.onlineCount} online):`);
    console.log(`      Records:    ${cluster.recordCount}`);
    console.log(`      Tombstones: ${cluster.tombstoneCount}`);
  }
};

interface ConvergenceResult<Data> {
  network: NetworkState<Data>;
  recordsDeleted: boolean;
  roundsToDeleteRecords: number;
  totalRounds: number;
}

const runToConvergence = <Data>(
  network: NetworkState<Data>,
  recordId: string,
  maxRounds: number,
  extraRoundsAfterDeletion: number = 100
): ConvergenceResult<Data> => {
  let rounds = 0;
  let state = network;
  let recordsDeleted = false;
  let roundsToDeleteRecords = 0;
  
  while (rounds < maxRounds && !recordsDeleted) {
    const stats = getClusterStats(state, recordId);
    if (stats.recordCount === 0) {
      recordsDeleted = true;
      roundsToDeleteRecords = rounds;
    }
    state = gossipRounds(state, recordId, 10);
    rounds += 10;
  }
  
  let extraRounds = 0;
  while (extraRounds < extraRoundsAfterDeletion) {
    state = gossipRounds(state, recordId, 10);
    extraRounds += 10;
    rounds += 10;
  }
  
  return {
    network: state,
    recordsDeleted,
    roundsToDeleteRecords,
    totalRounds: rounds,
  };
};

const addRecordToNetwork = <Data>(network: NetworkState<Data>, nodeId: string, recordId: string, data: Data): NetworkState<Data> => {
  const node = network.nodes.get(nodeId);
  if (!node) return network;
  
  const newRecords = new Map(node.records);
  newRecords.set(recordId, createRecord(recordId, data, nodeId));
  const newNodes = new Map(network.nodes);
  newNodes.set(nodeId, { ...node, records: newRecords });
  return { nodes: newNodes };
};

const addTombstoneToNetwork = <Data>(network: NetworkState<Data>, nodeId: string, recordId: string): NetworkState<Data> => {
  const node = network.nodes.get(nodeId);
  if (!node) return network;
  
  const record = node.records.get(recordId);
  if (!record) return network;
  
  const newTombstones = new Map(node.tombstones);
  newTombstones.set(recordId, createTombstone(record, nodeId));
  const newNodes = new Map(network.nodes);
  newNodes.set(nodeId, { ...node, tombstones: newTombstones });
  return { nodes: newNodes };
};

const setNodeOnline = <Data>(network: NetworkState<Data>, nodeId: string, isOnline: boolean): NetworkState<Data> => {
  const node = network.nodes.get(nodeId);
  if (!node) return network;
  
  const newNodes = new Map(network.nodes);
  newNodes.set(nodeId, { ...node, isOnline });
  return { nodes: newNodes };
};

const setNodePartition = <Data>(network: NetworkState<Data>, nodeId: string, partitionId: string): NetworkState<Data> => {
  const node = network.nodes.get(nodeId);
  if (!node) return network;
  
  const newNodes = new Map(network.nodes);
  newNodes.set(nodeId, { ...node, partitionId });
  return { nodes: newNodes };
};

const setMultipleNodesPartition = <Data>(
  network: NetworkState<Data>, 
  nodeIds: string[], 
  partitionId: string
): NetworkState<Data> => {
  let result = network;
  for (const nodeId of nodeIds) {
    result = setNodePartition(result, nodeId, partitionId);
  }
  return result;
};

// === Test Scenarios ===

const testSingleNodeDeletion = (): void => {
  const trials = 50;
  const maxRounds = 99999;
  let deletedCount = 0;
  let totalDeletionRounds = 0;
  let totalRounds = 0;
  let finalRecords = 0;
  let finalTombstones = 0;
  
  for (let trial = 0; trial < trials; trial++) {
    let network = createNetwork<string>(15);
    const recordId = `test-${trial}`;
    
    network = addRecordToNetwork(network, "node-0", recordId, "Test Data");
    network = gossipRounds(network, recordId, 20);
    network = addTombstoneToNetwork(network, "node-0", recordId);
    
    const result = runToConvergence(network, recordId, maxRounds);
    
    if (result.recordsDeleted) {
      deletedCount++;
      totalDeletionRounds += result.roundsToDeleteRecords;
    }
    totalRounds += result.totalRounds;
    
    const stats = getClusterStats(result.network, recordId);
    finalRecords += stats.recordCount;
    finalTombstones += stats.tombstoneCount;
  }
  
  printSimulationResult({
    testName: `Single Node Deletion (${trials} trials)`,
    recordsDeleted: deletedCount === trials,
    roundsToDeleteRecords: deletedCount > 0 ? Math.round(totalDeletionRounds / deletedCount) : 0,
    totalRounds: Math.round(totalRounds / trials),
    clusters: [{
      name: 'all',
      nodeCount: 15 * trials,
      recordCount: finalRecords,
      tombstoneCount: finalTombstones,
      onlineCount: 15 * trials,
    }],
  });
};

const testNodeOfflineDuringTombstone = (): void => {
  const trials = 50;
  const maxRounds = 99999;
  let deletedCount = 0;
  let totalDeletionRounds = 0;
  let totalRounds = 0;
  let finalRecords = 0;
  let finalTombstones = 0;
  
  for (let trial = 0; trial < trials; trial++) {
    let network = createNetwork<string>(15);
    const recordId = `offline-${trial}`;
    const offlineNodeId = "node-5";
    
    // Propagate record to all nodes
    network = addRecordToNetwork(network, "node-0", recordId, "Test Data");
    network = gossipRounds(network, recordId, 20);
    
    // Take node-5 offline
    network = setNodeOnline(network, offlineNodeId, false);
    
    // Create tombstone while node-5 is offline
    network = addTombstoneToNetwork(network, "node-0", recordId);
    
    // Run gossip while node-5 is offline (tombstone propagates to online nodes)
    network = gossipRounds(network, recordId, 50);
    
    // Bring node-5 back online
    network = setNodeOnline(network, offlineNodeId, true);
    
    // Continue - the stale record on node-5 should be deleted when it receives tombstone
    const result = runToConvergence(network, recordId, maxRounds);
    
    if (result.recordsDeleted) {
      deletedCount++;
      totalDeletionRounds += result.roundsToDeleteRecords + 50;
    }
    totalRounds += result.totalRounds + 50;
    
    const stats = getClusterStats(result.network, recordId);
    finalRecords += stats.recordCount;
    finalTombstones += stats.tombstoneCount;
  }
  
  printSimulationResult({
    testName: `Node Offline During Tombstone (${trials} trials)`,
    recordsDeleted: deletedCount === trials,
    roundsToDeleteRecords: deletedCount > 0 ? Math.round(totalDeletionRounds / deletedCount) : 0,
    totalRounds: Math.round(totalRounds / trials),
    clusters: [{
      name: 'all',
      nodeCount: 15 * trials,
      recordCount: finalRecords,
      tombstoneCount: finalTombstones,
      onlineCount: 15 * trials,
    }],
  });
};

const testMultipleNodesOffline = (): void => {
  const trials = 50;
  const maxRounds = 99999;
  let deletedCount = 0;
  let totalDeletionRounds = 0;
  let totalRounds = 0;
  let finalRecords = 0;
  let finalTombstones = 0;
  
  for (let trial = 0; trial < trials; trial++) {
    let network = createNetwork<string>(20);
    const recordId = `multi-offline-${trial}`;
    const offlineNodes = ["node-3", "node-7", "node-12", "node-15"];
    
    // Propagate record to all nodes
    network = addRecordToNetwork(network, "node-0", recordId, "Test Data");
    network = gossipRounds(network, recordId, 25);
    
    // Take multiple nodes offline
    for (const nodeId of offlineNodes) {
      network = setNodeOnline(network, nodeId, false);
    }
    
    // Create tombstone
    network = addTombstoneToNetwork(network, "node-0", recordId);
    
    // Run gossip while nodes are offline
    network = gossipRounds(network, recordId, 60);
    
    // Bring nodes back online one by one with some rounds in between
    for (const nodeId of offlineNodes) {
      network = setNodeOnline(network, nodeId, true);
      network = gossipRounds(network, recordId, 15);
    }
    
    const result = runToConvergence(network, recordId, maxRounds);
    
    if (result.recordsDeleted) {
      deletedCount++;
      totalDeletionRounds += result.roundsToDeleteRecords + 60 + offlineNodes.length * 15;
    }
    totalRounds += result.totalRounds + 60 + offlineNodes.length * 15;
    
    const stats = getClusterStats(result.network, recordId);
    finalRecords += stats.recordCount;
    finalTombstones += stats.tombstoneCount;
  }
  
  printSimulationResult({
    testName: `Multiple Nodes Offline (${trials} trials, 4 nodes offline)`,
    recordsDeleted: deletedCount === trials,
    roundsToDeleteRecords: deletedCount > 0 ? Math.round(totalDeletionRounds / deletedCount) : 0,
    totalRounds: Math.round(totalRounds / trials),
    clusters: [{
      name: 'all',
      nodeCount: 20 * trials,
      recordCount: finalRecords,
      tombstoneCount: finalTombstones,
      onlineCount: 20 * trials,
    }],
  });
};

const testNetworkPartition = (): void => {
  const trials = 50;
  const maxRounds = 99999;
  let deletedCount = 0;
  let totalDeletionRounds = 0;
  let totalRounds = 0;
  let finalRecordsA = 0;
  let finalTombstonesA = 0;
  let finalRecordsB = 0;
  let finalTombstonesB = 0;
  
  for (let trial = 0; trial < trials; trial++) {
    let network = createNetwork<string>(20);
    const recordId = `partition-${trial}`;
    
    // Propagate record to all nodes (all in same partition initially)
    network = addRecordToNetwork(network, "node-0", recordId, "Test Data");
    network = gossipRounds(network, recordId, 25);
    
    // Split network into two partitions
    const partitionA = ["node-0", "node-1", "node-2", "node-3", "node-4", 
                        "node-5", "node-6", "node-7", "node-8", "node-9"];
    const partitionB = ["node-10", "node-11", "node-12", "node-13", "node-14",
                        "node-15", "node-16", "node-17", "node-18", "node-19"];
    
    network = setMultipleNodesPartition(network, partitionA, "partition-a");
    network = setMultipleNodesPartition(network, partitionB, "partition-b");
    
    // Create tombstone in partition A
    network = addTombstoneToNetwork(network, "node-0", recordId);
    
    // Run gossip while partitioned (tombstone only propagates in partition A)
    network = gossipRounds(network, recordId, 80);
    
    // Check state while partitioned
    const statsADuringPartition = getClusterStats(network, recordId, "partition-a");
    const statsBDuringPartition = getClusterStats(network, recordId, "partition-b");
    
    // Heal partition (move all nodes back to main)
    network = setMultipleNodesPartition(network, [...partitionA, ...partitionB], "main");
    
    // Continue after heal
    const result = runToConvergence(network, recordId, maxRounds);
    
    if (result.recordsDeleted) {
      deletedCount++;
      totalDeletionRounds += result.roundsToDeleteRecords + 80;
    }
    totalRounds += result.totalRounds + 80;
    
    // Get final stats per original partition membership
    let recordsA = 0, tombstonesA = 0;
    let recordsB = 0, tombstonesB = 0;
    for (const nodeId of partitionA) {
      const node = result.network.nodes.get(nodeId)!;
      if (node.records.has(recordId)) recordsA++;
      if (node.tombstones.has(recordId)) tombstonesA++;
    }
    for (const nodeId of partitionB) {
      const node = result.network.nodes.get(nodeId)!;
      if (node.records.has(recordId)) recordsB++;
      if (node.tombstones.has(recordId)) tombstonesB++;
    }
    
    finalRecordsA += recordsA;
    finalTombstonesA += tombstonesA;
    finalRecordsB += recordsB;
    finalTombstonesB += tombstonesB;
  }
  
  printSimulationResult({
    testName: `Network Partition & Heal (${trials} trials)`,
    recordsDeleted: deletedCount === trials,
    roundsToDeleteRecords: deletedCount > 0 ? Math.round(totalDeletionRounds / deletedCount) : 0,
    totalRounds: Math.round(totalRounds / trials),
    clusters: [
      { name: 'partition-a (origin)', nodeCount: 10 * trials, recordCount: finalRecordsA, tombstoneCount: finalTombstonesA, onlineCount: 10 * trials },
      { name: 'partition-b (stale)', nodeCount: 10 * trials, recordCount: finalRecordsB, tombstoneCount: finalTombstonesB, onlineCount: 10 * trials },
    ],
  });
};

const testClusterSeparation = (): void => {
  const trials = 50;
  const maxRounds = 99999;
  let deletedCount = 0;
  let totalDeletionRounds = 0;
  let totalRounds = 0;
  let finalRecordsMain = 0;
  let finalTombstonesMain = 0;
  let finalRecordsIsolated = 0;
  let finalTombstonesIsolated = 0;
  
  for (let trial = 0; trial < trials; trial++) {
    let network = createNetwork<string>(25);
    const recordId = `cluster-sep-${trial}`;
    
    // Propagate record to all nodes
    network = addRecordToNetwork(network, "node-0", recordId, "Test Data");
    network = gossipRounds(network, recordId, 30);
    
    // Isolate a cluster of 5 nodes (simulating a data center going offline together)
    const isolatedCluster = ["node-10", "node-11", "node-12", "node-13", "node-14"];
    network = setMultipleNodesPartition(network, isolatedCluster, "isolated");
    
    // Create tombstone in main partition
    network = addTombstoneToNetwork(network, "node-0", recordId);
    
    // Run for extended period while cluster is isolated
    network = gossipRounds(network, recordId, 150);
    
    // Rejoin the isolated cluster
    network = setMultipleNodesPartition(network, isolatedCluster, "main");
    
    const result = runToConvergence(network, recordId, maxRounds);
    
    if (result.recordsDeleted) {
      deletedCount++;
      totalDeletionRounds += result.roundsToDeleteRecords + 150;
    }
    totalRounds += result.totalRounds + 150;
    
    // Get final stats
    let recordsMain = 0, tombstonesMain = 0;
    let recordsIsolated = 0, tombstonesIsolated = 0;
    for (const [nodeId, node] of result.network.nodes) {
      const isIsolated = isolatedCluster.includes(nodeId);
      if (node.records.has(recordId)) {
        if (isIsolated) recordsIsolated++; else recordsMain++;
      }
      if (node.tombstones.has(recordId)) {
        if (isIsolated) tombstonesIsolated++; else tombstonesMain++;
      }
    }
    
    finalRecordsMain += recordsMain;
    finalTombstonesMain += tombstonesMain;
    finalRecordsIsolated += recordsIsolated;
    finalTombstonesIsolated += tombstonesIsolated;
  }
  
  printSimulationResult({
    testName: `Cluster Separation (${trials} trials, 5-node cluster isolated)`,
    recordsDeleted: deletedCount === trials,
    roundsToDeleteRecords: deletedCount > 0 ? Math.round(totalDeletionRounds / deletedCount) : 0,
    totalRounds: Math.round(totalRounds / trials),
    clusters: [
      { name: 'main (20 nodes)', nodeCount: 20 * trials, recordCount: finalRecordsMain, tombstoneCount: finalTombstonesMain, onlineCount: 20 * trials },
      { name: 'isolated (5 nodes)', nodeCount: 5 * trials, recordCount: finalRecordsIsolated, tombstoneCount: finalTombstonesIsolated, onlineCount: 5 * trials },
    ],
  });
};

const testConcurrentTombstones = (): void => {
  const trials = 50;
  const maxRounds = 99999;
  let deletedCount = 0;
  let totalDeletionRounds = 0;
  let totalRounds = 0;
  let finalRecords = 0;
  let finalTombstones = 0;
  
  for (let trial = 0; trial < trials; trial++) {
    let network = createNetwork<string>(20);
    const recordId = `concurrent-delete-${trial}`;
    
    network = addRecordToNetwork(network, "node-0", recordId, "Test Data");
    network = gossipRounds(network, recordId, 30);
    
    // Multiple nodes create tombstones simultaneously
    network = addTombstoneToNetwork(network, "node-0", recordId);
    network = addTombstoneToNetwork(network, "node-5", recordId);
    network = addTombstoneToNetwork(network, "node-10", recordId);
    
    const result = runToConvergence(network, recordId, maxRounds);
    
    if (result.recordsDeleted) {
      deletedCount++;
      totalDeletionRounds += result.roundsToDeleteRecords;
    }
    totalRounds += result.totalRounds;
    
    const stats = getClusterStats(result.network, recordId);
    finalRecords += stats.recordCount;
    finalTombstones += stats.tombstoneCount;
  }
  
  printSimulationResult({
    testName: `Concurrent Tombstones (${trials} trials, 3 nodes delete)`,
    recordsDeleted: deletedCount === trials,
    roundsToDeleteRecords: deletedCount > 0 ? Math.round(totalDeletionRounds / deletedCount) : 0,
    totalRounds: Math.round(totalRounds / trials),
    clusters: [{
      name: 'all',
      nodeCount: 20 * trials,
      recordCount: finalRecords,
      tombstoneCount: finalTombstones,
      onlineCount: 20 * trials,
    }],
  });
};

const testStaggeredNodeRecovery = (): void => {
  const trials = 50;
  const maxRounds = 99999;
  let deletedCount = 0;
  let totalDeletionRounds = 0;
  let totalRounds = 0;
  let finalRecords = 0;
  let finalTombstones = 0;
  
  for (let trial = 0; trial < trials; trial++) {
    let network = createNetwork<string>(20);
    const recordId = `staggered-${trial}`;
    const offlineNodes = ["node-4", "node-8", "node-12", "node-16"];
    
    // Propagate record to all nodes
    network = addRecordToNetwork(network, "node-0", recordId, "Test Data");
    network = gossipRounds(network, recordId, 25);
    
    // All nodes go offline
    for (const nodeId of offlineNodes) {
      network = setNodeOnline(network, nodeId, false);
    }
    
    // Create tombstone
    network = addTombstoneToNetwork(network, "node-0", recordId);
    
    // Run while offline
    network = gossipRounds(network, recordId, 40);
    
    // Bring nodes back online at staggered intervals
    let roundsSinceStart = 40;
    for (let i = 0; i < offlineNodes.length; i++) {
      // Run some rounds
      network = gossipRounds(network, recordId, 20);
      roundsSinceStart += 20;
      
      // Bring next node online
      network = setNodeOnline(network, offlineNodes[i], true);
    }
    
    const result = runToConvergence(network, recordId, maxRounds);
    
    if (result.recordsDeleted) {
      deletedCount++;
      totalDeletionRounds += result.roundsToDeleteRecords + roundsSinceStart;
    }
    totalRounds += result.totalRounds + roundsSinceStart;
    
    const stats = getClusterStats(result.network, recordId);
    finalRecords += stats.recordCount;
    finalTombstones += stats.tombstoneCount;
  }
  
  printSimulationResult({
    testName: `Staggered Node Recovery (${trials} trials)`,
    recordsDeleted: deletedCount === trials,
    roundsToDeleteRecords: deletedCount > 0 ? Math.round(totalDeletionRounds / deletedCount) : 0,
    totalRounds: Math.round(totalRounds / trials),
    clusters: [{
      name: 'all',
      nodeCount: 20 * trials,
      recordCount: finalRecords,
      tombstoneCount: finalTombstones,
      onlineCount: 20 * trials,
    }],
  });
};

const testOriginNodeGoesOffline = (): void => {
  const trials = 50;
  const maxRounds = 99999;
  let deletedCount = 0;
  let totalDeletionRounds = 0;
  let totalRounds = 0;
  let finalRecords = 0;
  let finalTombstones = 0;
  
  for (let trial = 0; trial < trials; trial++) {
    let network = createNetwork<string>(15);
    const recordId = `origin-offline-${trial}`;
    
    // Node-0 creates and propagates record
    network = addRecordToNetwork(network, "node-0", recordId, "Test Data");
    network = gossipRounds(network, recordId, 20);
    
    // Node-0 creates tombstone then immediately goes offline
    network = addTombstoneToNetwork(network, "node-0", recordId);
    network = setNodeOnline(network, "node-0", false);
    
    // The tombstone should still propagate via other nodes
    const result = runToConvergence(network, recordId, maxRounds);
    
    // Bring node-0 back online for final check
    network = setNodeOnline(result.network, "node-0", true);
    const finalResult = runToConvergence(network, recordId, maxRounds, 50);
    
    if (finalResult.recordsDeleted) {
      deletedCount++;
      totalDeletionRounds += result.roundsToDeleteRecords;
    }
    totalRounds += result.totalRounds + finalResult.totalRounds;
    
    const stats = getClusterStats(finalResult.network, recordId);
    finalRecords += stats.recordCount;
    finalTombstones += stats.tombstoneCount;
  }
  
  printSimulationResult({
    testName: `Origin Node Goes Offline (${trials} trials)`,
    recordsDeleted: deletedCount === trials,
    roundsToDeleteRecords: deletedCount > 0 ? Math.round(totalDeletionRounds / deletedCount) : 0,
    totalRounds: Math.round(totalRounds / trials),
    clusters: [{
      name: 'all',
      nodeCount: 15 * trials,
      recordCount: finalRecords,
      tombstoneCount: finalTombstones,
      onlineCount: 15 * trials,
    }],
  });
};

const testFlappingNode = (): void => {
  const trials = 50;
  const maxRounds = 99999;
  let deletedCount = 0;
  let totalDeletionRounds = 0;
  let totalRounds = 0;
  let finalRecords = 0;
  let finalTombstones = 0;
  
  for (let trial = 0; trial < trials; trial++) {
    let network = createNetwork<string>(15);
    const recordId = `flapping-${trial}`;
    const flappingNode = "node-7";
    
    // Propagate record
    network = addRecordToNetwork(network, "node-0", recordId, "Test Data");
    network = gossipRounds(network, recordId, 20);
    
    // Create tombstone
    network = addTombstoneToNetwork(network, "node-0", recordId);
    
    // Simulate a flapping node (repeatedly going offline/online)
    let rounds = 0;
    let recordsDeleted = false;
    let roundsToDelete = 0;
    
    while (rounds < maxRounds && !recordsDeleted) {
      // Toggle node state every 5 rounds
      if (rounds % 10 < 5) {
        network = setNodeOnline(network, flappingNode, true);
      } else {
        network = setNodeOnline(network, flappingNode, false);
      }
      
      const stats = getClusterStats(network, recordId);
      if (stats.recordCount === 0) {
        recordsDeleted = true;
        roundsToDelete = rounds;
      }
      
      network = gossipRounds(network, recordId, 5);
      rounds += 5;
    }
    
    // Stabilize the node and run to convergence
    network = setNodeOnline(network, flappingNode, true);
    const result = runToConvergence(network, recordId, maxRounds);
    
    if (result.recordsDeleted || recordsDeleted) {
      deletedCount++;
      totalDeletionRounds += recordsDeleted ? roundsToDelete : (result.roundsToDeleteRecords + rounds);
    }
    totalRounds += result.totalRounds + rounds;
    
    const stats = getClusterStats(result.network, recordId);
    finalRecords += stats.recordCount;
    finalTombstones += stats.tombstoneCount;
  }
  
  printSimulationResult({
    testName: `Flapping Node (${trials} trials, node toggles online/offline)`,
    recordsDeleted: deletedCount === trials,
    roundsToDeleteRecords: deletedCount > 0 ? Math.round(totalDeletionRounds / deletedCount) : 0,
    totalRounds: Math.round(totalRounds / trials),
    clusters: [{
      name: 'all',
      nodeCount: 15 * trials,
      recordCount: finalRecords,
      tombstoneCount: finalTombstones,
      onlineCount: 15 * trials,
    }],
  });
};

const testPartitionDuringKeeperElection = (): void => {
  const trials = 50;
  const maxRounds = 99999;
  let deletedCount = 0;
  let totalDeletionRounds = 0;
  let totalRounds = 0;
  let finalRecords = 0;
  let finalTombstones = 0;
  
  for (let trial = 0; trial < trials; trial++) {
    let network = createNetwork<string>(20);
    const recordId = `partition-during-gc-${trial}`;
    
    // Propagate record
    network = addRecordToNetwork(network, "node-0", recordId, "Test Data");
    network = gossipRounds(network, recordId, 25);
    
    // Create tombstone and let it propagate briefly
    network = addTombstoneToNetwork(network, "node-0", recordId);
    network = gossipRounds(network, recordId, 15);
    
    // Now partition the network during keeper election phase
    const partitionA = Array.from({ length: 10 }, (_, i) => `node-${i}`);
    const partitionB = Array.from({ length: 10 }, (_, i) => `node-${i + 10}`);
    
    network = setMultipleNodesPartition(network, partitionA, "partition-a");
    network = setMultipleNodesPartition(network, partitionB, "partition-b");
    
    // Run while partitioned (keeper election happens independently)
    network = gossipRounds(network, recordId, 100);
    
    // Heal partition
    network = setMultipleNodesPartition(network, [...partitionA, ...partitionB], "main");
    
    const result = runToConvergence(network, recordId, maxRounds);
    
    if (result.recordsDeleted) {
      deletedCount++;
      totalDeletionRounds += result.roundsToDeleteRecords + 15 + 100;
    }
    totalRounds += result.totalRounds + 15 + 100;
    
    const stats = getClusterStats(result.network, recordId);
    finalRecords += stats.recordCount;
    finalTombstones += stats.tombstoneCount;
  }
  
  printSimulationResult({
    testName: `Partition During Keeper Election (${trials} trials)`,
    recordsDeleted: deletedCount === trials,
    roundsToDeleteRecords: deletedCount > 0 ? Math.round(totalDeletionRounds / deletedCount) : 0,
    totalRounds: Math.round(totalRounds / trials),
    clusters: [{
      name: 'all',
      nodeCount: 20 * trials,
      recordCount: finalRecords,
      tombstoneCount: finalTombstones,
      onlineCount: 20 * trials,
    }],
  });
};

const runAllTests = (): void => {
  console.log("=== HyperLogLog Tombstone Simulation ===");
  console.log("Model: Fully connected network with offline nodes and partitions\n");
  
  testSingleNodeDeletion();
  testNodeOfflineDuringTombstone();
  testMultipleNodesOffline();
  testNetworkPartition();
  testClusterSeparation();
  testConcurrentTombstones();
  testStaggeredNodeRecovery();
  testOriginNodeGoesOffline();
  testFlappingNode();
  testPartitionDuringKeeperElection();
  
  console.log("\n=== Simulation Complete ===");
};

runAllTests();