feat: add timestamp to vertex

packages/node/src/handlers.ts

@@ -72,6 +72,7 @@ async function updateHandler(node: DRPNode, data: Uint8Array, sender: string) {
 					value: v.operation?.value,
 				},
 				dependencies: v.dependencies,
+				timestamp: v.timestamp,
 			};
 		}),
 	);
@@ -147,6 +148,7 @@ function syncAcceptHandler(node: DRPNode, sender: string, data: Uint8Array) {
 				value: v.operation?.value,
 			},
 			dependencies: v.dependencies,
+			timestamp: v.timestamp,
 		};
 	});
 

packages/object/src/hashgraph/index.ts

@@ -89,6 +89,7 @@ export class HashGraph {
 				value: null,
 			},
 			dependencies: [],
+			timestamp: 0,
 		};
 		this.vertices.set(HashGraph.rootHash, rootVertex);
 		this.frontier.push(HashGraph.rootHash);
@@ -107,6 +108,7 @@ export class HashGraph {
 			nodeId: this.nodeId,
 			operation: operation ?? { type: OperationType.NOP },
 			dependencies: deps,
+			timestamp: Date.now(),
 		};
 
 		this.vertices.set(hash, vertex);
@@ -145,23 +147,40 @@ export class HashGraph {
 	 * If the vertex already exists, return the hash of the existing vertex.
 	 * Throws an error if any of the dependencies are not present in the hashgraph.
 	 */
-	addVertex(operation: Operation, deps: Hash[], nodeId: string): Hash {
+	addVertex(
+		operation: Operation,
+		deps: Hash[],
+		nodeId: string,
+		timestamp: number,
+	): Hash {
 		const hash = computeHash(nodeId, operation, deps);
 		if (this.vertices.has(hash)) {
 			return hash; // Vertex already exists
 		}
 
-		if (
-			!deps.every((dep) => this.forwardEdges.has(dep) || this.vertices.has(dep))
-		) {
-			throw new Error("Invalid dependency detected.");
+		for (const dep of deps) {
+			const vertex = this.vertices.get(dep);
+			if (vertex === undefined) {
+				throw new Error("Invalid dependency detected.");
+			}
+			if (vertex.timestamp > timestamp) {
+				// Vertex's timestamp must not be less than any of its dependencies' timestamps
+				throw new Error("Invalid timestamp detected.");
+			}
+		}
+
+		const currentTimestamp = Date.now();
+		if (timestamp > currentTimestamp) {
+			// Vertex created in the future is invalid
+			throw new Error("Invalid timestamp detected.");
 		}
 
 		const vertex: Vertex = {
 			hash,
 			nodeId,
 			operation,
 			dependencies: deps,
+			timestamp,
 		};
 		this.vertices.set(hash, vertex);
 		this.frontier.push(hash);

packages/object/src/index.ts

@@ -126,6 +126,7 @@ export class DRPObject implements IDRPObject {
 			nodeId: vertex.nodeId,
 			operation: vertex.operation,
 			dependencies: vertex.dependencies,
+			timestamp: vertex.timestamp,
 		});
 		this.vertices.push(serializedVertex);
 		this._notify("callFn", [serializedVertex]);
@@ -148,6 +149,7 @@ export class DRPObject implements IDRPObject {
 					vertex.operation,
 					vertex.dependencies,
 					vertex.nodeId,
+					vertex.timestamp,
 				);
 
 				this._setState(vertex);

packages/object/src/proto/drp/object/v1/object.proto

@@ -14,6 +14,7 @@ message Vertex {
   string node_id = 2;
   Operation operation = 3;
   repeated string dependencies = 4;
+  int64 timestamp = 5;
 }
 
 message DRPObjectBase {

packages/object/tests/hashgraph.test.ts

@@ -69,6 +69,7 @@ describe("HashGraph construction tests", () => {
 			},
 			[],
 			"",
+			Date.now(),
 		);
 		obj1.hashGraph.addVertex(
 			{
@@ -77,6 +78,7 @@ describe("HashGraph construction tests", () => {
 			},
 			[hash],
 			"",
+			Date.now(),
 		);
 		expect(obj1.hashGraph.selfCheckConstraints()).toBe(false);
 
@@ -617,3 +619,66 @@ describe("Vertex state tests", () => {
 		expect(drpStateV8?.state.get("state").get(3)).toBe(undefined);
 	});
 });
+
+describe("Vertex timestamp tests", () => {
+	let obj1: DRPObject;
+	let obj2: DRPObject;
+	let obj3: DRPObject;
+
+	beforeEach(async () => {
+		obj1 = new DRPObject("peer1", new AddWinsSet<number>());
+		obj2 = new DRPObject("peer1", new AddWinsSet<number>());
+		obj3 = new DRPObject("peer1", new AddWinsSet<number>());
+	});
+
+	test("Test: Vertex created in the future is invalid", () => {
+		const drp1 = obj1.drp as AddWinsSet<number>;
+
+		drp1.add(1);
+
+		expect(() =>
+			obj1.hashGraph.addVertex(
+				{
+					type: "add",
+					value: 1,
+				},
+				obj1.hashGraph.getFrontier(),
+				"",
+				Number.POSITIVE_INFINITY,
+			),
+		).toThrowError("Invalid timestamp detected.");
+	});
+
+	test("Test: Vertex's timestamp must not be less than any of its dependencies' timestamps", () => {
+		/*
+		        __ V1:ADD(1) __
+		       /               \  
+		  ROOT -- V2:ADD(2) ---- V1:ADD(4) (invalid)
+		       \               /
+		        -- V3:ADD(3) --
+		*/
+
+		const drp1 = obj1.drp as AddWinsSet<number>;
+		const drp2 = obj2.drp as AddWinsSet<number>;
+		const drp3 = obj2.drp as AddWinsSet<number>;
+
+		drp1.add(1);
+		drp2.add(2);
+		drp3.add(3);
+
+		obj1.merge(obj2.hashGraph.getAllVertices());
+		obj1.merge(obj3.hashGraph.getAllVertices());
+
+		expect(() =>
+			obj1.hashGraph.addVertex(
+				{
+					type: "add",
+					value: 1,
+				},
+				obj1.hashGraph.getFrontier(),
+				"",
+				1,
+			),
+		).toThrowError("Invalid timestamp detected.");
+	});
+});