feat: OOR-Set CRDT & Tests (#72)

Co-authored-by: droak <[email protected]>

packages/crdt/src/crdts/OORSet/index.ts

@@ -0,0 +1,76 @@
+export interface ElementTuple<T> {
+  element: T,
+  tag: number,
+  nodeId: string
+}
+
+/* Implementation of the Optimized Observed-Remove Set CRDT
+  Based on the paper: https://pages.lip6.fr/Marek.Zawirski/papers/RR-8083.pdf
+*/
+export class OORSet<T> {
+  elements: Set<ElementTuple<T>> = new Set<ElementTuple<T>>();
+  summary: Map<string, number> = new Map<string, number>();
+  nodeId: string= "";
+
+  constructor(nodeId?: string, elements?: Set<ElementTuple<T>>) {
+    if(nodeId !== undefined) {
+      this.nodeId = nodeId;
+      this.summary = new Map<string, number>([[this.nodeId,this.elements.size]]);
+    }
+
+    if(elements !== undefined) {
+      this.elements = elements;
+    }
+  }
+
+  lookup(element: T): boolean {
+    return [...this.elements].some(elem => elem.element === element);
+  }
+
+  add(nodeId: string, element: T): void {
+    let tag: number = this.summary.get(this.nodeId)! + 1;
+    this.summary.set(this.nodeId, tag);
+    this.elements.add({ element, tag, nodeId: nodeId });
+  }
+
+  remove(element: T): void {
+    for (let tuple of this.elements.values()) {
+      if (tuple.element === element) {
+        this.elements.delete(tuple); //removes element from the elements
+      }
+    }
+  }
+
+  // When comparing both element sets, it just needs to compare them one way because
+  // the "tag" and "nodeId" are going to be unique for a given element so there are 
+  // not equal elements in the set before they're merged
+  compare(peerSet: OORSet<T>): boolean {
+    return (this.elements.size == peerSet.elements.size &&
+      [...this.elements].every((value) => peerSet.elements.has(value)));
+  }
+
+  merge(peerSet: OORSet<T>): void {
+    // place: [local, remote, both]
+    // sets: [elements, removed]
+    // existence: [in, notIn]
+    let bothInElements = [...this.elements].filter((element) => peerSet.elements.has(element));
+    let localInElementsRemoteNotInRemoved = [...this.elements].filter((element) =>
+      !peerSet.elements.has(element) && element.tag > peerSet.summary.get(element.nodeId)!
+    );
+    let localNotInRemovedRemoteInElements = [...peerSet.elements].filter((element) =>
+      !this.elements.has(element) && element.tag > this.summary.get(element.nodeId)!
+    );
+
+    this.elements = new Set<ElementTuple<T>>([...bothInElements, ...localInElementsRemoteNotInRemoved, ...localNotInRemovedRemoteInElements]);
+    this.elements = new Set(
+      [...this.elements].filter((e) =>
+        [...this.elements].every((e2) => e.tag > e2.tag)
+      )
+    );
+
+    // update summary
+    for (let e of peerSet.summary.entries()) {
+      this.summary.set(e[0], Math.max(e[1], this.summary.get(e[0])!));
+    }
+  }
+}

packages/crdt/src/index.ts

@@ -4,7 +4,8 @@ export * from "./crdts/GSet/index.js";
 export * from "./crdts/IPSet/index.js";
 export * from "./crdts/LWWElementSet/index.js";
 export * from "./crdts/LWWRegister/index.js";
+export * from "./crdts/OORSet/index.js";
 export * from "./crdts/PNCounter/index.js";
 export * from "./crdts/RGA/index.js";
 
-export * from "./cros/AddWinsSet/index.js";
+export * from "./cros/AddWinsSet/index.js";

packages/crdt/tests/OORSet.test.ts

@@ -0,0 +1,44 @@
+import { describe, test, expect, beforeEach } from "vitest";
+import { OORSet, ElementTuple } from "../src/crdts/OORSet";
+
+describe("OR-Set Tests", () => {
+  let set1: OORSet<string>;
+  let set2: OORSet<string>;
+
+  const testValues = ["walter", "jesse", "mike"];
+
+  beforeEach(() => {
+    set1 = new OORSet<string>("set1", new Set<ElementTuple<string>>());
+    set2 = new OORSet<string>("set2", new Set<ElementTuple<string>>());
+
+    testValues.forEach((value) => {
+      set1.add("set1",value);
+      set2.add("set2",value);
+    });
+  });
+
+  test("Test Add Elements", () => {
+    expect(set1.lookup("gustavo")).toBe(false);
+
+    set1.add("set1","gustavo");
+
+    expect(set1.lookup("gustavo")).toBe(true);
+  });
+
+  test("Test Remove Elements", () => {
+    expect(set1.lookup("mike")).toBe(true);
+
+    set1.remove("mike");
+
+    expect(set1.lookup("mike")).toBe(false);
+  });
+
+  test("Test Merge Elements", () => {
+    expect(set1.compare(set2)).toBe(false);
+
+    set1.merge(set2);
+    set2.merge(set1);
+
+    expect(set1.compare(set2)).toBe(true);
+  });
+});

packages/crdt/tests/RGA.test.ts

@@ -88,4 +88,4 @@ describe("Replicable Growable Array Tests", () => {
 		peerRGA.merge(rga);
 		expect(peerRGA.getArray()).toEqual(rga.getArray());
 	});
-});
+});