feat(NODE-6031): add t and i to Timestamp

src/timestamp.ts

@@ -28,6 +28,8 @@ export interface TimestampExtended {
 /**
  * @public
  * @category BSONType
+ *
+ * A special type for _internal_ MongoDB use and is **not** associated with the regular Date type.
  */
 export class Timestamp extends LongWithoutOverridesClass {
   get _bsontype(): 'Timestamp' {
@@ -36,6 +38,20 @@ export class Timestamp extends LongWithoutOverridesClass {
 
   static readonly MAX_VALUE = Long.MAX_UNSIGNED_VALUE;
 
+  /**
+   * An incrementing ordinal for operations within a given second.
+   */
+  get i(): number {
+    return this.low >>> 0;
+  }
+
+  /**
+   * A `time_t` value measuring seconds since the Unix epoch
+   */
+  get t(): number {
+    return this.high >>> 0;
+  }
+
   /**
    * @param int - A 64-bit bigint representing the Timestamp.
    */
@@ -127,7 +143,7 @@ export class Timestamp extends LongWithoutOverridesClass {
 
   /** @internal */
   toExtendedJSON(): TimestampExtended {
-    return { $timestamp: { t: this.high >>> 0, i: this.low >>> 0 } };
+    return { $timestamp: { t: this.t, i: this.i } };
   }
 
   /** @internal */
@@ -144,8 +160,8 @@ export class Timestamp extends LongWithoutOverridesClass {
 
   inspect(depth?: number, options?: unknown, inspect?: InspectFn): string {
     inspect ??= defaultInspect;
-    const t = inspect(this.high >>> 0, options);
-    const i = inspect(this.low >>> 0, options);
+    const t = inspect(this.t, options);
+    const i = inspect(this.i, options);
     return `new Timestamp({ t: ${t}, i: ${i} })`;
   }
 }

test/node/timestamp.test.ts

@@ -9,6 +9,37 @@ describe('Timestamp', () => {
     });
   });
 
+  describe('get i() and get t()', () => {
+    it('i returns lower bits', () => {
+      const l = new BSON.Long(1, 2);
+      const ts = new BSON.Timestamp(l);
+      expect(ts.i).to.equal(l.low);
+    });
+
+    it('t returns higher bits', () => {
+      const l = new BSON.Long(1, 2);
+      const ts = new BSON.Timestamp(l);
+      expect(ts.t).to.equal(l.high);
+    });
+
+    describe('when signed negative input is provided to the constructor', () => {
+      it('t and i return unsigned values', () => {
+        const l = new BSON.Long(-1, -2);
+        // Check the assumption that Long did NOT change the values to unsigned.
+        expect(l).to.have.property('low', -1);
+        expect(l).to.have.property('high', -2);
+
+        const ts = new BSON.Timestamp(l);
+        expect(ts).to.have.property('i', 0xffffffff); // -1 unsigned
+        expect(ts).to.have.property('t', 0xfffffffe); // -2 unsigned
+
+        // Timestamp is a subclass of Long, high and low do not change:
+        expect(ts).to.have.property('low', -1);
+        expect(ts).to.have.property('high', -2);
+      });
+    });
+  });
+
   it('should always be an unsigned value', () => {
     let bigIntInputs: Timestamp[] = [];
     if (!__noBigInt__) {
@@ -23,7 +54,8 @@ describe('Timestamp', () => {
       new BSON.Timestamp({ t: 0xffff_ffff, i: 0xffff_ffff }),
       // @ts-expect-error We do not advertise support for Int32 in the constructor of Timestamp
       // We do expect it to work so that round tripping the Int32 instance inside a Timestamp works
-      new BSON.Timestamp({ t: new BSON.Int32(0x7fff_ffff), i: new BSON.Int32(0x7fff_ffff) })
+      new BSON.Timestamp({ t: new BSON.Int32(0x7fff_ffff), i: new BSON.Int32(0x7fff_ffff) }),
+      new BSON.Timestamp(new BSON.Timestamp({ t: 0xffff_ffff, i: 0xffff_ffff }))
     ];
 
     for (const timestamp of table) {
@@ -69,6 +101,12 @@ describe('Timestamp', () => {
       expect(timestamp.toExtendedJSON()).to.deep.equal({ $timestamp: input });
     });
 
+    it('accepts timestamp object as input', () => {
+      const input = new BSON.Timestamp({ t: 89, i: 144 });
+      const timestamp = new BSON.Timestamp(input);
+      expect(timestamp.toExtendedJSON()).to.deep.equal({ $timestamp: { t: input.t, i: input.i } });
+    });
+
     it('accepts { t, i } object as input and coerce to integer', () => {
       const input = { t: new BSON.Int32(89), i: new BSON.Int32(144) };
       // @ts-expect-error We do not advertise support for Int32 in the constructor of Timestamp

test/types/bson.test-d.ts

@@ -82,3 +82,6 @@ expectType<(depth?: number | undefined, options?: unknown, inspect?: InspectFn |
 expectNotDeprecated(new ObjectId('foo'));
 expectDeprecated(new ObjectId(42));
 expectNotDeprecated(new ObjectId(42 as string | number));
+
+// Timestamp accepts timestamp because constructor allows: {i:number, t:number}
+new Timestamp(new Timestamp(0n))