Fix logic

Author: hsubox76

packages/app/src/heartbeatSize.test.ts

@@ -15,6 +15,7 @@
  * limitations under the License.
  */
 
+import { base64Encode } from '@firebase/util';
 import { expect } from 'chai';
 import '../test/setup';
 import {
@@ -41,7 +42,7 @@ function generateDates(count: number): string[] {
   return dates;
 }
 
-describe.only('splitHeartbeatsCache()', () => {
+describe('splitHeartbeatsCache()', () => {
   it('returns empty heartbeatsToKeep if it cannot get under maxSize', () => {
     const heartbeats = [
       { userAgent: generateUserAgentString(1), dates: generateDates(1) }
@@ -86,3 +87,28 @@ describe.only('splitHeartbeatsCache()', () => {
     );
   });
 });
+
+describe('countBytes()', () => {
+  it('counts how many bytes there will be in a stringified, encoded header', () => {
+    const heartbeats = [
+      { userAgent: generateUserAgentString(1), dates: generateDates(1) },
+      { userAgent: generateUserAgentString(3), dates: generateDates(2) }
+    ];
+    let size: number = 0;
+    const headerString = base64Encode(
+      JSON.stringify({ version: 2, heartbeats })
+    );
+    console.log(JSON.stringify({ version: 2, heartbeats }));
+    // We don't use this measurement method in the app because user
+    // environments are much more unpredictable while we know the
+    // tests will run in either a standard headless browser or Node.
+    if (typeof Blob !== 'undefined') {
+      const blob = new Blob([headerString]);
+      size = blob.size;
+    } else if (typeof Buffer !== 'undefined') {
+      const buffer = Buffer.from(headerString);
+      size = buffer.byteLength;
+    }
+    expect(countBytes(heartbeats)).to.equal(size);
+  });
+});

packages/app/src/heartbeatSize.ts

@@ -15,11 +15,13 @@
  * limitations under the License.
  */
 
+import { base64Encode } from '@firebase/util';
 import { HeartbeatsByUserAgent } from './types';
 
-const BASE64_SIZE_MULTIPLIER = 4 / 3;
-const BYTES_PER_DATE = 12 * BASE64_SIZE_MULTIPLIER;
-
+/**
+ * Calculate byte length of a string. From:
+ * https://codereview.stackexchange.com/questions/37512/count-byte-length-of-string
+ */
 function getByteLength(str: string): number {
   let byteLength = 0;
   for (let i = 0; i < str.length; i++) {
@@ -41,7 +43,7 @@ function getByteLength(str: string): number {
  * being stringified and converted to base64.
  */
 export function countHeartbeatBytes(heartbeat: HeartbeatsByUserAgent): number {
-  return getByteLength(JSON.stringify(heartbeat)) * BASE64_SIZE_MULTIPLIER;
+  return getByteLength(base64Encode(JSON.stringify(heartbeat)));
 }
 
 /**
@@ -51,13 +53,9 @@ export function countHeartbeatBytes(heartbeat: HeartbeatsByUserAgent): number {
  */
 export function countBytes(heartbeatsCache: HeartbeatsByUserAgent[]): number {
   // heartbeatsCache wrapper properties
-  let count =
-    getByteLength(JSON.stringify({ version: 2, heartbeats: [] })) *
-    BASE64_SIZE_MULTIPLIER;
-  for (const heartbeat of heartbeatsCache) {
-    count += countHeartbeatBytes(heartbeat);
-  }
-  return count;
+  return getByteLength(
+    base64Encode(JSON.stringify({ version: 2, heartbeats: heartbeatsCache }))
+  );
 }
 
 /**
@@ -73,6 +71,9 @@ export function splitHeartbeatsCache(
   heartbeatsToSend: HeartbeatsByUserAgent[];
   heartbeatsToKeep: HeartbeatsByUserAgent[];
 } {
+  const BYTES_PER_DATE = getByteLength(
+    base64Encode(JSON.stringify('2022-12-12'))
+  );
   let totalBytes = 0;
   const heartbeatsToSend = [];
   const heartbeatsToKeep = [...heartbeatsCache];