Tests and fixes to MeanList (#74)

packages/backend/package.json

@@ -8,7 +8,8 @@
   "scripts": {
     "start": "tsc && node build/index.js",
     "build": "tsc",
-    "check": "tsc --noEmit"
+    "check": "tsc --noEmit",
+    "test": "node ./test | tap-spec"
   },
   "dependencies": {
     "@types/express": "^4.16.0",
@@ -18,5 +19,9 @@
     "iplocation": "^5.0.1",
     "typescript": "^2.9.2",
     "ws": "5.2.0"
+  },
+  "devDependencies": {
+    "tap-spec": "^5.0.0",
+    "tape": "^4.9.1"
   }
 }

packages/backend/src/MeanList.ts

@@ -1,8 +1,8 @@
 import { Maybe, Types, timestamp } from '@dotstats/common';
 
 export class MeanList<T extends number> {
-  private periodIndex = 0;
-  private period = Array<T>(32).fill(0 as T);
+  private periodCount = 0;
+  private periodSum = 0;
   private meanIndex = 0;
   private means = Array<T>(20).fill(0 as T);
   private ticksPerMean = 1;
@@ -15,9 +15,14 @@ export class MeanList<T extends number> {
    * @return {boolean}
    */
   public push(val: T): boolean {
-    this.period[this.periodIndex++] = val;
+    if (this.meanIndex === 20 && this.ticksPerMean < 32) {
+      this.squashMeans();
+    }
 
-    if (this.periodIndex === this.ticksPerMean) {
+    this.periodSum += val as number;
+    this.periodCount += 1;
+
+    if (this.periodCount === this.ticksPerMean) {
       this.pushMean();
       return true;
     }
@@ -34,27 +39,17 @@ export class MeanList<T extends number> {
   }
 
   private pushMean() {
-    let sum = 0;
+    const mean = (this.periodSum / this.periodCount) as T;
 
-    for (let i = 0; i < this.periodIndex; i++) {
-      sum += this.period[i] as number;
-    }
-
-    const mean = (sum / this.periodIndex) as T;
-
-    if (this.meanIndex === 20) {
-      if (this.ticksPerMean === 32) {
-        this.means.copyWithin(0, 1);
-        this.means[20] = mean;
-      } else {
-        this.squashMeans();
-        this.means[this.meanIndex++] = mean;
-      }
+    if (this.meanIndex === 20 && this.ticksPerMean === 32) {
+      this.means.copyWithin(0, 1);
+      this.means[19] = mean;
     } else {
       this.means[this.meanIndex++] = mean;
     }
 
-    this.periodIndex = 0;
+    this.periodSum = 0;
+    this.periodCount = 0;
   }
 
   private squashMeans() {

packages/backend/test/index.js

@@ -0,0 +1,110 @@
+const test = require('tape');
+const { MeanList } = require('../build/MeanList');
+
+test('MeanList', (assert) => {
+  let list = new MeanList();
+
+  assert.same(list.get(), [], 'Inits empty');
+
+  list.push(0);
+
+  assert.same(list.get(), [0], 'Stores the first value');
+
+  list.push(1);
+  list.push(2);
+  list.push(3);
+  list.push(4);
+  list.push(5);
+  list.push(6);
+  list.push(7);
+  list.push(8);
+  list.push(9);
+
+  assert.same(list.get(), [0,1,2,3,4,5,6,7,8,9], 'Stores the first 10 values');
+
+  list.push(10);
+  list.push(11);
+  list.push(12);
+  list.push(13);
+  list.push(14);
+  list.push(15);
+  list.push(16);
+  list.push(17);
+  list.push(18);
+  list.push(19);
+
+  assert.same(list.get(), [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19], 'Stores the first 20 values');
+
+  list.push(20);
+
+  assert.same(list.get(), [0.5,2.5,4.5,6.5,8.5,10.5,12.5,14.5,16.5,18.5], 'Squashes values on 21st entry');
+
+  list.push(21);
+
+  assert.same(list.get(), [0.5,2.5,4.5,6.5,8.5,10.5,12.5,14.5,16.5,18.5,20.5], 'Adds a mean on 22nd entry');
+
+  list.push(22);
+
+  assert.same(list.get(), [0.5,2.5,4.5,6.5,8.5,10.5,12.5,14.5,16.5,18.5,20.5], 'Keeps track of 23rd entry internally');
+
+  list.push(23);
+
+  assert.same(list.get(), [0.5,2.5,4.5,6.5,8.5,10.5,12.5,14.5,16.5,18.5,20.5,22.5], 'Adds a mean on 24th entry');
+
+  list.push(24);
+  list.push(25);
+  list.push(26);
+  list.push(27);
+  list.push(28);
+  list.push(29);
+  list.push(30);
+  list.push(31);
+  list.push(32);
+  list.push(33);
+  list.push(34);
+  list.push(35);
+  list.push(36);
+  list.push(37);
+  list.push(38);
+  list.push(39);
+
+  assert.same(list.get(), [
+     0.5,  2.5,  4.5,  6.5,  8.5, 10.5, 12.5, 14.5, 16.5, 18.5,
+    20.5, 22.5, 24.5, 26.5, 28.5, 30.5, 32.5, 34.5, 36.5, 38.5
+  ], 'Adds means up to 40th entry');
+
+  list.push(40);
+
+  assert.same(list.get(), [
+     1.5,  5.5,  9.5, 13.5, 17.5, 21.5, 25.5, 29.5, 33.5, 37.5,
+  ], 'Squashes values on 41st entry');
+
+  list = new MeanList();
+
+  for (var i = 0; i < 640; i++) {
+    list.push(i);
+  }
+
+  assert.same(list.get(), [
+     15.5,   47.5,  79.5, 111.5, 143.5, 175.5, 207.5, 239.5, 271.5, 303.5,
+     335.5, 367.5, 399.5, 431.5, 463.5, 495.5, 527.5, 559.5, 591.5, 623.5
+  ], 'Squashes values up to 32 degrees');
+
+  for (var i = 0; i < 31; i++) {
+    list.push(i);
+  }
+
+  assert.same(list.get(), [
+     15.5,   47.5,  79.5, 111.5, 143.5, 175.5, 207.5, 239.5, 271.5, 303.5,
+     335.5, 367.5, 399.5, 431.5, 463.5, 495.5, 527.5, 559.5, 591.5, 623.5
+  ], 'Keeps track of 31 entries internally');
+
+  list.push(31);
+
+  assert.same(list.get(), [
+       47.5,  79.5, 111.5, 143.5, 175.5, 207.5, 239.5, 271.5, 303.5, 335.5,
+      367.5, 399.5, 431.5, 463.5, 495.5, 527.5, 559.5, 591.5, 623.5,  15.5
+  ], 'Pushes a new mean on 32nd value');
+
+  assert.end();
+});