feature: add sustainable web design model

package.json

@@ -5,6 +5,7 @@
   "main": "src/index.js",
   "scripts": {
     "test": "jest",
+    "test:watch": "jest --watch",
     "lint": "eslint .",
     "lint:fix": "eslint . --fix",
     "travis": "npm run lint && jest"

src/constants/file-size.js

@@ -0,0 +1,5 @@
+const GIGABYTE = 1024 * 1024 * 1024;
+
+module.exports = {
+  GIGABYTE,
+};

src/constants/index.js

@@ -0,0 +1,3 @@
+const fileSize = require("./file-size");
+
+module.exports = { fileSize };

src/helpers/index.js

@@ -0,0 +1,5 @@
+const formatNumber = (num) => parseFloat(num.toFixed(2));
+
+module.exports = {
+  formatNumber,
+};

src/sustainable-web-design.js

@@ -0,0 +1,66 @@
+"use strict";
+
+/**
+ * Sustainable Web Design
+ *
+ * Newly update calculations and figures from
+ * https://sustainablewebdesign.org/calculating-digital-emissions/
+ *
+ *
+ */
+const { fileSize } = require("./constants");
+const { formatNumber } = require("./helpers");
+
+// Taken from: https://sustainablewebdesign.org/calculating-digital-emissions/#:~:text=TWh/EB%20or-,0.81%20kWH/GB,-Carbon%20factor%20(global
+const KWH_PER_GB = 0.81;
+// Taken from: https://www.iea.org/reports/renewables-2021
+const GLOBAL_INTENSITY = 440;
+// Taken from: https://gitlab.com/wholegrain/carbon-api-2-0/-/blob/master/includes/carbonapi.php
+const FIRST_TIME_VIEWING_PERCENTAGE = 0.25;
+const RETURNING_VISITOR_PERCENTAGE = 0.75;
+const PERCENTAGE_OF_DATA_LOADED_ON_SUBSEQUENT_LOAD = 0.02;
+// Taken from: https://sustainablewebdesign.org/calculating-digital-emissions/#:~:text=Consumer%20device%20energy%20%3D%20AE%20x%200.52
+const END_USER_DEVICE_ENERGY = 0.52;
+
+class SustainableWebDesign {
+  constructor(options) {
+    this.options = options;
+  }
+
+  energyPerVisit(bytes) {
+    const transferedBytesToGb = bytes / fileSize.GIGABYTE;
+
+    const newVisitorEnergy =
+      transferedBytesToGb * KWH_PER_GB * FIRST_TIME_VIEWING_PERCENTAGE;
+    const returningVisitorEnergy =
+      transferedBytesToGb *
+      KWH_PER_GB *
+      RETURNING_VISITOR_PERCENTAGE *
+      PERCENTAGE_OF_DATA_LOADED_ON_SUBSEQUENT_LOAD;
+
+    return newVisitorEnergy + returningVisitorEnergy;
+  }
+
+  emissionsPerVisitInGrams(energyPerVisit, globalIntensity = GLOBAL_INTENSITY) {
+    return formatNumber(energyPerVisit * globalIntensity);
+  }
+
+  annualEnergyInKwh(energyPerVisit, monthlyVisitors = 1000) {
+    return energyPerVisit * monthlyVisitors * 12;
+  }
+
+  annualEmissionsInGrams(co2grams, monthlyVisitors = 1000) {
+    return co2grams * monthlyVisitors * 12;
+  }
+
+  annualSegmentEnergy(annualEnergy) {
+    return {
+      consumerDeviceEnergy: formatNumber(annualEnergy * END_USER_DEVICE_ENERGY),
+      networkEnergy: formatNumber(annualEnergy * 0.14),
+      dataCenterEnergy: formatNumber(annualEnergy * 0.15),
+      productionEnergy: formatNumber(annualEnergy * 0.19),
+    };
+  }
+}
+
+module.exports = SustainableWebDesign;

src/sustainable-web-design.test.js

@@ -0,0 +1,57 @@
+const fs = require("fs");
+const path = require("path");
+const SustainableWebDesign = require("./sustainable-web-design");
+
+describe("sustainable web design model", () => {
+  const swd = new SustainableWebDesign();
+  const averageWebsiteInBytes = 2257715.2;
+
+  describe("energyPerVisit", function () {
+    it("should return a number", () => {
+      expect(typeof swd.energyPerVisit(2257715.2)).toBe("number");
+    });
+
+    it("should calculate the correct energy", () => {
+      expect(swd.energyPerVisit(2257715.2)).toBe(0.0004513362121582032);
+    });
+  });
+
+  describe("emissionsPerVisitInGrams", function () {
+    it("should calculate the correct co2 per visit", () => {
+      const averageWebsiteInBytes = 2257715.2;
+      const energy = swd.energyPerVisit(averageWebsiteInBytes);
+      expect(swd.emissionsPerVisitInGrams(energy)).toEqual(0.2);
+    });
+
+    it("should accept a dynamic KwH value", () => {
+      const averageWebsiteInBytes = 2257715.2;
+      const energy = swd.energyPerVisit(averageWebsiteInBytes);
+      expect(swd.emissionsPerVisitInGrams(energy, 245)).toEqual(0.11);
+    });
+  });
+
+  describe("annualEnergyInKwh", function () {
+    it("should calculate the correct energy in kWh", () => {
+      expect(swd.annualEnergyInKwh(averageWebsiteInBytes)).toBe(27092582400);
+    });
+  });
+
+  describe("annualEmissionsInGrams", function () {
+    it("should calculate the corrent energy in grams", () => {
+      expect(swd.annualEmissionsInGrams(averageWebsiteInBytes)).toBe(
+        27092582400
+      );
+    });
+  });
+
+  describe("annualSegmentEnergy", function () {
+    it("should return the correct values", () => {
+      expect(swd.annualSegmentEnergy(averageWebsiteInBytes)).toEqual({
+        consumerDeviceEnergy: 1174011.9,
+        dataCenterEnergy: 338657.28,
+        networkEnergy: 316080.13,
+        productionEnergy: 428965.89,
+      });
+    });
+  });
+});