services/chartjs: Use date-fns instead of Moment.js

This is based on the implementation in https://github.com/chartjs/chartjs-adapter-date-fns, but stripped down to only support the formats that we need to save a few bytes.

Author: Turbo87

app/components/download-graph.js

@@ -30,7 +30,7 @@ export default class DownloadGraph extends Component {
           padding: 10,
         },
         scales: {
-          xAxes: [{ type: 'time', time: { stepSize: 7, tooltipFormat: 'MMM D', unit: 'day' } }],
+          xAxes: [{ type: 'time', time: { stepSize: 7, tooltipFormat: 'MMM d', unit: 'day' } }],
           yAxes: [{ stacked: true, ticks: { min: 0, precision: 0 } }],
         },
         tooltips: {

app/services/chartjs.js

@@ -1,10 +1,57 @@
+import { assert } from '@ember/debug';
 import Service from '@ember/service';
 
+import addDays from 'date-fns/addDays';
+import differenceInDays from 'date-fns/differenceInDays';
+import endOfDay from 'date-fns/endOfDay';
+import format from 'date-fns/format';
+import startOfDay from 'date-fns/startOfDay';
 import { task } from 'ember-concurrency';
 
 export default class ChartJsLoader extends Service {
   @(task(function* () {
     let Chart = yield import('chart.js').then(module => module.default);
+
+    Chart._adapters._date.override({
+      _id: 'date-fns', // DEBUG
+
+      formats() {
+        return { day: 'MMM d' };
+      },
+
+      parse(value) {
+        if (value === null || value === undefined) {
+          return null;
+        }
+        assert('`value` must be a `Date`', value instanceof Date);
+        return !isNaN(value) ? value.getTime() : null;
+      },
+
+      format(time, fmt) {
+        return format(time, fmt, this.options);
+      },
+
+      add(time, amount, unit) {
+        assert('This basic Chart.js adapter only supports `unit: day`', unit === 'day');
+        return addDays(time, amount);
+      },
+
+      diff(max, min, unit) {
+        assert('This basic Chart.js adapter only supports `unit: day`', unit === 'day');
+        return differenceInDays(max, min);
+      },
+
+      startOf(time, unit) {
+        assert('This basic Chart.js adapter only supports `unit: day`', unit === 'day');
+        return startOfDay(time);
+      },
+
+      endOf(time, unit) {
+        assert('This basic Chart.js adapter only supports `unit: day`', unit === 'day');
+        return endOfDay(time);
+      },
+    });
+
     Chart.platform.disableCSSInjection = true;
     return Chart;
   }).drop())

ember-cli-build.js

@@ -28,6 +28,7 @@ module.exports = function (defaults) {
     autoImport: {
       webpack: {
         externals: {
+          // prevent Chart.js from bundling Moment.js
           moment: 'moment',
         },
       },