1 files changed, 68 insertions, 0 deletions
diff --git a/app/assets/javascripts/analytics/usage_trends/utils.js b/app/assets/javascripts/analytics/usage_trends/utils.js
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+++ b/app/assets/javascripts/analytics/usage_trends/utils.js
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+import { masks } from 'dateformat';
+import { get } from 'lodash';
+import { formatDate } from '~/lib/utils/datetime_utility';
+
+const { isoDate } = masks;
+
+/**
+ * Takes an array of items and returns one item per month with the average of the `count`s from that month
+ * @param  {Array} items
+ * @param  {Number} items[index].count value to be averaged
+ * @param  {String} items[index].recordedAt item dateTime time stamp to be collected into a month
+ * @param  {Object} options
+ * @param  {Object} options.shouldRound an option to specify whether the retuned averages should be rounded
+ * @return {Array} items collected into [month, average],
+ * where month is a dateTime string representing the first of the given month
+ * and average is the average of the count
+ */
+export function getAverageByMonth(items = [], options = {}) {
+  const { shouldRound = false } = options;
+  const itemsMap = items.reduce((memo, item) => {
+    const { count, recordedAt } = item;
+    const date = new Date(recordedAt);
+    const month = formatDate(new Date(date.getFullYear(), date.getMonth(), 1), isoDate);
+    if (memo[month]) {
+      const { sum, recordCount } = memo[month];
+      return { ...memo, [month]: { sum: sum + count, recordCount: recordCount + 1 } };
+    }
+
+    return { ...memo, [month]: { sum: count, recordCount: 1 } };
+  }, {});
+
+  return Object.keys(itemsMap).map((month) => {
+    const { sum, recordCount } = itemsMap[month];
+    const avg = sum / recordCount;
+    if (shouldRound) {
+      return [month, Math.round(avg)];
+    }
+
+    return [month, avg];
+  });
+}
+
+/**
+ * Takes an array of usage counts and returns the last item in the list
+ * @param  {Array} arr array of usage counts in the form { count: Number, recordedAt: date String }
+ * @return {String} the 'recordedAt' value of the earliest item
+ */
+export const getEarliestDate = (arr = []) => {
+  const len = arr.length;
+  return get(arr, `[${len - 1}].recordedAt`, null);
+};
+
+/**
+ * Takes an array of queries and produces an object with the query identifier as key
+ * and a supplied defaultValue as its value
+ * @param  {Array} queries array of chart query configs,
+ *                 see ./analytics/usage_trends/components/charts_config.js
+ * @param  {any}   defaultValue value to set each identifier to
+ * @return {Object} key value pair of the form { queryIdentifier: defaultValue }
+ */
+export const generateDataKeys = (queries, defaultValue) =>
+  queries.reduce(
+    (acc, { identifier }) => ({
+      ...acc,
+      [identifier]: defaultValue,
+    }),
+    {},
+  );