Add utils to support time ranges

- Date time range utils to support basic time range operations
- Monitoring utils to support time ranges in the url of dashboards

app/assets/javascripts/lib/utils/datetime_range.js

 import dateformat from 'dateformat';
+import { pick, omit, isEqual, isEmpty } from 'lodash';
 import { secondsToMilliseconds } from './datetime_utility';
 
 const MINIMUM_DATE = new Date(0);
@@ -221,3 +222,99 @@ export function getRangeType(range) {
  */
 export const convertToFixedRange = dateTimeRange =>
   handlers[getRangeType(dateTimeRange)](dateTimeRange);
+
+/**
+ * Returns a copy of the object only with time range
+ * properties relevant to time range calculation.
+ *
+ * Filtered properties are:
+ * - 'start'
+ * - 'end'
+ * - 'anchor'
+ * - 'duration'
+ * - 'direction': if direction is already the default, its removed.
+ *
+ * @param {Object} timeRange - A time range object
+ * @returns Copy of time range
+ */
+const pruneTimeRange = timeRange => {
+  const res = pick(timeRange, ['start', 'end', 'anchor', 'duration', 'direction']);
+  if (res.direction === DEFAULT_DIRECTION) {
+    return omit(res, 'direction');
+  }
+  return res;
+};
+
+/**
+ * Returns true if the time ranges are equal according to
+ * the time range calculation properties
+ *
+ * @param {Object} timeRange - A time range object
+ * @param {Object} other - Time range object to compare with.
+ * @returns true if the time ranges are equal, false otherwise
+ */
+export const isEqualTimeRanges = (timeRange, other) => {
+  const tr1 = pruneTimeRange(timeRange);
+  const tr2 = pruneTimeRange(other);
+  return isEqual(tr1, tr2);
+};
+
+/**
+ * Searches for a time range in a array of time ranges using
+ * only the properies relevant to time ranges calculation.
+ *
+ * @param {Object} timeRange - Time range to search (needle)
+ * @param {Array} timeRanges - Array of time tanges (haystack)
+ */
+export const findTimeRange = (timeRange, timeRanges) =>
+  timeRanges.find(element => isEqualTimeRanges(element, timeRange));
+
+// Time Ranges as URL Parameters Utils
+
+/**
+ * List of possible time ranges parameters
+ */
+export const timeRangeParamNames = ['start', 'end', 'anchor', 'duration_seconds', 'direction'];
+
+/**
+ * Converts a valid time range to a flat key-value pairs object.
+ *
+ * Duration is flatted to avoid having nested objects.
+ *
+ * @param {Object} A time range
+ * @returns key-value pairs object that can be used as parameters in a URL.
+ */
+export const timeRangeToParams = timeRange => {
+  let params = pruneTimeRange(timeRange);
+  if (timeRange.duration) {
+    const durationParms = {};
+    Object.keys(timeRange.duration).forEach(key => {
+      durationParms[`duration_${key}`] = timeRange.duration[key].toString();
+    });
+    params = { ...durationParms, ...params };
+    params = omit(params, 'duration');
+  }
+  return params;
+};
+
+/**
+ * Converts a valid set of flat params to a time range object
+ *
+ * Parameters that are not part of time range object are ignored.
+ *
+ * @param {params} params - key-value pairs object.
+ */
+export const timeRangeFromParams = params => {
+  const timeRangeParams = pick(params, timeRangeParamNames);
+  let range = Object.entries(timeRangeParams).reduce((acc, [key, val]) => {
+    // unflatten duration
+    if (key.startsWith('duration_')) {
+      acc.duration = acc.duration || {};
+      acc.duration[key.slice('duration_'.length)] = parseInt(val, 10);
+      return acc;
+    }
+    return { [key]: val, ...acc };
+  }, {});
+  range = pruneTimeRange(range);
+  return !isEmpty(range) ? range : null;
+};

app/assets/javascripts/monitoring/utils.js

+import { queryToObject, mergeUrlParams, removeParams } from '~/lib/utils/url_utility';
+import {
+  timeRangeParamNames,
+  timeRangeFromParams,
+  timeRangeToParams,
+} from '~/lib/utils/datetime_range';
+
 /**
  * This method is used to validate if the graph data format for a chart component
  * that needs a time series as a response from a prometheus query (query_range) is
@@ -93,4 +100,35 @@ export const graphDataValidatorForAnomalyValues = graphData => {
   );
 };
 
+/**
+ * Returns a time range from the current URL params
+ *
+ * @returns {Object} The time range defined by the
+ * current URL, reading from `window.location.search`
+ */
+export const timeRangeFromUrl = (search = window.location.search) => {
+  const params = queryToObject(search);
+  return timeRangeFromParams(params);
+};
+
+/**
+ * Returns a URL with no time range based on the current URL.
+ *
+ * @param {String} New URL
+ */
+export const removeTimeRangeParams = (url = window.location.href) =>
+  removeParams(timeRangeParamNames, url);
+
+/**
+ * Returns a URL for the a different time range based on the
+ * current URL and a time range.
+ *
+ * @param {String} New URL
+ */
+export const timeRangeToUrl = (timeRange, url = window.location.href) => {
+  const toUrl = removeTimeRangeParams(url);
+  const params = timeRangeToParams(timeRange);
+  return mergeUrlParams(params, toUrl);
+};
+
 export default {};

spec/frontend/monitoring/utils_spec.js

 import * as monitoringUtils from '~/monitoring/utils';
+import { queryToObject, mergeUrlParams, removeParams } from '~/lib/utils/url_utility';
 import {
+  mockHost,
+  mockProjectDir,
   graphDataPrometheusQuery,
   graphDataPrometheusQueryRange,
   anomalyMockGraphData,
 } from './mock_data';
 
+jest.mock('~/lib/utils/url_utility');
+
+const mockPath = `${mockHost}${mockProjectDir}/-/environments/29/metrics`;
+
+const generatedLink = 'http://chart.link.com';
+
+const chartTitle = 'Some metric chart';
+
+const range = {
+  start: '2019-01-01T00:00:00.000Z',
+  end: '2019-01-10T00:00:00.000Z',
+};
+
+const rollingRange = {
+  duration: { seconds: 120 },
+};
+
 describe('monitoring/utils', () => {
-  const generatedLink = 'http://chart.link.com';
-  const chartTitle = 'Some metric chart';
+  afterEach(() => {
+    mergeUrlParams.mockReset();
+    queryToObject.mockReset();
+  });
 
   describe('trackGenerateLinkToChartEventOptions', () => {
     it('should return Cluster Monitoring options if located on Cluster Health Dashboard', () => {
@@ -117,4 +139,75 @@ describe('monitoring/utils', () => {
       expect(monitoringUtils.graphDataValidatorForAnomalyValues(fourMetrics)).toBe(false);
     });
   });
+
+  describe('timeRangeFromUrl', () => {
+    const { timeRangeFromUrl } = monitoringUtils;
+
+    it('returns a fixed range when query contains `start` and `end` paramters are given', () => {
+      queryToObject.mockReturnValueOnce(range);
+
+      expect(timeRangeFromUrl()).toEqual(range);
+    });
+
+    it('returns a rolling range when query contains `duration_seconds` paramters are given', () => {
+      const { seconds } = rollingRange.duration;
+
+      queryToObject.mockReturnValueOnce({
+        dashboard: '.gitlab/dashboard/my_dashboard.yml',
+        duration_seconds: `${seconds}`,
+      });
+
+      expect(timeRangeFromUrl()).toEqual(rollingRange);
+    });
+
+    it('returns null when no time range paramters are given', () => {
+      const params = {
+        dashboard: '.gitlab/dashboards/custom_dashboard.yml',
+        param1: 'value1',
+        param2: 'value2',
+      };
+
+      expect(timeRangeFromUrl(params, mockPath)).toBe(null);
+    });
+  });
+
+  describe('removeTimeRangeParams', () => {
+    const { removeTimeRangeParams } = monitoringUtils;
+
+    it('returns when query contains `start` and `end` paramters are given', () => {
+      removeParams.mockReturnValueOnce(mockPath);
+
+      expect(removeTimeRangeParams(`${mockPath}?start=${range.start}&end=${range.end}`)).toEqual(
+        mockPath,
+      );
+    });
+  });
+
+  describe('timeRangeToUrl', () => {
+    const { timeRangeToUrl } = monitoringUtils;
+
+    it('returns a fixed range when query contains `start` and `end` paramters are given', () => {
+      const toUrl = `${mockPath}?start=${range.start}&end=${range.end}`;
+      const fromUrl = mockPath;
+
+      removeParams.mockReturnValueOnce(fromUrl);
+      mergeUrlParams.mockReturnValueOnce(toUrl);
+
+      expect(timeRangeToUrl(range)).toEqual(toUrl);
+      expect(mergeUrlParams).toHaveBeenCalledWith(range, fromUrl);
+    });
+
+    it('returns a rolling range when query contains `duration_seconds` paramters are given', () => {
+      const { seconds } = rollingRange.duration;
+
+      const toUrl = `${mockPath}?duration_seconds=${seconds}`;
+      const fromUrl = mockPath;
+
+      removeParams.mockReturnValueOnce(fromUrl);
+      mergeUrlParams.mockReturnValueOnce(toUrl);
+
+      expect(timeRangeToUrl(rollingRange)).toEqual(toUrl);
+      expect(mergeUrlParams).toHaveBeenCalledWith({ duration_seconds: `${seconds}` }, fromUrl);
+    });
+  });
 });