[Discover] fix histogram min interval

This commit fix the missing bars on the histogram of Discover.
Discover is passing a minInterval parameter in milliseconds that is not
the the minimum interval in milliseconds between the buckets. Calendar intervals
are not fixed and this value change depending on time range and the time zone.
To avoid patching the elastic-chart and upgrading the dependency we applied a temporary patch
to the histogram code. For the feature version this patch will be removed
and a correct minInterval computation will be done directly in elastic-charts.

fix #52152

src/legacy/core_plugins/kibana/public/discover/directives/histogram.test.ts

@@ -0,0 +1,106 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { findMinInterval } from './histogram';
+import moment from 'moment-timezone';
+
+const ONE_HOUR = 60 * 60 * 1000;
+const ONE_DAY = 24 * ONE_HOUR;
+describe('DiscoverHistogram', () => {
+  it('shall find the min interval with a single unit, single value', () => {
+    const oneMs = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([oneMs], 1, 'ms', 'UTC')).toBe(1);
+
+    const oneSecond = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([oneSecond], 1, 's', 'UTC')).toBe(1000);
+
+    // all are calendar intervals
+    const oneMinute = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([oneMinute], 1, 'm', 'UTC')).toBe(1000 * 60);
+
+    const oneHour = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([oneHour], 1, 'h', 'UTC')).toBe(ONE_HOUR);
+
+    const oneDay = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([oneDay], 1, 'd', 'UTC')).toBe(ONE_DAY);
+
+    const oneWeek = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([oneWeek], 1, 'w', 'UTC')).toBe(7 * ONE_DAY);
+
+    const oneMonth = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([oneMonth], 1, 'M', 'UTC')).toBe(29 * ONE_DAY);
+
+    const oneYear = moment('2015-01-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([oneYear], 1, 'y', 'UTC')).toBe(365 * ONE_DAY);
+
+    const oneLeapYear = moment('2016-01-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([oneLeapYear], 1, 'y', 'UTC')).toBe(366 * ONE_DAY);
+  });
+
+  it('shall find the min interval with a single unit, single value DST', () => {
+    // if configured timeZone is UTC, there is no DST
+    const utcDay = moment('2019-03-31T00:00:00.000Z').valueOf();
+    expect(findMinInterval([utcDay], 1, 'd', 'UTC')).toBe(ONE_DAY);
+
+    const dstDay = moment.tz('2019-03-31 00:00:00.000', 'Europe/Rome').valueOf();
+    expect(findMinInterval([dstDay], 1, 'd', 'Europe/Rome')).toBe(ONE_DAY - ONE_HOUR);
+
+    const dstAddDay = moment.tz('2019-10-27 00:00:00.000', 'Europe/Rome').valueOf();
+    // the 27th has 25 hours
+    expect(findMinInterval([dstAddDay], 1, 'd', 'Europe/Rome')).toBe(ONE_DAY + ONE_HOUR);
+  });
+
+  it('shall find the min interval with a single unit, multi value DST', () => {
+    // if configured timeZone is UTC, there is no DST
+    const utcStartDay = moment('2019-03-31T00:00:00.000Z').valueOf();
+    const utcEndDay = moment('2019-04-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([utcStartDay, utcEndDay], 1, 'd', 'UTC')).toBe(ONE_DAY);
+
+    const dstStartDay = moment.tz('2019-03-31 00:00:00.000', 'Europe/Rome').valueOf();
+    const dstEndDay = moment.tz('2019-04-01 00:00:00.000', 'Europe/Rome').valueOf();
+    expect(findMinInterval([dstStartDay, dstEndDay], 1, 'd', 'Europe/Rome')).toBe(
+      ONE_DAY - ONE_HOUR
+    );
+
+    const dstAddStartDay = moment.tz('2019-10-27 00:00:00.000', 'Europe/Rome').valueOf();
+    const dstAddEndDay = moment.tz('2019-10-28 00:00:00.000', 'Europe/Rome').valueOf();
+    // the 27th has 25 hours and the 28 has 24 hours, so the min is 24
+    expect(findMinInterval([dstAddStartDay, dstAddEndDay], 1, 'd', 'Europe/Rome')).toBe(ONE_DAY);
+  });
+
+  it('shall find the min interval with a multi unit, single value', () => {
+    // all are fixed intervals
+    const fiveMs = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([fiveMs], 5, 'ms', 'UTC')).toBe(5);
+
+    const fiveSecond = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([fiveSecond], 5, 's', 'UTC')).toBe(1000 * 5);
+
+    const fiveMinute = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([fiveMinute], 5, 'm', 'UTC')).toBe(1000 * 60 * 5);
+
+    const fiveHour = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([fiveHour], 5, 'h', 'UTC')).toBe(ONE_HOUR * 5);
+
+    const fiveDay = moment('2016-02-01T00:00:00.000Z').valueOf();
+    expect(findMinInterval([fiveDay], 5, 'd', 'UTC')).toBe(ONE_DAY * 5);
+
+    // multiple week, month and years are not allowed see parse_es_interval.ts
+  });
+});

src/legacy/core_plugins/kibana/public/discover/directives/histogram.tsx

@@ -19,6 +19,7 @@
 
 import { EuiFlexGroup, EuiFlexItem, EuiIcon, EuiSpacer } from '@elastic/eui';
 import moment from 'moment-timezone';
+import { unitOfTime } from 'moment';
 import React, { Component } from 'react';
 import PropTypes from 'prop-types';
 import lightEuiTheme from '@elastic/eui/dist/eui_theme_light.json';
@@ -60,6 +61,48 @@ interface DiscoverHistogramState {
   chartsTheme: EuiChartThemeType['theme'];
 }
 
+function findIntervalFromDuration(dateValue: number, esUnit: unitOfTime.Base, timeZone: string) {
+  const date = moment.tz(dateValue, timeZone);
+  const startOfDate = moment.tz(date, timeZone).startOf(esUnit);
+  const endOfDate = moment
+    .tz(date, timeZone)
+    .startOf(esUnit)
+    .add(1, esUnit);
+  return endOfDate.valueOf() - startOfDate.valueOf();
+}
+
+function getSingleUnitInterval(value: number, esUnit: unitOfTime.Base, timeZone: string) {
+  switch (esUnit) {
+    case 's':
+      return 1000;
+    case 'ms':
+      return 1;
+    default:
+      return findIntervalFromDuration(value, esUnit, timeZone);
+  }
+}
+
+export function findMinInterval(
+  xValues: number[],
+  esValue: number,
+  esUnit: string,
+  timeZone: string
+): number {
+  // if the interval is a single unit we need to find the minimum fixed interval in ms
+  // between the available dates
+  if (esValue === 1) {
+    return xValues.reduce((minInterval, currentXvalue) => {
+      return Math.min(
+        minInterval,
+        getSingleUnitInterval(currentXvalue, esUnit as unitOfTime.Base, timeZone)
+      );
+    }, Number.MAX_SAFE_INTEGER);
+  } else {
+    // if it's a multiple unit interval, than it's a fixed interval directly convertible to ms
+    return +moment.duration(esValue, esUnit as unitOfTime.Base);
+  }
+}
+
 export class DiscoverHistogram extends Component<DiscoverHistogramProps, DiscoverHistogramState> {
   public static propTypes = {
     chartData: PropTypes.object,
@@ -161,7 +204,7 @@ export class DiscoverHistogram extends Component<DiscoverHistogramProps, Discove
      * see https://github.com/elastic/kibana/issues/27410
      * TODO: Once the Discover query has been update, we should change the below to use the new field
      */
-    const xInterval = chartData.ordered.interval;
+    const { intervalESValue, intervalESUnit, interval: xInterval } = chartData.ordered;
 
     const xValues = chartData.xAxisOrderedValues;
     const lastXValue = xValues[xValues.length - 1];
@@ -176,7 +219,7 @@ export class DiscoverHistogram extends Component<DiscoverHistogramProps, Discove
     const xDomain = {
       min: domainMin,
       max: domainMax,
-      minInterval: xInterval,
+      minInterval: findMinInterval(xValues, intervalESValue, intervalESUnit, timeZone),
     };
 
     // Domain end of 'now' will be milliseconds behind current time, so we extend time by 1 minute and check if

src/legacy/ui/public/agg_response/point_series/__tests__/_init_x_axis.js

@@ -108,6 +108,8 @@ describe('initXAxis', function () {
 
   it('reads the date interval param from the x agg', function () {
     chart.aspects.x[0].params.interval = 'P1D';
+    chart.aspects.x[0].params.intervalESValue = 1;
+    chart.aspects.x[0].params.intervalESUnit = 'd';
     chart.aspects.x[0].params.date = true;
     initXAxis(chart, table);
     expect(chart)
@@ -117,6 +119,8 @@ describe('initXAxis', function () {
 
     expect(moment.isDuration(chart.ordered.interval)).to.be(true);
     expect(chart.ordered.interval.toISOString()).to.eql('P1D');
+    expect(chart.ordered.intervalESValue).to.be(1);
+    expect(chart.ordered.intervalESUnit).to.be('d');
   });
 
   it('reads the numeric interval param from the x agg', function () {

src/legacy/ui/public/agg_response/point_series/_init_x_axis.js

@@ -29,9 +29,19 @@ export function initXAxis(chart, table) {
   chart.xAxisFormat = format;
   chart.xAxisLabel = title;
 
-  if (params.interval) {
-    chart.ordered = {
-      interval: params.date ? moment.duration(params.interval) : params.interval,
-    };
+  const { interval, date } = params;
+  if (interval) {
+    if(date) {
+      const { intervalESUnit, intervalESValue } = params;
+      chart.ordered = {
+        interval: moment.duration(interval),
+        intervalESUnit: intervalESUnit,
+        intervalESValue: intervalESValue,
+      };
+    } else {
+      chart.ordered = {
+        interval,
+      };
+    }
   }
 }

src/legacy/ui/public/visualize/loader/pipeline_helpers/build_pipeline.ts

@@ -437,6 +437,8 @@ export const buildVislibDimensions = async (
       dimensions.x.params.date = true;
       const { esUnit, esValue } = xAgg.buckets.getInterval();
       dimensions.x.params.interval = moment.duration(esValue, esUnit);
+      dimensions.x.params.intervalESValue = esValue;
+      dimensions.x.params.intervalESUnit = esUnit;
       dimensions.x.params.format = xAgg.buckets.getScaledDateFormat();
       dimensions.x.params.bounds = xAgg.buckets.getBounds();
     } else if (xAgg.type.name === 'histogram') {