chore(core/utils): Add typings to datemath.ts (#16195)

* Add typings

* Remove explicit cast

public/app/core/specs/datemath.test.ts

@@ -12,8 +12,8 @@ describe('DateMath', () => {
   let clock;
 
   describe('errors', () => {
-    it('should return undefined if passed something falsy', () => {
-      expect(dateMath.parse(false)).toBe(undefined);
+    it('should return undefined if passed empty string', () => {
+      expect(dateMath.parse('')).toBe(undefined);
     });
 
     it('should return undefined if I pass an operator besides [+-/]', () => {

public/app/core/utils/datemath.ts

@@ -3,17 +3,34 @@ import moment from 'moment';
 
 const units = ['y', 'M', 'w', 'd', 'h', 'm', 's'];
 
-export function parse(text, roundUp?, timezone?) {
+type Timezone = 'utc';
+
+/**
+ * Parses different types input to a moment instance. There is a specific formatting language that can be used
+ * if text arg is string. See unit tests for examples.
+ * @param text
+ * @param roundUp See parseDateMath function.
+ * @param timezone Only string 'utc' is acceptable here, for anything else, local timezone is used.
+ */
+export function parse(
+  text: string | moment.Moment | Date,
+  roundUp?: boolean,
+  timezone?: Timezone
+): moment.Moment | undefined {
   if (!text) {
     return undefined;
   }
+
+  if (typeof text !== 'string') {
     if (moment.isMoment(text)) {
       return text;
     }
     if (_.isDate(text)) {
       return moment(text);
     }
-
+    // We got some non string which is not a moment nor Date. TS should be able to check for that but not always.
+    return undefined;
+  } else {
     let time;
     let mathString = '';
     let index;
@@ -44,9 +61,15 @@ export function parse(text, roundUp?, timezone?) {
     }
 
     return parseDateMath(mathString, time, roundUp);
+  }
 }
 
-export function isValid(text) {
+/**
+ * Checks if text is a valid date which in this context means that it is either a Moment instance or it can be parsed
+ * by parse function. See parse function to see what is considered acceptable.
+ * @param text
+ */
+export function isValid(text: string | moment.Moment): boolean {
   const date = parse(text);
   if (!date) {
     return false;
@@ -59,7 +82,13 @@ export function isValid(text) {
   return false;
 }
 
-export function parseDateMath(mathString, time, roundUp?) {
+/**
+ * Parses math part of the time string and shifts supplied time according to that math. See unit tests for examples.
+ * @param mathString
+ * @param time
+ * @param roundUp If true it will round the time to endOf time unit, otherwise to startOf time unit.
+ */
+export function parseDateMath(mathString: string, time: moment.Moment, roundUp?: boolean): moment.Moment | undefined {
   const dateTime = time;
   let i = 0;
   const len = mathString.length;
@@ -80,13 +109,13 @@ export function parseDateMath(mathString, time, roundUp?) {
       return undefined;
     }
 
-    if (isNaN(mathString.charAt(i))) {
+    if (isNaN(parseInt(mathString.charAt(i), 10))) {
       num = 1;
     } else if (mathString.length === 2) {
       num = mathString.charAt(i);
     } else {
       const numFrom = i;
-      while (!isNaN(mathString.charAt(i))) {
+      while (!isNaN(parseInt(mathString.charAt(i), 10))) {
         i++;
         if (i > 10) {
           return undefined;

public/app/features/explore/TimePicker.tsx

@@ -120,7 +120,7 @@ export default class TimePicker extends PureComponent<TimePickerProps, TimePicke
     } else if (direction === 1) {
       nextTo = to.valueOf() + timespan;
       nextFrom = from.valueOf() + timespan;
-      if (nextTo > Date.now() && to < Date.now()) {
+      if (nextTo > Date.now() && to.valueOf() < Date.now()) {
         nextTo = Date.now();
         nextFrom = from.valueOf();
       }