feat(core/reports): xlsreport date functions

projects/core/models/src/utils/expression-utils.md

@@ -131,9 +131,17 @@ For example, `OP([1, 2, 3], [10, 20, 30], elemA + elemB)` returns `[11, 22, 33]`
 
 ## Date functions
 
+Dates are strings in the format 2000-12-31, unless otherwise specified.
+
 `TODAY(format = "yyyy-MM-dd")`  
 Returns today's date.
 
+`ADD_DAYS(date, days)`  
+Returns the date obtained by adding days to date.
+
+`DAYS_DIFF(a, b)`  
+Returns the difference in days (a - b) between the two dates.
+
 `IS_BEFORE(date, dateToCompare)`  
 Returns true if date is before dateToCompare.
 

projects/core/models/src/utils/expression-utils.spec.ts

@@ -1,4 +1,15 @@
-import {ALL_VALUES_OF, SUM, MainForm, MEAN, COUNT_FORMS, JOIN_FORMS, FILTER_BY, evaluateExpression} from './expression-utils';
+import {
+  MainForm,
+  evaluateExpression,
+  ALL_VALUES_OF,
+  SUM,
+  MEAN,
+  COUNT_FORMS,
+  JOIN_FORMS,
+  FILTER_BY,
+  ADD_DAYS,
+  DAYS_DIFF,
+} from './expression-utils';
 
 const forms: MainForm[] = [
   {
@@ -116,3 +127,14 @@ describe('MAP', () => {
     expect(result).toEqual([2, 1, 0]);
   });
 });
+
+describe('date functions', () => {
+  it('ADD_DAYS', () => {
+    expect(ADD_DAYS('2000-12-31', 1)).toBe('2001-01-01');
+    expect(ADD_DAYS('2000-12-30', -15)).toBe('2000-12-15');
+  });
+  it('DAYS_DIFF', () => {
+    expect(DAYS_DIFF('2000-12-31', '2000-12-29')).toBe(2);
+    expect(DAYS_DIFF('1998-12-31', '1999-12-31')).toBe(-365);
+  });
+});

projects/core/models/src/utils/expression-utils.ts

@@ -152,6 +152,8 @@ export class AjfExpressionUtils {
     buildWidgetDatasetWithDialog: {fn: buildWidgetDatasetWithDialog},
     FILTER_BY_VARS: {fn: FILTER_BY_VARS},
     FILTER_BY: {fn: FILTER_BY},
+    ADD_DAYS: {fn: ADD_DAYS},
+    DAYS_DIFF: {fn: DAYS_DIFF},
     IS_BEFORE: {fn: IS_BEFORE},
     IS_AFTER: {fn: IS_AFTER},
     IS_WITHIN_INTERVAL: {fn: IS_WITHIN_INTERVAL},
@@ -1799,6 +1801,25 @@ export function REMOVE_DUPLICATES(arr: any[]): any[] {
   return [...new Map(arr.map(v => [JSON.stringify(v), v])).values()];
 }
 
+// Returns the date obtained by adding days to date.
+export function ADD_DAYS(date: string, days: number): string {
+  const d = new Date(date);
+  d.setDate(d.getDate() + days);
+  return d.toJSON().slice(0, 10);
+}
+
+// Returns the difference in days (a - b) between the two dates.
+export function DAYS_DIFF(a: string, b: string): number {
+  const dateA = new Date(a);
+  const dateB = new Date(b);
+  // UTC avoids bugs with daylight saving time.
+  const utcA = Date.UTC(dateA.getFullYear(), dateA.getMonth(), dateA.getDate());
+  const utcB = Date.UTC(dateB.getFullYear(), dateB.getMonth(), dateB.getDate());
+
+  const millisPerDay = 1000 * 60 * 60 * 24;
+  return Math.floor((utcA - utcB) / millisPerDay);
+}
+
 /**
  * Returns true if date is before dateToCompare.
  *

projects/core/reports/src/xls-report/hindikit-parser.ts

@@ -419,6 +419,8 @@ const functionArgs: {[name: string]: string[]} = {
   APPLY_LABELS: ["arg", "arg", "arg"],
   BUILD_DATASET: ["arg", "arg?"],
   ROUND: ["arg", "arg?"],
+  ADD_DAYS: ["arg", "arg"],
+  DAYS_DIFF: ["arg", "arg"],
   IS_BEFORE: ["arg", "arg"],
   IS_AFTER: ["arg", "arg"],
   IS_WITHIN_INTERVAL: ["arg", "arg", "arg"],