Merge pull request #3670 from openstax/fix/interval

fix date interval to always end after start

Author: nathanstitt

shared/specs/model/time.spec.ts

@@ -57,4 +57,13 @@ describe('time class', () => {
         expect(future.isAfter(past, 'hour')).toBe(false)
     })
 
+    it('converts to interval with human display', () => {
+        const past = new Time('2021-01-15T10:00:00.000Z')
+        const future = new Time('2021-01-15T10:58:00.000Z')
+        const interval = future.intervalTo(past)
+        // it flipped start/end so start always comes first
+        expect(interval.start.isSame(past, 'millisecond')).toBe(true)
+        expect(interval.humanized).toEqual('58 minutes')
+    })
+
 })

shared/src/model/time.ts

@@ -99,8 +99,15 @@ export default class Time {
     get asDate() { return this._value.toJSDate() }
     get asDateTime() { return this._value }
 
-    get intervalToNow() { return new Interval({ start: this, end: Time.now }) }
-    intervalTo(other: TimeInputs) { return new Interval({ start: this, end: toLDT(other) }) }
+    get intervalToNow() { return this.intervalTo(Time.now) }
+    intervalTo(other: TimeInputs) {
+        const end = toLDT(other)
+        if (this.isBefore(end)) {
+            return new Interval({ start: this, end })
+        }
+        return new Interval({ start: end, end: this })
+    }
+
 
     toISOString() { return this.asISOString }
     toString() { return this.asISOString }