WIP WIP, nae nae

time.go

@@ -25,20 +25,20 @@ func main() {
 	fmt.Println("Loc", now.In(loc))
 
 	/* boundary checks */
-	CheckInput([]int{2019, 11, 10,
-		01, 02, 56, 0})
-	CheckInput([]int{2019, 11, 10,
-		01, 02, 60, 0})
-	CheckInput([]int{2019, 11, 10,
-		01, 60, 59, 0})
-	CheckInput([]int{2019, 11, 10,
-		24, 59, 59, 0})
-	CheckInput([]int{2019, 11, 10,
-		25, 59, 59, 0})
-	CheckInput([]int{2019, 11, 10,
-		23, 59, 59, 0})
-	CheckInput([]int{2019, 11, 31,
-		23, 0, 0, 0})
+	for _, st := range [][]int{
+		[]int{2019, 11, 10, 01, 02, 56, 0},
+		[]int{2019, 11, 10, 01, 02, 60, 0},
+		[]int{2019, 11, 10, 01, 60, 59, 0},
+		[]int{2019, 11, 10, 24, 59, 59, 0},
+		[]int{2019, 11, 10, 25, 59, 59, 0},
+		[]int{2019, 11, 10, 23, 59, 59, 0},
+		[]int{2019, 11, 31, 23, 0, 0, 0},
+	} {
+		err := Exists(st, "America/Denver")
+		if nil != err {
+			fmt.Println(err)
+		}
+	}
 
 	/* funky times */
 	tz := "America/Denver"
@@ -75,41 +75,94 @@ func main() {
 		05, 01, 00, 0}, tz)
 }
 
-func CheckInput2(st []int, tzstr string) {
-	m := time.Month(st[1])
+type ErrNoExist struct {
+	e string
+	t []int
+	z string
+}
+
+func (err ErrNoExist) Error() string {
+	return fmt.Sprintf("E_INVALID_TIME: '%#v' is not a valid timestamp at '%s': %s", err.t, err.z, err.e)
+}
+
+// Check if the time is a real time in the given timezone.
+//
+// For example: 2:30am doesn't happen on 2019 Nov 3rd according
+// to America/Denver local time, due to the end of Daylight Savings Time,
+// but it did happen in America/Phoenix.
+//
+// Also rejects times that are parsable and return a valid date object,
+// but are not canonical, such as 24:60:75 November 31st, 2020.
+// (which would be represented as `2020-12-02 02:01:15 +0000 UTC`)
+//
+// Example of parsable, but non-canonical time:
+//
+//     fmt.Println(time.Date(2020, time.November, 31, 25, 60, 0, 0, time.UTC))
+//     "2020-12-02 02:01:15 +0000 UTC"
+//
+// Example of a canonical, but non-parsable time (the 2016 leap second):
+//
+//     fmt.Println(time.Date(2016, time.December, 31, 23, 59, 60, 0, time.UTC))
+//     "2020-12-02 02:00:00 +0000 UTC" // should be "2016-12-31 23:59:60 +0000 UTC"
+func Exists(st []int, tzstr string) error {
 	tz, err := time.LoadLocation(tzstr)
 	if nil != err {
-		fmt.Println("screwed the pooch")
-		return
+		return err
 	}
 
-	// Does the time exist
+	m := time.Month(st[1])
 	t1 := time.Date(st[0], m, st[2], st[3], st[4], st[5], st[6], tz)
 	if st[5] != t1.Second() {
-		fmt.Println("Bad Second", st, t1)
-		return
+		return ErrNoExist{
+			t: st,
+			z: tzstr,
+			e: "invalid second, probably just bad math on your part",
+		}
 	}
 	if st[4] != t1.Minute() {
-		fmt.Println("Bad Minute", st, t1.Minute())
-		return
+		return ErrNoExist{
+			t: st,
+			z: tzstr,
+			e: "invalid minute, probably just bad math on your part, but perhaps a half-hour daylight savings or summer time",
+		}
 	}
 	if st[3] != t1.Hour() {
-		fmt.Println("Bad Hour", st, t1)
-		return
+		return ErrNoExist{
+			t: st,
+			z: tzstr,
+			e: "invalid hour, possibly a Daylight Savings or Summer Time error, or perhaps bad math on your part",
+		}
 	}
 	if st[2] != t1.Day() {
-		fmt.Println("Bad Day of Month", st, t1)
-		return
+		return ErrNoExist{
+			t: st,
+			z: tzstr,
+			e: "invalid day of month, most likely bad math on your part. Remember: 31 28¼ 31 30 31 30 31 31 30 31 30 31",
+		}
 	}
 	if st[1] != int(t1.Month()) {
-		fmt.Println("Bad Month", st, t1)
-		return
+		return ErrNoExist{
+			t: st,
+			z: tzstr,
+			e: "invalid month, most likely bad math on your part. Remember: Decemberween isn't until next year",
+		}
 	}
 	if st[0] != t1.Year() {
-		fmt.Println("Bad Year", st, t1)
-		return
+		return ErrNoExist{
+			t: st,
+			z: tzstr,
+			e: "invalid year, must have reached the end of time...",
+		}
 	}
 
+	return nil
+}
+
+func IsAmbigious(st []int, tzstr string) error {
+	return fmt.Errorf("Not Implemented")
+}
+
+func CheckInput2(st []int, tzstr string) error {
 	// Does the time exist twice?
 	// (if I change the time in UTC, do I still get the same time)
 	// Note: Some timezones change by half or quarter hour
@@ -122,6 +175,12 @@ func CheckInput2(st []int, tzstr string) {
 	// https://en.wikipedia.org/wiki/Summer_time_in_Europe
 	// https://en.wikipedia.org/wiki/Daylight_saving_time_in_the_Americas
 	// If I change the time iadd or subtract time in UTC, do I see the same difference in TZ?
+	tz, err := time.LoadLocation(tzstr)
+	if nil != err {
+		return err
+	}
+	m := time.Month(st[1])
+	t1 := time.Date(st[0], m, st[2], st[3], st[4], st[5], st[6], tz)
 	u1 := t1.UTC()
 	// A better way to do this would probably be to parse the timezone database, but... yeah...
 	for _, n := range []int{ /*-120, -60,*/ 30, 60, 120} {
@@ -131,39 +190,11 @@ func CheckInput2(st []int, tzstr string) {
 			fmt.Println("Ambiguous Time")
 			fmt.Printf("%s, %s, %+d\n", t1, u1, n)
 			fmt.Printf("%s, %s, %+d\n", t2, u2, n)
-			return
+			return nil
 		}
 	}
 	//ta :=
-}
-
-func CheckInput(st []int) {
-	m := time.Month(st[1])
-	t1 := time.Date(st[0], m, st[2], st[3], st[4], st[5], st[6], time.UTC)
-	if st[5] != t1.Second() {
-		fmt.Println("Bad Second", st)
-		return
-	}
-	if st[4] != t1.Minute() {
-		fmt.Println("Bad Minute", st, t1.Minute())
-		return
-	}
-	if st[3] != t1.Hour() {
-		fmt.Println("Bad Hour", st)
-		return
-	}
-	if st[2] != t1.Day() {
-		fmt.Println("Bad Day of Month", st)
-		return
-	}
-	if st[1] != int(t1.Month()) {
-		fmt.Println("Bad Month", st)
-		return
-	}
-	if st[0] != t1.Year() {
-		fmt.Println("Bad Year", st)
-		return
-	}
+	return nil
 }
 
 /*