More interface refinement

ymdflag.go

@@ -30,6 +30,8 @@ type YMDFlag struct {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+// TODO: internal error consts how?
+
 // YMDtoTime returns the Time corresponding to the YYYYMMDD in the specified location.
 // A nil location implies local time.
 func YMDToTime(yyyymmdd int, loc *time.Location) time.Time {
@@ -52,6 +54,27 @@ func TimeToYMD(t time.Time) int {
 	}
 }
 
+// ValidateYMD returns nil if the passed `yyyymmdd` is of a proper YYYYMMDD form.  Zero is a valid value, indicating auto-detection.
+// Otherwise, returns an error.
+// This function is not forgiving like `time.Date`, e.g. 10/32 (Oct 32) is not considered 11/01 (Nov 1).
+func ValidateYMD(yyyymmdd int) error {
+	if yyyymmdd == 0 {
+		return nil
+	} else if yyyymmdd < 0 {
+		return fmt.Errorf("yyyymmdd is negative")
+	} else if yyyymmdd > 99999999 {
+		return fmt.Errorf("yyyymmdd is more than 8 digits")
+	}
+	var year int = yyyymmdd / 10000
+	var month int = (yyyymmdd % 10000) / 100
+	var day int = yyyymmdd % 100
+	dt := time.Date(year, time.Month(month), day, 0, 0, 0, 0, time.Local)
+	if year != dt.Year() || month != int(dt.Month()) || day != dt.Day() {
+		return fmt.Errorf("yyyymmdd is bad or unnormalized")
+	}
+	return nil
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // flag.Value interface
 
@@ -110,9 +133,12 @@ func NewYMDFlagWithLocation(loc *time.Location) YMDFlag {
 }
 
 // NewYMDFlag creates a new YMDFlag for the given integral `YYYYMMDD` value, for example `20230704`.
-// No validation is performed.
-func NewYMDFlagFromInt(i int, loc *time.Location) YMDFlag {
-	return YMDFlag{yyyymmdd: i, loc: loc}
+// Returns a non-nil error if YMDFlag is malformed.  `0` is a valid value.
+func NewYMDFlagFromInt(i int, loc *time.Location) (YMDFlag, error) {
+	if err := ValidateYMD(i); err != nil {
+		return YMDFlag{}, err
+	}
+	return YMDFlag{yyyymmdd: i, loc: loc}, nil
 }
 
 // GetYMD returns the YMDFlag as integer `YYYYMMDD`.  It may be zero.
@@ -151,13 +177,13 @@ func (ymd *YMDFlag) AsYMDString() string {
 // AsDirPath returns the YMDFlag as `"YYYY/MM/DD"` using the OS path seperator
 // If the YMDFlag is nil, then a date fetch occurs, updating it to the current date according to the YMDFlag timezone.
 func (ymd *YMDFlag) AsDirPath() string {
-	return formatDirPath(ymd.AsTime())
+	return formatDirPath(ymd.AsTime(), os.PathSeparator)
 }
 
-// AsDirPathNoCheck returns the YMDFlag as `"YYYY/MM/DD"` using the OS path seperator
-// Note: This method does not check if zeroed. Ensure you call it with a non-zero YMDFlag
-func (ymd YMDFlag) AsDirPathNoCheck() string {
-	return formatDirPath(ymd.AsTimeNoCheck())
+// AsDirPath returns the YMDFlag as `"YYYY/MM/DD"` using given path seperator
+// If the YMDFlag is nil, then a date fetch occurs, updating it to the current date according to the YMDFlag timezone.
+func (ymd *YMDFlag) AsDirPathSep(separator rune) string {
+	return formatDirPath(ymd.AsTime(), separator)
 }
 
 // AsTime returns the YMDFlag as a time.Time in the YMDFlag's location.
@@ -188,10 +214,9 @@ func (ymd *YMDFlag) UpdateNilToNow() {
 
 //////////////////////////////////////////////////////////////////////////////
 
-// formatDirPath returns the `time` as `"YYYY/MM/DD"` using the OS path seperator.
-func formatDirPath(time time.Time) string {
-	return time.Format(fmt.Sprintf(
-		"2006%c01%c02", os.PathSeparator, os.PathSeparator))
+// formatDirPath returns the `time` as `"YYYY/MM/DD"` using the given path seperator.
+func formatDirPath(time time.Time, sep rune) string {
+	return time.Format(fmt.Sprintf("2006%c01%c02", sep, sep))
 }
 
 // isInt checks if a string can be converted safely to an int

ymdflag_test.go

@@ -31,9 +31,9 @@ func Test_uninitializaed_flag_becomes_today_when_accessed(t *testing.T) {
 func TestNonMutatingMethods(t *testing.T) {
 	ymdFlag := NewYMDFlag(time.Date(2020, time.January, 2, 1, 2, 3, 4, time.UTC))
 
-	var dirPath = ymdFlag.AsDirPathNoCheck()
-	assert.Equal(t, "2020/01/02", dirPath, "should match given date")
-
 	var timeValue = ymdFlag.AsTimeNoCheck()
 	assert.Equal(t, time.Date(2020, time.January, 2, 0, 0, 0, 0, time.UTC), timeValue, "should not have a time component")
+
+	var dirPath = formatDirPath(timeValue, '/')
+	assert.Equal(t, "2020/01/02", dirPath, "should match given date path")
 }