add new x/timex sub-package

x/timex/weekday.go

@@ -0,0 +1,121 @@
+package timex
+
+import "time"
+
+// RangeDate returns a function which returns a time
+// between "start" and "end". When the iteration finishes
+// the returned time is zero.
+func RangeDate(start, end time.Time) func() time.Time {
+	y, m, d := start.Date()
+	start = time.Date(y, m, d, 0, 0, 0, 0, start.Location())
+	y, m, d = end.Date()
+	end = time.Date(y, m, d, 0, 0, 0, 0, end.Location())
+
+	return func() time.Time {
+		if start.After(end) {
+			return time.Time{}
+		}
+		date := start
+		start = start.AddDate(0, 0, 1)
+		return date
+	}
+}
+
+type DateRangeType string
+
+const (
+	DayRange   DateRangeType = "day"
+	MonthRange DateRangeType = "month"
+	WeekRange  DateRangeType = "week"
+	YearRange  DateRangeType = "year"
+)
+
+// Between returns the dates from "start" to "end".
+func Between(start, end time.Time) []time.Time {
+	var dates []time.Time
+	for df := RangeDate(start, end); ; {
+		d := df()
+		if d.IsZero() {
+			break
+		}
+		dates = append(dates, d)
+	}
+	return dates
+}
+
+// Backwards returns a list of dates between "end" and -n (years, months, weeks or days).
+func Backwards(typ DateRangeType, end time.Time, n int) []time.Time {
+	var start time.Time
+
+	switch typ {
+	case DayRange:
+		n = n - 1 // -7 should be -6 to get the week from today.
+		start = end.AddDate(0, 0, -n)
+	case WeekRange:
+		// 7 should be 6 to get the week.
+		start = end.AddDate(0, 0, -n*6)
+	case MonthRange:
+		start = end.AddDate(0, -n, 0)
+	case YearRange:
+		start = end.AddDate(-n, 0, 0)
+	}
+
+	return Between(start, end)
+}
+
+// BackwardsN returns the dates from back to "n" years, months, weeks or days from today.
+func BackwardsN(typ DateRangeType, n int) []time.Time {
+	end := time.Now()
+	return Backwards(typ, end, n)
+}
+
+// BackwardsToMonday returns the dates between "end" (including "end")
+// until the previous monday of the current week (including monday).
+func BackwardsToMonday(end time.Time) []time.Time {
+	dates := []time.Time{end}
+	for end.Weekday() != time.Monday {
+		end = end.AddDate(0, 0, -1)
+		dates = append(dates, end)
+	}
+	return dates
+}
+
+func GetWeekDate(now time.Time, weekday, start, end time.Weekday) time.Time {
+	dates := GetWeekdays(now, start, end)
+	for _, d := range dates {
+		if d.Weekday() == weekday {
+			return d
+		}
+	}
+
+	return time.Time{}
+}
+
+// GetWeekStart returns the date of the first week day (startWeekday) of the current now's week.
+func GetWeekStart(now time.Time, startWeekday time.Weekday) time.Time {
+	offset := (int(startWeekday) - int(now.Weekday()) - 7) % 7
+	date := now.Add(time.Duration(offset*24) * time.Hour)
+	return date
+}
+
+// GetWeekEnd returns the date of the last week day (endWeekday) of the current now's week.
+func GetWeekEnd(now time.Time, endWeekday time.Weekday) time.Time {
+	offset := (int(endWeekday) - int(now.Weekday()) + 7) % 7
+	date := now.Add(time.Duration(offset*24) * time.Hour)
+	return date
+}
+
+// GetWeekdays returns the range between "startWeekday" and "endWeekday" of the current week.
+func GetWeekdays(now time.Time, startWeekday, endWeekday time.Weekday) (dates []time.Time) {
+	return Between(GetWeekStart(now, startWeekday), GetWeekEnd(now, endWeekday))
+}
+
+// GetMonthStart returns the date of the first month day of the current now's month.
+func GetMonthStart(now time.Time) time.Time {
+	return time.Date(now.Year(), now.Month(), 1, 0, 0, 0, 0, now.Location())
+}
+
+// GetYearStart returns the date of the first year of the current now's year.
+func GetYearStart(now time.Time) time.Time {
+	return time.Date(now.Year(), 1, 1, 0, 0, 0, 0, now.Location())
+}