grokify/mogo

package timeutil

import (
    "fmt"
    "strings"
    "time"
)

const (
    NanosecondString  = "naonsecond"
    MicrosecondString = "microsecond"
    MillisecondString = "millisecond"
    SecondString      = "second"
    MinuteString      = "minute"
    HourString        = "hour"
    DayString         = "day"
    WeekString        = "week"
    MonthString       = "month"
    QuarterString     = "quarter"
    HalfYearString    = "halfyear"
    YearString        = "year"
    DecadeString      = "decade"
    ScoreString       = "score"
    CenturyString     = "century"
    MillenniaString   = "millennia"
)

type Interval int

const (
    IntervalNanosecond Interval = iota
    IntervalMicrosecond
    IntervalMillisecond
    IntervalSecond
    IntervalMinute
    IntervalHour
    IntervalDay
    IntervalWeek
    IntervalMonth
    IntervalQuarter
    IntervalHalfYear
    IntervalYear
    IntervalDecade
    IntervalScore
    IntervalCentury
    IntervalMillennia
)

var intervals = [...]string{
    NanosecondString,
    MicrosecondString,
    MillisecondString,
    SecondString,
    MinuteString,
    HourString,
    DayString,
    WeekString,
    MonthString,
    QuarterString,
    HalfYearString,
    YearString,
    DecadeString,
    ScoreString,
    CenturyString,
    MillenniaString,
}

func (i Interval) String() string { return intervals[i] }

func ParseInterval(src string) (Interval, error) {
    canonical := strings.ToLower(strings.TrimSpace(src))
    for i, try := range intervals {
        if canonical == try {
            return Interval(i), nil
        }
    }
    return 0, fmt.Errorf("interval [%v] not found", src)
}

func intervalStart(dt time.Time, interval Interval, d time.Weekday) (time.Time, error) {
    switch interval.String() {
    case YearString:
        return yearStart(dt), nil
    case QuarterString:
        return quarterStart(dt), nil
    case MonthString:
        return monthStart(dt), nil
    case WeekString:
        return weekStart(dt, d), nil
    case DayString:
        return dayStart(dt), nil
    default:
        return time.Time{}, fmt.Errorf("interval (%s) not supported in timeutil.IntervalStart", interval.String())
    }
}