grokify/mogo

package month

import (
    "fmt"
    "time"

    "github.com/grokify/base36"
    "github.com/grokify/mogo/math/mathutil"
    "github.com/grokify/mogo/time/timeutil"
)

func DayofmonthToEnglish(i uint16) string {
    days := []string{
        "zeorth",
        "first", "second", "third", "fourth", "fifth",
        "sixth", "seventh", "eighth", "ninth", "tenth",
        "eleventh", "twelfth", "thirteenth", "fourteenth", "fifteenth",
        "sixteenth", "seventeenth", "eighteenth", "nineteenth", "twentieth",
    }
    tenZero := []string{"tenth", "twentieth", "thirtieth", "fourtieth", "fiftieth"}
    tenPlus := []string{"ten", "twenty", "thirty", "forty", "fifty"}
    if i < 21 {
        return days[i]
    }
    if i > 59 {
        panic("E_OUT_OF_RANGE")
    }
    quotient, remainder := i/10, i%10
    if remainder == 0 {
        return tenZero[quotient-1]
    }
    return tenPlus[quotient-1] + " " + days[remainder]
}

func YearMonthBase36(yyyy, mm uint64) string {
    return fmt.Sprintf("%04s", base36.Encode(yyyy*100+mm))
}

func YearMonthBase36Time(t time.Time) string {
    return YearMonthBase36(uint64(t.Year()), uint64(t.Month()))
}

// MonthStart allows you to add/subtract months resulting
// in the first day of each month while avoiding Go's
// `AddDate` normalization where "adding one month to
// October 31 yields December 1, the normalized form for
// November 31." Setting `deltaMonths` to 0 indicates the
// current month.
func MonthStart(t time.Time, deltaMonths int) time.Time {
    year := t.Year()
    month := int(t.Month())
    if deltaMonths > 0 {
        for i := 0; i < deltaMonths; i++ {
            if month == 12 {
                month = 1
                year++
            } else {
                month++
            }
        }
    } else if deltaMonths < 0 {
        for i := 0; i > deltaMonths; i-- {
            if month == 1 {
                month = 12
                year--
            } else {
                month--
            }
        }
    }
    return time.Date(year, time.Month(month), 1, 0, 0, 0, 0, t.Location())
}

// YearMonthToMonthContinuous converts a year and month to
// a continuous month integer. This is useful when an even
// even spacing between months is desired, such as with
// charting x-axis values.
func YearMonthToMonthContinuous(year, month uint64) uint64 {
    return year*12 + month
}

// MonthContinuousToYearMonth converts a continuous month value (e.g. number of months from year 0).
func MonthContinuousToYearMonth(mc uint64) (uint64, uint64) {
    quotient, remainder := mathutil.DivideInt64(
        int64(mc-1), int64(12))
    return uint64(quotient), uint64(remainder + 1)
}

// TimeToMonthContinuous converts a `time.Time` value to a continuous month.
func TimeToMonthContinuous(t time.Time) uint64 {
    t = t.UTC()
    return YearMonthToMonthContinuous(
        uint64(t.Year()), uint64(t.Month()))
}

// MonthContinuousToTime converts a continuous month value to a `time.Time` value.
func MonthContinuousToTime(mc uint64) time.Time {
    year, month := MonthContinuousToYearMonth(mc)
    return time.Date(
        int(year), time.Month(int(month)), 1,
        0, 0, 0, 0, time.UTC)
}

func MonthContinuousIsQuarterStart(mc uint64) bool {
    month := MonthContinuousToTime(mc).Month()
    return month == 1 || month == 4 || month == 7 || month == 10
}

func MonthContinuousIsYearStart(mc uint64) bool {
    return MonthContinuousToTime(mc).Month() == 1
}

// TimesMonthStarts returns time series of months given start and end input times.
func TimesMonthStarts(times ...time.Time) timeutil.Times {
    timesStarts := timeutil.Times{}
    if len(times) == 0 {
        return timesStarts
    }
    min, max := timeutil.SliceMinMax(times)
    minMonth := timeutil.NewTimeMore(min, 0).MonthStart()
    maxMonth := timeutil.NewTimeMore(max, 0).MonthStart()
    curMonth := minMonth
    for curMonth.Before(maxMonth) || curMonth.Equal(maxMonth) {
        timesStarts = append(timesStarts, curMonth)
        // curMonth = timeutil.TimeDt6AddNMonths(curMonth, 1)
        curMonth = curMonth.AddDate(0, 1, 0)
    }
    return timesStarts
}