grokify/mogo

package quarter

import (
    "time"

    "github.com/grokify/mogo/math/mathutil"
)

// YearQuarterToQuarterContinuous converts a year and quarteer to
// a continuous quarter integer. This is useful when an even
// even spacing between months is desired, such as with
// charting x-axis values.
func YearQuarterToQuarterContinuous(year, quarter uint64) uint64 {
    return year*4 + quarter
}

// QuarterContinuousToYearQuarter converts a continuous quarter value (e.g. numerof months from year 0).
func QuarterContinuousToYearQuarter(qc uint64) (uint64, uint64) {
    quotient, remainder := mathutil.DivideInt64(
        int64(qc-1), int64(4))
    return uint64(quotient), uint64(remainder + 1)
}

// TimeToQuarterContinuous converts a `time.Time` value to a continuous quarter.
func TimeToQuarterContinuous(t time.Time) uint64 {
    return YearQuarterToQuarterContinuous(
        uint64(t.Year()), MonthToQuarter(uint64(t.Month())))
}

func MonthToQuarter(month uint64) uint64 {
    if month <= 3 {
        return uint64(1)
    } else if month <= 6 {
        return uint64(2)
    } else if month <= 9 {
        return uint64(3)
    }
    return uint64(4)
}

// QuarterContinuousToTime converts a continuous quarter value to a `time.Time` value.
func QuarterContinuousToTime(qc uint64) time.Time {
    year, quarter := QuarterContinuousToYearQuarter(qc)
    month := 1
    if quarter == 2 {
        month = 4
    } else if quarter == 3 {
        month = 7
    } else if quarter == 4 {
        month = 10
    }
    return time.Date(
        int(year), time.Month(month), 1,
        0, 0, 0, 0, time.UTC)
}

func QuarterContinuousIsQuarterStart(qc uint64) bool {
    month := QuarterContinuousToTime(qc).Month()
    return month == 1 || month == 4 || month == 7 || month == 10
}

func QuarterContinuousIsYearStart(qc uint64) bool {
    return QuarterContinuousToTime(qc).Month() == 1
}