source: code/trunk/vendor/github.com/dustin/go-humanize/times.go@ 822

package humanize

import (
        "fmt"
        "math"
        "sort"
        "time"
)

// Seconds-based time units
const (
        Day      = 24 * time.Hour
        Week     = 7 * Day
        Month    = 30 * Day
        Year     = 12 * Month
        LongTime = 37 * Year
)

// Time formats a time into a relative string.
//
// Time(someT) -> "3 weeks ago"
func Time(then time.Time) string {
        return RelTime(then, time.Now(), "ago", "from now")
}

// A RelTimeMagnitude struct contains a relative time point at which
// the relative format of time will switch to a new format string.  A
// slice of these in ascending order by their "D" field is passed to
// CustomRelTime to format durations.
//
// The Format field is a string that may contain a "%s" which will be
// replaced with the appropriate signed label (e.g. "ago" or "from
// now") and a "%d" that will be replaced by the quantity.
//
// The DivBy field is the amount of time the time difference must be
// divided by in order to display correctly.
//
// e.g. if D is 2*time.Minute and you want to display "%d minutes %s"
// DivBy should be time.Minute so whatever the duration is will be
// expressed in minutes.
type RelTimeMagnitude struct {
        D      time.Duration
        Format string
        DivBy  time.Duration
}

var defaultMagnitudes = []RelTimeMagnitude{
        {time.Second, "now", time.Second},
        {2 * time.Second, "1 second %s", 1},
        {time.Minute, "%d seconds %s", time.Second},
        {2 * time.Minute, "1 minute %s", 1},
        {time.Hour, "%d minutes %s", time.Minute},
        {2 * time.Hour, "1 hour %s", 1},
        {Day, "%d hours %s", time.Hour},
        {2 * Day, "1 day %s", 1},
        {Week, "%d days %s", Day},
        {2 * Week, "1 week %s", 1},
        {Month, "%d weeks %s", Week},
        {2 * Month, "1 month %s", 1},
        {Year, "%d months %s", Month},
        {18 * Month, "1 year %s", 1},
        {2 * Year, "2 years %s", 1},
        {LongTime, "%d years %s", Year},
        {math.MaxInt64, "a long while %s", 1},
}

// RelTime formats a time into a relative string.
//
// It takes two times and two labels.  In addition to the generic time
// delta string (e.g. 5 minutes), the labels are used applied so that
// the label corresponding to the smaller time is applied.
//
// RelTime(timeInPast, timeInFuture, "earlier", "later") -> "3 weeks earlier"
func RelTime(a, b time.Time, albl, blbl string) string {
        return CustomRelTime(a, b, albl, blbl, defaultMagnitudes)
}

// CustomRelTime formats a time into a relative string.
//
// It takes two times two labels and a table of relative time formats.
// In addition to the generic time delta string (e.g. 5 minutes), the
// labels are used applied so that the label corresponding to the
// smaller time is applied.
func CustomRelTime(a, b time.Time, albl, blbl string, magnitudes []RelTimeMagnitude) string {
        lbl := albl
        diff := b.Sub(a)

        if a.After(b) {
                lbl = blbl
                diff = a.Sub(b)
        }

        n := sort.Search(len(magnitudes), func(i int) bool {
                return magnitudes[i].D > diff
        })

        if n >= len(magnitudes) {
                n = len(magnitudes) - 1
        }
        mag := magnitudes[n]
        args := []interface{}{}
        escaped := false
        for _, ch := range mag.Format {
                if escaped {
                        switch ch {
                        case 's':
                                args = append(args, lbl)
                        case 'd':
                                args = append(args, diff/mag.DivBy)
                        }
                        escaped = false
                } else {
                        escaped = ch == '%'
                }
        }
        return fmt.Sprintf(mag.Format, args...)
}