duration.go

package main

import (
	"fmt"
	"regexp"
	"strconv"
	"time"
)

// Duration with support for periodes larger than "hours"
type Duration time.Duration

var durationRE = regexp.MustCompile("^([0-9]+)(y|w|d|h|m|s|ms)$")

// ParseDuration parses a string into a time.Duration, assuming that a year
// always has 365d, a week always has 7d, and a day always has 24h.
func ParseDuration(durationStr string) (Duration, error) {
	matches := durationRE.FindStringSubmatch(durationStr)
	if len(matches) != 3 {
		return 0, fmt.Errorf("not a valid duration string: %q", durationStr)
	}
	var (
		n, _ = strconv.Atoi(matches[1])
		dur  = time.Duration(n) * time.Millisecond
	)
	switch unit := matches[2]; unit {
	case "y":
		dur *= 1000 * 60 * 60 * 24 * 365
	case "w":
		dur *= 1000 * 60 * 60 * 24 * 7
	case "d":
		dur *= 1000 * 60 * 60 * 24
	case "h":
		dur *= 1000 * 60 * 60
	case "m":
		dur *= 1000 * 60
	case "s":
		dur *= 1000
	case "ms":
		// Value already correct
	default:
		return 0, fmt.Errorf("invalid time unit in duration string: %q", unit)
	}
	return Duration(dur), nil
}

func (d Duration) String() string {
	var (
		ms   = int64(time.Duration(d) / time.Millisecond)
		unit = "ms"
	)
	if ms == 0 {
		return "0s"
	}
	factors := map[string]int64{
		"y":  1000 * 60 * 60 * 24 * 365,
		"w":  1000 * 60 * 60 * 24 * 7,
		"d":  1000 * 60 * 60 * 24,
		"h":  1000 * 60 * 60,
		"m":  1000 * 60,
		"s":  1000,
		"ms": 1,
	}

	switch int64(0) {
	case ms % factors["y"]:
		unit = "y"
	case ms % factors["w"]:
		unit = "w"
	case ms % factors["d"]:
		unit = "d"
	case ms % factors["h"]:
		unit = "h"
	case ms % factors["m"]:
		unit = "m"
	case ms % factors["s"]:
		unit = "s"
	}
	return fmt.Sprintf("%v%v", ms/factors[unit], unit)
}

// MarshalYAML implements the yaml.Marshaler interface.
func (d Duration) MarshalYAML() (interface{}, error) {
	return d.String(), nil
}

// UnmarshalYAML implements the yaml.Unmarshaler interface.
func (d *Duration) UnmarshalYAML(unmarshal func(interface{}) error) error {
	var s string
	if err := unmarshal(&s); err != nil {
		return err
	}
	dur, err := ParseDuration(s)
	if err != nil {
		return err
	}
	*d = dur
	return nil
}