duration.go

package schema

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

var durationRegexp = regexp.MustCompile(
	`P(?P<years>\d+Y)?(?P<months>\d+M)?(?P<days>\d+D)?T?(?P<hours>\d+H)?(?P<minutes>\d+M)?(?P<seconds>\d+\.?\d*S)?`)

const (
	hoursInYear  = time.Duration(24*36) * time.Hour
	hoursInMonth = time.Duration(24*30) * time.Hour
	hoursInDay   = time.Duration(24) * time.Hour
)

func castDuration(value string) (time.Duration, error) {
	matches := durationRegexp.FindStringSubmatch(value)
	if len(matches) == 0 {
		return 0, fmt.Errorf("Invalid duration:\"%s\"", value)
	}
	years := parseIntDuration(matches[1], hoursInYear)
	months := parseIntDuration(matches[2], hoursInMonth)
	days := parseIntDuration(matches[3], hoursInDay)
	hours := parseIntDuration(matches[4], time.Hour)
	minutes := parseIntDuration(matches[5], time.Minute)
	seconds := parseSeconds(matches[6])
	return years + months + days + hours + minutes + seconds, nil
}

func parseIntDuration(v string, multiplier time.Duration) time.Duration {
	if len(v) == 0 {
		return 0
	}
	// Ignoring error here because only digits could come from the regular expression.
	d, _ := strconv.Atoi(v[0 : len(v)-1])
	return time.Duration(d) * multiplier
}

func parseSeconds(v string) time.Duration {
	if len(v) == 0 {
		return 0
	}
	// Ignoring error here because only valid arbitrary precision floats could come from the regular expression.
	d, _ := strconv.ParseFloat(v[0:len(v)-1], 64)
	return time.Duration(d * 10e8)
}