package main

import (
	"errors"
	"regexp"
	"strconv"
	"time"

	log "github.com/sirupsen/logrus"
)

func Expiration(now time.Time, deadline string) (time.Time, error) {
	log.WithFields(log.Fields{"now": now, "deadline": deadline}).Debugf("starting")
	defer log.WithFields(log.Fields{"now": now, "deadline": deadline}).Debugf("done")

	if deadline == "forever" {
		return time.Unix(1<<63-1, 0), nil
	}

	reExpiration := regexp.MustCompile(`([0-9]+)([a-z]+)`)
	for _, v := range reExpiration.FindAllStringSubmatch(deadline, -1) {
		log.WithFields(log.Fields{"now": now, "deadline": deadline}).Debugf("duration[%d] : %v", len(v), v)
		count, _ := strconv.Atoi(v[1])
		switch v[2] {
		case "y":
			now = now.AddDate(count, 0, 0)
		case "m":
			now = now.AddDate(0, count, 0)
		case "d":
			now = now.AddDate(0, 0, count)
		case "h":
			now = now.Add(time.Duration(time.Duration(count) * time.Hour))
		default:
			err := errors.New("invalid duration")
			log.WithFields(log.Fields{"now": now, "deadline": deadline, "attr": v[2], "error": err}).Errorf("")
			return time.Now(), err
		}
	}

	return now, nil
}