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// Copyright © 2022 siddharth ravikumar <s@ricketyspace.net>
// SPDX-License-Identifier: ISC
// ISO 8601 utility functions
package time
import (
"fmt"
"regexp"
"strconv"
"strings"
"time"
)
// ISO 8601 Duration regex for matching duration in P18DT3H4M60S format.
var durationRegex = regexp.MustCompile(`P(([0-9]{1,})?D)?T(([0-9]{1,2})?H)?(([0-9]{1,2})?M)?(([0-9]{1,2}?)S)?`)
// Converts ISO 8601 duration[1] to time.Duration
//
// Recognizes durations in this format: P18DT3H4M60S
//
// [1]: https://en.wikipedia.org/wiki/ISO_8601#Durations
func Duration(duration string) (time.Duration, error) {
m := durationRegex.FindStringSubmatch(duration)
if m == nil || len(m) == 0 {
return 0, fmt.Errorf("duration invalid: %v", duration)
}
days, err := strconv.Atoi(m[2])
if err != nil {
days = 0
}
hours, err := strconv.Atoi(m[4])
if err != nil {
hours = 0
}
mins, err := strconv.Atoi(m[6])
if err != nil {
mins = 0
}
secs, err := strconv.Atoi(m[8])
if err != nil {
secs = 0
}
// Add 'em all together.
secs += days * 86400
secs += hours * 3600
secs += mins * 60
// Convert seconds to time.Duration.
d, err := time.ParseDuration(fmt.Sprintf("%ds", secs))
return d, nil
}
// Checks if the given ISO 8601 time is within the current time
// period.
//
// `t` must be in 2022-08-07T02:00:00+00:00/PT1H format
//
// Returns true if the time `t` is the current time period; false
// otherwise.
func IsCurrent(t string) (bool, error) {
parts := strings.Split(t, "/")
if len(parts) != 2 {
return false, fmt.Errorf("time invalid")
}
// Parse time `t` into time intervals t1 and t2.
t1, err := time.Parse(time.RFC3339, parts[0])
if err != nil {
return false, fmt.Errorf("time invalid: %s", err)
}
d, err := Duration(parts[1])
if err != nil {
return false, fmt.Errorf("time invalid: %s", err)
}
t2 := t1.Add(d)
// Time `t` is in the current time period if current time is
// within the interval t1 and t2.
now := time.Now()
if t1.Before(now) && now.Before(t2) {
return true, nil
}
if t1.Equal(now) || t2.Equal(now) {
return true, nil
}
return false, nil
}
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