57 lines
1.2 KiB
Go
57 lines
1.2 KiB
Go
package main
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import (
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"errors"
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"fmt"
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"regexp"
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"strconv"
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)
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// ErrZoneOffsetInvalid is thrown when a zone string is an invalid zone offset
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var ErrZoneOffsetInvalid = errors.New("offset zone invalid")
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const zoneHour = 60 * 60
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const zoneMinute = 60
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var zoneOffsetRegexp = regexp.MustCompile(`^[+-][0-9]{2}:[0-9]{2}$`)
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// ParseZoneOffset parses a zone string into an offset
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func ParseZoneOffset(zone string) (int, error) {
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if !zoneOffsetRegexp.MatchString(zone) {
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return 0, ErrZoneOffsetInvalid
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}
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// Assume that if it satisfies the regex, it satisfies the length and won't
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// fail to parse
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d := 0
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if zone[0] == '+' {
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d = 1
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}
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if zone[0] == '-' {
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d = -1
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}
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h, _ := strconv.ParseUint(zone[1:1+2], 10, 64)
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// Allow hour offsets greater that 24
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m, _ := strconv.ParseUint(zone[1+3:1+3+2], 10, 64)
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if m >= 60 {
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return 0, ErrZoneOffsetInvalid
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}
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offset := d * (int(h)*zoneHour + int(m)*zoneMinute)
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return offset, nil
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}
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// FormatZoneOffset formats an offset into a string
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func FormatZoneOffset(offset int) string {
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neg := offset < 0
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s := '+'
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if neg {
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s = '-'
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offset = -offset
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}
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if offset == 0 {
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return "\u00B100:00"
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}
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h := offset / zoneHour
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m := (offset % zoneHour) / zoneMinute
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return fmt.Sprintf("%c%02d:%02d", s, h, m)
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}
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