| 1 | package geo |
| 2 | |
| 3 | import ( |
| 4 | _ "embed" |
| 5 | "regexp" |
| 6 | "strconv" |
| 7 | "strings" |
| 8 | "sync" |
| 9 | ) |
| 10 | |
| 11 | //go:embed data/zone.tab |
| 12 | var zoneTab string |
| 13 | |
| 14 | //go:embed data/links.txt |
| 15 | var linksTxt string |
| 16 | |
| 17 | //go:embed data/VERSION |
| 18 | var tzVersion string |
| 19 | |
| 20 | // TZDataVersion is the IANA release the embedded tables came from. |
| 21 | func TZDataVersion() string { return strings.TrimSpace(tzVersion) } |
| 22 | |
| 23 | var ( |
| 24 | tzOnce sync.Once |
| 25 | zonePoints map[string]Point // lowercased zone name -> point |
| 26 | zoneLinks map[string]string |
| 27 | countryOne map[string]Point // countries with exactly one row |
| 28 | rowsPerCC map[string]int |
| 29 | ) |
| 30 | |
| 31 | // zoneShape is spec §6.2 step 1: at most 64 bytes, one to three |
| 32 | // "/"-separated segments of [A-Za-z0-9_+-]. |
| 33 | var zoneShape = regexp.MustCompile(`^[A-Za-z0-9_+\-]+(/[A-Za-z0-9_+\-]+){0,2}$`) |
| 34 | |
| 35 | // notAPlace names an offset or a machine, not a place (R3). |
| 36 | var notAPlace = map[string]bool{ |
| 37 | "": true, "local": true, "localtime": true, "posixrules": true, |
| 38 | "utc": true, "uct": true, "gmt": true, "universal": true, "zulu": true, |
| 39 | "factory": true, |
| 40 | } |
| 41 | |
| 42 | func loadTZ() { |
| 43 | zonePoints = map[string]Point{} |
| 44 | countryOne = map[string]Point{} |
| 45 | rowsPerCC = map[string]int{} |
| 46 | for _, line := range strings.Split(zoneTab, "\n") { |
| 47 | if line == "" || strings.HasPrefix(line, "#") { |
| 48 | continue |
| 49 | } |
| 50 | f := strings.Split(line, "\t") |
| 51 | if len(f) < 3 { |
| 52 | continue |
| 53 | } |
| 54 | p, ok := parseISO6709(f[1]) |
| 55 | if !ok { |
| 56 | continue |
| 57 | } |
| 58 | zonePoints[strings.ToLower(f[2])] = p |
| 59 | cc := strings.ToUpper(f[0]) |
| 60 | rowsPerCC[cc]++ |
| 61 | countryOne[cc] = p |
| 62 | } |
| 63 | zoneLinks = map[string]string{} |
| 64 | for _, line := range strings.Split(linksTxt, "\n") { |
| 65 | f := strings.Fields(line) |
| 66 | if len(f) == 2 { |
| 67 | zoneLinks[strings.ToLower(f[1])] = strings.ToLower(f[0]) |
| 68 | } |
| 69 | } |
| 70 | } |
| 71 | |
| 72 | // ZonePoint maps an IANA zone name to its principal location, following |
| 73 | // tzdata links (at most 4 hops). It refuses anything that is not a place. |
| 74 | func ZonePoint(name string) (Point, bool) { |
| 75 | tzOnce.Do(loadTZ) |
| 76 | name = strings.TrimSpace(name) |
| 77 | if len(name) > 64 || !zoneShape.MatchString(name) { |
| 78 | return Point{}, false |
| 79 | } |
| 80 | low := strings.ToLower(name) |
| 81 | if notAPlace[low] || strings.HasPrefix(low, "etc/") { |
| 82 | return Point{}, false |
| 83 | } |
| 84 | return resolveLinks(low, zoneLinks, zonePoints) |
| 85 | } |
| 86 | |
| 87 | func resolveLinks(name string, links map[string]string, points map[string]Point) (Point, bool) { |
| 88 | for hop := 0; hop <= 4; hop++ { |
| 89 | if p, ok := points[name]; ok { |
| 90 | return p, true |
| 91 | } |
| 92 | next, ok := links[name] |
| 93 | if !ok { |
| 94 | return Point{}, false |
| 95 | } |
| 96 | name = next |
| 97 | } |
| 98 | return Point{}, false |
| 99 | } |
| 100 | |
| 101 | // countryOverride names the principal zone of every country with more |
| 102 | // than one zone.tab row (tzdata 2026b). TestCountryOverridesCoverEvery |
| 103 | // MultiZoneCountry fails when a refresh adds a multi-row country. |
| 104 | var countryOverride = map[string]string{ |
| 105 | "AQ": "Antarctica/McMurdo", "AR": "America/Argentina/Buenos_Aires", |
| 106 | "AU": "Australia/Sydney", "BR": "America/Sao_Paulo", "CA": "America/Toronto", |
| 107 | "CD": "Africa/Kinshasa", "CL": "America/Santiago", "CN": "Asia/Shanghai", |
| 108 | "CY": "Asia/Nicosia", "DE": "Europe/Berlin", "EC": "America/Guayaquil", |
| 109 | "ES": "Europe/Madrid", "FM": "Pacific/Pohnpei", "GL": "America/Nuuk", |
| 110 | "ID": "Asia/Jakarta", "KI": "Pacific/Tarawa", "KZ": "Asia/Almaty", |
| 111 | "MH": "Pacific/Majuro", "MN": "Asia/Ulaanbaatar", "MX": "America/Mexico_City", |
| 112 | "MY": "Asia/Kuala_Lumpur", "NZ": "Pacific/Auckland", "PF": "Pacific/Tahiti", |
| 113 | "PG": "Pacific/Port_Moresby", "PS": "Asia/Gaza", "PT": "Europe/Lisbon", |
| 114 | "RU": "Europe/Moscow", "UA": "Europe/Kyiv", "UM": "Pacific/Wake", |
| 115 | "US": "America/New_York", "UZ": "Asia/Tashkent", |
| 116 | } |
| 117 | |
| 118 | // CountryPoint maps an ISO 3166-1 alpha-2 code to a point: its only |
| 119 | // zone.tab row, or its override's zone. |
| 120 | func CountryPoint(iso2 string) (Point, bool) { |
| 121 | tzOnce.Do(loadTZ) |
| 122 | cc := strings.ToUpper(strings.TrimSpace(iso2)) |
| 123 | if zone, ok := countryOverride[cc]; ok { |
| 124 | return ZonePoint(zone) |
| 125 | } |
| 126 | if rowsPerCC[cc] == 1 { |
| 127 | return countryOne[cc], true |
| 128 | } |
| 129 | return Point{}, false |
| 130 | } |
| 131 | |
| 132 | func zoneRowsPerCountry() map[string]int { tzOnce.Do(loadTZ); return rowsPerCC } |
| 133 | |
| 134 | // parseISO6709 reads zone.tab's ±DDMM±DDDMM or ±DDMMSS±DDDMMSS. |
| 135 | func parseISO6709(s string) (Point, bool) { |
| 136 | i := strings.IndexAny(s[1:], "+-") + 1 |
| 137 | if i <= 0 { |
| 138 | return Point{}, false |
| 139 | } |
| 140 | lat, ok1 := dms(s[:i], 2) |
| 141 | lon, ok2 := dms(s[i:], 3) |
| 142 | return Point{lat, lon}, ok1 && ok2 |
| 143 | } |
| 144 | |
| 145 | func dms(s string, degDigits int) (float64, bool) { |
| 146 | sign := 1.0 |
| 147 | if s[0] == '-' { |
| 148 | sign = -1 |
| 149 | } |
| 150 | d := s[1:] |
| 151 | if len(d) != degDigits+2 && len(d) != degDigits+4 { |
| 152 | return 0, false |
| 153 | } |
| 154 | deg, err1 := strconv.Atoi(d[:degDigits]) |
| 155 | min, err2 := strconv.Atoi(d[degDigits : degDigits+2]) |
| 156 | sec := 0 |
| 157 | var err3 error |
| 158 | if len(d) == degDigits+4 { |
| 159 | sec, err3 = strconv.Atoi(d[degDigits+2:]) |
| 160 | } |
| 161 | if err1 != nil || err2 != nil || err3 != nil { |
| 162 | return 0, false |
| 163 | } |
| 164 | return sign * (float64(deg) + float64(min)/60 + float64(sec)/3600), true |
| 165 | } |
| 166 | |
amadan