/
main.go
263 lines (232 loc) · 6.55 KB
/
main.go
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// Code generation tool for embedding the timezone shapefile in the gotz package
// run "go generate" in the parent directory after changing the -release flag in gen.go
package main
import (
"archive/zip"
"bytes"
"compress/gzip"
"flag"
"fmt"
"io"
"log"
"net/http"
"os"
"sort"
json "github.com/json-iterator/go"
"github.com/paulmach/orb/geojson"
"github.com/paulmach/orb/simplify"
)
const dlURL = "https://github.com/evansiroky/timezone-boundary-builder/releases/download/%s/timezones.geojson.zip"
const versionTemplate = `// Generated by tzshapefilegen. DO NOT EDIT.
package localtimezone
// TZBoundaryVersion is the version of tzdata that was used to generate timezone boundaries
const TZBoundaryVersion = "%s"
// TZCount is the number of tzdata timezones supported
const TZCount = %d
// TZNames is an array of possible timezone names that may be returned by this library
var TZNames = []string{
%s}
`
const defaultRelease = "default"
func getMostCurrentRelease() (version string, url string, err error) {
resp, err := http.Get("https://api.github.com/repos/evansiroky/timezone-boundary-builder/releases")
if err != nil {
return "", "", err
}
body, err := io.ReadAll(resp.Body)
if err != nil {
return "", "", err
}
err = resp.Body.Close()
if err != nil {
return "", "", err
}
type asset struct {
Name string `json:"name"`
BrowserDownloadURL string `json:"browser_download_url"`
}
type release struct {
Name string `json:"name"`
Assets []asset `json:"assets"`
}
var response []release
err = json.Unmarshal(body, &response)
if err != nil {
return "", "", err
}
version = response[0].Name
for _, asset := range response[0].Assets {
if asset.Name != "timezones.geojson.zip" {
continue
}
url = asset.BrowserDownloadURL
}
if url == "" {
return "", "", fmt.Errorf("cannot find correct zip in latest timezone release")
}
return version, url, nil
}
func getGeoJSON(releaseURL string) ([]byte, error) {
resp, err := http.Get(releaseURL)
if err != nil {
log.Fatalf("Error: could not download tz shapefile: %v\n", err)
}
buffer := bytes.NewBuffer([]byte{})
_, err = io.Copy(buffer, resp.Body)
if err != nil {
log.Printf("Download failed: %v\n", err)
return nil, err
}
err = resp.Body.Close()
if err != nil {
return nil, err
}
bufferReader := bytes.NewReader(buffer.Bytes())
zipReader, err := zip.NewReader(bufferReader, resp.ContentLength)
if err != nil {
log.Printf("Could not access zipfile: %v\n", err)
return nil, err
}
if len(zipReader.File) == 0 {
log.Println("Error: release zip file have no files!")
return nil, err
} else if zipReader.File[0].Name != "combined.json" {
log.Println("Error: first file in zip file is not combined.json")
return nil, err
}
geojsonDataReader, err := zipReader.File[0].Open()
if err != nil {
log.Printf("Error: could not read from zip file: %v\n", err)
return nil, err
}
geojsonData, err := io.ReadAll(geojsonDataReader)
if err != nil {
log.Printf("Error: could not read combined.json from zip file: %v\n", err)
return nil, err
}
return geojsonData, nil
}
func orbExec(combinedJSON []byte) ([]byte, []string, error) {
geojson.CustomJSONMarshaler = json.ConfigFastest
geojson.CustomJSONUnmarshaler = json.ConfigFastest
fc, err := geojson.UnmarshalFeatureCollection(combinedJSON)
if err != nil {
log.Printf("Error: could not parse combined.json: %v\n", err)
return nil, nil, err
}
features := []*geojson.Feature{}
tzNames := []string{}
for _, feature := range fc.Features {
tzid := feature.Properties.MustString("tzid")
if tzid == "" {
break
}
feature.Geometry = simplify.Visvalingam(0.0001, 4).Simplify(feature.Geometry)
features = append(features, feature)
tzNames = append(tzNames, tzid)
}
sort.Slice(features, func(i, j int) bool {
return features[i].Properties.MustString("tzid") < features[j].Properties.MustString("tzid")
})
fc.Features = features
reducedJSON, err := fc.MarshalJSON()
if err != nil {
log.Printf("Error: could not marshal reduced.json: %v\n", err)
return nil, nil, err
}
tzNames = append(tzNames, "Etc/GMT")
for offset := 1; offset <= 12; offset += 1 {
tzNames = append(tzNames, fmt.Sprintf("Etc/GMT+%d", offset), fmt.Sprintf("Etc/GMT-%d", offset))
}
sort.Strings(tzNames)
return reducedJSON, tzNames, nil
}
func generateData(geoJSON []byte) ([]byte, error) {
buffer := bytes.NewBuffer([]byte{})
gzipper, err := gzip.NewWriterLevel(buffer, gzip.BestCompression)
if err != nil {
log.Printf("Error: could not create gzip writer: %v\n", err)
return nil, err
}
_, err = gzipper.Write(geoJSON)
if err != nil {
log.Printf("Error: could not copy data: %v\n", err)
return nil, err
}
if err := gzipper.Close(); err != nil {
log.Printf("Error: could not flush/close gzip: %v\n", err)
return nil, err
}
return buffer.Bytes(), nil
}
func writeData(content []byte) error {
err := os.WriteFile("data.json.gz", content, 0644)
if err != nil {
log.Printf("Error: could not write data.json.gz: %v\n", err)
return err
}
return nil
}
func writeVersion(release string, tzNames []string) error {
tzNamesFormatted := ""
for _, tzid := range tzNames {
tzNamesFormatted += fmt.Sprintf(" %q,\n", tzid)
}
content := fmt.Sprintf(versionTemplate, release, len(tzNames), tzNamesFormatted)
outfile, err := os.Create("version.go")
if err != nil {
log.Printf("Error: could not create version.go: %v", err)
return err
}
_, err = outfile.WriteString(content)
if err != nil {
log.Printf("Error: could not write content: %v", err)
return err
}
err = outfile.Close()
if err != nil {
return err
}
return nil
}
func main() {
release := flag.String("release", defaultRelease, "timezone boundary builder release version")
flag.Parse()
fmt.Println("*** GETTING TIMEZONE BOUNDARY RELEASE ***")
var releaseURL string
var err error
if *release == defaultRelease {
*release, releaseURL, err = getMostCurrentRelease()
if err != nil {
log.Fatalln(err)
}
} else {
releaseURL = fmt.Sprintf(dlURL, *release)
}
fmt.Printf("Downloading %s\n", releaseURL)
fmt.Println("*** GETTING TIMEZONE BOUNDARY DATA ***")
geojsonData, err := getGeoJSON(releaseURL)
if err != nil {
return
}
fmt.Println("*** SIMPLIFYING GEOJSON ***")
geojsonData, tzNames, err := orbExec(geojsonData)
if err != nil {
return
}
fmt.Println("*** GEOJSON FINISHED ***")
fmt.Println("*** GENERATING GO CODE ***")
content, err := generateData(geojsonData)
if err != nil {
return
}
err = writeData(content)
if err != nil {
return
}
err = writeVersion(*release, tzNames)
if err != nil {
return
}
fmt.Println("*** ALL DONE, YAY ***")
}