package main import ( "bufio" "encoding/json" "flag" "fmt" "io" "log" "net/http" "text/template" "time" ) const ( _urlTemplate = "https://api.meteo.lt/v1/stations/%s/observations/%s" _station = "vilniaus-ams" _promTemplate = `weather_station_air_temperature_celsius{station="{{ .Station }}"} {{ .AirTemperature }} {{ .TS }} weather_station_air_feels_like_celsius{station="{{ .Station }}"} {{ .FeelsLikeTemperature }} {{ .TS }} weather_station_wind_speed_ms{station="{{ .Station }}"} {{ .WindSpeed }} {{ .TS }} weather_station_wind_gust_ms{station="{{ .Station }}"} {{ .WindGust }} {{ .TS }} weather_station_wind_direction_degrees{station="{{ .Station }}"} {{ .WindDirection }} {{ .TS }}{{ if .CloudCover }} weather_station_cloud_cover_percent{station="{{ .Station }}"} {{ .CloudCover }} {{ .TS }}{{ end }} weather_station_sea_level_pressure_hpa{station="{{ .Station }}"} {{ .SeaLevelPressure }} {{ .TS }} weather_station_relative_humidity_percent{station="{{ .Station }}"} {{ .RelativeHumidity }} {{ .TS }} weather_station_precipitation_mm{station="{{ .Station }}"} {{ .Precipitation }} {{ .TS }}{{ if .ConditionCode }} weather_station_condition{station="{{ .Station }}",code="{{ .ConditionCode }}"} 1 {{ .TS }}{{ end }} ` ) var ( _tpl = template.Must(template.New("prom").Parse(_promTemplate)) _listen = flag.String("l", "127.0.0.1:9011", "listen on") ) func main() { flag.Parse() log.Printf("Listening on %s\n", *_listen) log.Fatal((&http.Server{ Addr: *_listen, Handler: http.HandlerFunc(handler), }).ListenAndServe()) } type observation struct { ObservationTimeUtc string `json:"observationTimeUtc"` AirTemperature float64 `json:"airTemperature"` FeelsLikeTemperature float64 `json:"feelsLikeTemperature"` WindSpeed float64 `json:"windSpeed"` WindGust float64 `json:"windGust"` WindDirection float64 `json:"windDirection"` CloudCover *float64 `json:"cloudCover"` SeaLevelPressure float64 `json:"seaLevelPressure"` RelativeHumidity float64 `json:"relativeHumidity"` Precipitation float64 `json:"precipitation"` ConditionCode *string `json:"conditionCode"` // template variables TS int64 Station string } func handler(w http.ResponseWriter, r *http.Request) { observations, err := getObservations(time.Now().UTC(), _station) if err != nil { log.Printf("Error getting observations: %v\n", err) http.Error(w, fmt.Sprintf("Internal error: %v", err.Error()), 500) return } w.Header().Add("Content-Type", "text/plain; version=0.0.4") bw := bufio.NewWriter(w) defer bw.Flush() for _, observation := range observations { ts, err := time.ParseInLocation( time.DateTime, observation.ObservationTimeUtc, time.UTC, ) if err != nil { log.Printf("error parsing time %q: %v\n", observation.ObservationTimeUtc, err) return } observation.TS = ts.UnixMilli() observation.Station = _station if err := _tpl.Execute(bw, observation); err != nil { log.Printf("error executing template: %v", err) return } } bw.WriteString("\n") } func getObservations(date time.Time, station string) ([]observation, error) { url := fmt.Sprintf(_urlTemplate, station, date.Format(time.DateOnly)) resp, err := http.Get(url) if err != nil { return nil, fmt.Errorf("get %q: %w", url, err) } defer func() { io.Copy(io.Discard, resp.Body) resp.Body.Close() }() if resp.StatusCode != 200 { return nil, fmt.Errorf("got non-200 http status code %d", resp.StatusCode) } decoder := json.NewDecoder(resp.Body) var incoming struct { Observations []observation `json:"observations"` } if err := decoder.Decode(&incoming); err != nil { return nil, fmt.Errorf("json decode: %w", err) } return incoming.Observations, nil }