rewrite weather in go

2024-09-15 07:36:17 +03:00
parent 65297845e5
commit 605d340aa0
6 changed files with 142 additions and 56 deletions
--- a/pkgs/weather/main.go
+++ b/pkgs/weather/main.go
@@ -0,0 +1,118 @@
+package main
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"text/template"
+	"time"
+)
+
+const (
+	_listen       = ":9011"
+	_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))
+
+func main() {
+	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
+}