weather/functions.go

package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"io/ioutil"
	"net/http"
	"os"
	"time"

	client "github.com/influxdata/influxdb1-client/v2"
	"gopkg.in/ini.v1"
)

// GetConfig fetch config from ini file
func GetConfig(weatherconfig *WeatherConfig, configfile string) error {
	flag.Usage = Usage

	config, err := ini.Load(configfile)
	if err != nil {
		return err
	}

	var wc WeatherConfig

	weatherSection := config.Section("weather")

	wc.WeatherAppID = weatherSection.Key("appid").MustString("appid")
	wc.WeatherCities = weatherSection.Key("cities").Strings(",")
	if len(wc.WeatherCities) < 1 {
		return fmt.Errorf("No cities provided in config")
	}
	wc.WeatherMeasurements = weatherSection.Key("measurements").Strings(",")
	if len(wc.WeatherMeasurements) < 1 {
		return fmt.Errorf("No measurements provided in config")
	}

	influxdbSection := config.Section("influxdb")
	wc.InfluxHost = influxdbSection.Key("hostname").MustString("localhost")
	wc.InfluxPort = influxdbSection.Key("port").MustInt(8086)
	wc.InfluxUser = influxdbSection.Key("username").MustString("username")
	wc.InfluxPass = influxdbSection.Key("password").MustString("password")
	wc.InfluxDB = influxdbSection.Key("database").MustString("me")

	*weatherconfig = wc

	return err
}

// FetchData fetch data from api
func FetchData(wc *WeatherConfig, city string) (Data, error) {
	var d Data

	pollTo := 30 * time.Millisecond

	c := &http.Client{Timeout: pollTo * time.Second, Transport: &http.Transport{
		IdleConnTimeout:    pollTo,
		DisableCompression: false,
	}}

	q := fmt.Sprintf("https://api.openweathermap.org/data/2.5/weather?q=%s&appid=%s&units=metric", city, wc.WeatherAppID)

	r, err := c.Get(q)
	if err != nil {
		return Data{}, err
	}

	b, err := ioutil.ReadAll(r.Body)
	if err != nil {
		return Data{}, err
	}

	err = json.Unmarshal(b, &d)
	if err != nil {
		return Data{}, err
	}

	d.Points = map[string]interface{}{"temperature": d.Main.Temperature,
		"humidity": d.Main.Humidity,
		"pressure": d.Main.Pressure}

	return d, nil
}

// SendToInflux sends time series data to influxdb
func SendToInflux(wc *WeatherConfig, d Data) error {

	wc.InfluxAddr = fmt.Sprintf("http://%s:%d", wc.InfluxHost, wc.InfluxPort)
	httpClient, err := client.NewHTTPClient(client.HTTPConfig{
		Addr:     wc.InfluxAddr,
		Username: wc.InfluxUser,
		Password: wc.InfluxPass,
	})
	if err != nil {
		return err
	}

	bp, err := client.NewBatchPoints(client.BatchPointsConfig{
		Database: wc.InfluxDB,
	})
	if err != nil {
		return err
	}

	for key, value := range d.Points {
		tags := map[string]string{"city": d.City}
		fields := map[string]interface{}{"value": value}

		point, err := client.NewPoint(
			key,
			tags,
			fields,
			time.Now(),
		)
		if err != nil {
			return err
		}

		bp.AddPoint(point)
		err = httpClient.Write(bp)
		if err != nil {
			return err
		}
	}

	return nil
}

// Usage displays possible arguments
func Usage() {
	flag.PrintDefaults()
	os.Exit(1)
}