weather/main.go

package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"

	"github.com/tidwall/gjson"
)

// free api for reverse geocoding based on IP
const revGeoURL = "http://ip-api.com/json/"

func main() {
	w := NewWeather()

	if err := w.getLatest(); err != nil {
		panic(err)
	}

	fmt.Println(w)
}

type Weather struct {
	Temperature float64
	Humidity    float64
	Conditions  string
	Icon        string
	*Location
	Static bool //
}

func NewWeather() *Weather {
	l := NewLocation()
	// try to set location
	if err := l.getCoords(); err != nil {
		panic(err)
	}

	if err := l.getStation(); err != nil {
		panic(err)
	}

	return &Weather{
		Location: l,
	}
}

func (w *Weather) getLatest() error {
	url := fmt.Sprintf("https://api.weather.gov/stations/%s/observations/latest", w.Location.Station)

	res, err := http.Get(url)

	if err != nil {
		return err
	}

	body, err := io.ReadAll(res.Body)
	res.Body.Close()
	if res.StatusCode > 299 {
		errMsg := fmt.Sprintf("Request failed with status code: %d\n", res.StatusCode)
		return errors.New(errMsg)
	}

	if err != nil {
		return err
	}

	temp := gjson.Get(string(body), "properties.temperature.value")
	humidity := gjson.Get(string(body), "properties.relativeHumidity.value")
	cond := gjson.Get(string(body), "properties.textDescription")

	// convert to Farenheit
	w.Temperature = temp.Float()*(9.0/5) + 32
	w.Humidity = humidity.Float()
	w.Conditions = cond.String()

	return nil
}

func (w *Weather) String() string {
	return fmt.Sprintf("%s %.1f deg %.1f%% RH in %s, %s", w.Conditions, w.Temperature, w.Humidity, w.Location.City, w.Location.State)
}

type Location struct {
	Lat     float32 `json:"lat"`
	Lon     float32 `json:"lon"`
	City    string  `json:"city"`
	State   string  `json:"region"`
	Zipcode string  `json:"zip"`
	Found   bool
	// NWS specific location data
	Station string
}

func NewLocation() *Location {
	return &Location{}
}

func (l *Location) getCoords() error {

	res, err := http.Get(revGeoURL)

	if err != nil {
		return err
	}

	body, err := io.ReadAll(res.Body)
	res.Body.Close()
	if res.StatusCode > 299 {
		errMsg := fmt.Sprintf("Request failed with status code: %d\n", res.StatusCode)
		return errors.New(errMsg)
	}

	if err != nil {
		return err
	}

	// unmarshall response into struct
	if err := json.Unmarshal(body, l); err != nil {
		return err
	}

	l.Found = true

	return nil
}

func (l *Location) getStation() error {
	// generate url based on coords
	url := fmt.Sprintf("https://api.weather.gov/points/%f,%f", l.Lat, l.Lon)

	res, err := http.Get(url)

	if err != nil {
		return err
	}

	body, err := io.ReadAll(res.Body)
	res.Body.Close()
	if res.StatusCode > 299 {
		errMsg := fmt.Sprintf("Request failed with status code: %d\n", res.StatusCode)
		return errors.New(errMsg)
	}

	if err != nil {
		return err
	}

	// send another request to station URL to find closest
	stationURL := gjson.Get(string(body), "properties.observationStations")

	res, err = http.Get(stationURL.String())

	if err != nil {
		return err
	}

	body, err = io.ReadAll(res.Body)
	res.Body.Close()
	if res.StatusCode > 299 {
		errMsg := fmt.Sprintf("Request failed with status code: %d\n", res.StatusCode)
		return errors.New(errMsg)
	}

	if err != nil {
		return err
	}

	station := gjson.Get(string(body), "features.0.properties.stationIdentifier")

	if station.String() == "" {
		return errors.New("Station not found")
	}

	l.Station = station.String()

	return nil
}

// for debugging
func (l *Location) String() string {

	return fmt.Sprintf("%s, %s %s (%f, %f) station: %s", l.City, l.State, l.Zipcode, l.Lat, l.Lon, l.Station)
}