sunset.go

package sunset

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"reflect"
	"time"

	"github.com/gorilla/schema"
	"github.com/nathan-osman/go-sunrise"
)

type request struct {
	Lat  float64   `schema:"lat"`
	Lon  float64   `schema:"lon"`
	Date time.Time `schema:"date"`
}

type response struct {
	Sunset  string `json:"sunset"`
	Sunrise string `json:"sunrise"`
}

/*SunTimes - All this function does is take a request
(which comes in as query parameters on the request URL),
performs a sunrise/sunset lookup, and returns a JSON-encoded response.
*/
func SunTimes(w http.ResponseWriter, r *http.Request) {
	var decoder = schema.NewDecoder()
	decoder.RegisterConverter(time.Time{}, dateConverter)

	// Parse the request from query string
	var req request
	if err := decoder.Decode(&req, r.URL.Query()); err != nil {
		// Report any parsing errors
		w.WriteHeader(http.StatusUnprocessableEntity)
		fmt.Fprintf(w, "Error: %s", err)
		return
	}
	log.Printf("Date %v, Lat %v, Lon %v", req.Date, req.Lat, req.Lon)
	if req.Date.IsZero() {
		req.Date = time.Now()
	}
	if req.Lat == 0 && req.Lon == 0 {
		req.Lat = 52.237
		req.Lon = 21.017
	}
	// Perform sunrise/sunset calculation
	sunrise, sunset := sunrise.SunriseSunset(
		req.Lat, req.Lon,
		req.Date.Year(), req.Date.Month(), req.Date.Day(),
	)
	location, _ := time.LoadLocation("Europe/Warsaw")
	set := sunset.In(location).Format("15:04:05")
	rise := sunrise.In(location).Format("15:04:05")
	// Send response back to client as JSON
	w.WriteHeader(http.StatusOK)
	response := response{set, rise}
	if err := json.NewEncoder(w).Encode(&response); err != nil {
		panic(err)
	}
}

func dateConverter(value string) reflect.Value {
	s, _ := time.Parse("2006-01-_2", value)
	return reflect.ValueOf(s)
}