fix: return empty response if no destinations are provided

main.go

@@ -4,12 +4,13 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"github.com/caarlos0/env"
-	"googlemaps.github.io/maps"
 	"log"
 	"net/http"
 	"strconv"
 	"strings"
+
+	"github.com/caarlos0/env"
+	"googlemaps.github.io/maps"
 )
 
 type config struct {
@@ -78,7 +79,16 @@ func makeHandler(fn func(http.ResponseWriter, *http.Request, *maps.Client), clie
 
 func handleDistanceMatrixRequest(w http.ResponseWriter, r *http.Request, client *maps.Client) {
 	origins := strings.Split(r.URL.Query().Get("origins"), "|")
-	destinations := strings.Split(r.URL.Query().Get("destinations"), "|")
+	destinationsString := r.URL.Query().Get("destinations")
+	if destinationsString == "" {
+		x := make([]origin, len(origins))
+		for i, o := range origins {
+			x[i] = origin{Origin: o}
+		}
+		writeResponse(distanceResponse{Origins: x}, w)
+		return
+	}
+	destinations := strings.Split(destinationsString, "|")
 
 	req := &maps.DistanceMatrixRequest{
 		Origins:      origins,
@@ -111,6 +121,11 @@ func handleDistanceMatrixRequest(w http.ResponseWriter, r *http.Request, client
 			res.Origins = append(res.Origins, origin{origins[i], dests})
 		}
 
+		writeResponse(res, w)
+	}
+}
+
+func writeResponse(res distanceResponse, w http.ResponseWriter) {
 	if response, err := json.Marshal(res); err != nil {
 		log.Fatalf("fatal error: %s", err)
 		w.WriteHeader(404)
@@ -118,7 +133,6 @@ func handleDistanceMatrixRequest(w http.ResponseWriter, r *http.Request, client
 		_, _ = w.Write(response)
 	}
 }
-}
 
 func handleAddressRequest(w http.ResponseWriter, r *http.Request, client *maps.Client) {
 	p := strings.Split(r.URL.Path[len("/address/"):], ",")