Changed parameter passing for /tv/state

internal/api/tv.go

@@ -2,8 +2,10 @@ package api
 
 import (
 	"encoding/json"
+	"fmt"
 	"log"
 	"net/http"
+	"net/url"
 	"strconv"
 
 	"github.com/JamesStewy/sse"
@@ -14,8 +16,8 @@ import (
 
 // tvState struct defines the state of the TV.
 type tvState struct {
-	LargeChannel *string `json:"large_channel"`
-	SmallChannel *string `json:"small_channel"`
+	LargeChannel string  `json:"large_channel"`
+	SmallChannel string  `json:"small_channel"`
 	Volume       float32 `json:"volume"`
 	SmallScale   float32 `json:"small_scale"`
 	ShowChat     bool    `json:"show_chat"`
@@ -24,13 +26,31 @@ type tvState struct {
 // state is the actual current state of the TV.
 // It is initialized with default values.
 var state = tvState{
-	LargeChannel: nil,
-	SmallChannel: nil,
+	LargeChannel: "",
+	SmallChannel: "",
 	Volume:       0.5,
 	SmallScale:   0.3,
 	ShowChat:     false,
 }
 
+// getQueryParam is a helper function to get an param from url.Values while making sure the param is present and has only a single value.
+func getQueryParam(v url.Values, param string) (value string, ok bool, err error) {
+	values, ok := v[param]
+	if !ok {
+		return
+	}
+
+	valuesCount := len(values)
+
+	if valuesCount == 1 {
+		value = values[0]
+		return
+	}
+
+	err = fmt.Errorf("Got %d values for parameter '%s' but expected only one: %s", valuesCount, param, values)
+	return
+}
+
 // clients holds the clients that are connected to the event handler. It is used to broadcast state changes to all SSE (Server-Sent Events) clients.
 // Note: the only reason we use a sse.Client => bool map is that we can call *delete* with the client as key. The actual bool value that is stored holds no significance whatsoever.
 // This is basically a *set* in go.
@@ -56,53 +76,65 @@ func stateHandleFunc(w http.ResponseWriter, r *http.Request) {
 	// we save the error messages of the 3 parsing steps here.
 	var errs error
 
-	if q := query.Get("large_channel"); q != "" {
-		if q == "null" {
-			newState.LargeChannel = nil
+	if value, ok, err := getQueryParam(query, "large_channel"); ok {
+		if err != nil {
+			errs = multierror.Append(err)
 		} else {
-			newState.LargeChannel = &q
+			newState.LargeChannel = value
 		}
 	}
 
-	if q := query.Get("small_channel"); q != "" {
-		if q == "null" {
-			newState.SmallChannel = nil
+	if value, ok, err := getQueryParam(query, "small_channel"); ok {
+		if err != nil {
+			errs = multierror.Append(err)
 		} else {
-			newState.SmallChannel = &q
+			newState.SmallChannel = value
 		}
 	}
 
-	if q := query.Get("show_chat"); q != "" {
-		newShowChat, err := strconv.ParseBool(q)
+	if value, ok, err := getQueryParam(query, "volume"); ok {
 		if err != nil {
-			errs = multierror.Append(errs, err)
+			errs = multierror.Append(err)
 		} else {
-			newState.ShowChat = newShowChat
+			newVolume, err := strconv.ParseFloat(value, 32)
+			if err != nil {
+				errs = multierror.Append(errs, err)
+			} else {
+				newState.Volume = float32(newVolume)
+			}
 		}
 	}
 
-	if q := query.Get("volume"); q != "" {
-		newVolume, err := strconv.ParseFloat(q, 32)
+	if value, ok, err := getQueryParam(query, "small_scale"); ok {
 		if err != nil {
-			errs = multierror.Append(errs, err)
+			errs = multierror.Append(err)
 		} else {
-			newState.Volume = float32(newVolume)
+			newSmallScale, err := strconv.ParseFloat(value, 32)
+			if err != nil {
+				errs = multierror.Append(errs, err)
+			} else {
+				newState.SmallScale = float32(newSmallScale)
+			}
 		}
 	}
 
-	if q := query.Get("small_scale"); q != "" {
-		newSmallScale, err := strconv.ParseFloat(q, 32)
+	if value, ok, err := getQueryParam(query, "show_chat"); ok {
 		if err != nil {
-			errs = multierror.Append(errs, err)
+			errs = multierror.Append(err)
 		} else {
-			newState.SmallScale = float32(newSmallScale)
+			newShowChat, err := strconv.ParseBool(value)
+			if err != nil {
+				errs = multierror.Append(errs, err)
+			} else {
+				newState.ShowChat = newShowChat
+			}
 		}
 	}
 
 	if errs != nil { // we had errors
 		http.Error(w, errs.Error(), http.StatusBadRequest)
 
-		log.Printf("Error(s) while parsing update query: %v\n", errs)
+		log.Printf("Error(s) while parsing /tv/state query: %v\n", errs)
 		return
 	}