Add the Config view: edit and save the settings, applied without a restart

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/sabnzbd/sabnzbd.go

@@ -11,16 +11,26 @@ import (
 	"net/url"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 )
 
 // Client talks to a SABnzbd instance.
 type Client struct {
+	mu      sync.RWMutex // guards baseURL and apiKey, which Reconfigure can change
 	baseURL string
 	apiKey  string
 	http    *http.Client
 }
 
+// Reconfigure points the client at another instance or key.
+func (c *Client) Reconfigure(baseURL, apiKey string) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.baseURL = strings.TrimRight(baseURL, "/")
+	c.apiKey = apiKey
+}
+
 // NewClient returns a client for the instance at baseURL.
 func NewClient(baseURL, apiKey string) *Client {
 	return &Client{
@@ -159,9 +169,12 @@ func boolParam(b bool) string {
 // {"status": false, "error": "..."}, which is turned into an error here.
 func (c *Client) call(ctx context.Context, params url.Values, out any) error {
 	params.Set("output", "json")
-	params.Set("apikey", c.apiKey)
+	c.mu.RLock()
+	baseURL, apiKey := c.baseURL, c.apiKey
+	c.mu.RUnlock()
+	params.Set("apikey", apiKey)
 
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.baseURL+"/api?"+params.Encode(), nil)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, baseURL+"/api?"+params.Encode(), nil)
 	if err != nil {
 		return stripURL(err)
 	}

internal/sabnzbd/sabnzbd_test.go

@@ -122,3 +122,22 @@ func TestTransportErrorHidesAPIKey(t *testing.T) {
 		t.Errorf("error leaks API key: %v", err)
 	}
 }
+
+func TestReconfigure(t *testing.T) {
+	var gotKey string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gotKey = r.URL.Query().Get("apikey")
+		w.Write([]byte(`{"version":"5.1"}`))
+	}))
+	defer srv.Close()
+
+	c := NewClient("http://127.0.0.1:1", "old") // unreachable until reconfigured
+	if _, err := c.Version(context.Background()); err == nil {
+		t.Fatal("expected a connection error")
+	}
+	c.Reconfigure(srv.URL+"/", "new")
+	v, err := c.Version(context.Background())
+	if err != nil || v != "5.1" || gotKey != "new" {
+		t.Errorf("version=%q key=%q err=%v", v, gotKey, err)
+	}
+}