feat: add draw.io theme toggle between minimal and sketch (#106)

- Add toggle button in chat input area to switch between min and sketch themes
- Show warning dialog before switching (clears messages and diagram)
- Persist theme selection in localStorage
- Default theme is minimal (hides shapes sidebar)

app/page.tsx

@@ -15,6 +15,13 @@ export default function Home() {
     const { drawioRef, handleDiagramExport } = useDiagram();
     const [isMobile, setIsMobile] = useState(false);
     const [isChatVisible, setIsChatVisible] = useState(true);
+    const [drawioUi, setDrawioUi] = useState<"min" | "sketch">(() => {
+        if (typeof window !== "undefined") {
+            const saved = localStorage.getItem("drawio-theme");
+            if (saved === "min" || saved === "sketch") return saved;
+        }
+        return "min";
+    });
     const chatPanelRef = useRef<ImperativePanelHandle>(null);
 
     useEffect(() => {
@@ -42,14 +49,14 @@ export default function Home() {
 
     useEffect(() => {
         const handleKeyDown = (event: KeyboardEvent) => {
-            if ((event.ctrlKey || event.metaKey) && event.key === 'b') {
+            if ((event.ctrlKey || event.metaKey) && event.key === "b") {
                 event.preventDefault();
                 toggleChatPanel();
             }
         };
 
-        window.addEventListener('keydown', handleKeyDown);
+        window.addEventListener("keydown", handleKeyDown);
-        return () => window.removeEventListener('keydown', handleKeyDown);
+        return () => window.removeEventListener("keydown", handleKeyDown);
     }, []);
 
     // Show confirmation dialog when user tries to leave the page
@@ -57,11 +64,12 @@ export default function Home() {
     useEffect(() => {
         const handleBeforeUnload = (event: BeforeUnloadEvent) => {
             event.preventDefault();
-            return '';
+            return "";
         };
 
-        window.addEventListener('beforeunload', handleBeforeUnload);
+        window.addEventListener("beforeunload", handleBeforeUnload);
-        return () => window.removeEventListener('beforeunload', handleBeforeUnload);
+        return () =>
+            window.removeEventListener("beforeunload", handleBeforeUnload);
     }, []);
 
     return (
@@ -77,7 +85,9 @@ export default function Home() {
                             Desktop Required
                         </h1>
                         <p className="text-sm text-muted-foreground leading-relaxed">
-                            This application works best on desktop or laptop devices. Please open it on a larger screen for the full experience.
+                            This application works best on desktop or laptop
+                            devices. Please open it on a larger screen for the
+                            full experience.
                         </p>
                     </div>
                 </div>
@@ -89,9 +99,11 @@ export default function Home() {
                     <div className="h-full relative p-2">
                         <div className="h-full rounded-xl overflow-hidden shadow-soft-lg border border-border/30 bg-white">
                             <DrawIoEmbed
+                                key={drawioUi}
                                 ref={drawioRef}
                                 onExport={handleDiagramExport}
                                 urlParameters={{
+                                    ui: drawioUi,
                                     spin: true,
                                     libraries: false,
                                     saveAndExit: false,
@@ -119,6 +131,12 @@ export default function Home() {
                         <ChatPanel
                             isVisible={isChatVisible}
                             onToggleVisibility={toggleChatPanel}
+                            drawioUi={drawioUi}
+                            onToggleDrawioUi={() => {
+                                const newTheme = drawioUi === "min" ? "sketch" : "min";
+                                localStorage.setItem("drawio-theme", newTheme);
+                                setDrawioUi(newTheme);
+                            }}
                         />
                     </div>
                 </ResizablePanel>

components/chat-input.tsx

@@ -5,6 +5,14 @@ import { Button } from "@/components/ui/button";
 import { Textarea } from "@/components/ui/textarea";
 import { ResetWarningModal } from "@/components/reset-warning-modal";
 import { SaveDialog } from "@/components/save-dialog";
+import {
+    Dialog,
+    DialogContent,
+    DialogDescription,
+    DialogFooter,
+    DialogHeader,
+    DialogTitle,
+} from "@/components/ui/dialog";
 import {
     Loader2,
     Send,
@@ -12,6 +20,8 @@ import {
     Image as ImageIcon,
     History,
     Download,
+    PenTool,
+    LayoutGrid,
 } from "lucide-react";
 import { toast } from "sonner";
 import { ButtonWithTooltip } from "@/components/button-with-tooltip";
@@ -97,6 +107,8 @@ interface ChatInputProps {
     onToggleHistory?: (show: boolean) => void;
     sessionId?: string;
     error?: Error | null;
+    drawioUi?: "min" | "sketch";
+    onToggleDrawioUi?: () => void;
 }
 
 export function ChatInput({
@@ -111,6 +123,8 @@ export function ChatInput({
     onToggleHistory = () => {},
     sessionId,
     error = null,
+    drawioUi = "min",
+    onToggleDrawioUi = () => {},
 }: ChatInputProps) {
     const { diagramHistory, saveDiagramToFile } = useDiagram();
     const textareaRef = useRef<HTMLTextAreaElement>(null);
@@ -118,6 +132,7 @@ export function ChatInput({
     const [isDragging, setIsDragging] = useState(false);
     const [showClearDialog, setShowClearDialog] = useState(false);
     const [showSaveDialog, setShowSaveDialog] = useState(false);
+    const [showThemeWarning, setShowThemeWarning] = useState(false);
 
     // Allow retry when there's an error (even if status is still "streaming" or "submitted")
     const isDisabled =
@@ -295,6 +310,50 @@ export function ChatInput({
                             showHistory={showHistory}
                             onToggleHistory={onToggleHistory}
                         />
+
+                        <ButtonWithTooltip
+                            type="button"
+                            variant="ghost"
+                            size="sm"
+                            onClick={() => setShowThemeWarning(true)}
+                            tooltipContent={drawioUi === "min" ? "Switch to Sketch theme" : "Switch to Minimal theme"}
+                            className="h-8 w-8 p-0 text-muted-foreground hover:text-foreground"
+                        >
+                            {drawioUi === "min" ? (
+                                <PenTool className="h-4 w-4" />
+                            ) : (
+                                <LayoutGrid className="h-4 w-4" />
+                            )}
+                        </ButtonWithTooltip>
+
+                        <Dialog open={showThemeWarning} onOpenChange={setShowThemeWarning}>
+                            <DialogContent>
+                                <DialogHeader>
+                                    <DialogTitle>Switch Theme?</DialogTitle>
+                                    <DialogDescription>
+                                        Switching themes will reload the diagram editor and clear any unsaved changes.
+                                    </DialogDescription>
+                                </DialogHeader>
+                                <DialogFooter>
+                                    <Button
+                                        variant="outline"
+                                        onClick={() => setShowThemeWarning(false)}
+                                    >
+                                        Cancel
+                                    </Button>
+                                    <Button
+                                        variant="destructive"
+                                        onClick={() => {
+                                            onClearChat();
+                                            onToggleDrawioUi();
+                                            setShowThemeWarning(false);
+                                        }}
+                                    >
+                                        Switch Theme
+                                    </Button>
+                                </DialogFooter>
+                            </DialogContent>
+                        </Dialog>
                     </div>
 
                     {/* Right actions */}

components/chat-panel.tsx

@@ -29,11 +29,15 @@ import {
 interface ChatPanelProps {
     isVisible: boolean;
     onToggleVisibility: () => void;
+    drawioUi: "min" | "sketch";
+    onToggleDrawioUi: () => void;
 }
 
 export default function ChatPanel({
     isVisible,
     onToggleVisibility,
+    drawioUi,
+    onToggleDrawioUi,
 }: ChatPanelProps) {
     const {
         loadDiagram: onDisplayChart,
@@ -531,6 +535,8 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
                     onToggleHistory={setShowHistory}
                     sessionId={sessionId}
                     error={error}
+                    drawioUi={drawioUi}
+                    onToggleDrawioUi={onToggleDrawioUi}
                 />
             </footer>