fix: persist settings in Electron by using fixed port (#415)

- Use fixed port 61337 in production instead of random ports (10000-65535)
- localStorage is origin-specific, so random ports caused settings loss
- Add locale save/restore since language is URL-based
- Fixes #399

app/[lang]/page.tsx

@@ -1,4 +1,5 @@
 "use client"
+import { usePathname, useRouter } from "next/navigation"
 import { useCallback, useEffect, useRef, useState } from "react"
 import { DrawIoEmbed } from "react-drawio"
 import type { ImperativePanelHandle } from "react-resizable-panels"
@@ -10,6 +11,7 @@ import {
     ResizablePanelGroup,
 } from "@/components/ui/resizable"
 import { useDiagram } from "@/contexts/diagram-context"
+import { i18n, type Locale } from "@/lib/i18n/config"
 
 const drawioBaseUrl =
     process.env.NEXT_PUBLIC_DRAWIO_BASE_URL || "https://embed.diagrams.net"
@@ -24,6 +26,8 @@ export default function Home() {
         showSaveDialog,
         setShowSaveDialog,
     } = useDiagram()
+    const router = useRouter()
+    const pathname = usePathname()
     const [isMobile, setIsMobile] = useState(false)
     const [isChatVisible, setIsChatVisible] = useState(true)
     const [drawioUi, setDrawioUi] = useState<"min" | "sketch">("min")
@@ -58,6 +62,18 @@ export default function Home() {
 
     // Load preferences from localStorage after mount
     useEffect(() => {
+        // Restore saved locale and redirect if needed
+        const savedLocale = localStorage.getItem("next-ai-draw-io-locale")
+        if (savedLocale && i18n.locales.includes(savedLocale as Locale)) {
+            const pathParts = pathname.split("/").filter(Boolean)
+            const currentLocale = pathParts[0]
+            if (currentLocale !== savedLocale) {
+                pathParts[0] = savedLocale
+                router.replace(`/${pathParts.join("/")}`)
+                return // Wait for redirect
+            }
+        }
+
         const savedUi = localStorage.getItem("drawio-theme")
         if (savedUi === "min" || savedUi === "sketch") {
             setDrawioUi(savedUi)
@@ -84,7 +100,7 @@ export default function Home() {
         }
 
         setIsLoaded(true)
-    }, [])
+    }, [pathname, router])
 
     const handleDarkModeChange = async () => {
         await saveDiagramToStorage()

components/settings-dialog.tsx

@@ -151,6 +151,9 @@ function SettingsContent({
     }, [open])
 
     const changeLanguage = (lang: string) => {
+        // Save locale to localStorage for persistence across restarts
+        localStorage.setItem("next-ai-draw-io-locale", lang)
+
         const parts = pathname.split("/")
         if (parts.length > 1 && i18n.locales.includes(parts[1] as Locale)) {
             parts[1] = lang

electron/main/port-manager.ts

@@ -3,16 +3,16 @@ import { app } from "electron"
 
 /**
  * Port configuration
+ * Using fixed ports to preserve localStorage across restarts
+ * (localStorage is origin-specific, so changing ports loses all saved data)
  */
 const PORT_CONFIG = {
     // Development mode uses fixed port for hot reload compatibility
     development: 6002,
-    // Production mode port range (will find first available)
-    production: {
-        min: 10000,
-        max: 65535,
-    },
-    // Maximum attempts to find an available port
+    // Production mode uses fixed port (61337) to preserve localStorage
+    // Falls back to sequential ports if unavailable
+    production: 61337,
+    // Maximum attempts to find an available port (fallback)
     maxAttempts: 100,
 }
 
@@ -36,19 +36,11 @@ export function isPortAvailable(port: number): Promise<boolean> {
     })
 }
 
-/**
- * Generate a random port within the production range
- */
-function getRandomPort(): number {
-    const { min, max } = PORT_CONFIG.production
-    return Math.floor(Math.random() * (max - min + 1)) + min
-}
-
 /**
  * Find an available port
  * - In development: uses fixed port (6002)
- * - In production: finds a random available port
- * - If a port was previously allocated, verifies it's still available
+ * - In production: uses fixed port (61337) to preserve localStorage
+ * - Falls back to sequential ports if preferred port is unavailable
  *
  * @param reuseExisting If true, try to reuse the previously allocated port
  * @returns Promise<number> The available port
@@ -56,6 +48,9 @@ function getRandomPort(): number {
  */
 export async function findAvailablePort(reuseExisting = true): Promise<number> {
     const isDev = !app.isPackaged
+    const preferredPort = isDev
+        ? PORT_CONFIG.development
+        : PORT_CONFIG.production
 
     // Try to reuse cached port if requested and available
     if (reuseExisting && allocatedPort !== null) {
@@ -69,29 +64,22 @@ export async function findAvailablePort(reuseExisting = true): Promise<number> {
         allocatedPort = null
     }
 
-    if (isDev) {
-        // Development mode: use fixed port
-        const port = PORT_CONFIG.development
-        const available = await isPortAvailable(port)
-        if (available) {
-            allocatedPort = port
-            return port
-        }
-        console.warn(
-            `Development port ${port} is in use, finding alternative...`,
-        )
+    // Try preferred port first
+    if (await isPortAvailable(preferredPort)) {
+        allocatedPort = preferredPort
+        return preferredPort
     }
 
-    // Production mode or dev port unavailable: find random available port
-    for (let attempt = 0; attempt < PORT_CONFIG.maxAttempts; attempt++) {
-        const port = isDev
-            ? PORT_CONFIG.development + attempt + 1
-            : getRandomPort()
+    console.warn(
+        `Preferred port ${preferredPort} is in use, finding alternative...`,
+    )
 
-        const available = await isPortAvailable(port)
-        if (available) {
+    // Fallback: try sequential ports starting from preferred + 1
+    for (let attempt = 1; attempt <= PORT_CONFIG.maxAttempts; attempt++) {
+        const port = preferredPort + attempt
+        if (await isPortAvailable(port)) {
             allocatedPort = port
-            console.log(`Allocated port: ${port}`)
+            console.log(`Allocated fallback port: ${port}`)
             return port
         }
     }