chore: remove dead code from previous #815 fix attempts

PR #840 fixed issue #815 in the Electron main process via
will-prevent-unload + preventDefault. The renderer-side workarounds
introduced by previous fix attempts (#642, #648) are no longer needed
and never had effect for their stated purpose.

Removed:
- configuration={ confirmExit: false } in DrawIoEmbed
  confirmExit is not a recognized draw.io config key (zero matches in
  jgraph/drawio source). This was always dead code.

- modified=0 / keepmodified=0 URL parameters
  Per drawio source (app.min.js:14898), these only suppress the
  post-save modified-flag clearing — they do not prevent edits from
  setting editor.modified=true. They were ineffective for blocking
  beforeunload prompts and actually prevented draw.io from clearing
  its modified flag after save.

- canPersist / canPersistChecked state and isIndexedDBUsable() probe
  Their only purpose was gating the dead config above. Removing them
  also removes a startup delay before the iframe renders.

- handleDrawioAutoSave wrapper
  After PR #780 stripped its body, it was a pure passthrough useCallback.
  Now passes handleDiagramAutoSave directly to onAutoSave.

- withDB / isClosingError / resetDBPromise / onversionchange / onclose
  / terminated handlers in lib/session-storage.ts and lib/template-storage.ts
  PR #648 added these to recover from 'IDBDatabase: connection is closing'
  errors that PR #642's first land caused via db.close() on the shared
  singleton. That bug was already fixed in c5de1a1 (re-land of #642),
  three minutes before PR #648 commits started. The retry handlers
  defend against multi-tab / version-change scenarios that cannot occur
  in this single-instance Electron app (requestSingleInstanceLock).
  template-storage.ts copied the same pattern when introduced by #773.

Verified:
- npx tsc --noEmit passes
- Manual test in dev mode: session save/load works, template create works,
  diagram-only persistence works.

app/[lang]/page.tsx

@@ -12,7 +12,6 @@ import {
 import { useDiagram } from "@/contexts/diagram-context"
 import { type DrawioTheme, isDrawioTheme } from "@/lib/drawio-themes"
 import { i18n, type Locale } from "@/lib/i18n/config"
-import { isIndexedDBUsable } from "@/lib/session-storage"
 
 export default function Home() {
     const {
@@ -33,8 +32,6 @@ export default function Home() {
     const [isLoaded, setIsLoaded] = useState(false)
     const [isDrawioReady, setIsDrawioReady] = useState(false)
     const [isElectron, setIsElectron] = useState(false)
-    const [canPersist, setCanPersist] = useState(false)
-    const [canPersistChecked, setCanPersistChecked] = useState(false)
     const [drawioBaseUrl, setDrawioBaseUrl] = useState(
         process.env.NEXT_PUBLIC_DRAWIO_BASE_URL || "https://embed.diagrams.net",
     )
@@ -85,11 +82,6 @@ export default function Home() {
             setDrawioBaseUrl(`${window.location.origin}/drawio/index.html`)
         }
 
-        void (async () => {
-            const usable = await isIndexedDBUsable()
-            setCanPersist(usable)
-            setCanPersistChecked(true)
-        })()
         setIsLoaded(true)
     }, [pathname, router])
 
@@ -98,13 +90,6 @@ export default function Home() {
         onDrawioLoad()
     }, [onDrawioLoad])
 
-    const handleDrawioAutoSave = useCallback(
-        (data: { xml?: string }) => {
-            handleDiagramAutoSave(data)
-        },
-        [handleDiagramAutoSave],
-    )
-
     const handleDarkModeChange = () => {
         const newValue = !darkMode
         setDarkMode(newValue)
@@ -187,7 +172,7 @@ export default function Home() {
                         }`}
                     >
                         <div className="h-full rounded-xl overflow-hidden shadow-soft-lg border border-border/30 relative">
-                            {isLoaded && canPersistChecked && (
+                            {isLoaded && (
                                 <div
                                     className={`h-full w-full ${isDrawioReady ? "" : "invisible absolute inset-0"}`}
                                 >
@@ -195,24 +180,14 @@ export default function Home() {
                                         key={`${drawioUi}-${darkMode}-${currentLang}-${isElectron}`}
                                         ref={drawioRef}
                                         autosave
-                                        onAutoSave={handleDrawioAutoSave}
+                                        onAutoSave={handleDiagramAutoSave}
                                         onExport={handleDiagramExport}
                                         onLoad={handleDrawioLoad}
                                         baseUrl={drawioBaseUrl}
-                                        configuration={
-                                            canPersist
-                                                ? { confirmExit: false }
-                                                : undefined
-                                        }
                                         urlParameters={{
                                             ui: drawioUi,
                                             spin: false,
                                             libraries: false,
-                                            // Disable modified tracking only when persistence is available
-                                            ...(canPersist && {
-                                                modified: false,
-                                                keepmodified: false,
-                                            }),
                                             saveAndExit: false,
                                             noSaveBtn: true,
                                             noExitBtn: true,

lib/session-storage.ts

@@ -58,33 +58,6 @@ interface ChatSessionDB extends DBSchema {
 
 // Database singleton
 let dbPromise: Promise<IDBPDatabase<ChatSessionDB>> | null = null
-const resetDBPromise = () => {
-    dbPromise = null
-}
-
-const isClosingError = (error: unknown): boolean => {
-    return (
-        error instanceof DOMException &&
-        error.name === "InvalidStateError" &&
-        /closing/i.test(error.message)
-    )
-}
-
-const withDB = async <T>(
-    action: (db: IDBPDatabase<ChatSessionDB>) => Promise<T>,
-): Promise<T> => {
-    try {
-        const db = await getDB()
-        return await action(db)
-    } catch (error) {
-        if (isClosingError(error)) {
-            resetDBPromise()
-            const db = await getDB()
-            return await action(db)
-        }
-        throw error
-    }
-}
 
 async function getDB(): Promise<IDBPDatabase<ChatSessionDB>> {
     if (!dbPromise) {
@@ -115,23 +88,7 @@ async function getDB(): Promise<IDBPDatabase<ChatSessionDB>> {
                     }
                 }
             },
-            terminated() {
-                resetDBPromise()
-            },
         })
-        dbPromise
-            .then((db) => {
-                db.onversionchange = () => {
-                    db.close()
-                    resetDBPromise()
-                }
-                db.onclose = () => {
-                    resetDBPromise()
-                }
-            })
-            .catch(() => {
-                resetDBPromise()
-            })
     }
     return dbPromise
 }
@@ -146,46 +103,31 @@ export function isIndexedDBAvailable(): boolean {
     }
 }
 
-// Check if IndexedDB is actually usable (not just present).
-// Note: Do NOT close the db here - getDB() returns a shared singleton connection
-// that other code depends on.
-export async function isIndexedDBUsable(): Promise<boolean> {
-    if (!isIndexedDBAvailable()) return false
-    try {
-        await getDB()
-        return true
-    } catch {
-        return false
-    }
-}
-
 // CRUD Operations
 export async function getAllSessionMetadata(): Promise<SessionMetadata[]> {
     if (!isIndexedDBAvailable()) return []
     try {
-        return await withDB(async (db) => {
-            const tx = db.transaction(STORE_NAME, "readonly")
-            const index = tx.store.index("by-updated")
-            const metadata: SessionMetadata[] = []
+        const db = await getDB()
+        const tx = db.transaction(STORE_NAME, "readonly")
+        const index = tx.store.index("by-updated")
+        const metadata: SessionMetadata[] = []
 
-            // Use cursor to read only metadata fields (avoids loading full messages/XML)
-            let cursor = await index.openCursor(null, "prev") // newest first
-            while (cursor) {
-                const s = cursor.value
-                metadata.push({
-                    id: s.id,
-                    title: s.title,
-                    createdAt: s.createdAt,
-                    updatedAt: s.updatedAt,
-                    messageCount: s.messages.length,
-                    hasDiagram:
-                        !!s.diagramXml && s.diagramXml.trim().length > 0,
-                    thumbnailDataUrl: s.thumbnailDataUrl,
-                })
-                cursor = await cursor.continue()
-            }
-            return metadata
-        })
+        // Use cursor to read only metadata fields (avoids loading full messages/XML)
+        let cursor = await index.openCursor(null, "prev") // newest first
+        while (cursor) {
+            const s = cursor.value
+            metadata.push({
+                id: s.id,
+                title: s.title,
+                createdAt: s.createdAt,
+                updatedAt: s.updatedAt,
+                messageCount: s.messages.length,
+                hasDiagram: !!s.diagramXml && s.diagramXml.trim().length > 0,
+                thumbnailDataUrl: s.thumbnailDataUrl,
+            })
+            cursor = await cursor.continue()
+        }
+        return metadata
     } catch (error) {
         console.error("Failed to get session metadata:", error)
         return []
@@ -195,9 +137,8 @@ export async function getAllSessionMetadata(): Promise<SessionMetadata[]> {
 export async function getSession(id: string): Promise<ChatSession | null> {
     if (!isIndexedDBAvailable()) return null
     try {
-        return await withDB(async (db) => {
-            return (await db.get(STORE_NAME, id)) || null
-        })
+        const db = await getDB()
+        return (await db.get(STORE_NAME, id)) || null
     } catch (error) {
         console.error("Failed to get session:", error)
         return null
@@ -207,9 +148,8 @@ export async function getSession(id: string): Promise<ChatSession | null> {
 export async function saveSession(session: ChatSession): Promise<boolean> {
     if (!isIndexedDBAvailable()) return false
     try {
-        await withDB(async (db) => {
-            await db.put(STORE_NAME, session)
-        })
+        const db = await getDB()
+        await db.put(STORE_NAME, session)
         return true
     } catch (error) {
         // Handle quota exceeded
@@ -221,9 +161,8 @@ export async function saveSession(session: ChatSession): Promise<boolean> {
             await deleteOldestSession()
             // Retry once
             try {
-                await withDB(async (db) => {
-                    await db.put(STORE_NAME, session)
-                })
+                const db = await getDB()
+                await db.put(STORE_NAME, session)
                 return true
             } catch (retryError) {
                 console.error(
@@ -242,9 +181,8 @@ export async function saveSession(session: ChatSession): Promise<boolean> {
 export async function deleteSession(id: string): Promise<void> {
     if (!isIndexedDBAvailable()) return
     try {
-        await withDB(async (db) => {
-            await db.delete(STORE_NAME, id)
-        })
+        const db = await getDB()
+        await db.delete(STORE_NAME, id)
     } catch (error) {
         console.error("Failed to delete session:", error)
     }
@@ -253,9 +191,8 @@ export async function deleteSession(id: string): Promise<void> {
 export async function getSessionCount(): Promise<number> {
     if (!isIndexedDBAvailable()) return 0
     try {
-        return await withDB(async (db) => {
-            return await db.count(STORE_NAME)
-        })
+        const db = await getDB()
+        return await db.count(STORE_NAME)
     } catch (error) {
         console.error("Failed to get session count:", error)
         return 0
@@ -265,15 +202,14 @@ export async function getSessionCount(): Promise<number> {
 export async function deleteOldestSession(): Promise<void> {
     if (!isIndexedDBAvailable()) return
     try {
-        await withDB(async (db) => {
-            const tx = db.transaction(STORE_NAME, "readwrite")
-            const index = tx.store.index("by-updated")
-            const cursor = await index.openCursor()
-            if (cursor) {
-                await cursor.delete()
-            }
-            await tx.done
-        })
+        const db = await getDB()
+        const tx = db.transaction(STORE_NAME, "readwrite")
+        const index = tx.store.index("by-updated")
+        const cursor = await index.openCursor()
+        if (cursor) {
+            await cursor.delete()
+        }
+        await tx.done
     } catch (error) {
         console.error("Failed to delete oldest session:", error)
     }

lib/template-storage.ts

@@ -57,33 +57,6 @@ export function generateDefaultTitle(prompt: string): string {
 
 // Database singleton
 let dbPromise: Promise<IDBPDatabase<TemplateDB>> | null = null
-const resetDBPromise = () => {
-    dbPromise = null
-}
-
-const isClosingError = (error: unknown): boolean => {
-    return (
-        error instanceof DOMException &&
-        error.name === "InvalidStateError" &&
-        /closing/i.test(error.message)
-    )
-}
-
-const withDB = async <T>(
-    action: (db: IDBPDatabase<TemplateDB>) => Promise<T>,
-): Promise<T> => {
-    try {
-        const db = await getDB()
-        return await action(db)
-    } catch (error) {
-        if (isClosingError(error)) {
-            resetDBPromise()
-            const db = await getDB()
-            return await action(db)
-        }
-        throw error
-    }
-}
 
 async function getDB(): Promise<IDBPDatabase<TemplateDB>> {
     if (!dbPromise) {
@@ -101,23 +74,7 @@ async function getDB(): Promise<IDBPDatabase<TemplateDB>> {
                     }
                 }
             },
-            terminated() {
-                resetDBPromise()
-            },
         })
-        dbPromise
-            .then((db) => {
-                db.onversionchange = () => {
-                    db.close()
-                    resetDBPromise()
-                }
-                db.onclose = () => {
-                    resetDBPromise()
-                }
-            })
-            .catch(() => {
-                resetDBPromise()
-            })
     }
     return dbPromise
 }
@@ -137,10 +94,9 @@ export function isIndexedDBAvailable(): boolean {
 export async function getAllTemplates(): Promise<Template[]> {
     if (!isIndexedDBAvailable()) return []
     try {
-        return await withDB(async (db) => {
-            const templates = await db.getAll(STORE_NAME)
-            return sortTemplates(templates)
-        })
+        const db = await getDB()
+        const templates = await db.getAll(STORE_NAME)
+        return sortTemplates(templates)
     } catch (error) {
         console.error("Failed to get templates:", error)
         return []
@@ -150,9 +106,8 @@ export async function getAllTemplates(): Promise<Template[]> {
 export async function getTemplate(id: string): Promise<Template | null> {
     if (!isIndexedDBAvailable()) return null
     try {
-        return await withDB(async (db) => {
-            return (await db.get(STORE_NAME, id)) || null
-        })
+        const db = await getDB()
+        return (await db.get(STORE_NAME, id)) || null
     } catch (error) {
         console.error("Failed to get template:", error)
         return null
@@ -182,9 +137,8 @@ export async function createTemplate(
     }
 
     try {
-        await withDB(async (db) => {
-            await db.put(STORE_NAME, template)
-        })
+        const db = await getDB()
+        await db.put(STORE_NAME, template)
         return template
     } catch (error) {
         console.error("Failed to create template:", error)
@@ -198,20 +152,19 @@ export async function updateTemplate(
 ): Promise<Template | null> {
     if (!isIndexedDBAvailable()) return null
     try {
-        return await withDB(async (db) => {
-            const existing = await db.get(STORE_NAME, id)
-            if (!existing) return null
+        const db = await getDB()
+        const existing = await db.get(STORE_NAME, id)
+        if (!existing) return null
 
-            const updated: Template = {
-                ...existing,
-                ...updates,
-                id: existing.id,
-                createdAt: existing.createdAt,
-                updatedAt: Date.now(),
-            }
-            await db.put(STORE_NAME, updated)
-            return updated
-        })
+        const updated: Template = {
+            ...existing,
+            ...updates,
+            id: existing.id,
+            createdAt: existing.createdAt,
+            updatedAt: Date.now(),
+        }
+        await db.put(STORE_NAME, updated)
+        return updated
     } catch (error) {
         console.error("Failed to update template:", error)
         return null
@@ -221,9 +174,8 @@ export async function updateTemplate(
 export async function deleteTemplate(id: string): Promise<boolean> {
     if (!isIndexedDBAvailable()) return false
     try {
-        await withDB(async (db) => {
-            await db.delete(STORE_NAME, id)
-        })
+        const db = await getDB()
+        await db.delete(STORE_NAME, id)
         return true
     } catch (error) {
         console.error("Failed to delete template:", error)
@@ -237,25 +189,24 @@ export async function duplicateTemplate(
 ): Promise<Template | null> {
     if (!isIndexedDBAvailable()) return null
     try {
-        return await withDB(async (db) => {
-            const existing = await db.get(STORE_NAME, id)
-            if (!existing) return null
+        const db = await getDB()
+        const existing = await db.get(STORE_NAME, id)
+        if (!existing) return null
 
-            const now = Date.now()
-            const duplicate: Template = {
-                ...existing,
-                id: nanoid(),
-                title: `${existing.title} ${copySuffix}`,
-                createdAt: now,
-                updatedAt: now,
-                clickCount: 0,
-                runCount: 0,
-                lastUsedAt: 0,
-                pinned: false,
-            }
-            await db.put(STORE_NAME, duplicate)
-            return duplicate
-        })
+        const now = Date.now()
+        const duplicate: Template = {
+            ...existing,
+            id: nanoid(),
+            title: `${existing.title} ${copySuffix}`,
+            createdAt: now,
+            updatedAt: now,
+            clickCount: 0,
+            runCount: 0,
+            lastUsedAt: 0,
+            pinned: false,
+        }
+        await db.put(STORE_NAME, duplicate)
+        return duplicate
     } catch (error) {
         console.error("Failed to duplicate template:", error)
         return null
@@ -267,13 +218,12 @@ export async function duplicateTemplate(
 export async function incrementClickCount(id: string): Promise<void> {
     if (!isIndexedDBAvailable()) return
     try {
-        await withDB(async (db) => {
-            const template = await db.get(STORE_NAME, id)
-            if (!template) return
-            template.clickCount += 1
-            template.updatedAt = Date.now()
-            await db.put(STORE_NAME, template)
-        })
+        const db = await getDB()
+        const template = await db.get(STORE_NAME, id)
+        if (!template) return
+        template.clickCount += 1
+        template.updatedAt = Date.now()
+        await db.put(STORE_NAME, template)
     } catch (error) {
         console.error("Failed to increment click count:", error)
     }
@@ -282,15 +232,14 @@ export async function incrementClickCount(id: string): Promise<void> {
 export async function incrementRunCount(id: string): Promise<void> {
     if (!isIndexedDBAvailable()) return
     try {
-        await withDB(async (db) => {
-            const template = await db.get(STORE_NAME, id)
-            if (!template) return
-            const now = Date.now()
-            template.runCount += 1
-            template.lastUsedAt = now
-            template.updatedAt = now
-            await db.put(STORE_NAME, template)
-        })
+        const db = await getDB()
+        const template = await db.get(STORE_NAME, id)
+        if (!template) return
+        const now = Date.now()
+        template.runCount += 1
+        template.lastUsedAt = now
+        template.updatedAt = now
+        await db.put(STORE_NAME, template)
     } catch (error) {
         console.error("Failed to increment run count:", error)
     }
@@ -423,9 +372,8 @@ export async function importTemplates(
             pinned: typeof t.pinned === "boolean" ? t.pinned : false,
         }
         try {
-            await withDB(async (db) => {
-                await db.put(STORE_NAME, newTemplate)
-            })
+            const db = await getDB()
+            await db.put(STORE_NAME, newTemplate)
             existingKeys.add(key)
             imported++
         } catch (error) {