Add Sheets-first mirror mode

prisma/migrations/20260717181500_google_data_system_mode/migration.sql

@@ -0,0 +1,2 @@
+-- Track user-selected data ownership/system-of-record posture.
+ALTER TABLE "GoogleConnection" ADD COLUMN "dataSystemMode" TEXT NOT NULL DEFAULT 'backend_db';

prisma/schema.prisma

@@ -664,6 +664,7 @@ model GoogleConnection {
   driveMirrorStatus String @default("not_started")
   driveMirrorSpreadsheetUrl String?
   driveMirrorLastSyncedAt DateTime?
+  dataSystemMode String @default("backend_db")
   isConnected   Boolean   @default(true)
   connectedAt   DateTime  @default(now())
   lastSyncedAt  DateTime?

src/google/google.controller.ts

@@ -30,4 +30,10 @@ export class GoogleController {
   status(@CurrentUser() userId: string) {
     return this.googleService.getStatus(userId);
   }
+
+  @Post("data-system-mode")
+  @HttpCode(200)
+  dataSystemMode(@CurrentUser() userId: string, @Body() body: { mode: "backend_db" | "google_sheets_mirror" }) {
+    return this.googleService.updateDataSystemMode(userId, body.mode);
+  }
 }

src/google/google.service.ts

@@ -58,7 +58,7 @@ export class GoogleService {
     const { data } = await oauth2.userinfo.get();
     const googleEmail = data.email ?? "";
 
-    await this.prisma.googleConnection.upsert({
+    await (this.prisma as any).googleConnection.upsert({
       where: { userId },
       update: {
         googleEmail,
@@ -71,6 +71,7 @@ export class GoogleService {
         driveMirrorStatus: "pending_first_sync",
         driveMirrorSpreadsheetUrl: null,
         driveMirrorLastSyncedAt: null,
+        dataSystemMode: "backend_db",
       },
       create: {
         userId,
@@ -80,6 +81,7 @@ export class GoogleService {
         isConnected: true,
         driveMirrorEnabled: false,
         driveMirrorStatus: "pending_first_sync",
+        dataSystemMode: "backend_db",
       },
     });
 
@@ -93,7 +95,7 @@ export class GoogleService {
   }
 
   async getStatus(userId: string) {
-    const gc = await this.prisma.googleConnection.findUnique({ where: { userId } });
+    const gc = await (this.prisma as any).googleConnection.findUnique({ where: { userId } });
     if (!gc || !gc.isConnected) return { connected: false };
     return {
       connected: true,
@@ -107,6 +109,41 @@ export class GoogleService {
         lastSyncedAt: gc.driveMirrorLastSyncedAt ?? gc.lastSyncedAt,
         ownership: "user_google_drive",
       },
+      dataSystem: {
+        mode: gc.dataSystemMode,
+        operationalSystemOfRecord: "ledgerone_backend_db",
+        userOwnedMirror: gc.dataSystemMode === "google_sheets_mirror",
+        note: gc.dataSystemMode === "google_sheets_mirror"
+          ? "LedgerOne writes a best-effort user-owned Google Sheets mirror while the application database remains the operational store."
+          : "LedgerOne uses the application database as the operational store. Google Sheets can be enabled as a user-owned mirror.",
+      },
+    };
+  }
+
+  async updateDataSystemMode(userId: string, mode: "backend_db" | "google_sheets_mirror") {
+    if (!["backend_db", "google_sheets_mirror"].includes(mode)) {
+      throw new BadRequestException("Unsupported data system mode.");
+    }
+    const connection = await (this.prisma as any).googleConnection.findUnique({ where: { userId } });
+    if (!connection || !connection.isConnected) {
+      throw new BadRequestException("Google account must be connected before enabling Sheets-first mirror mode.");
+    }
+
+    const updated = await (this.prisma as any).googleConnection.update({
+      where: { userId },
+      data: {
+        dataSystemMode: mode,
+        driveMirrorEnabled: mode === "google_sheets_mirror" ? true : connection.driveMirrorEnabled,
+        driveMirrorStatus: mode === "google_sheets_mirror" && !connection.spreadsheetId ? "pending_first_sync" : connection.driveMirrorStatus,
+      },
+    });
+
+    return {
+      mode: updated.dataSystemMode,
+      driveMirrorEnabled: updated.driveMirrorEnabled,
+      status: updated.driveMirrorStatus,
+      operationalSystemOfRecord: "ledgerone_backend_db",
+      userOwnedMirror: updated.dataSystemMode === "google_sheets_mirror",
     };
   }
 }