fix: prevent duplicate calendar account linking

packages/app-store/googlecalendar/api/callback.ts

@@ -68,6 +68,25 @@ async function getHandler(req: NextApiRequest, res: NextApiResponse) {
     const primaryCal = cals.data.items?.find((cal) => cal.primary);
 
     if (primaryCal?.id) {
+      const existingCalendar = await prisma.selectedCalendar.findUnique({
+        where: {
+          userId_integration_externalId: {
+            userId: req.session.user.id,
+            externalId: primaryCal.id,
+            integration: "google_calendar",
+          },
+        },
+      });
+
+      if (existingCalendar) {
+        await prisma.credential.delete({
+          where: {
+            id: credential.id,
+          },
+        });
+        throw new HttpError({ statusCode: 409, message: "Account is already linked." });
+      }
+
       await prisma.selectedCalendar.create({
         data: {
           userId: req.session.user.id,

packages/app-store/office365calendar/api/callback.ts

@@ -4,6 +4,7 @@ import type { NextApiRequest, NextApiResponse } from "next";
 import { WEBAPP_URL } from "@calcom/lib/constants";
 import { handleErrorsJson } from "@calcom/lib/errors";
 import { getSafeRedirectUrl } from "@calcom/lib/getSafeRedirectUrl";
+import { HttpError } from "@calcom/lib/http-error";
 import prisma from "@calcom/prisma";
 
 import getAppKeysFromSlug from "../../_utils/getAppKeysFromSlug";
@@ -110,6 +111,25 @@ export default async function handler(req: NextApiRequest, res: NextApiResponse)
   }
 
   if (defaultCalendar?.id && req.session?.user?.id) {
+    const existingCalendar = await prisma.selectedCalendar.findUnique({
+      where: {
+        userId_integration_externalId: {
+          userId: req.session?.user.id,
+          integration: "office365_calendar",
+          externalId: defaultCalendar.id,
+        },
+      },
+    });
+
+    if (existingCalendar) {
+      await prisma.credential.delete({
+        where: {
+          id: credential.id,
+        },
+      });
+
+      throw new HttpError({ statusCode: 409, message: "Account is already linked." });
+    }
     await prisma.selectedCalendar.create({
       data: {
         userId: req.session?.user.id,

packages/app-store/zohocalendar/api/callback.ts

@@ -3,6 +3,7 @@
 
 import { WEBAPP_URL } from "@calcom/lib/constants";
 import { getSafeRedirectUrl } from "@calcom/lib/getSafeRedirectUrl";
+import { HttpError } from "@calcom/lib/http-error";
 import logger from "@calcom/lib/logger";
 import { defaultHandler, defaultResponder } from "@calcom/lib/server";
 import prisma from "@calcom/prisma";
@@ -82,9 +83,28 @@
   });
   const data = await calendarResponse.json();
 
   const primaryCalendar = data.calendars.find((calendar: any) => calendar.isdefault);
 
   if (primaryCalendar.uid) {
+    const existingCalendar = await prisma.selectedCalendar.findUnique({
+      where: {
+        userId_integration_externalId: {
+          userId: req.session.user.id,
+          integration: config.type,
+          externalId: primaryCalendar.uid,
+        },
+      },
+    });
+
+    if (existingCalendar) {
+      await prisma.credential.delete({
+        where: {
+          id: credential.id,
+        },
+      });
+
+      throw new HttpError({ statusCode: 409, message: "Account is already linked." });
+    }
     await prisma.selectedCalendar.create({
       data: {
         userId: req.session.user.id,