harden admin api authorization and add authz regression tests

apps/admin/src/app/api/trainer-client/route.ts

@@ -38,17 +38,110 @@ export async function GET(request: NextRequest) {
     const trainerId = searchParams.get("trainerId");
     const clientId = searchParams.get("clientId");
 
-    let assignments;
+    if (trainerId && clientId) {
+      const [trainer, client] = await Promise.all([
+        db.getUserById(trainerId),
+        db.getUserById(clientId),
+      ]);
 
-    if (trainerId) {
-      assignments = await db.getTrainerClientAssignments(trainerId);
-      // Filter by clientId if provided
-      if (clientId) {
-        assignments = assignments.filter((a) => a.clientId === clientId);
+      if (!trainer || !client) {
+        return NextResponse.json({ error: "User not found" }, { status: 404 });
       }
-    } else {
-      // Get all assignments (for admins, filtered by gym)
-      assignments = await db.getAllTrainerClientAssignments();
+
+      if (
+        currentUser.role !== "superAdmin" &&
+        (!currentUser.gymId ||
+          trainer.gymId !== currentUser.gymId ||
+          client.gymId !== currentUser.gymId)
+      ) {
+        return NextResponse.json(
+          { error: "Cannot access assignments from other gyms" },
+          { status: 403 },
+        );
+      }
+    }
+
+    if (trainerId && !clientId) {
+      const trainer = await db.getUserById(trainerId);
+      if (!trainer) {
+        return NextResponse.json(
+          { error: "Trainer not found" },
+          { status: 404 },
+        );
+      }
+
+      if (
+        currentUser.role !== "superAdmin" &&
+        (!currentUser.gymId || trainer.gymId !== currentUser.gymId)
+      ) {
+        return NextResponse.json(
+          { error: "Cannot access assignments from other gyms" },
+          { status: 403 },
+        );
+      }
+    }
+
+    if (!trainerId && clientId) {
+      const client = await db.getUserById(clientId);
+      if (!client) {
+        return NextResponse.json(
+          { error: "Client not found" },
+          { status: 404 },
+        );
+      }
+
+      if (
+        currentUser.role !== "superAdmin" &&
+        (!currentUser.gymId || client.gymId !== currentUser.gymId)
+      ) {
+        return NextResponse.json(
+          { error: "Cannot access assignments from other gyms" },
+          { status: 403 },
+        );
+      }
+    }
+
+    let assignments = trainerId
+      ? await db.getTrainerClientAssignments(trainerId)
+      : await db.getAllTrainerClientAssignments();
+
+    if (clientId) {
+      assignments = assignments.filter((a) => a.clientId === clientId);
+    }
+
+    if (currentUser.role !== "superAdmin") {
+      if (!currentUser.gymId) {
+        return NextResponse.json({ error: "No gym assigned" }, { status: 403 });
+      }
+
+      const involvedUserIds = Array.from(
+        new Set(
+          assignments.flatMap((assignment) => [
+            assignment.trainerId,
+            assignment.clientId,
+          ]),
+        ),
+      );
+
+      const users = await Promise.all(
+        involvedUserIds.map((userId) => db.getUserById(userId)),
+      );
+
+      const gymByUserId = new Map(
+        users
+          .filter((user): user is NonNullable<typeof user> => !!user)
+          .map((user) => [user.id, user.gymId]),
+      );
+
+      assignments = assignments.filter((assignment) => {
+        const trainerGymId = gymByUserId.get(assignment.trainerId);
+        const clientGymId = gymByUserId.get(assignment.clientId);
+
+        return (
+          trainerGymId === currentUser.gymId &&
+          clientGymId === currentUser.gymId
+        );
+      });
     }
 
     return NextResponse.json({ assignments });
@@ -121,6 +214,18 @@ export async function POST(request: NextRequest) {
       );
     }
 
+    if (
+      currentUser.role !== "superAdmin" &&
+      (!currentUser.gymId ||
+        trainer.gymId !== currentUser.gymId ||
+        client.gymId !== currentUser.gymId)
+    ) {
+      return NextResponse.json(
+        { error: "Cannot assign users from other gyms" },
+        { status: 403 },
+      );
+    }
+
     // Check if assignment already exists
     const existingAssignments = await db.getTrainerClientAssignments(trainerId);
     const existingAssignment = existingAssignments.find(