fix: correct member counts and member removal flow

VIEWER_ROLE_MIGRATION.sql

@@ -0,0 +1,7 @@
+-- Run this in Supabase SQL Editor to allow a read-only viewer role.
+alter table public.collection_members
+  drop constraint if exists collection_members_role_check;
+
+alter table public.collection_members
+  add constraint collection_members_role_check
+  check (role in ('owner', 'member', 'viewer'));

lib/services/collection_service.dart

@@ -115,17 +115,33 @@ class CollectionService {
       itemCounts[collectionId] = (itemCounts[collectionId] ?? 0) + 1;
     }
 
-    // Fetch all members for these collections in a single query and count them in memory.
+    final memberCounts = <String, int>{};
+    await Future.wait(collectionIdList.map((collectionId) async {
+      try {
+        final rows = await supabase.rpc('get_collection_members', params: {
+          'p_collection_id': collectionId,
+        });
+        memberCounts[collectionId] = (rows as List).length;
+      } catch (_) {
+        // Keep fallback below when RPC fails.
+      }
+    }));
+
+    // Fallback member count for collections where RPC did not return data.
+    final unresolvedIds = collectionIdList
+        .where((id) => !memberCounts.containsKey(id))
+        .toList(growable: false);
+    if (unresolvedIds.isNotEmpty) {
       final members = await supabase
           .from('collection_members')
           .select('id, collection_id')
-        .inFilter('collection_id', collectionIdList);
+          .inFilter('collection_id', unresolvedIds);
 
-    final memberCounts = <String, int>{};
       for (final member in members) {
         final collectionId = member['collection_id'] as String;
         memberCounts[collectionId] = (memberCounts[collectionId] ?? 0) + 1;
       }
+    }
 
     final collections = <Collection>[];
 
@@ -316,11 +332,22 @@ class CollectionService {
       throw Exception('This user is already a member of this collection.');
     }
 
+    try {
       await supabase.from('collection_members').insert({
         'collection_id': collectionId,
         'user_id': userId,
         'role': normalizedRole,
       });
+    } catch (e) {
+      final message = e.toString();
+      if (normalizedRole == 'viewer' &&
+          message.contains('collection_members_role_check')) {
+        throw Exception(
+          'Viewer role is not enabled in your database yet. Please apply the viewer-role migration first.',
+        );
+      }
+      rethrow;
+    }
   }
 
   /// Remove a member from a collection.
@@ -343,17 +370,7 @@ class CollectionService {
       throw Exception('Only the collection owner can remove members.');
     }
 
-    final target = await supabase
-        .from('collection_members')
-        .select('role, user_id')
-      .eq('user_id', memberUserId)
-        .eq('collection_id', collectionId)
-        .maybeSingle();
-
-    if (target == null) {
-      throw Exception('Member not found.');
-    }
-    if (target['role'] == 'owner') {
+    if (memberUserId == collection['owner_id']) {
       throw Exception('Collection owner cannot be removed.');
     }