Moved long running task to an isolate

lib/providers/tickets_provider.dart

@@ -3,6 +3,7 @@ import 'dart:async';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:supabase_flutter/supabase_flutter.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/foundation.dart';
 
 import '../models/office.dart';
 import '../models/ticket.dart';
@@ -127,58 +128,114 @@ final ticketsProvider = StreamProvider<List<Ticket>>((ref) {
       profile.role == 'dispatcher' ||
       profile.role == 'it_staff';
 
-  // Use stream for realtime updates, then apply pagination & search filters
-  // client-side because `.range(...)` is not supported on the stream builder.
-  final baseStream = client
-      .from('tickets')
-      .stream(primaryKey: ['id'])
-      .map((rows) => rows.map(Ticket.fromMap).toList());
+  // Use stream for realtime updates. Offload expensive client-side
+  // filtering/sorting/pagination to a background isolate via `compute`
+  // so UI navigation and builds remain smooth.
+  final baseStream = client.from('tickets').stream(primaryKey: ['id']);
 
-  return baseStream.map((allTickets) {
-    debugPrint('[ticketsProvider] stream event: ${allTickets.length} rows');
-    var list = allTickets;
+  return baseStream.asyncMap((rows) async {
+    // rows is List<dynamic> of maps coming from Supabase
+    final rowsList = (rows as List<dynamic>).cast<Map<String, dynamic>>();
 
-    if (!isGlobal) {
-      final officeIds =
-          assignmentsAsync.valueOrNull
-              ?.where((assignment) => assignment.userId == profile.id)
-              .map((assignment) => assignment.officeId)
-              .toSet()
-              .toList() ??
-          <String>[];
-      if (officeIds.isEmpty) return <Ticket>[];
-      final allowedOffices = officeIds.toSet();
-      list = list.where((t) => allowedOffices.contains(t.officeId)).toList();
-    }
+    // Prepare lightweight serializable args for background processing
+    final allowedOfficeIds =
+        assignmentsAsync.valueOrNull
+            ?.where((assignment) => assignment.userId == profile.id)
+            .map((assignment) => assignment.officeId)
+            .toList() ??
+        <String>[];
 
-    if (query.officeId != null) {
-      list = list.where((t) => t.officeId == query.officeId).toList();
-    }
-    if (query.status != null) {
-      list = list.where((t) => t.status == query.status).toList();
-    }
-    if (query.searchQuery.isNotEmpty) {
-      final q = query.searchQuery.toLowerCase();
-      list = list
-          .where(
-            (t) =>
-                t.subject.toLowerCase().contains(q) ||
-                t.description.toLowerCase().contains(q),
-          )
-          .toList();
-    }
+    final payload = <String, dynamic>{
+      'rows': rowsList,
+      'isGlobal': isGlobal,
+      'allowedOfficeIds': allowedOfficeIds,
+      'offset': query.offset,
+      'limit': query.limit,
+      'searchQuery': query.searchQuery,
+      'officeId': query.officeId,
+      'status': query.status,
+      'dateStart': query.dateRange?.start.millisecondsSinceEpoch,
+      'dateEnd': query.dateRange?.end.millisecondsSinceEpoch,
+    };
 
-    // Sort: newest first
-    list.sort((a, b) => b.createdAt.compareTo(a.createdAt));
+    final processed = await compute(_processTicketsInIsolate, payload);
 
-    // Pagination
-    final start = query.offset;
-    final end = (start + query.limit).clamp(0, list.length);
-    if (start >= list.length) return <Ticket>[];
-    return list.sublist(start, end);
+    // `processed` is List<Map<String,dynamic>> — convert to Ticket objects
+    final tickets = (processed as List<dynamic>)
+        .cast<Map<String, dynamic>>()
+        .map(Ticket.fromMap)
+        .toList();
+
+    debugPrint('[ticketsProvider] processed ${tickets.length} tickets');
+    return tickets;
   });
 });
 
+// Runs inside a background isolate. Accepts a serializable payload and
+// returns a list of ticket maps after filtering/sorting/pagination.
+List<Map<String, dynamic>> _processTicketsInIsolate(
+  Map<String, dynamic> payload,
+) {
+  final rows = (payload['rows'] as List).cast<Map<String, dynamic>>();
+  var list = List<Map<String, dynamic>>.from(rows);
+
+  final isGlobal = payload['isGlobal'] as bool? ?? false;
+  final allowedOfficeIds =
+      (payload['allowedOfficeIds'] as List?)?.cast<String>().toSet() ??
+      <String>{};
+
+  if (!isGlobal) {
+    if (allowedOfficeIds.isEmpty) return <Map<String, dynamic>>[];
+    list = list
+        .where((t) => allowedOfficeIds.contains(t['office_id']))
+        .toList();
+  }
+
+  final officeId = payload['officeId'] as String?;
+  if (officeId != null) {
+    list = list.where((t) => t['office_id'] == officeId).toList();
+  }
+  final status = payload['status'] as String?;
+  if (status != null) {
+    list = list.where((t) => t['status'] == status).toList();
+  }
+
+  final searchQuery = (payload['searchQuery'] as String?) ?? '';
+  if (searchQuery.isNotEmpty) {
+    final q = searchQuery.toLowerCase();
+    list = list.where((t) {
+      final subj = (t['subject'] as String?)?.toLowerCase() ?? '';
+      final desc = (t['description'] as String?)?.toLowerCase() ?? '';
+      return subj.contains(q) || desc.contains(q);
+    }).toList();
+  }
+
+  // Sort newest first. `created_at` may be ISO strings or timestamps;
+  // handle strings and numeric values.
+  int _parseCreatedAt(Map<String, dynamic> m) {
+    final v = m['created_at'];
+    if (v == null) return 0;
+    if (v is int) return v;
+    if (v is double) return v.toInt();
+    if (v is String) {
+      try {
+        return DateTime.parse(v).millisecondsSinceEpoch;
+      } catch (_) {
+        return 0;
+      }
+    }
+    return 0;
+  }
+
+  list.sort((a, b) => _parseCreatedAt(b).compareTo(_parseCreatedAt(a)));
+
+  final start = (payload['offset'] as int?) ?? 0;
+  final limit = (payload['limit'] as int?) ?? 50;
+  final end = (start + limit).clamp(0, list.length);
+  if (start >= list.length) return <Map<String, dynamic>>[];
+  return list.sublist(start, end);
+}
+
 /// Provider for ticket query parameters.
 final ticketsQueryProvider = StateProvider<TicketQuery>(
   (ref) => const TicketQuery(),