import 'dart:async';

import '../../../core/cache/cache_entry.dart';
import '../../../core/cache/cache_invalidator.dart';
import '../../../core/cache/hybrid_cache_store.dart';
import 'todo_api.dart';

class TodoRepository {
  static const String pendingListKey = 'todo:list:pending';

  final TodoApi api;
  final HybridCacheStore store;
  final CacheInvalidator invalidator;
  final DateTime Function() now;

  TodoRepository({
    required this.api,
    required this.store,
    required this.invalidator,
    DateTime Function()? now,
  }) : now = now ?? DateTime.now;

  Future<List<TodoResponse>> getPendingTodos({
    bool forceRefresh = false,
  }) async {
    if (!forceRefresh) {
      final cached = await store.read<CacheEntry<List<TodoResponse>>>(
        pendingListKey,
      );
      if (cached != null) {
        return cached.value;
      }
    }

    final remote = await api.getPendingTodos();
    await store.write<CacheEntry<List<TodoResponse>>>(
      pendingListKey,
      CacheEntry(value: remote, fetchedAt: now()),
    );
    return remote;
  }

  Future<void> completeTodo(String id) async {
    final cached = await store.read<CacheEntry<List<TodoResponse>>>(
      pendingListKey,
    );
    if (cached != null) {
      final next = cached.value
          .where((todo) => todo.id != id)
          .toList(growable: false);
      await store.write<CacheEntry<List<TodoResponse>>>(
        pendingListKey,
        CacheEntry(value: next, fetchedAt: now()),
      );
    }

    try {
      await api.completeTodo(id);
      invalidator.invalidate(pendingListKey);
    } catch (error) {
      if (cached != null) {
        await store.write<CacheEntry<List<TodoResponse>>>(
          pendingListKey,
          cached,
        );
      }
      rethrow;
    }
  }

  Future<void> invalidatePending() {
    invalidator.invalidate(pendingListKey);
    return Future<void>.value();
  }
}