import 'dart:async';
import 'dart:convert';

import 'package:localstore/localstore.dart';

import 'apiResponse.dart';

abstract class RequestCache<T extends ApiResponse?> {
  static const int cacheNothing = 0;
  static const int cacheMinute = 60;
  static const int cacheHour = 60 * 60;
  static const int cacheDay = 60 * 60 * 24;

  static String collection = 'MarianumMobile';

  int maxCacheTime;
  void Function(T)? onUpdate;
  void Function(Exception) onError;
  bool? renew;

  final Completer<void> _ready = Completer<void>();

  /// Resolves when [start] has finished, regardless of whether the network
  /// call succeeded, failed, or was skipped due to a fresh cache. Callers
  /// can await this to know when both the cache lookup and the network
  /// attempt have settled.
  Future<void> get ready => _ready.future;

  RequestCache(this.maxCacheTime, this.onUpdate, {this.onError = ignore, this.renew = false});

  static void ignore(Exception e) {}

  Future<void> start(String document) async {
    try {
      final tableData = await Localstore.instance.collection(collection).doc(document).get();
      if (tableData != null) {
        onUpdate?.call(onLocalData(tableData['json']));
      }

      if (DateTime.now().millisecondsSinceEpoch - (maxCacheTime * 1000) < (tableData?['lastupdate'] ?? 0)) {
        if (renew == null || !renew!) return;
      }

      try {
        final newValue = await onLoad();
        onUpdate?.call(newValue);
        Localstore.instance.collection(collection).doc(document).set({
          'json': jsonEncode(newValue),
          'lastupdate': DateTime.now().millisecondsSinceEpoch,
        });
      } on Exception catch (e) {
        onError(e);
      }
    } finally {
      if (!_ready.isCompleted) _ready.complete();
    }
  }

  T onLocalData(String json);
  Future<T> onLoad();

}