import 'package:flutter/widgets.dart';

class RefreshFutureBuilder<T> extends StatefulWidget {
  final Future<T> Function()? futureCreator;
  final T? initialData;
  final Widget Function(BuildContext context, Future Function() refresh, Future Function(Future<T> Function()) replaceFuture, RefreshFutureBuilderSnapshot<T> snapshot) builder;

  const RefreshFutureBuilder({ Key? key, this.futureCreator, this.initialData, required this.builder }) : super(key: key);

  @override
  _RefreshFutureBuilderState<T> createState() => _RefreshFutureBuilderState<T>();
}

class _RefreshFutureBuilderState<T> extends State<RefreshFutureBuilder<T>> {
  late RefreshFutureBuilderSnapshot<T> snapshot;
  Future<T> Function()? futureCreator;
  bool _disposed = false;

  @override
  void initState() {
    super.initState();
    snapshot = widget.initialData != null ? RefreshFutureBuilderSnapshot.initial(widget.initialData!) : RefreshFutureBuilderSnapshot.nothing();
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    if (futureCreator != widget.futureCreator) {
      futureCreator = widget.futureCreator;
      runFuture();
    }
  }

  Future runFuture() async {
    if (futureCreator == null) {
      return;
    }
    // Set state to signify loading
    setState(() {
      switch (snapshot.state) {
        case RefreshFutureBuilderState.none:
          snapshot = RefreshFutureBuilderSnapshot.waiting();
          break;
        case RefreshFutureBuilderState.initial:
          snapshot = RefreshFutureBuilderSnapshot.refresh(snapshot.data);
          break;
        case RefreshFutureBuilderState.waiting:
          return;
        case RefreshFutureBuilderState.error:
          snapshot = RefreshFutureBuilderSnapshot.waiting();
          break;
        case RefreshFutureBuilderState.done:
          snapshot = RefreshFutureBuilderSnapshot.refresh(snapshot.data);
          break;
        case RefreshFutureBuilderState.refreshing:
          return;
        case RefreshFutureBuilderState.refreshError:
          snapshot = RefreshFutureBuilderSnapshot.refresh(null, snapshot.error, snapshot.stackTrace);
          break;
        default:
      }
    });
    try {
      final data = await futureCreator!();
      if (_disposed) {
        return;
      }
      setState(() {
        snapshot = RefreshFutureBuilderSnapshot.withData(data);
      });
    }
    catch (e, st) {
      if (_disposed) {
        return;
      }
      setState(() {
        if (snapshot.state == RefreshFutureBuilderState.waiting) {
          snapshot = RefreshFutureBuilderSnapshot.withError(e, st);
        }
        else {
          snapshot = RefreshFutureBuilderSnapshot.refreshError(snapshot.data, e, st);
        }
      });
    }
  }

  Future replaceFutureCreator(Future<T> Function() newFutureCreator) {
    futureCreator = newFutureCreator;
    return runFuture();
  }

  @override
  void dispose() {
    _disposed = true;
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return widget.builder(
      context, 
      runFuture,
      replaceFutureCreator,
      snapshot,
    );
  }
}

class RefreshFutureBuilderSnapshot<T> {
  final RefreshFutureBuilderState state;
  final T? data;
  final Object? error;
  final StackTrace? stackTrace;

  bool get hasData => data != null;
  bool get hasError => error != null;

  const RefreshFutureBuilderSnapshot._(this.state, this.data, this.error, this.stackTrace);
  const RefreshFutureBuilderSnapshot.nothing() : state = RefreshFutureBuilderState.none, data = null, error = null, stackTrace = null;
  const RefreshFutureBuilderSnapshot.initial(this.data) : state = RefreshFutureBuilderState.initial, error = null, stackTrace = null;
  const RefreshFutureBuilderSnapshot.waiting() : state = RefreshFutureBuilderState.waiting, data = null, error = null, stackTrace = null;
  const RefreshFutureBuilderSnapshot.withError(this.error, [this.stackTrace]) : state = RefreshFutureBuilderState.error, data = null;
  const RefreshFutureBuilderSnapshot.withData(this.data) : state = RefreshFutureBuilderState.done, error = null, stackTrace = null;
  const RefreshFutureBuilderSnapshot.refresh(this.data, [this.error, this.stackTrace]) : state = RefreshFutureBuilderState.refreshing;
  const RefreshFutureBuilderSnapshot.refreshError(this.data, this.error, this.stackTrace) : state = RefreshFutureBuilderState.refreshError;
}

enum RefreshFutureBuilderState {
  none,
  initial,
  waiting,
  error,
  done,
  refreshing,
  refreshError,
}