GitJournal/lib/core/note_notifier.dart

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';

import 'note.dart';

typedef NoteModificationCallback = void Function(Note note);
typedef NoteRenameCallback = void Function(Note note, String oldPath);

class NotesNotifier implements ChangeNotifier {
  ObserverList<NoteModificationCallback>? _modListeners =
      ObserverList<NoteModificationCallback>();
  ObserverList<NoteRenameCallback>? _renameListeners =
      ObserverList<NoteRenameCallback>();

  void addModifiedListener(NoteModificationCallback listener) {
    _modListeners?.add(listener);
  }

  void removeModifiedListener(NoteModificationCallback listener) {
    assert(_modListeners!.contains(listener));
    _modListeners?.remove(listener);
  }

  void addRenameListener(NoteRenameCallback listener) {
    _renameListeners?.add(listener);
  }

  void removeRenameListener(NoteRenameCallback listener) {
    assert(_renameListeners!.contains(listener));
    _renameListeners?.remove(listener);
  }

  @mustCallSuper
  @override
  void dispose() {
    assert(_debugAssertNotDisposed());
    _modListeners = null;
    _renameListeners = null;
    _listeners = null;
  }

  //
  // ChangeNotifier implementation - How to not duplicate this?
  //
  ObserverList<VoidCallback>? _listeners = ObserverList<VoidCallback>();

  bool _debugAssertNotDisposed() {
    assert(() {
      if (_listeners == null) {
        throw FlutterError.fromParts(<DiagnosticsNode>[
          ErrorSummary('A $runtimeType was used after being disposed.'),
          ErrorDescription(
              'Once you have called dispose() on a $runtimeType, it can no longer be used.')
        ]);
      }
      return true;
    }());
    return true;
  }

  /// Whether any listeners are currently registered.
  ///
  /// Clients should not depend on this value for their behavior, because having
  /// one listener's logic change when another listener happens to start or stop
  /// listening will lead to extremely hard-to-track bugs. Subclasses might use
  /// this information to determine whether to do any work when there are no
  /// listeners, however; for example, resuming a [Stream] when a listener is
  /// added and pausing it when a listener is removed.
  ///
  /// Typically this is used by overriding [addListener], checking if
  /// [hasListeners] is false before calling `super.addListener()`, and if so,
  /// starting whatever work is needed to determine when to call
  /// [notifyListeners]; and similarly, by overriding [removeListener], checking
  /// if [hasListeners] is false after calling `super.removeListener()`, and if
  /// so, stopping that same work.
  @protected
  @override
  bool get hasListeners {
    assert(_debugAssertNotDisposed());
    return _listeners!.isNotEmpty;
  }

  /// Register a closure to be called when the object changes.
  ///
  /// This method must not be called after [dispose] has been called.
  @override
  void addListener(VoidCallback listener) {
    assert(_debugAssertNotDisposed());
    _listeners!.add(listener);
  }

  /// Remove a previously registered closure from the list of closures that are
  /// notified when the object changes.
  ///
  /// If the given listener is not registered, the call is ignored.
  ///
  /// This method must not be called after [dispose] has been called.
  ///
  /// If a listener had been added twice, and is removed once during an
  /// iteration (i.e. in response to a notification), it will still be called
  /// again. If, on the other hand, it is removed as many times as it was
  /// registered, then it will no longer be called. This odd behavior is the
  /// result of the [ChangeNotifier] not being able to determine which listener
  /// is being removed, since they are identical, and therefore conservatively
  /// still calling all the listeners when it knows that any are still
  /// registered.
  ///
  /// This surprising behavior can be unexpectedly observed when registering a
  /// listener on two separate objects which are both forwarding all
  /// registrations to a common upstream object.
  @override
  void removeListener(VoidCallback listener) {
    assert(_debugAssertNotDisposed());
    _listeners!.remove(listener);
  }

  /// Call all the registered listeners.
  ///
  /// Call this method whenever the object changes, to notify any clients the
  /// object may have. Listeners that are added during this iteration will not
  /// be visited. Listeners that are removed during this iteration will not be
  /// visited after they are removed.
  ///
  /// Exceptions thrown by listeners will be caught and reported using
  /// [FlutterError.reportError].
  ///
  /// This method must not be called after [dispose] has been called.
  ///
  /// Surprising behavior can result when reentrantly removing a listener (i.e.
  /// in response to a notification) that has been registered multiple times.
  /// See the discussion at [removeListener].
  @protected
  @visibleForTesting
  @override
  void notifyListeners() {
    assert(_debugAssertNotDisposed());
    if (_listeners != null) {
      final List<VoidCallback> localListeners =
          List<VoidCallback>.from(_listeners!);
      for (VoidCallback listener in localListeners) {
        try {
          if (_listeners!.contains(listener)) {
            listener();
          }
        } catch (exception, stack) {
          FlutterError.reportError(FlutterErrorDetails(
            exception: exception,
            stack: stack,
            library: 'foundation library',
            context: ErrorDescription(
                'while dispatching notifications for $runtimeType'),
            informationCollector: () sync* {
              yield DiagnosticsProperty<ChangeNotifier>(
                'The $runtimeType sending notification was',
                this,
                style: DiagnosticsTreeStyle.errorProperty,
              );
            },
          ));
        }
      }
    }
  }

  void notifyModifiedListeners(Note note) {
    assert(_debugAssertNotDisposed());
    if (_modListeners != null) {
      final localListeners =
          List<NoteModificationCallback>.from(_modListeners!);
      for (var listener in localListeners) {
        try {
          if (_modListeners!.contains(listener)) {
            listener(note);
          }
        } catch (exception, stack) {
          FlutterError.reportError(FlutterErrorDetails(
            exception: exception,
            stack: stack,
            library: 'foundation library',
            context: ErrorDescription(
                'while dispatching notifications for $runtimeType'),
            informationCollector: () sync* {
              yield DiagnosticsProperty<ChangeNotifier>(
                'The $runtimeType sending notification was',
                this,
                style: DiagnosticsTreeStyle.errorProperty,
              );
            },
          ));
        }
      }
    }
  }

  void notifyRenameListeners(Note note, String oldPath) {
    assert(_debugAssertNotDisposed());
    if (_renameListeners != null) {
      final localListeners = List<NoteRenameCallback>.from(_renameListeners!);
      for (var listener in localListeners) {
        try {
          if (_renameListeners!.contains(listener)) {
            listener(note, oldPath);
          }
        } catch (exception, stack) {
          FlutterError.reportError(FlutterErrorDetails(
            exception: exception,
            stack: stack,
            library: 'foundation library',
            context: ErrorDescription(
                'while dispatching notifications for $runtimeType'),
            informationCollector: () sync* {
              yield DiagnosticsProperty<ChangeNotifier>(
                'The $runtimeType sending notification was',
                this,
                style: DiagnosticsTreeStyle.errorProperty,
              );
            },
          ));
        }
      }
    }
  }
}