import '../../core/region/geo.dart';

/// A place the user has named and kept.
///
/// The anchor everything location-shaped hangs off: which part of the region the
/// radar map opens on, and — once the worker publishes them — which alert zone
/// and which rain cell the notifications for this place should follow.
///
/// A free point rather than a station: people think in terms of home and work,
/// not in terms of which weather station happens to represent them. The nearest
/// station is derived from the point when readings are shown, so the user can
/// always see how far away the measurement actually came from.
class SavedPlace {
  const SavedPlace({
    required this.id,
    required this.name,
    required this.point,
    required this.createdAt,
  });

  factory SavedPlace.fromJson(Map<String, Object?> json) {
    final id = json['id'];
    final name = json['name'];
    final longitude = json['lng'];
    final latitude = json['lat'];
    final createdAt = json['createdAt'];

    if (id is! String || id.isEmpty) {
      throw const FormatException('saved place id must be a non-empty string');
    }
    if (name is! String || name.isEmpty) {
      throw const FormatException(
        'saved place name must be a non-empty string',
      );
    }
    if (longitude is! num || latitude is! num) {
      throw const FormatException('saved place coordinates must be numbers');
    }
    if (createdAt is! int) {
      throw const FormatException(
        'saved place createdAt must be an epoch in ms',
      );
    }

    return SavedPlace(
      id: id,
      name: name,
      point: GeoPoint(longitude.toDouble(), latitude.toDouble()),
      createdAt: DateTime.fromMillisecondsSinceEpoch(createdAt, isUtc: true),
    );
  }

  /// Longest name the UI will accept.
  ///
  /// Not a storage limit — it keeps a name readable in the one-line list and in
  /// a notification title, where a long string would simply be truncated
  /// somewhere unhelpful.
  static const int maxNameLength = 40;

  final String id;
  final String name;
  final GeoPoint point;
  final DateTime createdAt;

  Map<String, Object?> toJson() => <String, Object?>{
    'id': id,
    'name': name,
    'lng': point.longitude,
    'lat': point.latitude,
    'createdAt': createdAt.millisecondsSinceEpoch,
  };

  SavedPlace copyWith({String? name, GeoPoint? point}) => SavedPlace(
    id: id,
    name: name ?? this.name,
    point: point ?? this.point,
    createdAt: createdAt,
  );

  @override
  String toString() => 'SavedPlace($id, $name, $point)';

  @override
  bool operator ==(Object other) =>
      other is SavedPlace &&
      other.id == id &&
      other.name == name &&
      other.point == point &&
      other.createdAt == createdAt;

  @override
  int get hashCode => Object.hash(id, name, point, createdAt);
}

/// Why a place could not be saved.
///
/// Modelled rather than returned as a bare bool so the UI can say which rule was
/// broken instead of a generic failure.
enum SavedPlaceRejection {
  /// The name was empty or only whitespace.
  emptyName,

  /// The name exceeded [SavedPlace.maxNameLength].
  nameTooLong,

  /// The point lies outside the region the app has data for.
  outsideRegion,

  /// Another saved place already uses that name.
  duplicateName,
}

class SavedPlaceException implements Exception {
  const SavedPlaceException(this.rejection);

  final SavedPlaceRejection rejection;

  @override
  String toString() => 'SavedPlaceException(${rejection.name})';
}