Add custom dynamic entity data source

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// Copyright 2026 Esri
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

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

import 'package:arcgis_maps/arcgis_maps.dart';
import 'package:arcgis_maps_sdk_flutter_samples/common/common.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class AddCustomDynamicEntityDataSource extends StatefulWidget {
  const AddCustomDynamicEntityDataSource({super.key});

  @override
  State<AddCustomDynamicEntityDataSource> createState() =>
      _AddCustomDynamicEntityDataSourceState();
}

class _AddCustomDynamicEntityDataSourceState
    extends State<AddCustomDynamicEntityDataSource>
    with SampleStateSupport {
  // Create a controller for the map view.
  final _mapViewController = ArcGISMapView.createController();

  // A flag for when the map view is ready and controls can be used.
  var _ready = false;

  // Dynamic entity layer for identify.
  DynamicEntityLayer? _dynamicEntityLayer;


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        top: false,
        left: false,
        right: false,
        child: Stack(
          children: [
            Column(
              children: [
                Expanded(
                  // Add a map view to the widget tree and set a controller.
                  child: ArcGISMapView(
                    controllerProvider: () => _mapViewController,
                    onMapViewReady: onMapViewReady,
                    onTap: onTap,
                  ),
                ),
              ],
            ),
            // Display a progress indicator and prevent interaction until state is ready.
            LoadingIndicator(visible: !_ready),
          ],
        ),
      ),
    );
  }

  void onMapViewReady() {
    // Create map with oceans basemap.
    final map = ArcGISMap.withBasemapStyle(BasemapStyle.arcGISOceans);
    _mapViewController.arcGISMap = map;

    // Initial viewpoint (Pacific Northwest).
    _mapViewController.setViewpoint(
      Viewpoint.fromCenter(
        ArcGISPoint(
          x: -123.657,
          y: 47.984,
          spatialReference: SpatialReference.wgs84,
        ),
        scale: 3000000,
      ),
    );

    // Create the custom data provider.
    final provider = VesselDynamicEntityDataProvider();

    // Create the data source driven by the provider.
    final dataSource = CustomDynamicEntityDataSource(provider);

    // Create the dynamic entity layer.
    final dynamicEntityLayer = DynamicEntityLayer(dataSource);

    // Configure track display properties.
    final trackProps = dynamicEntityLayer.trackDisplayProperties;
    trackProps.showTrackLine = true;
    trackProps.showPreviousObservations = true;
    trackProps.maximumObservations = 20;

    // Configure labeling (vessel name).
    _configureLabeling(dynamicEntityLayer);

    // Add layer to the map.
    map.operationalLayers.add(dynamicEntityLayer);

    _dynamicEntityLayer = dynamicEntityLayer;

    setState(() => _ready = true);
  }

  Future<void> onTap(Offset screenPoint) async {
    if (!_ready || _dynamicEntityLayer == null) return;

    // Dismiss any existing callout.
    _mapViewController.callout.dismiss(animated: false);

    final identifyResult = await _mapViewController.identifyLayer(
      _dynamicEntityLayer!,
      screenPoint: screenPoint,
      tolerance: 22,
    );

    if (!mounted ||
        identifyResult.error != null ||
        identifyResult.geoElements.isEmpty) {
      return;
    }

    final geoElement = identifyResult.geoElements.first;

    final dynamicEntity = switch (geoElement) {
      final DynamicEntity entity => entity,
      final DynamicEntityObservation observation =>
        observation.getDynamicEntity(),
      _ => null,
    };

    if (dynamicEntity == null) return;

    _showCallout(dynamicEntity);
  }

  void _showCallout(DynamicEntity entity) {
    _mapViewController.callout.showCalloutForGeoElement(
      entity,
      title: 'Vessel',
      detailExpression: r'''
concatenate(
  "Name: ", $feature.VesselName,
  "\nCall Sign: ", $feature.CallSign,
  "\nCOG: ", $feature.COG,
  "\nSOG: ", $feature.SOG
)
''',
      animated: false,
    );
  }
}

void _configureLabeling(DynamicEntityLayer layer) {
  final labelDefinition = LabelDefinition(
    labelExpression: SimpleLabelExpression(simpleExpression: '[VesselName]'),
    textSymbol: TextSymbol(color: Colors.red, size: 12),
  );

  labelDefinition.placement = LabelingPlacement.pointAboveCenter;

  layer.labelDefinitions.add(labelDefinition);
  layer.labelsEnabled = true;
}

/// A custom implementation of [CustomDynamicEntityDataProvider] that demonstrates
/// how to create a dynamic entity data source for streaming real-time geospatial data.
///
/// This sample provider reads vessel tracking data from a JSON Lines (.jsonl) asset
/// file and emits observations sequentially to simulate a live data stream. Each
/// observation includes vessel position (latitude/longitude), movement data
/// (speed over ground, course over ground), and identifying information (MMSI, name, etc.).
///
/// ## Key Implementation Points:
///
/// * **onLoad()**: Initializes the data source by loading the asset file and defining
///   the observation schema with field definitions for all vessel attributes.
///
/// * **onConnect()**: Starts emitting observations by creating a periodic timer that
///   calls [_emitNextObservation] at regular intervals.
///
/// * **onDisconnect()**: Stops the observation stream by canceling the timer.
///
/// * **_emitNextObservation()**: Parses each JSON line, constructs an observation
///   with geometry (point) and attributes, and emits it using [handleEntityDataEvent].
///
/// This pattern can be adapted to work with web sockets, REST APIs, IoT sensors,
/// or any other real-time data source by modifying the data loading and emission logic.
///
/// See also:
/// * [CustomDynamicEntityDataProvider], the base class for creating custom data providers.
/// * [DynamicEntityLayer], which visualizes dynamic entities from this data source.

class VesselDynamicEntityDataProvider extends CustomDynamicEntityDataProvider {
  // Field name that uniquely identifies each vessel entity.
  static const String _entityIdFieldName = 'MMSI';

  // Delay between emitted observations to simulate live streaming data
  static const Duration _emissionDelay = Duration(milliseconds: 10);

  Timer? _timer;
  late final List<String> _jsonLines;
  int _currentIndex = 0;

  // Path to the JSON Lines asset containing vessel observation data
  static const String _dataAsset =
      'assets/AIS_MarineCadastre_SelectedVessels_CustomDataSource.jsonl';

  @override
  Future<DynamicEntityDataSourceInfo> onLoad() async {
    final rawText = await rootBundle.loadString(_dataAsset);
    _jsonLines = rawText
        .split('\n')
        .map((line) => line.trim())
        .where((line) => line.isNotEmpty)
        .toList();

    final info = DynamicEntityDataSourceInfo(
      entityIdFieldName: _entityIdFieldName,
      fields: _schema,
    );
    info.spatialReference = SpatialReference.wgs84;
    return info;
  }

  // Starts emitting observations sequentially.
  @override
  Future<void> onConnect() async {
    if (_timer != null) {
      return; // Already connected
    }
    _timer = Timer.periodic(_emissionDelay, (_) => _emitNextObservation());
  }

  // Stops emitting observations and cleans up resources.
  @override
  Future<void> onDisconnect() async {
    _timer?.cancel();
    _timer = null;
  }

  // Decodes and emits the next observation.
  void _emitNextObservation() {
    if (_currentIndex >= _jsonLines.length) {
      _timer?.cancel();
      _timer = null; // Allow reconnect to restart cleanly.
      _currentIndex = 0;
      return;
    }

    final line = _jsonLines[_currentIndex++];
    Map<String, dynamic> json;

    try {
      json = jsonDecode(line) as Map<String, dynamic>;
    } on Exception catch (_) {
      // Skip malformed JSON lines.
      return;
    }

    final geometryJson = json['geometry'] as Map<String, dynamic>?;
    final attributesJson = json['attributes'] as Map<String, dynamic>?;

    if (geometryJson == null || attributesJson == null) {
      return;
    }

    final x = (geometryJson['x'] as num).toDouble();
    final y = (geometryJson['y'] as num).toDouble();

    final point = ArcGISPoint(
      x: x,
      y: y,
      spatialReference: SpatialReference.wgs84,
    );

    final attributes = <String, dynamic>{};
    for (final field in _schema) {
      attributes[field.name] = attributesJson[field.name];
    }

    // Emit a CustomDynamicEntityDataEvent with the current observation.
    handleEntityDataEvent(NewObservation(point, attributes));
  }

  // Schema defining all fields for vessel observations.
  static final List<Field> _schema = [
    Field.text(name: 'MMSI', alias: 'MMSI', length: 256),
    Field.double(name: 'BaseDateTime', alias: 'BaseDateTime'),
    Field.double(name: 'LAT', alias: 'LAT'),
    Field.double(name: 'LONG', alias: 'LONG'),
    Field.double(name: 'SOG', alias: 'SOG'),
    Field.double(name: 'COG', alias: 'COG'),
    Field.double(name: 'Heading', alias: 'Heading'),
    Field.text(name: 'VesselName', alias: 'VesselName', length: 256),
    Field.text(name: 'IMO', alias: 'IMO', length: 256),
    Field.text(name: 'CallSign', alias: 'CallSign', length: 256),
    Field.text(name: 'VesselType', alias: 'VesselType', length: 256),
    Field.text(name: 'Status', alias: 'Status', length: 256),
    Field.double(name: 'Length', alias: 'Length'),
    Field.double(name: 'Width', alias: 'Width'),
    Field.text(name: 'Cargo', alias: 'Cargo', length: 256),
    Field.text(name: 'globalid', alias: 'globalid', length: 256),
  ];
}