feat: adding Group layer support for layerByName (#51)

* adding Group layer support for layerByName

* adding CHANGELOG entry

* changing CHANGELOG entry to [Next]

Author: kurtome

CHANGELOG.md

@@ -1,4 +1,5 @@
 ## [Next]
+* Adding support for searching `Group` layer children when using `map.layerByName`.
 * Add parser support for Tiled hex colors as `ui.Color`
 * BREAKING CHANGE: re-named string color fields to `colorHex` such as `layer.tintColorHex` and 
   added a new `color` field paired with each `colorHex` field of type `ui.Color`.

lib/src/tiled_map.dart

@@ -220,11 +220,32 @@ class TiledMap {
     return imageSet.toList();
   }
 
+  /// Finds the first layer with the matching [name], or throw an
+  /// [ArgumentError] if one cannot be found.
+  /// Will search recursively through [Group] children.
   Layer layerByName(String name) {
-    return layers.firstWhere(
-      (element) => element.name == name,
-      orElse: () => throw ArgumentError('Layer $name not found'),
-    );
+    final toSearch = Queue<List<Layer>>();
+    toSearch.add(layers);
+
+    Layer? found;
+    while (found == null && toSearch.isNotEmpty) {
+      final currentLayers = toSearch.removeFirst();
+      currentLayers.forEach((layer) {
+        if (layer.name == name) {
+          found = layer;
+          return;
+        } else if (layer is Group) {
+          toSearch.add(layer.layers);
+        }
+      });
+    }
+
+    if (found != null) {
+      return found!;
+    }
+
+    // Couldn't find it in any layer
+    throw ArgumentError('Layer $name not found');
   }
 
   Tileset tilesetByName(String name) {

lib/tiled.dart

@@ -1,5 +1,6 @@
 library tiled;
 
+import 'dart:collection';
 import 'dart:convert';
 import 'dart:math' show Rectangle;
 import 'dart:typed_data';

test/complexmap_infinite_test.dart

@@ -16,11 +16,16 @@ void main() {
 
   group('Layer.tiles Json', () {
     late TileLayer layer;
+    late Group groupLayer;
     setUp(() {
+      groupLayer = complexMapInfinite.layerByName('group_layer') as Group;
       layer = complexMapInfinite.layerByName('top') as TileLayer;
     });
     test('is expected to be infinite with chunks', () {
       expect(complexMapInfinite.infinite, isTrue);
+      expect(groupLayer, isNotNull);
+      expect(groupLayer.layers[1], equals(layer));
+      expect(layer, isNotNull);
       expect(layer.tileData, isNull);
       expect(layer.chunks!.length, equals(9));
       expect(layer.chunks![0].tileData.length, equals(16));