Add chess bloc.

lib/chess_bloc/chess_bloc.dart

@@ -0,0 +1,52 @@
+import 'dart:async';
+
+import 'package:flutter_bloc/flutter_bloc.dart';
+
+import 'package:mchess/chessapp/chess_utils.dart';
+import 'package:mchess/chessapp/chess_square.dart';
+
+class ChessBloc extends Bloc<ChessEvent, ChessBoardState> {
+  static final ChessBloc _instance = ChessBloc._internal();
+
+  ChessBloc._internal() : super(ChessBoardState.init()) {
+    on<PieceMoved>(moveHandler);
+  }
+
+  factory ChessBloc.getInstance() {
+    return ChessBloc();
+  }
+
+  factory ChessBloc() {
+    return _instance;
+  }
+
+  FutureOr<void> moveHandler(
+    PieceMoved event,
+    Emitter<ChessBoardState> emit,
+  ) {
+    emit(ChessBoardState(
+      !state.flipped,
+      ChessColor.black,
+      state.position,
+    ));
+  }
+}
+
+abstract class ChessEvent {}
+
+class PieceMoved extends ChessEvent {}
+
+class BoardFlippedEvent extends ChessEvent {}
+
+class ChessBoardState {
+  final bool flipped;
+  final ChessColor turnColor;
+  final Map<ChessCoordinate, ChessPiece> position;
+
+  ChessBoardState(this.flipped, this.turnColor, this.position);
+
+  ChessBoardState.init()
+      : flipped = false,
+        turnColor = ChessColor.white,
+        position = {};
+}