More changes. Memory error when accessing state.position in ChessBloc.

lib/chess_bloc/chess_bloc.dart

@@ -1,6 +1,8 @@
 import 'dart:async';
 
+import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:mchess/chessapp/chess_board.dart';
 
 import 'package:mchess/chessapp/chess_utils.dart';
 import 'package:mchess/chessapp/chess_square.dart';
@@ -10,6 +12,7 @@ class ChessBloc extends Bloc<ChessEvent, ChessBoardState> {
 
   ChessBloc._internal() : super(ChessBoardState.init()) {
     on<PieceMoved>(moveHandler);
+    on<PreCheckMove>(preCheckHandler);
   }
 
   factory ChessBloc.getInstance() {
@@ -24,17 +27,42 @@ class ChessBloc extends Bloc<ChessEvent, ChessBoardState> {
     PieceMoved event,
     Emitter<ChessBoardState> emit,
   ) {
+    Map<ChessCoordinate, ChessPiece> newPosition = {};
+
+    newPosition[ChessCoordinate(5, 5)] =
+        ChessPiece(ChessPieceName.blackBishop, ChessColor.black);
+
+    ChessPiece? piece =
+        state.position[ChessCoordinate.copyFrom(event.startSquare)];
+
+    newPosition[event.endSquare] = piece!;
+    newPosition[event.startSquare] = const ChessPiece.none();
+
     emit(ChessBoardState(
-      !state.flipped,
+      state.flipped,
       ChessColor.black,
-      state.position,
+      newPosition,
     ));
   }
+
+  FutureOr<bool> preCheckHandler(
+    PreCheckMove event,
+    Emitter<ChessBoardState> emit,
+  ) {
+    return false;
+  }
 }
 
 abstract class ChessEvent {}
 
-class PieceMoved extends ChessEvent {}
+class PieceMoved extends ChessEvent {
+  final ChessCoordinate startSquare;
+  final ChessCoordinate endSquare;
+
+  PieceMoved({required this.startSquare, required this.endSquare});
+}
+
+class PreCheckMove extends ChessEvent {}
 
 class BoardFlippedEvent extends ChessEvent {}
 
@@ -43,10 +71,28 @@ class ChessBoardState {
   final ChessColor turnColor;
   final Map<ChessCoordinate, ChessPiece> position;
 
-  ChessBoardState(this.flipped, this.turnColor, this.position);
+  ChessBoardState._(this.flipped, this.turnColor, this.position);
 
-  ChessBoardState.init()
-      : flipped = false,
-        turnColor = ChessColor.white,
-        position = {};
+  factory ChessBoardState(
+    bool flipped,
+    ChessColor turnColor,
+    Map<ChessCoordinate, ChessPiece> position,
+  ) {
+    return ChessBoardState._(flipped, turnColor, position);
+  }
+
+  factory ChessBoardState.init() {
+    bool flipped = false;
+    ChessColor turnColor = ChessColor.white;
+    Map<ChessCoordinate, ChessPiece> position = {};
+
+    for (int row = 1; row <= 8; row++) {
+      for (int col = 1; col <= 8; col++) {
+        position[ChessCoordinate(row, col)] =
+            ChessPiece(ChessPieceName.none, ChessColor.white);
+      }
+    }
+
+    return ChessBoardState._(flipped, turnColor, position);
+  }
 }

lib/chessapp/chess_board.dart

@@ -8,7 +8,7 @@ class ChessBoard extends StatelessWidget {
   final ChessBoardState bState;
   final List<ChessSquare> squares;
 
-  ChessBoard._({required this.bState, required this.squares});
+  const ChessBoard._({required this.bState, required this.squares});
 
   factory ChessBoard({required ChessBoardState bState}) {
     List<ChessSquare> squares = List.empty(growable: true);

lib/chessapp/chess_square.dart

@@ -3,7 +3,7 @@ import 'package:mchess/chess_bloc/chess_bloc.dart';
 
 import 'chess_utils.dart';
 
-class ChessSquare extends StatefulWidget {
+class ChessSquare extends StatelessWidget {
   final ChessCoordinate coordinate;
   late ChessPiece? containedPiece;
   static const double pieceWidth = 200;
@@ -11,11 +11,6 @@ class ChessSquare extends StatefulWidget {
 
   ChessSquare({required this.coordinate, this.containedPiece, super.key});
 
-  @override
-  State<StatefulWidget> createState() => _ChessSquareState();
-}
-
-class _ChessSquareState extends State<ChessSquare> {
   late Color color;
 
   @override
@@ -30,7 +25,7 @@ class _ChessSquareState extends State<ChessSquare> {
       draggableFdbSize = 0.15 * windowHeight;
     }
 
-    color = _getSquareColor(widget.coordinate);
+    color = _getSquareColor(coordinate);
 
     return DragTarget<ChessMove>(
       builder: (context, candidateData, rejectedData) {
@@ -40,23 +35,19 @@ class _ChessSquareState extends State<ChessSquare> {
           height: ChessSquare.pieceWidth,
           child: Draggable<ChessMove>(
             /* We create the move with the startSquare == endSquare. The receiving widget will give the correct value to end square. */
-            data: ChessMove(
-                widget.coordinate, widget.coordinate, widget.containedPiece),
+            data: ChessMove(coordinate, coordinate, containedPiece),
             feedback: FractionalTranslation(
               translation: const Offset(-0.5, -0.75),
               child: SizedBox(
                   height: draggableFdbSize,
                   width: draggableFdbSize,
-                  child: widget.containedPiece),
+                  child: containedPiece),
             ),
             childWhenDragging: Container(),
             dragAnchorStrategy: pointerDragAnchorStrategy,
-            child: widget.containedPiece ?? Container(),
-            onDragCompleted: () {
-              setState(() {
-                widget.containedPiece = null;
-              });
-            },
+            child: containedPiece ?? Container(),
+            onDragCompleted: () {},
+            onDragStarted: () {},
           ),
         );
       },
@@ -65,7 +56,11 @@ class _ChessSquareState extends State<ChessSquare> {
         return true;
       },
       onAccept: (move) {
-        ChessBloc().add(PieceMoved());
+        move.endSquare = coordinate;
+        ChessBloc().add(PieceMoved(
+          startSquare: move.startSquare,
+          endSquare: move.endSquare,
+        ));
       },
     );
   }

lib/chessapp/chess_utils.dart

@@ -32,6 +32,7 @@ Map<ChessPieceName, String> chessPiecesAssets = {
   ChessPieceName.blackRook: 'assets/pieces/black/rook.svg',
   ChessPieceName.blackQueen: 'assets/pieces/black/queen.svg',
   ChessPieceName.blackKing: 'assets/pieces/black/king.svg',
+  ChessPieceName.none: '',
 };
 
 class ChessCoordinate {
@@ -39,6 +40,9 @@ class ChessCoordinate {
   late int row;
 
   ChessCoordinate(this.column, this.row);
+  ChessCoordinate.copyFrom(ChessCoordinate original)
+      : column = original.column,
+        row = original.row;
 
   static String columnIntToColumnString(int col) {
     String colStr;
@@ -58,14 +62,23 @@ class ChessCoordinate {
 class ChessPiece extends StatelessWidget {
   final ChessColor color;
   final ChessPieceName pieceName;
-  late final Widget pieceImage;
+  final Widget? pieceImage;
 
-  ChessPiece(this.pieceName, this.color, {super.key}) {
-    String pieceAssetUrl = chessPiecesAssets[pieceName]!;
+  const ChessPiece._(this.pieceName, this.color, this.pieceImage);
+
+  factory ChessPiece(ChessPieceName name, ChessColor color) {
+    Widget? pieceImage;
+    String pieceAssetUrl = chessPiecesAssets[name]!;
 
     pieceImage = SvgPicture.asset(pieceAssetUrl);
+    return ChessPiece._(name, color, pieceImage);
   }
 
+  const ChessPiece.none({super.key})
+      : pieceName = ChessPieceName.none,
+        color = ChessColor.white,
+        pieceImage = null;
+
   @override
   Widget build(BuildContext context) {
     return SizedBox(