mchess-client/lib/chessapp/chess_square.dart

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';

import 'package:mchess/chess_bloc/chess_events.dart';
import 'package:mchess/chess_bloc/chess_bloc.dart';

import 'chess_utils.dart';

class ChessSquare extends StatelessWidget {
  final ChessCoordinate coordinate;
  final ChessPiece? containedPiece;
  static const double pieceWidth = 200;
  static const double pieceHeight = 200;

  final Color color;

  const ChessSquare._(
      {required this.coordinate,
      required this.containedPiece,
      required this.color});

  factory ChessSquare(ChessCoordinate coord, ChessPiece? piece) {
    Color lightSquares = Colors.brown.shade50;
    Color darkSquares = Colors.brown.shade400;

    Color squareColor;

    if (coord.row % 2 == 0) {
      if (coord.column % 2 == 0) {
        squareColor = darkSquares;
      } else {
        squareColor = lightSquares;
      }
    } else {
      if (coord.column % 2 == 0) {
        squareColor = lightSquares;
      } else {
        squareColor = darkSquares;
      }
    }

    return ChessSquare._(
      coordinate: coord,
      containedPiece: piece,
      color: squareColor,
    );
  }

  @override
  Widget build(BuildContext context) {
    double windowWidth = MediaQuery.of(context).size.width;
    double windowHeight = MediaQuery.of(context).size.height;
    double draggableFdbSize;

    if (windowWidth < windowHeight) {
      draggableFdbSize = 0.15 * windowWidth;
    } else {
      draggableFdbSize = 0.15 * windowHeight;
    }

    return DragTarget<ChessMove>(
      builder: (context, candidateData, rejectedData) {
        return Container(
          color: color,
          width: ChessSquare.pieceWidth,
          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(coordinate, coordinate, containedPiece),
            feedback: FractionalTranslation(
              translation: const Offset(-0.5, -0.75),
              child: SizedBox(
                  height: draggableFdbSize,
                  width: draggableFdbSize,
                  child: containedPiece),
            ),
            childWhenDragging: Container(),
            dragAnchorStrategy: pointerDragAnchorStrategy,
            child: containedPiece ?? Container(),
            onDragCompleted: () {},
            onDragStarted: () {},
          ),
        );
      },
      onWillAccept: (move) {
        final legalMove = context
            .read<ChessBloc>()
            .preCheckHandler(PreCheckMove(move: move!));
        print('onWillAccept returns $legalMove');
        return legalMove;
      },
      onAccept: (move) {
        move.endSquare = coordinate;

        if (move.endSquare != move.startSquare) {
          context.read<ChessBloc>().add(
                PieceMoved(
                  startSquare: move.startSquare,
                  endSquare: move.endSquare,
                ),
              );
        }
      },
    );
  }
}