mchess-client/lib/chess/chess_square.dart

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

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

import '../chess_bloc/chess_events.dart';
import '../utils/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<PieceDragged>(
      onWillAccept: (move) {
        if (move?.fromSquare == coordinate) {
          return false;
        }
        return true;
      },
      onAccept: (pieceDragged) {
        // Replace the dummy value with the actual target of the move.
        pieceDragged.toSquare = coordinate;

        if (isPromotionMove(pieceDragged)) {
          var move = ChessMove(
              from: pieceDragged.fromSquare, to: pieceDragged.toSquare);
          PromotionBloc.getInstance().add(PawnMovedToPromotionField(
              move: move, colorMoved: ChessBloc.myColor!));
        } else if (coordinate != pieceDragged.fromSquare) {
          ChessBloc.getInstance().add(OwnPieceMoved(
              startSquare: pieceDragged.fromSquare,
              endSquare: pieceDragged.toSquare,
              piece: pieceDragged.movedPiece!));
        }
      },
      builder: (context, candidateData, rejectedData) {
        var maxDrags = kDebugMode
            ? 1
            : ((ChessBloc.turnColor == ChessBloc.myColor) &&
                    (containedPiece?.color == ChessBloc.turnColor)
                ? 1
                : 0);

        return Container(
          color: color,
          width: ChessSquare.pieceWidth,
          height: ChessSquare.pieceWidth,
          child: Draggable<PieceDragged>(
            /* We create the move with the startSquare == endSquare. The receiving widget will give the correct value to end square. */
            data: PieceDragged(coordinate, coordinate, containedPiece),
            maxSimultaneousDrags: maxDrags,
            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: () {},
          ),
        );
      },
    );
  }

  bool isPromotionMove(PieceDragged move) {
    bool isPromotion = false;
    if (move.movedPiece!.pieceClass != ChessPieceClass.pawn) {
      return isPromotion;
    }

    switch (ChessBloc.myColor) {
      case ChessColor.black:
        if (move.toSquare.row == 1) {
          isPromotion = true;
        }
        break;
      case ChessColor.white:
        if (move.toSquare.row == 8) {
          isPromotion = true;
        }
        break;
      case null:
        break;
    }

    return isPromotion;
  }
}