Demo classes for moving chess pieces

Chess.php

<?php
/**
 * @description An abstract class for all chess pieces
 * @author Benjamin Kuker
 */
abstract class ChessPiece {
	
	protected $color = null;
	protected $constraints = array();
	protected $currentPosition = null;
	protected $history = array();
	protected $name = null;
	
	/**
	 * @param string $name - The name of the chess piece: B=Bishop, R=Rook, Q=Queen, K=King, N=Knight, and an empty 
	 * 	string should be used for Pawns 
	 * @param string $startingPosition - The starting position of the chess piece, in algebraic notation
	 * @param string $color - Either 'black' or 'white'
	 */
	function __construct($name, $startingPosition, $color){
		$this->name = "$color $name";
		$this->currentPosition = $startingPosition;
		$this->color = $color;
	}

	/**
	 * @description Gets the shorthand name of the chess piece
	 * @return - The shorthand name of the chess piece
	 */
	public function getName(){
		return $this->name;
	}
	
	/**
	 * @description Gets the color of the chess piece.
	 * @return - The color of the chess piece, either 'black' or 'white'
	 */
	public function getColor(){
		return $this->color;
	}
	
	/**
	 * @description Gets the valid moves for the piece
	 * @param array $boardState - A multi-dimensional array of type $boardState[row][column], with 8 rows and 8 lettered 
	 * 	columns (a-h) in each row. The value of each column should reflect the status of that square. If it is empty, 
	 * 	the value should be null, if it is occupied by a piece, it should contain an object representing that piece.
	 * @return array An array of valid moves for the piece, given the current board and the piece's current position 
	 */
	abstract public function getValidMoves(array $boardState);
	
	/**
	 * @description Checks possible moves for conflicts with pieces on the same team
	 * @param array $possibleMoves - An array of possible moves to check for conflicts
	 * @param array $boardState - A multi-dimensional array of type $boardState[row][column], with 8 rows and 8 lettered 
	 * 	columns (a-h) in each row. The value of each column should reflect the status of that square. If it is empty, 
	 * 	the value should be null, if it is occupied by a piece, it should contain an object representing that piece.
	 * @return array An array of valid moves for the piece, given the current board and the piece's current position 
	 */
	abstract protected function checkTeamConflicts(array $possibleMoves, array $boardState);

	/**
	 * @description Checks a move to see if it is valid
	 * @param string $move The proposed position of the chess piece, in algebraic notation
	 * @param array $boardState - A multi-dimensional array of type $boardState[row][column], with 8 rows and 8 lettered 
	 * 	columns (a-h) in each row. The value of each column should reflect the status of that square. If it is empty, 
	 * 	the value should be null, if it is occupied by a piece, it should contain an object representing that piece.
	 * @return boolean
	 */
	public function isValidMove($move, array $boardState){
		return (in_array($move, $this->getValidMoves($boardState)));
	}
	
	/**
	 * @description Moves a piece, if the move is valid, and records the move to the piece's history
	 * @param string $move The proposed position of the chess piece, in algebraic notation
	 * @param array $boardState - A multi-dimensional array of type $boardState[row][column], with 8 rows and 8 lettered 
	 * 	columns (a-h) in each row. The value of each column should reflect the status of that square. If it is empty, 
	 * 	the value should be null, if it is occupied by a piece, it should contain an object representing that piece.
	 * @param boolean $captures - Whether or not the move will result in capturing an opposing piece
	 * @return boolean - TRUE if the move was successful, FALSE otherwise
	 */
	public function movePiece($move, array $boardState, $captures = false){
		if (isValidMove($move, $boardState)){
			if ($captures){
				if ($this->name === ''){ //Pawn captures
					$previousPosition = explode('', $this->currentPosition);
					$this->history[] = $name.$previousPosition[0].'x'.$move;
				} else {
					$this->history[] = $name.'x'.$move;
				}
			} else {
				$this->history[] = $name.$move;
			}
			$this->currentPosition = $move;
			return true;
		}
		return false;
	}
	
	/**
	 * @description Gets the history of the piece
	 * @return array The history of the piece, with each move as an array item
	 */
	public function getHistory(){
		return $this->history;
	}
	
	/**
	 * @description Gets the last move of the piece
	 * @return string The last move of the piece, in algebraic notation
	 */
	public function getLastMove(){
		return end($this->history);
	}

	/**
	 * @description Gets the current position of the piece
	 * @return string The current position of the piece, in algebraic notation
	 */	
	public function getCurrentPosition(){
		return $this->currentPosition;
	}
}

/**
 * @description A class for controlling a knight
 * @author Benjamin Kuker
 */
class Knight extends ChessPiece {

	/**
	 * @param string $startingPosition - The starting position of the chess piece, in algebraic notation
	 * @param string $color - Either 'black' or 'white'
	 */	
	function __construct($startingPosition, $color){
		parent::__construct('N', $startingPosition, $color);
	}

	/**
	 * (non-PHPdoc)
	 * @see ChessPiece::getValidMoves()
	 */
	public function getValidMoves(array $boardState){
		$allColumns = array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h');
		$position = str_split($this->currentPosition);
		$column = array_search($position[0], $allColumns);
		$row = $position[1] - 1;
		$possibleMoves = array();
		
		if ($column > 0){ //Near left side is available
			$newColumn = $column - 1;
			if (($row + 2) < 7){
				$possibleMoves[] = $allColumns[$newColumn].($row + 3);
			}
			if (($row - 2) >= 0){
				$possibleMoves[] = $allColumns[$newColumn].($row - 1);
			}			
		}
		
		if ($column > 1){ //Far left side is available
			$newColumn = $column - 2;
			if (($row + 1) < 7){
				$possibleMoves[] = $allColumns[$newColumn].($row + 2);
			}
			if (($row - 1) > 0){
				$possibleMoves[] = $allColumns[$newColumn].$row;
			}			
		}		
		
		if ($column < 7){ //Near right side is available
			$newColumn = $column + 1;
			if (($row + 2) < 7){
				$possibleMoves[] = $allColumns[$newColumn].($row + 3);
			}
			if (($row - 2) >= 0){
				$possibleMoves[] = $allColumns[$newColumn].($row - 1);
			}			
		}
		
		if ($column < 6){ //Far right side is available
			$newColumn = $column + 2;
			if (($row + 1) < 7){
				$possibleMoves[] = $allColumns[$newColumn].($row + 2);
			}
			if (($row - 1) > 0){
				$possibleMoves[] = $allColumns[$newColumn].$row;
			}		
		}
				
		return $this->checkTeamConflicts($possibleMoves, $boardState);
	}
	
	/**
	 * (non-PHPdoc)
	 * @see ChessPiece::checkTeamConflicts()
	 */
	protected function checkTeamConflicts($possibleMoves, array $boardState){
		$validMoves = array();
		foreach($possibleMoves as $move){
			list($column, $row) = str_split($move);
			$row -= 1;
			$square = $boardState[$row][$column];
			if ((!$square) || ($square->getColor() !== $this->color)){
				$validMoves[] = $move;
			}
		}
		return $validMoves;		
	}
}

/**
 * @description A generic chess piece class used only for demonstration purposes
 * @author Benjamin Kuker
 */
class GenericPiece extends ChessPiece {

	/**
	 * @param string $startingPosition - The starting position of the chess piece, in algebraic notation
	 * @param string $color - Either 'black' or 'white'
	 */
	function __construct($startingPosition, $color){
		parent::__construct('GP', $startingPosition, $color);
	}
	
	/**
	 * (non-PHPdoc)
	 * @see ChessPiece::getValidMoves()
	 */
	public function getValidMoves(array $boardState){}
	
	/**
	 * (non-PHPdoc)
	 * @see ChessPiece::checkTeamConflicts()
	 */
	protected function checkTeamConflicts($possibleMoves, array $boardState){}
}

/**
 * Demonstration - Uncomment the following examples to see how the class would be used
 */

/**
 * Get moves on an empty board
 */
/* (Just add a / to the beginning of the line to uncomment the code)
$emptyBoard = array(
	array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
	array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
	array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
	array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
	array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
	array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
	array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
	array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null)								
);

$knight = new Knight('e4', 'white');
var_dump($knight->getValidMoves($emptyBoard));
//*/

/**
 * Get moves on a board with pieces from same team
 */
/* (Just add a / to the beginning of the line to uncomment the code)
$whitePiece1 = new GenericPiece('f6', 'white');
$whitePiece2 = new GenericPiece('f2', 'white');

$board = array(
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>$whitePiece2, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>$whitePiece1, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null)
);

$knight = new Knight('e4', 'white');
var_dump($knight->getValidMoves($board));
//*/

/**
 * Get moves on a board with pieces from opposite team
 */
/* (Just add a / to the beginning of the line to uncomment the code)
$blackPiece1 = new GenericPiece('d6', 'black');
$blackPiece2 = new GenericPiece('d2', 'black');

$board = array(
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>$blackPiece2, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>$blackPiece1, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null)
);

$knight = new Knight('e4', 'white');
var_dump($knight->getValidMoves($board));
//*/

/**
 * Get moves on a board with pieces from both teams
 */
/* (Just add a / to the beginning of the line to uncomment the code)
$blackPiece1 = new GenericPiece('d6', 'black');
$blackPiece2 = new GenericPiece('d2', 'black');
$whitePiece1 = new GenericPiece('f6', 'white');
$whitePiece2 = new GenericPiece('f2', 'white');

$board = array(
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>$blackPiece2, 'e'=>null, 'f'=>$whitePiece2, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>$blackPiece1, 'e'=>null, 'f'=>$whitePiece1, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null),
		array('a'=>null, 'b'=>null, 'c'=>null, 'd'=>null, 'e'=>null, 'f'=>null, 'g'=>null, 'h'=>null)
);

$knight = new Knight('e4', 'white');
var_dump($knight->getValidMoves($board));
//*/