comments

src/backend/AutoPlayer.java

@@ -4,13 +4,7 @@ import java.util.ArrayList;
 import java.util.Random;
 
 public class AutoPlayer {
-	
+	//Creates an Empty list to hold all the legal moves for the current player
-	
-	/**
-	 * returns the best Move to try on provided board for active player
-	 * @param board
-	 * @return
-	 */
 	public Move computeBestMove(Board board) {ArrayList<Move> possibleMoves = new ArrayList<>();
     boolean isWhiteTurn = board.isTurnWhite();
 
@@ -26,7 +20,7 @@ public class AutoPlayer {
         }
     }
 
-    // If there are no moves available, return null
+    // If there are no moves available, return null- Handles checkmate or stalemate
     if (possibleMoves.isEmpty()) {
         return null;
     }

src/backend/Board.java

@@ -5,24 +5,30 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class Board {
+	//class fields - All core game state lives here
 	private int width;
 	private int height;
 	private ArrayList<Piece> pieces;
 	private int turnNumber = 0;
 	private boolean turnWhite = true;
+	//for UI State
 	private int[] selected = null; //for user touch
 	private ArrayList<int[]> highlighted = new ArrayList<>();
+	//for Undo and Special rules
 	private ArrayList<Move> moveHistory = new ArrayList<>();
 	private int[] enPassantTarget = null;
 
+	//Constructors - Initialize the empty board of the specific size 8*8
 	public Board(int colNum, int lineNum) {
 		this.width = colNum;
 		this.height = lineNum;
 		this.pieces = new ArrayList<>();
 	    this.enPassantTarget = null;
 	}
-	
+	//Deep Copy - clones the entire board to simulate without mutating the original
+	//Allows safe simulation without side effects on the source board
 	public Board(Board other) {
+		//copy primitives and simple fields
 	    this.width = other.width;
 	    this.height = other.height;
 	    this.turnNumber = other.turnNumber;
@@ -33,22 +39,26 @@ public class Board {
 	            : null;
 
 
+	    //Deep copy each piece
 	    this.pieces = new ArrayList<>();
 	    for (Piece p : other.pieces) {
 	        this.pieces.add(new Piece(p)); // uses Piece copy constructor (next step)
 	    }
 
+	    //Copy UI Highlights
 	    this.highlighted = new ArrayList<>();
 	    for (int[] pos : other.highlighted) {
 	        this.highlighted.add(new int[]{pos[0], pos[1]});
 	       
 	    }
-	   
+	   //shallow copy move history
 	    this.moveHistory = new ArrayList<>(other.moveHistory);
 	}
 
 
 
+	//Simple Getters
+	//returns board with column
 	public int getWidth() {
 		return width;
 	}
@@ -61,10 +71,13 @@ public class Board {
 		return turnNumber;
 	}
 
+	//return true if its white turn to move
 	public boolean isTurnWhite() {
 		return turnWhite;
 	}
 
+	//places a new piece of a given colour & type at (x,y)
+	//used by populateBoard
 	public void setPiece(boolean isWhite, PieceType type, int x, int y) {
 		Piece piece = new Piece(isWhite, type, x, y);
 	    pieces.add(piece);
@@ -73,11 +86,12 @@ public class Board {
 	public void populateBoard() {
 		cleanBoard();  // clear any existing pieces
 
-	    // White pieces
+	    // White pieces- Places white pawns at rank 1
 	    for (int i = 0; i < 8; i++) {
 	        setPiece(true, PieceType.Pawn, i, 1);
 	    }
-	    setPiece(true, PieceType.Rook, 0, 0);
+	    //places white back-rank pieces
+	    setPiece(true, PieceType.Rook, 1, 0);
 	    setPiece(true, PieceType.Knight, 1, 0);
 	    setPiece(true, PieceType.Bishop, 2, 0);
 	    setPiece(true, PieceType.Queen, 3, 0);
@@ -86,7 +100,7 @@ public class Board {
 	    setPiece(true, PieceType.Knight, 6, 0);
 	    setPiece(true, PieceType.Rook, 7, 0);
 
-	    // Black pieces
+	    // Black pieces - positions
 	    for (int i = 0; i < 8; i++) {
 	        setPiece(false, PieceType.Pawn, i, 6);
 	    }
@@ -100,11 +114,17 @@ public class Board {
 	    setPiece(false, PieceType.Rook, 7, 7);
 	}
 	
+	//empties the board state 
+	//used before populating or loading new positions
+	//resets all pieces and reset en passant state
 	public void cleanBoard() {
 		pieces.clear();
 	    enPassantTarget = null;
 	}
 	
+	//renders the board as ASCII art (eg. "..p......")
+	//one rank per line and uses Uppercase for BLACK and lowercase for White
+	//could have used char[][] for memory efficiency
 	public String toString() {
 		String[][] grid = new String[height][width];
 
@@ -137,10 +157,13 @@ public class Board {
 	}
 
 
+	//Lookup by coordinates and helpful for move generation and UI
+	//return all active pieces on the board
 	public ArrayList<Piece> getPieces() {
 		return pieces;
 	}
-	
+	//finds the king side - necessary for check/checkmate
+	//returns the king piece for the given colour , or null if missing 
 	public Piece getKing(boolean isWhite) {
 	    for (Piece p : pieces) {
 	        if (p.isWhite() == isWhite && p.getType() == PieceType.King) {
@@ -149,7 +172,7 @@ public class Board {
 	    }
 	    return null;
 	}
-	
+	//Scans every opponent move to see if it lands on your king
 	public boolean isInCheck(boolean whitePlayer) {
 	    Piece king = getKing(whitePlayer);
 	    if (king == null) return false;
@@ -170,10 +193,11 @@ public class Board {
 	    return false;
 	}
 
-	
+	//Declares Checkmate if in check and no legal moves left
 	public boolean isCheckmate(boolean whitePlayer) {
 	    if (!isInCheck(whitePlayer)) return false;
 
+	    //if any legal moves exists - not checkmate
 	    for (Piece p : pieces) {
 	        if (p.isWhite() == whitePlayer) {
 	            ArrayList<int[]> legalMoves = getLegalMoves(p);
@@ -184,6 +208,8 @@ public class Board {
 	    return true;
 	}
 
+	//Implements a two-tap GUI: First selects a Piece
+	//then highlights the move and second tap either moves , reselect or deselects
 	public void userTouch(int x, int y) {
 	    Piece clickedPiece = getPieceAt(x, y);
 
@@ -195,6 +221,7 @@ public class Board {
 	        }
 	    } else {
 	        // Second click: check if move is legal
+	    	//it also checks if target is highlighted,then play move
 	        if (isHighlighted(x, y)) {
 	            Piece piece = getPieceAt(selected[0], selected[1]);
 	            Piece captured = getPieceAt(x, y);
@@ -225,6 +252,7 @@ public class Board {
 	public boolean isSimulateOnly() {
 	    return simulateOnly;
 	}
+	//is used to validate castling and pinned-piece moves
 	private boolean isSquareUnderAttack(boolean byWhite, int x, int y) {
 	    for (Piece p : pieces) {
 	        if (p.isWhite() != byWhite) continue;
@@ -237,6 +265,7 @@ public class Board {
 	}
 
 
+	//generates a pseudo-legal moves by piece type and then filters out those that leave your king in check
 	public ArrayList<int[]> getLegalMoves(Piece piece) {
 	    return getLegalMoves(piece, true); // default: check for king safety
 	}
@@ -248,6 +277,8 @@ public class Board {
 
 	    switch (piece.getType()) {
 	        case Pawn:
+	        	//single & double advance
+	        	//captures(including en passant)
 	            int forwardY = y + dir;
 
 	            if (isInBounds(x, forwardY) && getPieceAt(x, forwardY) == null) {
@@ -300,6 +331,7 @@ public class Board {
 	            break;
 
 	        case King:
+	        	//one square in every direction + castling
 	            for (int dx = -1; dx <= 1; dx++) {
 	                for (int dy = -1; dy <= 1; dy++) {
 	                    if (dx == 0 && dy == 0) continue;
@@ -312,8 +344,7 @@ public class Board {
 	                    }
 	                }
 	            }
-
+	            
-	            // Castling logic
 	         // Castling logic
 	            if (!piece.hasMoved() && (!validateCheck || !isInCheck(piece.isWhite()))) {
 	                int row = piece.isWhite() ? 0 : 7;
@@ -388,7 +419,8 @@ public class Board {
 	    return legalMoves;
 	}
 
-	
+	//walks in direction (dx,dy) adding empty squares and a single capture
+	//Avoids repeating rook/bishop/queen code
 	private void addLinearMoves(ArrayList<int[]> moves, Piece piece, int dx, int dy) {
 	    int x = piece.getX(), y = piece.getY();
 	    while (true) {
@@ -406,6 +438,8 @@ public class Board {
 	    }
 	}
 	
+	//helpers for bounds checks and UI flags
+	//return true of (x,y) is a valid board square
 	private boolean isInBounds(int x, int y) {
 	    return x >= 0 && y >= 0 && x < width && y < height;
 	}
@@ -417,27 +451,22 @@ public class Board {
 
 	
 	/* saving-loading feature :*/
-
+	// @return each line representing one piece, plus a header:
-	// in Board.java
+	//   Line 0: width,height,turnNumber,turnWhite,enPassantX,enPassantY
-
+	//   Lines 1–N: serialized Pieces
-	/**
-	 * @return each line representing one piece, plus a header:
-	 *   Line 0: width,height,turnNumber,turnWhite,enPassantX,enPassantY
-	 *   Lines 1–N: serialized Pieces
-	 */
 	public String[] toFileRep() {
 	    List<String> lines = new ArrayList<>();
 
 	    int epX = enPassantTarget == null ? -1 : enPassantTarget[0];
 	    int epY = enPassantTarget == null ? -1 : enPassantTarget[1];
-	    // header
+	    // header:width,height,turnNumber,turnWhite,enPassantX,enpassantY
 	    lines.add(width + "," +
 	              height + "," +
 	              turnNumber + "," +
 	              turnWhite + "," +
 	              epX + "," + epY);
 
-	    // pieces
+	    // pieces - each piece's own serialization
 	    for (Piece p : pieces) {
 	        lines.add(p.toFileRep());
 	    }
@@ -445,12 +474,9 @@ public class Board {
 	    return lines.toArray(new String[0]);
 	}
 
-
-	// in Board.java
-
 	public Board(String[] array) {
 	    this.pieces = new ArrayList<>();
-	    // parse header
+	    // parse header fields
 	    String[] hdr = array[0].split(",");
 	    this.width      = Integer.parseInt(hdr[0]);
 	    this.height     = Integer.parseInt(hdr[1]);
@@ -466,13 +492,13 @@ public class Board {
 	        this.pieces.add(p);
 	    }
 
-	    // clear other state
+	    // clear other state - resets UI and History
 	    this.selected     = null;
 	    this.highlighted  = new ArrayList<>();
 	    this.moveHistory  = new ArrayList<>();
 	}
 
-	
+	//return the Piece at (x,y) or null if none present
 	public Piece getPieceAt(int x, int y) {
 	    for (Piece piece : pieces) {
 	        if (piece.getX() == x && piece.getY() == y) {
@@ -482,17 +508,14 @@ public class Board {
 	    return null;
 	}
 
-	
+	//returns true if (x,y) is one of the highlighted legal moves
-	/* The following methods require more work ! */
-
 	public boolean isHighlighted(int x, int y) {
 		for (int[] pos : highlighted) {
 	        if (pos[0] == x && pos[1] == y) return true;
 	    }
-		//TODO
 		return false;
 	}
-
+//reverses the very last playMove including rook reposition for castling and recovers captured pawns
 public void undoLastMove() {
 	    
 		if (moveHistory.isEmpty()) return;
@@ -539,7 +562,7 @@ public void undoLastMove() {
 	    selected = null;
 	    highlighted.clear();
 	}
-	
+	//applies every rule: castling,en passant,captures,promotions,history and turn switching
 public void playMove(Move move) {
     Piece piece = move.getPieceMoved();
     int fromX = move.getFromX(), fromY = move.getFromY();
@@ -614,7 +637,8 @@ public void playMove(Move move) {
     highlighted.clear();
 }
 
-	public int evaluateBoard() {
+	//Simple static evaluation for negamax
+    public int evaluateBoard() {
 	    int score = 0;
 	    for (Piece piece : pieces) {
 	        int value = 0;
@@ -637,9 +661,8 @@ public void playMove(Move move) {
         BLACK_WINS  // white is checkmated
     }
 
-    /**
+
-     * @return the current game result: ONGOING, DRAW, WHITE_WINS or BLACK_WINS.
+    //@return the current game result: ONGOING, DRAW, WHITE_WINS or BLACK_WINS.
-     */
     public GameResult getGameResult() {
         // if White is checkmated → Black wins
         if (isCheckmate(true))  return GameResult.BLACK_WINS;
@@ -650,10 +673,8 @@ public void playMove(Move move) {
         return GameResult.ONGOING;
     }
 
-    /**
+     //@param whitePlayer whose turn we're checking for stalemate
-     * @param whitePlayer whose turn we're checking for stalemate
+     //@return true if whitePlayer is not in check and has no legal moves
-     * @return true if whitePlayer is not in check and has no legal moves
-     */
     private boolean isStalemate(boolean whitePlayer) {
         // must not be in check
         if (isInCheck(whitePlayer)) return false;

src/backend/ChessClock.java

@@ -1,19 +1,16 @@
 package backend;
 
-/**
+
- * A simple two‐player chess clock with an optional increment.
+//A simple two‐player chess clock with an optional increment.
- * Getters do NOT mutate state; only switchPlayer() and pause() do.
+//Getters do NOT mutate state; only switchPlayer() and pause() do.
- */
 public class ChessClock {
     private long whiteTimeMs, blackTimeMs;   // stored remaining times
     private final long incrementMs;          // per‐move bonus
     private boolean whiteToMove;             // whose clock is running
     private long lastTimestamp;              // when current turn started
-
+    
-    /** 
+     //@param initialTimeMs starting time per player (ms)
-     * @param initialTimeMs starting time per player (ms)
+//@param incrementMs   per‐move increment (ms)
-     * @param incrementMs   per‐move increment (ms)
-     */
     public ChessClock(long initialTimeMs, long incrementMs) {
         this.whiteTimeMs    = initialTimeMs;
         this.blackTimeMs    = initialTimeMs;
@@ -22,10 +19,9 @@ public class ChessClock {
         this.lastTimestamp  = System.currentTimeMillis();
     }
 
-    /** 
+     
-     * Called only when a move is made to flip the clock. 
+     //Called only when a move is made to flip the clock. 
-     * Subtracts the elapsed time, adds the increment, and switches sides.
+   //Subtracts the elapsed time, adds the increment, and switches sides.
-     */
     public void switchPlayer() {
         long now     = System.currentTimeMillis();
         long elapsed = now - lastTimestamp;
@@ -40,10 +36,10 @@ public class ChessClock {
         lastTimestamp = now;
     }
 
-    /** 
+     
-     * Pause the clock (e.g. at game end). 
+     //Pause the clock (e.g. at game end). 
-     * Subtracts elapsed from whichever side was running.
+     // Subtracts elapsed from whichever side was running.
-     */
+  
     public void pause() {
         long now     = System.currentTimeMillis();
         long elapsed = now - lastTimestamp;
@@ -55,9 +51,9 @@ public class ChessClock {
         lastTimestamp = now;
     }
 
-    /** 
+    
-     * @return White’s remaining time (ms), computed without mutating state 
+     //@return White’s remaining time (ms), computed without mutating state 
-     */
+     
     public long getWhiteTimeMs() {
         long now     = System.currentTimeMillis();
         if (whiteToMove) {
@@ -68,9 +64,9 @@ public class ChessClock {
         }
     }
 
-    /** 
+    
-     * @return Black’s remaining time (ms), computed without mutating state 
+     //@return Black’s remaining time (ms), computed without mutating state 
-     */
+     
     public long getBlackTimeMs() {
         long now     = System.currentTimeMillis();
         if (!whiteToMove) {
@@ -81,16 +77,16 @@ public class ChessClock {
         }
     }
 
-    /** 
+    
-     * @return true if either player has run out of time 
+     //@return true if either player has run out of time 
-     */
+     
     public boolean isFlagged() {
         return getWhiteTimeMs() <= 0 || getBlackTimeMs() <= 0;
     }
 
-    /** 
+    
-     * Format mm:ss for display 
+     //Format mm:ss for display 
-     */
+     
     public static String format(long timeMs) {
         long totalSec = Math.max(timeMs / 1000, 0);
         long minutes  = totalSec / 60;