// $Id: chessutils.js,v 1.1 2009/02/18 19:27:41 kgarcia Exp $

 /* these are utility functions used by other functions */
var Files = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'];

var pieceNameToLtr = new Array();
pieceNameToLtr = {'king':'k', 'queen':'q', 'rook':'r', 'bishop':'b', 'knight':'n', 'pawn':'p'};

var pieceLtrToName = new Array();
pieceLtrToName = {'k':'king', 'q':'queen', 'r':'rook', 'b':'bishop', 'n':'knight', 'p':'pawn'};

var pieceColor = new Array();
pieceColor = {'K':'w', 'Q':'w', 'R':'w', 'B':'w', 'N':'w', 'P':'w',
        'k':'b', 'q':'b', 'r':'b', 'b':'b', 'n':'b', 'p':'b'};

var colorLtrToName = new Array();
colorLtrToName = {'w':'white', 'b':'black'};

function isInBoard(row, col)
{
  if ((row >= 0) && (row <= 7) && (col >= 0) && (col <= 7))
    return true;
  else
    return false;
}

  function getPieceColor(piece)
  {
    if (BLACK & piece)
      return "black";
    else
      return "white";
  }

  function getPieceName(piece)
  {
    var pieceName = new Array();
    pieceName[PAWN] = "pawn";
    pieceName[ROOK] = "rook";
    pieceName[KNIGHT] = "knight";
    pieceName[BISHOP] = "bishop";
    pieceName[QUEEN] = "queen";
    pieceName[KING] = "king";

    return pieceName[piece & COLOR_MASK];
  }

  function getPieceCode(color, piece)
  {
    var code;
    switch(piece)
    {
      case "pawn":
        code = PAWN;
        break;
      case "knight":
        code = KNIGHT;
        break;
      case "bishop":
        code = BISHOP;
        break;
      case "rook":
        code = ROOK;
        break;
      case "queen":
        code = QUEEN;
        break;
      case "king":
        code = KING;
        break;
    }

    if (color == "black")
      code = BLACK | code;

    return code;
  }

  function highlight(row, col)
  {
    if (board[parseInt(row)][parseInt(col)] != "")
    {
      var square = parseInt(row) * 8 + parseInt(col);
//      eval("document.images['pos" + row + "-" + col + "'].src = 'images/' + CURRENTTHEME + '/' + getPieceColor(board[row][col]) + '_' + getPieceName(board[row][col]) + '_highlighted.gif'");
      eval("document.images['sq" + square + "'].src = '" + Drupal.settings.chess.base_path + "images/' + CURRENTTHEME + '/' + getPieceColor(board[row][col]) + '_' + getPieceName(board[row][col]) + '_highlighted.gif'");
    }

    return true;
  }

  function unhighlight(row, col)
  {
    if (DEBUG)
      alert("unhighlight -> row = " + row + ", col = " + col);

    if (board[parseInt(row)][parseInt(col)] != "")
    {
      var square = parseInt(row) * 8 + parseInt(col);
//      eval("document.images['pos" + row + "-" + col + "'].src = 'images/' + CURRENTTHEME + '/' + getPieceColor(board[row][col]) + '_' + getPieceName(board[row][col]) + '.gif'");
      eval("document.images['sq" + square + "'].src = '" + Drupal.settings.chess.base_path + "images/' + CURRENTTHEME + '/' + getPieceColor(board[row][col]) + '_' + getPieceName(board[row][col]) + '.gif'");
    }

    return true;
  }

  function getOtherColor(color)
  {
    if (color == "white")
      return "black";
    else
      return "white";
  }

//
// FEN functions
//

function ExpandFEN(FEN) {
  var ones = new Array ('', '1' ,'11', '111', '1111', '11111', '111111', '1111111', '11111111');
  var theFEN = '';
  for(var i=0; i < FEN.length; i++) {
    if(FEN.charAt(i) > '1' && FEN.charAt(i) < '9') {
      theFEN += (ones[Number(FEN.charAt(i))]);
    } else {
      theFEN = theFEN + '' +  FEN.charAt(i);
    }
  }
  return theFEN.replace(/\//g, "");                     // Leave only pieces and empty squares
///////////// The following caused an error (only) in IE5. Replaced with the above code
  var theFEN = FEN.replace(/[2-8]/g,  // Expand contiguous empty squares
    function strRepeat(count) {      //   e.g. change '4' to '1111'
      var strOut = '';
      for(var i=0; i < count; i++) {
       strOut += '1';
      }
     return strOut;
    }
  );
  return theFEN.replace(/\//g, "");    // Leave only pieces and empty squares
}

function SetSquare(Square, Piece) {
  var rank = 7 - parseInt(Square / 8);
  var file = Square % 8;
  var s;
  if(Piece == '1') {
    s = 0;
  } else {
    s = getPieceCode(colorLtrToName[pieceColor[Piece]], pieceLtrToName[Piece.toLowerCase()]);
  }
  board[rank][file] = s;
}

function FENToBoard(FEN) {
  var FENItems = new Array();
  FENItems = FEN.split(' ');
  var ExpFEN = ExpandFEN(FENItems[0]);
  var c;
  for(var i=0; i < 64; i++) {
    c = ExpFEN.charAt(i);
    SetSquare(i, c);
  }
  curColor = colorLtrToName[FENItems[1]];
};

function PackFEN(piecePlacement, activeColor, castlingAvail, epSquare, halfmoveClock, fullmoveNumber)
{ // Pack all the FEN fields into one string
  var FEN = '';
  var idx = 0;
  var empty = 0;
  var c = '';
  for(var i=0; i < 64; i++)
  { // Generate the correct piece placement string
    if(i > 0 && (i % 8 == 0))
    { // New row
      if(empty > 0)
      { // Count of empty squares does not continue across rows
        FEN += empty + "";
        empty = 0;
        idx++;
      }
      FEN += '/';  // New row
    }
    c = piecePlacement.charAt(i);
    if(c == '1')
    { // Count consecutive empty squares
      empty++;
    }
    else
    { // Non-empty square
      if(empty > 0)
      { // Add the number of consecutive empty squares to the output string
        FEN += empty + "";
        empty = 0;
        idx++;
      }
      FEN += c + "";
      idx++;
    }
  }
  if(empty > 0)
  {
    FEN += empty + "";
  }
  return FEN + ' ' + activeColor + ' ' + castlingAvail + ' ' + epSquare + ' ' + halfmoveClock + ' ' + fullmoveNumber;
}

function getFENStartPos()
{
  return 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1';
}

// Returns an array of FEN strings for the current game
// Note that this function assumes that the game started from the normal initial position
function historyToFEN()
{
  var FEN = new Array();
  FEN[0] = getFENStartPos();  // The start position
  var activeColor = 'w';
  var wKS = 'K';  // Castling availability
  var wQS = 'Q';
  var bKS = 'k';
  var bQS = 'q';
  var castlingAvail = 'KQkq';
  var epSquare = '-';  // The en passant square
  var halfmoveClock = 0;  // Number of half moves since last capture or pawn move
  var fullmoveNumber = 1;  // The move number
  var piece = '';
  for (var i = 0; i <= numMoves; i++)
  {
    FEN[i+1] = ExpandFEN(FEN[i]).slice(0, 64);  // Get the piece placement from the FEN string
    if(chessHistory[i][CURCOLOR] == 'white')
      activeColor = 'b';
    else
    {
      activeColor = 'w';
      fullmoveNumber++;
    }
    var fromCol = chessHistory[i][FROMCOL];
    var fromRow = chessHistory[i][FROMROW];
    var row = chessHistory[i][TOROW];
    var col = chessHistory[i][TOCOL];
    if(FEN[i+1].charAt(col + (7 - row) * 8) != '1' || chessHistory[i][CURPIECE] == 'pawn')
      halfmoveClock = 0;  // Restart the count after pawn move or capture
    else
      halfmoveClock++;
    if(typeof chessHistory[i][PROMOTEDTO] == "undefined")
      piece = FEN[i+1].charAt((7 - fromRow) * 8 + fromCol);
    else
    {
      piece = pieceNameToLtr[chessHistory[i][PROMOTEDTO]];
      if(chessHistory[i][CURCOLOR] == 'white')
        piece = piece.toUpperCase();
    }
    FEN[i+1] = FEN[i+1].slice(0, (7 - fromRow) * 8 + fromCol) + '1' + FEN[i+1].slice((7 - fromRow) * 8 + fromCol + 1);
    FEN[i+1] = FEN[i+1].slice(0, (7 - row) * 8 + col) + piece + FEN[i+1].slice((7 - row) * 8 + col + 1);

    if (chessHistory[i][CURPIECE] == 'king')
    { // Can't castle after the king has been moved
      if(chessHistory[i][CURCOLOR] == 'white')
      {
        wKS = '';
        wQS = '';
      }
      else
      {
        bKS = '';
        bQS = '';
      }
      /* if this is a castling move the rook must also be moved */
      if (Math.abs(col - fromCol) == 2)
      {  // The king only moves two squares when castling
        var rookCol = 0;
        var rookToCol = 3
        if (col - fromCol == 2)
        {  // Kingside castling (would be == -2 if queenside)
          rookCol = 7;
          rookToCol = 5;
        }
        FEN[i+1] = FEN[i+1].slice(0, (7 - row) * 8 + rookToCol) + FEN[i+1].charAt((7 - row) * 8 + rookCol) + FEN[i+1].slice((7 - row) * 8 + rookToCol + 1);
        FEN[i+1] = FEN[i+1].slice(0, (7 - row) * 8 + rookCol) + '1' + FEN[i+1].slice((7 - row) * 8 + rookCol + 1);
      }
    }
    else if (chessHistory[i][CURPIECE] == 'rook')
    {
      if(chessHistory[i][CURCOLOR] == 'white')
      {
        if(fromRow == 0)
        {
          if(fromCol == 0)
            wQS = '';
          else
            wKS = '';
        }
      }
      else
      {
        if(fromRow == 7)
        {
          if(fromCol == 0)
            bQS = '';
          else
            bKS = '';
        }
      }
    }
    else if(chessHistory[i][CURPIECE] == 'pawn' && Math.abs(chessHistory[i][TOROW] - chessHistory[i][FROMROW]) == 2)
    { // Pawn double advance, so en passant capture may be possible on the next move
      if(chessHistory[i][CURCOLOR] == 'white')
      {
        epSquare = Files[fromCol] + '3';
      }
      else
      {
        epSquare = Files[fromCol] + '6';
      }
    }
    castlingAvail = wKS + wQS + bKS + bQS;
    if(castlingAvail == '')
      castlingAvail = '-';
    FEN[i+1] = PackFEN(FEN[i+1], activeColor, castlingAvail, epSquare, halfmoveClock, fullmoveNumber);
    epSquare = '-';
  }
  return FEN;
}