var g_startOffset = null;
var g_selectedPiece = null;
var moveNumber = 1;

var g_allMoves = [];
var g_playerWhite = true;
var g_changingFen = false;
var g_analyzing = false;

var g_uiBoard;
var g_cellSize = 45;

function UINewGame() {
	moveNumber = 1;

	var pgnTextBox = document.getElementById('PgnTextBox');
	pgnTextBox.value = '';

	EnsureAnalysisStopped();
	ResetGame();
	if (InitializeBackgroundEngine()) {
		g_backgroundEngine.postMessage('go');
	}
	g_allMoves = [];
	RedrawBoard();

	if (!g_playerWhite) {
		SearchAndRedraw();
	}
}

function UIClose() {
	window.location = 'byond://?src=' + hSrc + ';close=1';
}

function EnsureAnalysisStopped() {
	if (g_analyzing && g_backgroundEngine != null) {
		g_backgroundEngine.terminate();
		g_backgroundEngine = null;
	}
}

function UIAnalyzeToggle() {
	if (InitializeBackgroundEngine()) {
		if (!g_analyzing) {
			g_backgroundEngine.postMessage('analyze');
		} else {
			EnsureAnalysisStopped();
		}
		g_analyzing = !g_analyzing;
		document.getElementById('AnalysisToggleLink').innerText = g_analyzing ? 'Analysis: On' : 'Analysis: Off';
	} else {
		alert('Your browser must support web workers for analysis - (chrome4, ff4, safari)');
	}
}

function UIChangeFEN() {
	if (!g_changingFen) {
		var fenTextBox = document.getElementById('FenTextBox');
		var result = InitializeFromFen(fenTextBox.value);
		if (result.length != 0) {
			UpdatePVDisplay(result);
			return;
		} else {
			UpdatePVDisplay('');
		}
		g_allMoves = [];

		EnsureAnalysisStopped();
		InitializeBackgroundEngine();

		g_playerWhite = !!g_toMove;
		g_backgroundEngine.postMessage('position ' + GetFen());

		RedrawBoard();
	}
}

function UIChangeStartPlayer() {
	g_playerWhite = !g_playerWhite;
	RedrawBoard();
}

function UpdatePgnTextBox(move) {
	var pgnTextBox = document.getElementById('PgnTextBox');
	if (g_toMove != 0) {
		pgnTextBox.value += moveNumber + '. ';
		moveNumber++;
	}
	pgnTextBox.value += GetMoveSAN(move) + ' ';
}

function UIChangeTimePerMove() {
	var timePerMove = document.getElementById('TimePerMove');
	g_timeout = parseInt(timePerMove.value, 10);
}

function FinishMove(bestMove, value, timeTaken, ply) {
	if (bestMove != null) {
		UIPlayMove(bestMove, BuildPVMessage(bestMove, value, timeTaken, ply));
	} else {
		window.location = 'byond://?src=' + hSrc + ';checkmate=1';
	}
}

function UIPlayMove(move, pv) {
	UpdatePgnTextBox(move);

	g_allMoves[g_allMoves.length] = move;
	MakeMove(move);

	UpdatePVDisplay(pv);

	UpdateFromMove(move);
}

function UIUndoMove() {
	if (g_allMoves.length == 0) {
		return;
	}

	if (g_backgroundEngine != null) {
		g_backgroundEngine.terminate();
		g_backgroundEngine = null;
	}

	UnmakeMove(g_allMoves[g_allMoves.length - 1]);
	g_allMoves.pop();

	if (g_playerWhite != !!g_toMove && g_allMoves.length != 0) {
		UnmakeMove(g_allMoves[g_allMoves.length - 1]);
		g_allMoves.pop();
	}

	RedrawBoard();
}

function UpdatePVDisplay(pv) {
	if (pv != null) {
		var outputDiv = document.getElementById('output');
		if (outputDiv.firstChild != null) {
			outputDiv.removeChild(outputDiv.firstChild);
		}
		outputDiv.appendChild(document.createTextNode(pv));
	}
}

function SearchAndRedraw() {
	if (g_analyzing) {
		EnsureAnalysisStopped();
		InitializeBackgroundEngine();
		g_backgroundEngine.postMessage('position ' + GetFen());
		g_backgroundEngine.postMessage('analyze');
		return;
	}

	if (InitializeBackgroundEngine()) {
		g_backgroundEngine.postMessage('search ' + g_timeout);
	} else {
		Search(FinishMove, 99, null);
	}
}

var g_backgroundEngineValid = true;
var g_backgroundEngine;

function InitializeBackgroundEngine() {
	if (!g_backgroundEngineValid) {
		return false;
	}

	if (g_backgroundEngine == null) {
		g_backgroundEngineValid = true;
		try {
			g_backgroundEngine = new Worker('garbochess.js');
			g_backgroundEngine.onmessage = function (e) {
				if (e.data.match('^pv') == 'pv') {
					UpdatePVDisplay(e.data.substr(3, e.data.length - 3));
				} else if (e.data.match('^message') == 'message') {
					EnsureAnalysisStopped();
					UpdatePVDisplay(e.data.substr(8, e.data.length - 8));
				} else {
					UIPlayMove(GetMoveFromString(e.data), null);
				}
			};
			g_backgroundEngine.error = function (e) {
				alert('Error from background worker:' + e.message);
			};
			g_backgroundEngine.postMessage('position ' + GetFen());
		} catch (error) {
			g_backgroundEngineValid = false;
		}
	}

	return g_backgroundEngineValid;
}

function UpdateFromMove(move) {
	var fromX = (move & 0xf) - 4;
	var fromY = ((move >> 4) & 0xf) - 2;
	var toX = ((move >> 8) & 0xf) - 4;
	var toY = ((move >> 12) & 0xf) - 2;

	if (!g_playerWhite) {
		fromY = 7 - fromY;
		toY = 7 - toY;
		fromX = 7 - fromX;
		toX = 7 - toX;
	}

	if (move & moveflagCastleKing || move & moveflagCastleQueen || move & moveflagEPC || move & moveflagPromotion) {
		RedrawPieces();
	} else {
		var fromSquare = g_uiBoard[fromY * 8 + fromX];
		$(g_uiBoard[toY * 8 + toX])
			.empty()
			.append($(fromSquare).children());
	}
}

function RedrawPieces() {
	for (y = 0; y < 8; ++y) {
		for (x = 0; x < 8; ++x) {
			var td = g_uiBoard[y * 8 + x];
			var pieceY = g_playerWhite ? y : 7 - y;
			var piece = g_board[(pieceY + 2) * 0x10 + (g_playerWhite ? x : 7 - x) + 4];
			var pieceName = null;
			switch (piece & 0x7) {
				case piecePawn:
					pieceName = 'pawn';
					break;
				case pieceKnight:
					pieceName = 'knight';
					break;
				case pieceBishop:
					pieceName = 'bishop';
					break;
				case pieceRook:
					pieceName = 'rook';
					break;
				case pieceQueen:
					pieceName = 'queen';
					break;
				case pieceKing:
					pieceName = 'king';
					break;
			}
			if (pieceName != null) {
				pieceName += '_';
				pieceName += piece & 0x8 ? 'white' : 'black';
			}

			if (pieceName != null) {
				var img = document.createElement('div');
				$(img).addClass('sprite-' + pieceName);
				img.style.backgroundImage = "url('sprites.png')";
				img.width = g_cellSize;
				img.height = g_cellSize;
				var divimg = document.createElement('div');
				divimg.appendChild(img);

				$(divimg).draggable({
					start: function (e, ui) {
						if (g_selectedPiece === null) {
							g_selectedPiece = this;
							var offset = $(this).closest('table').offset();
							g_startOffset = {
								left: e.pageX - offset.left,
								top: e.pageY - offset.top,
							};
						} else {
							return g_selectedPiece == this;
						}
					},
				});

				$(divimg).mousedown(function (e) {
					if (g_selectedPiece === null) {
						var offset = $(this).closest('table').offset();
						g_startOffset = {
							left: e.pageX - offset.left,
							top: e.pageY - offset.top,
						};
						e.stopPropagation();
						g_selectedPiece = this;
						g_selectedPiece.style.backgroundImage = "url('img/transpBlue50.png')";
					} else if (g_selectedPiece === this) {
						g_selectedPiece.style.backgroundImage = null;
						g_selectedPiece = null;
					}
				});

				$(td).empty().append(divimg);
			} else {
				$(td).empty();
			}
		}
	}
}

function RedrawBoard() {
	var div = $('#board')[0];

	var table = document.createElement('table');
	table.cellPadding = '0px';
	table.cellSpacing = '0px';
	$(table).addClass('no-highlight');

	var tbody = document.createElement('tbody');

	g_uiBoard = [];

	var dropPiece = function (e, ui) {
		var endX = e.pageX - $(table).offset().left;
		var endY = e.pageY - $(table).offset().top;

		endX = Math.floor(endX / g_cellSize);
		endY = Math.floor(endY / g_cellSize);

		var startX = Math.floor(g_startOffset.left / g_cellSize);
		var startY = Math.floor(g_startOffset.top / g_cellSize);

		if (!g_playerWhite) {
			startY = 7 - startY;
			endY = 7 - endY;
			startX = 7 - startX;
			endX = 7 - endX;
		}

		var moves = GenerateValidMoves();
		var move = null;
		for (var i = 0; i < moves.length; i++) {
			if ((moves[i] & 0xff) == MakeSquare(startY, startX) && ((moves[i] >> 8) & 0xff) == MakeSquare(endY, endX)) {
				move = moves[i];
			}
		}

		if (!g_playerWhite) {
			startY = 7 - startY;
			endY = 7 - endY;
			startX = 7 - startX;
			endX = 7 - endX;
		}

		g_selectedPiece.style.left = 0;
		g_selectedPiece.style.top = 0;

		if (!(startX == endX && startY == endY) && move != null) {
			UpdatePgnTextBox(move);

			if (InitializeBackgroundEngine()) {
				g_backgroundEngine.postMessage(FormatMove(move));
			}

			g_allMoves[g_allMoves.length] = move;
			MakeMove(move);

			UpdateFromMove(move);

			g_selectedPiece.style.backgroundImage = null;
			g_selectedPiece = null;

			var fen = GetFen();
			document.getElementById('FenTextBox').value = fen;

			setTimeout('SearchAndRedraw()', 0);
		} else {
			g_selectedPiece.style.backgroundImage = null;
			g_selectedPiece = null;
		}
	};

	for (y = 0; y < 8; ++y) {
		var tr = document.createElement('tr');

		for (x = 0; x < 8; ++x) {
			var td = document.createElement('td');
			td.style.width = g_cellSize + 'px';
			td.style.height = g_cellSize + 'px';
			td.style.backgroundColor = (y ^ x) & 1 ? '#D18947' : '#FFCE9E';
			tr.appendChild(td);
			g_uiBoard[y * 8 + x] = td;
		}

		tbody.appendChild(tr);
	}

	table.appendChild(tbody);

	$('body').droppable({ drop: dropPiece });
	$(table).mousedown(function (e) {
		if (g_selectedPiece !== null) {
			dropPiece(e);
		}
	});

	RedrawPieces();

	$(div).empty();
	div.appendChild(table);

	g_changingFen = true;
	document.getElementById('FenTextBox').value = GetFen();
	g_changingFen = false;
}