/*
 
 File:Puzzler.js
 
 Abstract: JavaScript for the index.html file
 
 Version: <1.0>
 
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 install, modify or redistribute this Apple software.
 
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 Neither the name, trademarks, service marks or logos of Apple Inc. 
 may be used to endorse or promote products derived from the Apple
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 The Apple Software is provided by Apple on an "AS IS" basis.  APPLE
 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
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 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.
 
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 */ 
 
 // Set up basic in-game variables
// The number of columns (numberOfColumns) and rows (numberOfRows) of the game. 
//The grid array contains numbers ranging from 1 to 5, which represent the different ball images.
//The selected array contains either true or false. True indicates that the current cell is selected.
//The dirty array contains either true or false values. True indicates that the current cell contains a grey ball. 

var numberOfColumns = 7;
var numberOfRows = 7;

var grid = [];
var selected = [];
var dirty = [];
var allowClicks = true;


//Remove all elements of the grid
function removeAllChildren (parent)
{
	while (parent.hasChildNodes()) {
		parent.removeChild(parent.firstChild);
	}
}

//Reset the grid
function resetGrid()
{

	grid = new Array(numberOfColumns);
	selected = new Array(numberOfColumns);
	dirty = new Array(numberOfColumns);
	
	for( var x = 0; x < numberOfColumns; x++ ) {
		grid[x] = new Array(numberOfRows);
		selected[x] = new Array(numberOfRows);
		dirty[x] = new Array(numberOfRows);
		
		for( var y = 0; y < numberOfRows; y++ ) {
			grid[x][y] = 1 + Math.floor(Math.random() * 5);
			selected[x][y] = false;
			dirty[x][y] = false;
		}
	}
}

//Set up the game on the page using DOM elements
function setup()
{
	resetGrid();
	
	var gridTable = document.getElementById('grid');
	removeAllChildren(gridTable);
	for( var y = 0; y < numberOfRows; y++ ) {
		var row = document.createElement('tr');
		for( var x = 0; x < numberOfColumns; x++ ) {
			var col = document.createElement('td');
			var img = document.createElement('img');
			img.setAttribute("onclick", "click("+x+","+y+")");
			img.setAttribute("src", "ball-"+grid[x][y]+".png");
			img.setAttribute("id", x+"_"+y);
			img.setAttribute("numberOfColumns", 32);
			img.setAttribute("numberOfRows", 32);
			img.setAttribute("width", 44);
			img.setAttribute("height", 44);
			col.appendChild(img);
			
			row.appendChild(col);
		}
		gridTable.appendChild(row);
	}
}

//Update image at position represented by (x,y)
function updateCell(x, y)
{
    var newSrc;
	if( selected[x][y] ){
        newSrc = "ball-sel.png";
    }    
    else {
        newSrc = "ball-"+grid[x][y]+".png"
    }    
        
	document.images[x+"_"+y].src = newSrc;
}


//Update all images on the grid
function updateAllCells()
{
	for( var y = 0; y < numberOfRows; y++ ) {
		for( var x = 0; x < numberOfColumns; x++ ) {
			updateCell(x, y);
		}
	}
}


function updateAllDirtyCells()
{
	for( var y = 0; y < numberOfRows; y++ ) {
		for( var x = 0; x < numberOfColumns; x++ ) {
			if( dirty[x][y] ) {
				updateCell(x, y);
				dirty[x][y] = false;
			}
		}
	}
}

function removeSelectedCells()
{

	for( var y = 0; y < numberOfRows; y++ ) {
		for( var x = 0; x < numberOfColumns; x++ ) {
			if( selected[x][y] ) {
				grid[x][y] = 0;
				selected[x][y] = false;
				dirty[x][y] = true;
			}
		}
	}
}


function fallDown()
{

    var fallTo,foundGap;
	for( var x = numberOfColumns-1; x >= 0; x-- ) {
		foundGap = false;
		for( var y = numberOfRows-1; y >= 0; y-- ) {
			if( grid[x][y] == 0 ) {
				if( ! foundGap ) {
					fallTo = y;
					foundGap = true;
				}
			}
			else { // grid occupied
				if( foundGap ) {
					grid[x][fallTo] = grid[x][y];
					grid[x][y] = 0;
					dirty[x][fallTo] = true;
					dirty[x][y] = true;
					fallTo -= 1;
				}
			}
		}
	}
}


function fallRight()
{

     var fallTo,foundGap;
	for( var y = numberOfRows-1; y >= 0; y-- ) {
	    foundGap = false;
		for( var x = numberOfColumns-1; x >= 0; x-- ) {
			if( grid[x][y] == 0 ) {
				if( ! foundGap ) {
					fallTo = x;
					foundGap = true;
				}
			}
			else { // grid occupied
				if( foundGap ) {
					grid[fallTo][y] = grid[x][y];
					grid[x][y] = 0;
					dirty[fallTo][y] = true;
					dirty[x][y] = true;
					fallTo -= 1;
				}
			}
		}
	}
}

function deselectAllCells()
{
	for( var y = 0; y < numberOfRows; y++ ) {
		for( var x = 0; x < numberOfColumns; x++ ) {
			if( selected[x][y] ) {
				selected[x][y] = false;
				dirty[x][y] = true;
			}
		}
	}
}

//Determines whether each of the 4 neighbors(top,bottom,left, and right) of a
//cell is equal to that current cell
function cellHasIdenticalNeighbour(x, y)
{
	var cell = grid[x][y];
	if( ( x+1 < numberOfColumns  && cell == grid[x+1][y] )
	 || ( x-1 >= 0     && cell == grid[x-1][y] )
	 || ( y+1 < numberOfRows && cell == grid[x][y+1] )
	 || ( y-1 >= 0     && cell == grid[x][y-1] ) ) {
		return true;
	}
	else {
		return false;
	}
}

//Select all contiguous cells of the same color
function selectCellAndContiguousCells(cell, x, y)
{
	if( x >= 0 && x < numberOfColumns && y >= 0 && y < numberOfRows ) {
		if( cell == grid[x][y] && ! selected[x][y] ) {
			selected[x][y] = true;
			dirty[x][y] = true;
			selectCellAndContiguousCells( cell, x+1, y );
			selectCellAndContiguousCells( cell, x-1, y );
			selectCellAndContiguousCells( cell, x, y+1 );
			selectCellAndContiguousCells( cell, x, y-1 );
		}
	}
}

function fallRightAndAllowClicks()
{
	fallRight();
	updateAllDirtyCells();
	allowClicks = true;
}


function fallDownThenFallRightAndAllowClicks()
{
	fallDown();
	updateAllDirtyCells();
    fallRightAndAllowClicks();

}

function click(x, y)
{
	// - if a given cell is selected:
	//   - remove all the selected cells
	//   - fall down
	//   - fall right
	//   - if the bottom-left cell is empty, add another (partial) column on the left and let it fall right
	// - if that cell is not selected, but is occupied:
	//   - deselect all cells
	//   - if there is an adjacent cell of the same color
	//     - select all contiguous cells of the same color
	
	if( ! allowClicks ){
		return;
	}	
	
	if( selected[x][y] ) {
		removeSelectedCells();
		updateAllDirtyCells();

		allowClicks = false;
		setTimeout("fallDownThenFallRightAndAllowClicks();", 100);
	}
	else if( grid[x][y] != 0 ) {
		deselectAllCells();
		if( cellHasIdenticalNeighbour( x, y ) ){
			selectCellAndContiguousCells( grid[x][y], x, y );
		}	
		updateAllDirtyCells();
	}
}