/*
 
 File:Puzzler.js
 
 Abstract: JavaScript properties for the Puzzler sample
 
 Version: <1.0>
 
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 */ 

/********************
Modified November 2007 by Beth Katz
- making numberOfBallChoices a variable instead of hard-coded 5
- made prefix of files a variable so that it can be easily changed
- added score field and calculation
- added a button to make it easier or harder toggling between 4 and 5
  ball choices
*********************/

 
//Puzzler draws a grid with 7 columns and 6 rows
var numberOfColumns = 7;
var numberOfRows = 6;

//The grid array contains numbers ranging from 1 to numberOfBallChoices, 
//which represent the different available ball images.
//1 = yellow ball
//2 = light blue ball
//3 = green ball
//4 = dark blue ball 
//5 = red ball

var grid = [];
var numberOfBallChoices = 5;
var lessVariety = 4;
var moreVariety = 5;
var filePrefix = "ball-";

//The selected array contains either true or false. True indicates that 
//the current cell is selected (a user clicked on the ball)
var selected = [];

//The dirty array contains either true or false values. True indicates 
//that the current cell contains a grey ball
var dirty = [];
var allowClicks = true;

//Score rewards larger blocks being removed
var score = 0;

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

// resets score to zero
function resetScore( )
{
    score = 0;
    document.score.field.value = score;
}

//adds amount to score
function updateScore(amount)
{
    score += amount;
    document.score.field.value = score;
}

//Initialize or Reinitialize the grid. Remove all balls on the grid.
function resetGrid()
{
    grid = new Array(numberOfColumns);
    selected = new Array(numberOfColumns);
    dirty = new Array(numberOfColumns);
    
    for( var column=0; column< numberOfColumns; column++ )
    {
          grid[column] = new Array(numberOfRows);
          selected[column] = new Array(numberOfRows);
          dirty[column] = new Array(numberOfRows);
          
          for( var row=0; row < numberOfRows; row++ )
          {
              //Generate numbers ranging from 1 to numberOfBallChoices randomly. 
              var ballNumber= 1 + 
                  Math.floor(Math.random() * numberOfBallChoices);
              grid[column][row] = ballNumber;
              
              //No ball is selected initially
              selected[column][row] = false;
              
              //The grid does not contain any grey balls initially
              dirty[column][row] = false;
          }
    }
    resetScore();
}


//Set up the game on the page using DOM elements
function setup()
{
    resetGrid();
    resetScore();
    
    var gridTable = document.getElementById('grid');
    //Remove any current ball on the grid 
    removeAllChildren(gridTable);
    
    //Loop thru the grid, Create numberOfRows rows, add them to the grid.
    //For each row, generate numberOfColumns columns that contain each an image
    for( var row=0; row < numberOfRows; row++ ) 
    {
        //Create a row 
        var gridRow = document.createElement('tr'); 
        
        //Create columns for the row generated above
        for( var column=0; column< numberOfColumns; column++ )
        {
              //Create a new column 
              var gridColumn = document.createElement('td');  
              
              //Create a new image 
              var img = document.createElement('img');        
              
              //Set the image attributes
              img.setAttribute("onclick", "click("+column+","+row+")");
              img.setAttribute("src", filePrefix+grid[column][row]+".png");
              img.setAttribute("id", column+"_"+row);
              img.setAttribute("numberOfColumns", 32);
              img.setAttribute("numberOfRows", 32);
              img.setAttribute("width", 40);
              img.setAttribute("height", 40);
              
              //Append the new image to this column 
              gridColumn.appendChild(img); 
              
              //Add this column to the curent row 
              gridRow.appendChild(gridColumn);          
        }
        //Add this row to the grid 
        gridTable.appendChild(gridRow);   
    }
}


// changes number of balls easier or harder
function changeDifficulty()
{
   if (numberOfBallChoices == lessVariety) {
      numberOfBallChoices = moreVariety;
      document.score.difficulty.value = "Easier";
   } else {
      numberOfBallChoices = lessVariety;
      document.score.difficulty.value = "Harder";
   }
   setup( );
}

//Update image at position represented by (column,row)
function updateCell(column,row)
{
    var newSrc;
    
    //Append a grey ball at the position given by (column, row) 
    //if the current ball is selected
    if( selected[column][row] )
    {
        newSrc = filePrefix+"sel.png";
    }    
    else 
    {
        //Append a ball at the position given by (column, row) 
        //if the current ball is not selected
        //The color of the ball is determined by grid[column][row], 
        //which returns a number ranging from 1 to 5
        newSrc = filePrefix+grid[column][row]+".png"
    }        
    document.images[column+"_"+row].src = newSrc;
    }


//Update all images on the grid 
function updateAllCells()
{
     //Loop thru all rows and columns, then update each image at position 
     //specified by column and row
    for( var row=0; row< numberOfRows; row++ ) 
    {
        for( var column= 0; column< numberOfColumns; column++ ) 
        {
            updateCell(column,row);
        }
    }
}


//Check the dirty array for any true value, if true is found at a position(column,row), update the associated cell
function updateAllDirtyCells()
{
    for( var row=0; row< numberOfRows; row++ )
    {
        for( var column=0; column< numberOfColumns; column++ )
        {
            if( dirty[column][row] ) 
            {
                //Place a grey ball at this position
                updateCell(column, row);
                dirty[column][row]= false;
            }
        }
    }
}


//Remove all selected balls on the grid 
function removeSelectedCells()
{
    var numRemoved = 0;

    for( var row=0; row< numberOfRows; row++ ) 
    {
        for( var column=0; column< numberOfColumns; column++ )
        {
            if( selected[column][row] ) 
            {
                //Remove the ball at this position
                grid[column][row] = 0;
                selected[column][row] = false;
                dirty[column][row] = true;
                numRemoved++;
            }
        }
    }
    updateScore(numRemoved*numRemoved);
}


//Look for empty cells along the vertical axis on the grid 
function fallDown()
{
    var fallTo,foundGap;
    for( var column= numberOfColumns-1; column >= 0; column-- ) 
    {
        //Indicate whether a ball at a given position is grey 
        foundGap = false;
        for( var row= numberOfRows-1; row >= 0; row-- )
        {
             //Check if cell at position(column,row) is empty
            if( grid[column][row] == 0 ) 
            {
                if( ! foundGap )
                {
                    //Get position (along the vertical axis) of the cell 
                    //that contains a grey ball 
                    fallTo = row;
                    foundGap = true;
                }
            }
            else 
            { 
                 //If cell contains a ball, check if the ball is grey 
                if( foundGap ) 
                {
                    //Insert a new ball at this position  
                    grid[column][fallTo] = grid[column][row];
                    grid[column][row] = 0;
                    dirty[column][fallTo] = true;
                    dirty[column][row] = true;
                    fallTo -= 1;
                }
            }
        }
    }
}


//Look for empty cells along the horizontal axis on the grid 
function fallRight()
{
    var fallTo,foundGap;
    for( var row= numberOfRows-1; row >= 0; row-- )
    {
        //Indicate whether a ball at a given position is grey 
        foundGap = false;
        for( var column= numberOfColumns-1; column >= 0; column-- ) 
        {
            //Check if cell at position(column,row) is empty
            if( grid[column][row] == 0 ) 
            {
                if( ! foundGap ) 
                { 
                    // Get position (along the horizontal axis) of the cell 
                    // that contains a grey ball
                    fallTo = column;
                    foundGap = true;
                }
            }
            else 
            { 
                //Check if cell at position(column,row) contains a grey ball
                if( foundGap) 
                {
                    //Insert a new ball at this position  
                    grid[fallTo][row] = grid[column][row];
                    grid[column][row] = 0;
                    dirty[fallTo][row] = true;
                    dirty[column][row] = true;
                    fallTo -= 1;
                }
            }
        }
    }
}


//Unselect all balls on the grid 
function deselectAllCells()
{
    for( var row= 0; row < numberOfRows; row++ ) 
    {
        for( var column= 0; column < numberOfColumns; column++ ) 
        {
            //Remove position from the selected array 
            if( selected[column][row] ) 
            {
                selected[column][row] = false;
                
                //Set value to true, so grey ball can be added at that position
                dirty[column][row] = true;
            }
        }
    }
}


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


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


//Update cells along the horizontal axis
function fallRightAndAllowClicks()
{
    fallRight();
    updateAllDirtyCells();
    allowClicks = true;
}


//Update all cells on the grid
function fallDownThenFallRightAndAllowClicks()
{
    fallDown();
    updateAllDirtyCells();
    fallRightAndAllowClicks();
}


//Handle clicks on the grid 
function click(column, row)
{
    if( ! allowClicks )
    {
        return;
    } 
    
    // if a given cell is selected
    if( selected[column][row] )
    {
        // remove all selected cells
        removeSelectedCells();
        
        //Check the grid for selected values, then add grey balls at their positions
        updateAllDirtyCells();
        
        allowClicks = false;
        setTimeout("fallDownThenFallRightAndAllowClicks();", 100);
    }
    else if( grid[column][row] != 0 )
    {   
        //If a given cell is not selected, but contains a ball, deselect all cells
        deselectAllCells();
        
        //Check whether there is an adjacent cell of the same color
        if( cellHasIdenticalNeighbour(column,row ))
        {
            //select all contiguous cells of the same color
            selectCellAndContiguousCells( grid[column][row], column, row);
        } 
        updateAllDirtyCells();
    }
}