var game_board = clear_board();
var last_symbol_played="";
var latest_position;

//GUI FUNCTIONS START HERE
function disable_buttons(){


  $('#r0c0').attr('disabled','disabled');
  $('#r0c1').attr('disabled','disabled');
  $('#r0c2').attr('disabled','disabled');
  $('#r1c0').attr('disabled','disabled');
  $('#r1c1').attr('disabled','disabled');
  $('#r1c2').attr('disabled','disabled');
  $('#r2c0').attr('disabled','disabled');
  $('#r2c1').attr('disabled','disabled');
  $('#r2c2').attr('disabled','disabled');
  
 
  
}
function draw_board(board){
  //var new_board=remove_underscores(board);
  var positions=get_position(board);
 
  for (var i in positions){
    if (positions[i]==="_"){
      $('#'+i).html(" ");
    }
    else{
    $('#'+i).html(positions[i]);
    }
  }
  
}
function enable_buttons(){
   $('#r0c0').removeAttr('disabled');
  $('#r0c1').removeAttr('disabled');
  $('#r0c2').removeAttr('disabled');
  $('#r1c0').removeAttr('disabled');
  $('#r1c1').removeAttr('disabled');
  $('#r1c2').removeAttr('disabled');
  $('#r2c0').removeAttr('disabled');
  $('#r2c1').removeAttr('disabled');
  $('#r2c2').removeAttr('disabled'); 
}
function start(){
  $("#choice").addClass('hidden');
  $("#box_area").removeClass('hidden');
   $("#reset_area").removeClass('hidden');
  enable_buttons();

  var comp_symbol = flip_symbol($('input[name=selection]:checked').val());
 // $('#quack').html(comp_symbol);
  var done=false;
  
  computer_play_handler(comp_symbol);
  

/*have button to start
option to choose x and o
ALL code should happen here
don't change any other functions
*/
  
}
function computer_play_handler(comp_symbol){
  var comp_symbol;
   if (last_symbol_played.length === 0){
 //   comp_symbol="x";
   }
  else{
    comp_symbol=flip_symbol(last_symbol_played);
  }
  
    //5 seconds delay and display a "spinner" that shows the computer is thinking
    var move=next_move(comp_symbol,game_board);
   
    if (move!==-1){
      var cp=play(comp_symbol,move,game_board);
      
      game_board=cp;
      last_symbol_played=comp_symbol;
      
      draw_board(game_board);
      //5 seconds delay and display a "spinner" that shows the computer is thinking
    } 
   if (winner(game_board)==="x" || winner(game_board)==="o"){
    // $("#box_area").addClass('hidden');
     disable_buttons();

    beep.play();  
  }
  
}
function play_handler(id){
  var position={};
  position['r0c0']=0;
  position['r0c1']=1;
  position['r0c2']=2;
  position['r1c0']=3;
  position['r1c1']=4;
  position['r1c2']=5;
  position['r2c0']=6;
  position['r2c1']=7;
  position['r2c2']=8;
  
  latest_position=position[id];
  
  var cp;
  var new_symbol;
 
  if (last_symbol_played.length === 0){
    new_symbol="x";
    cp=play(new_symbol,latest_position,game_board)
  }
  else {
    new_symbol=flip_symbol(last_symbol_played);
    cp=play(new_symbol,latest_position,game_board)
  }
  if (cp!==null){
    last_symbol_played=new_symbol;
    game_board=cp;//this may need to be taken out
  }
  
  if (winner(game_board)==="x" || winner(game_board)==="o"){
    
    draw_board(game_board); //this may be a new function that will draw a line through teh winning board
    
    beep.play();  
    
  }
  else{
    draw_board(cp);
    computer_play_handler();
    
    
  }

  //
  
  
}
function get_position(board){
  
  var position={};
  position['r0c0']=board[0];
  position['r0c1']=board[1];
  position['r0c2']=board[2];
  position['r1c0']=board[3];
  position['r1c1']=board[4];
  position['r1c2']=board[5];
  position['r2c0']=board[6];
  position['r2c1']=board[7];
  position['r2c2']=board[8];
  
  return position;
}
function tester(){
  //var board=["x","x","x","x","_","o","x","o","x"]
  play_handler();
  location=3;
  //draw_board(board);
  //clear_board(board);
  
}
//GUI FUNCTIONS END HERE
//ENGINE FUNCTIONS START HERE
function reset(){
  game_board=clear_board();
  draw_board(game_board);
  last_symbol_played="";
  $("#choice").removeClass('hidden');
  $("#box_area").addClass('hidden');
  $("#reset_area").addClass('hidden');
  
}
function flip_symbol(symbol){
  if (symbol==="_"){return "_";}
  if (symbol==="x"){  
    symbol="o";
  }
  else{
    symbol="x"
  }
  return symbol;
}
function show_initial_board(){
  //game_board=clear_board();
  //draw_board(game_board);
  disable_buttons();

    
   //     $("#box_area").hide();


  
  
}
function play(symbol,location,board){
  //play (symbol, location, board) updates the board with the symbol returns the updated board. return null if board cannot be updated 

  var new_board=[];
  for (var i in board){
    new_board.push(board[i]);
  }
  if (board[location] === "_"){
    new_board[location]=symbol;
    
  }
  else{
    new_board=null;
  }
  //console.log(new_board);
  return new_board;
  
}
function winner(board) {
  // returns x or o if one of them  is a winner - if not returns null
  var result=null;
  var i=0;
  var done=false;
  var all_wins=['012','345','678','036','147','258','048','246'];
  while (!done && i < all_wins.length){
    var a=Number(all_wins[i][0]);
    var b=Number(all_wins[i][1]);
    var c=Number(all_wins[i][2]);
   
   if (board[a]===board[b] && board[b]===board[c] && board[a]!=="_" ){
     done=true;
     result=board[a];    
     
   }
      i++
   
  }

  return result;
}
function next_move(symbol,board){

  var move=-1;
  /*The following may appear strange but I am doing so because javascript objects are mutable
   if board is an object which it is (it is an array and arrays are objects) and I use:
   var new_board=board; 
   new_board is not a copy of board. It is board. Both point to the same object. Any changes to new_board will also change board, because they are the same object. For the CS kinds this is pass by reference not pass by value
  */
  var new_board=[];
  for (var i in board){
    new_board.push(board[i]);
  }

  var os=open_slots(new_board);
  
  if (os.length===0){
    return null;
  }
  
  //console.log(os.length)
  var done=false;
  var i=0;
  
  while (i<os.length && !done){
     
      if(symbol===winner(play(symbol,os[i],new_board))){
        
        done=true;
        move=os[i];
       
      }
    
           
      i++ ;
  }
    
  if (move ===-1) {
    symbol=flip_symbol(symbol);
    i=0;
     while (i<os.length && !done){
     
      if(symbol===winner(play(symbol,os[i],new_board))){
        done=true;
        move=os[i];
       
      }
    
           
      i++ ;
     }
     	
  }
  //code is not elegant
  if (move===-1){
    for (var i in os){
      if (os[i]===4){
        move=os[4]
      }
    }
    if (move===-1){
      move=os[0];
    }
  }

  return move;
}
function clear_board(){
  
  game_board=["_","_","_","_","_","_","_","_","_"];
  
  return game_board;
}
function open_slots(board){
  //board=["x","_","x","_","o","_","_","_","_"];
  var open_slots=[];
  for (var i=0; i<board.length; i++){
    if(board[i] === "_"){
      open_slots.push(i);
    }
    
  }

  return open_slots;
}