/* 
   "guessing.js" is a simple guessing game written to introduce students to
   the basics of game programming. Written by David Johnston in 2016 whilst
   employed by the NSW Department of Education.
*/

// game constants -------------------------------------------------------------

const TITLE = "Guessing Game";
const MAXNUM = 20;
const CLUELOWER = "It's lower than that.";
const CLUEHIGHER = "It's higher than that.";
const REPSUCCESS = "Yes! You got it!";
const REPINIT = "Guess the correct number before your score reaches zero!";
const NAIREPLY = "That doesn't appear to be an integer. Try again.";

   // insults at: [http://goo.gl/AH99cv] datahamster.com/autoinsult/
   
const R00 = "Ha! Ha! You're wrong!";
const R01 = "Nope! Try again.";
const R02 = "Sigh. You're not very good at this.";

const ENTERKEY = 13;              // the keycode for the enter key

// game variables -------------------------------------------------------------

var theNumber = Math.floor(Math.random() * MAXNUM);
var guess = "0";  // will be *string* entered by player
var score = MAXNUM; //score counts down from this number
var replies = [R00, R01, R02];
var repliesIndex = 0;
var comment = "This will be changed later in the code.";
var gameIsOver = false;

// get and setup the page title -----------------------------------------------

var pageTitle = document.getElementById("pageTitle");
pageTitle.innerHTML = TITLE;

var headingArea = document.getElementById("headingArea");
headingArea.innerHTML = TITLE;

// get and setup (if needed) the other page elements --------------------------

var scoreArea = document.getElementById("scoreArea");
scoreArea.innerHTML = "Score: " + MAXNUM;

var instructionArea = document.getElementById("instructionArea");
instructionArea.innerHTML = "Guess an integer between 0 and " + MAXNUM + ".";

var playArea = document.getElementById("playArea");

var commentArea = document.getElementById("commentArea");
commentArea.innerHTML = REPINIT;

var guessField = document.getElementById("guessField");
var guessLength = ((MAXNUM.toString()).length).toString();
guessField.setAttribute("maxlength", guessLength);
guessField.setAttribute("size", guessLength);

var guessButton = document.getElementById("guessButton");
guessButton.setAttribute("onclick","checkGuess()");

var resetButton = document.getElementById("resetButton");
resetButton.setAttribute("onclick","location.reload()");

// listen for the enter key ---------------------------------------------------

document.onkeyup = checkLift;
function checkLift(e)
{
   if (e.keyCode === ENTERKEY)
      checkGuess();      
}

// give the guess field the focus ---------------------------------------------

window.onload = selectGuessField;
function selectGuessField()
{
   guessField.select();
   guessField.focus();
}

// the game "loop" ------------------------------------------------------------

function checkGuess()
{   
   // ***** get inputs *****
   
   guess = parseFloat(guessField.value);
   
   // ***** calculate new state *****
   
   if (Number.isInteger(guess)) // an integer was entered
   {
      if (guess == theNumber) // the guess was correct (collision detection)
      {
         comment = REPSUCCESS;
         gameIsOver = true;
      }
      else // the guess was incorrect
      {
         repliesIndex = Math.floor(Math.random() * replies.length);
         score = score - 1;
      
         if (guess > theNumber) // the guess is too large
         {
            comment = replies[repliesIndex] + " " + CLUELOWER;
         }
         else // the guess must be too small (equality is already handled)
         {
            comment = replies[repliesIndex] + " " + CLUEHIGHER;
         }
      }
   }
   else // an integer was not entered
   {
      comment = NAIREPLY;  
   }
   
   // ***** render new state *****
   
   commentArea.innerHTML = comment;
   scoreArea.innerHTML = "Score: " + score;
   
   if (gameIsOver)
   {
      playArea.innerHTML = "▶ ▶ ▶  " 
         + guess + "  ◀ ◀ ◀";
   }
   else
   {
      selectGuessField();
   }
}