/*

TODO:

    Limit number input

    Disallow . from being entered multiple times

    Clean up structure

*/

(function() {

  "use strict";

  // Shortcut to get elements

  var el = function(element) {

    if (element.charAt(0) === "#") { // If passed an ID...

      return document.querySelector(element); // ... returns single element

    }

    return document.querySelectorAll(element); // Otherwise, returns a nodelist

  };

  // Variables

  var viewer = el("#viewer"), // Calculator screen where result is displayed

    equals = el("#equals"), // Equal button

    nums = el(".num"), // List of numbers

    ops = el(".ops"), // List of operators

    theNum = "", // Current number

    oldNum = "", // First number

    resultNum, // Result

    operator; // Batman

  // When: Number is clicked. Get the current number selected

  var setNum = function() {

    if (resultNum) { // If a result was displayed, reset number

      theNum = this.getAttribute("data-num");

      resultNum = "";

    } else { // Otherwise, add digit to previous number (this is a string!)

      theNum += this.getAttribute("data-num");

    }

    viewer.innerHTML = theNum; // Display current number

  };

  // When: Operator is clicked. Pass number to oldNum and save operator

  var moveNum = function() {

    oldNum = theNum;

    theNum = "";

    operator = this.getAttribute("data-ops");

    equals.setAttribute("data-result", ""); // Reset result in attr

  };

  // When: Equals is clicked. Calculate result

  var displayNum = function() {

    // Convert string input to numbers

    oldNum = parseFloat(oldNum);

    theNum = parseFloat(theNum);

    // Perform operation

    switch (operator) {

      case "plus":

        resultNum = oldNum + theNum;

        break;

      case "minus":

        resultNum = oldNum - theNum;

        break;

      case "times":

        resultNum = oldNum * theNum;

        break;

      case "divided by":

        resultNum = oldNum / theNum;

        break;

        // If equal is pressed without an operator, keep number and continue

      default:

        resultNum = theNum;

    }

    // If NaN or Infinity returned

    if (!isFinite(resultNum)) {

      if (isNaN(resultNum)) { // If result is not a number; set off by, eg, double-clicking operators

        resultNum = "You broke it!";

      } else { // If result is infinity, set off by dividing by zero

        resultNum = "Look at what you've done";

        el('#calculator').classList.add("broken"); // Break calculator

        el('#reset').classList.add("show"); // And show reset button

      }

    }

    // Display result, finally!

    viewer.innerHTML = resultNum;

    equals.setAttribute("data-result", resultNum);

    // Now reset oldNum & keep result

    oldNum = 0;

    theNum = resultNum;

  };

  // When: Clear button is pressed. Clear everything

  var clearAll = function() {

    oldNum = "";

    theNum = "";

    viewer.innerHTML = "0";

    equals.setAttribute("data-result", resultNum);

  };

  /* The click events */

  // Add click event to numbers

  for (var i = 0, l = nums.length; i < l; i++) {

    nums[i].onclick = setNum;

  }

  // Add click event to operators

  for (var i = 0, l = ops.length; i < l; i++) {

    ops[i].onclick = moveNum;

  }

  // Add click event to equal sign

  equals.onclick = displayNum;

  // Add click event to clear button

  el("#clear").onclick = clearAll;

  // Add click event to reset button

  el("#reset").onclick = function() {

    window.location = window.location;

  };

}());