function JSEval (code) {
  try {
    return eval(code);
  } catch (err) {
    console.error(err);
  }
}

function supportsVB () {
  return typeof window.VBSEval === 'unknown' && typeof window.VBSExecute === 'unknown'
}

window.onload = function () {
  var output = document.getElementById("output");
  var input = document.getElementById("input");
  var languageSelect = document.getElementById("languageselect");
  var runButton = document.getElementById("runbutton");
  var clearButton = document.getElementById("clearbutton");

  if (!String.prototype.trim) {
    var _r = /(^\s+|\s+$)/g;
    String.prototype.trim = function () {
      return this.replace(_r, '');
    }
  }

  function removeCarriageReturns (value) {
    return value.replace(/\r/g, '');
  }

  function getSelectedText (element) {
    if (typeof element.selectionStart === 'number' && typeof element.selectionEnd === 'number') {
      return element.value.substring(element.selectionStart, element.selectionEnd);
    }
    var range = document.selection.createRange();
    if (!range || range.parentElement() !== element) return '';
    
    var normalizedValue = removeCarriageReturns(element.value);
    
    var inputRange = element.createTextRange();
    inputRange.moveToBookmark(range.getBookmark());
    
    var endRange = element.createTextRange();
    endRange.collapse(false);
    
    // Selection begins at the end of the input, so it's empty
    if (inputRange.compareEndPoints('StartToEnd', endRange) > -1) return '';
    
    var start = -inputRange.moveStart('character', -element.value.length);
    start += normalizedValue.slice(0, start).split('\n').length - 1;
    
    var end = element.value.length;
    if (inputRange.compareEndPoints('EndToEnd', endRange) < 0) {
      end = -inputRange.moveEnd('character', -element.value.length);
      end += normalizedValue.slice(0, end).split('\n').length - 1;
    }
    
    return element.value.substring(start, end)
  }

  // Try to output something cleanly as a string despite IE's disagreement.
  // TODO: Cool object output and errors with stack traces?
  function tryString (value) {
    try {
      return removeCarriageReturns(new String(value).toString());
    } catch (err) {
      // Give up, just print the type.
      return '[' + typeof value + ']';
    }
  }

  var originalConsole = window.console;
  window.console = {};

  function makeLogger (name, color) {
    return function () {
      if (originalConsole && originalConsole[name] && originalConsole[name].apply) originalConsole[name].apply(originalConsole, arguments);
      var entry = document.createElement('div');
      entry.style.margin = '0';
      entry.style.padding = '1px';
      entry.style.borderBottom = '1px solid lightgray';
      if (color) entry.style.color = color;
      var outputText = '';
      for (var i = 0; i < arguments.length; i++) {
        outputText += tryString(arguments[i]);
        if (i + 1 !== arguments.length) outputText += ' ';
      }
      entry.appendChild(document.createTextNode(outputText));
      output.appendChild(entry);
      entry.scrollIntoView();
    }
  }

  console.log = makeLogger('log');
  console.debug = makeLogger('debug', 'darkgray');
  console.info = makeLogger('info');
  console.warn = makeLogger('warn', 'orange');
  console.error = makeLogger('error', 'red');

  console.assert = function (assertion) {
    if (assertion) return;
    var argArray = Array.prototype.slice.call(arguments);
    argArray.shift();
    console.error.apply(null, argArray);
  }

  console.trace = function () {
    var current = arguments.callee.caller;
    var stack = 'console.trace(): \n ';
    while (current) {
      try {
        var funcString = current.toString();
        funcString = funcString.substring(funcString.indexOf('function') + 8);
        stack += funcString.substring(0, funcString.indexOf('(')).trim() || 'anonymous';
      } catch (err) {
        stack += 'unknown function';
      }
      stack += '\n ';
      current = current.caller;
    }
    console.log(stack.trim());
  }
  
  console.clear = function () {
    if (originalConsole && originalConsole.clear) {
      if (originalConsole.clear.apply) originalConsole.clear.apply(originalConsole, arguments);
      else originalConsole.clear();
    }
    output.innerHTML = "";
  }

  var inputLogger = makeLogger('log', 'lightblue');
  function run () {
    var code = getSelectedText(input) || input.value;
    if (!code.trim()) return;

    inputLogger(code);
    try {
      switch (languageSelect.value) {
        case 'js':
          result = JSEval(code);
          break;
        case 'vbs-eval':
          result = VBSEval(code);
          break;
        case 'vbs-execute':
          result = VBSExecute(code);
          break;
        default:
          console.error('Unsupported language', languageSelect.value);
          return;
      }
      console.log(result);
    } catch (err) {
      console.error(err);
    }
  }

  input.onkeypress = function (event) {
    if (!event) event = window.event;
    // Run code if Shift+Enter is pressed
    if (event && event.keyCode === 13 && event.shiftKey) {
      event.cancelBubble = true;
      event.returnValue = false;
      if (event.stopPropagation) event.stopPropagation();
      if (event.preventDefault) event.preventDefault();
      run();
    }
  }

  languageSelect.onchange = function () {
    switch (languageSelect.value) {
      case 'js':
        languageSelect.setAttribute('placeholder', 'Type some JavaScript to run and press Shift+Enter');
        break;
      case 'vbs-eval':
        languageSelect.setAttribute('placeholder', 'Type a VBScript expression to evaluate and press Shift+Enter');
        break;
      case 'vbs-execute':
        languageSelect.setAttribute('placeholder', 'Type some VBScript to run and press Shift+Enter');
        break;
      default:
        languageSelect.setAttribute('placeholder', 'Type the name of a demonic entity to summon and press Shift+Enter');
        break;
    }
  }

  runButton.onclick = run;
  clearButton.onclick = console.clear;

  if (/MSIE 7.0/.test(navigator.userAgent)) {
    /*
     * For some reason, IE 7 messes up the textarea's width and height
     * pretty badly. We hardcode the height, removing a little margin,
     * and add some margin to the output.
     * Setting the input's width causes it to somehow divide itself by 2
     * on every keystroke.
     */
    input.style.height = document.documentElement.clientHeight - 7 + 'px';
    output.style.marginLeft = '7px';
  }

  if (!supportsVB()) {
    for (var i = 0; i < languageSelect.children.length; i++) {
      if (languageSelect.children[i].value.slice(0, 3) === 'vbs') {
        languageSelect.children[i].disabled = true;
        languageSelect.children[i].title = 'VBScript is not supported in this browser.';
      }
    }
  }
}

// Try to detect the wizard extensions.
if (supportsVB() && InWebWizard()) {
  window.external.SetHeaderText('Windows Scripting Console', "Explore this wizard's scripting environment.");
  window.external.SetWizardButtons(1, 0, 0);
  // An onback function is required by the web wizard specification
  window.onback = function () {
    window.external.FinalBack();
  }
}