/* copyright Mingyi Liu 2004-06

This javascript creates the "auto-complete" behavior for web forms
displayed in Internet Explorer (one may call the behavior "type-ahead", "find-as-you-type" etc.

This script is freeware by author Mingyi Liu and comes with no warranty whatsoever.
in no case should the author be held liable for anything including loss/damage of any
kind as the result of using this script.

The author hereby grants you license to freely distribute or modify the scriipt
for whatever purposes.  For any bug report or feature request, please send
email to mingyiliu@yahoo.com

This version is 1.1.
*/

var ml_autocomplete = {
  keyTime : null,
  keyStr : '',
  allOpts : null,
  lastElement : null,
  onChange : null, // callback function reference
  delay : 500, // do type-ahead if two keys were pressed within 500 milliseconds (0.5 second, one can change this value for customization)
  
  populate : function(srcEvent)
  {
    var element = (srcEvent)? ((srcEvent.target)? srcEvent.target : srcEvent.srcElement) : window.event.srcElement;
    if(this.lastElement != element)
    {
      this.allOpts = new Array();
      for(var i = 0; i < element.options.length; i++)
        this.allOpts[i] = element.options[i].text.toLowerCase();
      this.lastElement = element;
    }
  },
  setSelection : function(srcEvent)
  {
    var myEvent = (srcEvent)? srcEvent : window.event;
    var element = (myEvent.target)? myEvent.target : myEvent.srcElement;
    var keyCode = myEvent.keyCode;
    if(keyCode == 13 && this.onChange)
    {
      this.onChange(element.value);
      this.keyTime = null; // reset time after enter key's pressed
      return;
    }
    // messy JS keycodes force me to preprocess. Note: I use a US keyboard, other keyboards may vary?
    if((keyCode > 47 && keyCode < 58) || (keyCode > 64 && keyCode < 91 || keyCode == 32)) ; // space or alphanumerical characters, leave them alone
    else if(keyCode > 95 && keyCode < 106) keyCode -= 48; // keypad numbers
    else if(keyCode > 105 && keyCode < 112) keyCode -= 64; // keypad '+', '-', '/', '*', '.'
    else if(keyCode > 187 && keyCode < 192) keyCode -= 144; // '/', '.', ',', '-'
    else if(keyCode > 218 && keyCode < 222) keyCode -= 128; // '\', '[', ']'
    else
    {
      switch(keyCode)
      {
        case 187: keyCode = 61; break; // '='
        case 222: keyCode = 39; break; // '''
        case 192: keyCode = 96; break; // '`'
        case 186: keyCode = 59; break; // ';'
        default: return; // do not process non printable characters (unfortunately backspace cannot be supported because browsers like IE interpret backspace as go back a page in history)
      }
    }
    var currentKey = String.fromCharCode(keyCode).toLowerCase();
    var idx, currentSIdx = element.selectedIndex, useOld = false;
    var newTime = new Date().getTime();
    if(this.keyTime != null && newTime - this.keyTime < this.delay) 
    {
      this.keyStr += currentKey;
      idx = this.findIdx(currentSIdx);
      if(idx == -1)
      {
        this.keyTime = newTime;
        return; // not found, keep current selection then (leave the incorrect keyStr alone)
      }
    }
    else // handle default browser behavior
    {
      this.keyStr = currentKey;
      idx = this.findIdx(currentSIdx);
    }
    if(idx >= 0) // if keyStr is found in an option, select the option
    {
      if(currentSIdx >= 0) element.options[currentSIdx].selected = false;
      // gecko-based browsers have a very strange bug that strikes when user presses
      // the same character multiple times (like 'AAA', 'BBBB'), which could be "fixed"
      // in a strange way too (actually the idx > 0 test is not even necessary!)
      // first make a pattern to check if it's same character multiple times
      var pattern = new RegExp('^' + this.keyStr.charAt(0) + '+$', "i");
      if((navigator.userAgent.toLowerCase().indexOf("gecko") != -1 && navigator.userAgent.toLowerCase().indexOf("chrome") == -1) && pattern.test(this.keyStr) && idx > 0) element.options[idx-1].selected = true;
      else element.options[idx].selected = true;
    }
    this.keyTime = newTime;
  },
  findIdx : function(currentSIdx)
  {
    // full scan to find the smallest idx that match string keyStr (case-insensitive)
    var len = this.keyStr.length;
    var startidx = (currentSIdx < 0)? 0 : ((len == 1)? currentSIdx + 1 : currentSIdx);
    for(var i = startidx; i < this.allOpts.length; i++)
      if(this.allOpts[i].length >= len && this.allOpts[i].substring(0, len) == this.keyStr)
        return i;
    for(var i = 0; i < startidx; i++)
      if(this.allOpts[i].length >= len && this.allOpts[i].substring(0, len) == this.keyStr)
        return i;
    return -1;
  },
  cancel : function(srcEvent)
  {
    var myEvent = (srcEvent)? srcEvent : window.event;
    if(myEvent.keyCode == 9) return true;
    else return false;
  }
};