/*
By Anders Ytterström 2012.

Example use:
<script src="autocomplete.js"></script>
<script>
  var values = ["Hansi", "Andre", "The Omen", "Marcus", "Prince Charles"],
    callback = function (k) {
      console.log(k);
    };

  autocomplete("bg", values, callback);
</script>
*/

/*jslint indent: 2, maxlen: 90, browser: true */
var autocomplete = function (id, values, callback) {
  "use strict";
  var autoCompleteTimer,
    stopDefaultAction,
    getPosition,
    field,
    initAutoComplete,
    keydownAutoComplete,
    generateDropdown,
    autoComplete,
    mouseoverDropdown,
    mouseoutDropdown,
    mousedownDropdown,
    assignMouseListeners,
    blurAutoComplete,
    closeDropdown;

  stopDefaultAction = function (event) {
    event.returnValue = false;
    if (typeof event.preventDefault !== "undefined") {
      event.preventDefault();
    }
    return true;
  };

  getPosition = function (theElement) {
    var positionX = 0,
      positionY = 0;
    while (theElement !== null) {
      positionX += theElement.offsetLeft;
      positionY += theElement.offsetTop;
      theElement = theElement.offsetParent;
    }
    return [positionX, positionY];
  };

  initAutoComplete = function () {
    field = document.getElementById(id);
    field.setAttribute("autocomplete", "off");
    if (window.attachEvent) {
      field.attachEvent("onkeydown", keydownAutoComplete);
    } else {
      field.addEventListener("keydown", keydownAutoComplete);
    }
    field.onblur = function () {
      blurAutoComplete();
    };
  };

  keydownAutoComplete = function (event) {
    var target = event.target || event.srcElement,
      autoCompleteDropdown,
      childLis,
      selected,
      i,
      max,
      inputRanges;
    if (typeof event === "undefined") {
      event = window.event;
    }
    switch (event.keyCode) {
    case 9:     // tab
    case 13:    // enter
    case 16:    // shift
    case 17:    // ctrl
    case 18:    // alt
    case 20:    // caps lock
    case 27:    // esc
    case 33:    // page up
    case 34:    // page down
    case 35:    // end
    case 36:    // home
    case 37:    // left arrow
    case 39:    // right arrow
      break;
    case 38:    // up arrow
      autoCompleteDropdown = document.getElementById("autoCompleteDropdown");
      if (autoCompleteDropdown !== null) {
        childLis = autoCompleteDropdown.childNodes;
        selected = false;
        for (i = 0, max = childLis.length; i < max; i += 1) {
          if (childLis[i].className === "hover") {
            selected = true;
            if (i > 0) {
              childLis[i].className = "";
              childLis[i - 1].className = "hover";
              target.value = childLis[i - 1].firstChild.nodeValue;
            }
            break;
          }
        }
        if (!selected) {
          childLis[0].className = "hover";
          target.value = childLis[0].firstChild.nodeValue;
        }
      }
      stopDefaultAction(event);
      break;
    case 40:    // down arrow
      autoCompleteDropdown = document.getElementById("autoCompleteDropdown");
      if (autoCompleteDropdown !== null) {
        childLis = autoCompleteDropdown.childNodes;
        selected = false;
        for (i = 0, max = childLis.length; i < max; i += 1) {
          if (childLis[i].className === "hover") {
            selected = true;

            if (i < childLis.length - 1) {
              childLis[i].className = "";
              childLis[i + 1].className = "hover";
              target.value = childLis[i + 1].firstChild.nodeValue;
            }
            break;
          }
        }
        if (!selected) {
          childLis[0].className = "hover";
          target.value = childLis[0].firstChild.nodeValue;
        }
      }
      stopDefaultAction(event);
      break;
    case 8:     // backspace
    case 46:    // delete
      if (typeof autoCompleteTimer !== "undefined") {
        clearTimeout(autoCompleteTimer);
      }
      autoCompleteTimer = setTimeout(function () {
        generateDropdown(false);
      }, 500);
      break;
    default:
      if (typeof autoCompleteTimer !== "undefined") {
        clearTimeout(autoCompleteTimer);
      }
      target = event.target || event.srcElement;
      inputRanges = "false";
      if (typeof target.createTextRange !== "undefined"
          || typeof target.setSelectionRange !== "undefined") {
        inputRanges = "true";
      }
      autoCompleteTimer = setTimeout(function () {
        generateDropdown(inputRanges);
      }, 500);
    }
    return true;
  };

  assignMouseListeners = function (e) {
    e.onmouseover = function () {
      mouseoverDropdown(this);
    };
    e.mouseout = function () {
      mouseoutDropdown(this);
    };
    e.mousedown = function () {
      mousedownDropdown(this);
    };
  };

  generateDropdown = function (doAutoComplete) {
    closeDropdown();
    var input = document.getElementById(id),
      newUl = document.createElement("div"),
      newLi,
      i,
      max = values.length;
    newUl.setAttribute("id", "autoCompleteDropdown");
    newUl.autoCompleteInput = input;
    newUl.style.position = "absolute";
    newUl.style.left = getPosition(input)[0] + "px";
    newUl.style.top = getPosition(input)[1] + input.offsetHeight - 2 + "px";
    newUl.style.width = input.offsetWidth - 3 + "px";
    for (i = 0; i < max; i += 1) {
      if (values[i].indexOf(input.value) === 0) {
        newLi = document.createElement("button");
        newLi.innerHTML = values[i];
        assignMouseListeners(newLi);
        newUl.appendChild(newLi);
      }
    }
    if (newUl.firstChild !== null) {
      document.getElementsByTagName("body")[0].appendChild(newUl);
    }
    if (typeof doAutoComplete !== "undefined" && doAutoComplete) {
      autoComplete();
    }
    return true;
  };

  autoComplete = function () {
    var input = document.getElementById(id),
      cursorMidway = false,
      range,
      originalValue,
      autoCompleteDropdown;
    if (typeof document.selection !== "undefined") {
      range = document.selection.createRange();
      if (range.move("character", 1) !== 0) {
        cursorMidway = true;
      }
    } else if (typeof input.selectionStart !== "undefined"
        && input.selectionStart < input.value.length) {
      cursorMidway = true;
    }
    originalValue = input.value;
    autoCompleteDropdown = document.getElementById("autoCompleteDropdown");
    if (autoCompleteDropdown !== null && !cursorMidway) {
      autoCompleteDropdown.firstChild.className = "hover";
      input.value = autoCompleteDropdown.firstChild.firstChild.nodeValue;
      if (typeof input.createTextRange !== "undefined") {
        range = input.createTextRange();
        range.moveStart("character", originalValue.length);
        range.select();
      } else if (typeof input.setSelectionRange !== "undefined") {
        input.setSelectionRange(originalValue.length, input.value.length);
      }
      if (autoCompleteDropdown.childNodes.length === 1) {
        setTimeout(function () {
          closeDropdown();
        }, 10);
      }
    }
    return true;
  };

  mouseoverDropdown = function (target) {
    var childLis, i, max;
    while (target.nodeName.toLowerCase() !== "button") {
      target = target.parentNode;
    }
    childLis = target.parentNode.childNodes;
    max = childLis.length;
    for (i = 0; i < max; i += 1) {
      childLis[i].className = "";
    }
    target.className = "hover";
    return true;
  };

  mouseoutDropdown = function (target) {
    while (target.nodeName.toLowerCase() !== "button") {
      target = target.parentNode;
    }
    target.className = "";
    return true;
  };

  mousedownDropdown = function (target) {
    while (target.nodeName.toLowerCase() !== "button") {
      target = target.parentNode;
    }
    target.parentNode.autoCompleteInput.value = target.firstChild.nodeValue;
    closeDropdown();
    return true;
  };

  blurAutoComplete = function () {
    if (typeof autoCompleteTimer !== "undefined") {
      clearTimeout(autoCompleteTimer);
    }
    closeDropdown();
    callback(field.value);
    return true;
  };

  closeDropdown = function () {
    var autoCompleteDropdown = document.getElementById("autoCompleteDropdown");
    if (autoCompleteDropdown !== null) {
      autoCompleteDropdown.parentNode.removeChild(autoCompleteDropdown);
    }
    return true;
  };
  initAutoComplete();
};