var SelectBox = {

    cache: new Object(),

    init: function(id) {

        var box = document.getElementById(id);

        var node;

        SelectBox.cache[id] = new Array();

        var cache = SelectBox.cache[id];

        for (var i = 0; (node = box.options[i]); i++) {

            cache.push({ value: node.value, text: node.text, displayed: 1 });

        }

    },

    redisplay: function(id) {

        // Repopulate HTML select box from cache

        var box = document.getElementById(id);

        box.options.length = 0; // clear all options

        for (var i = 0, j = SelectBox.cache[id].length; i < j; i++) {

            var node = SelectBox.cache[id][i];

            if (node.displayed) {

                box.options[box.options.length] = new Option(node.text, node.value, false, false);

            }

        }

    },

    filter: function(id, text) {

        // Redisplay the HTML select box, displaying only the choices containing ALL

        // the words in text. (It's an AND search.)

        var tokens = text.toLowerCase().split(/\s+/);

        var node, token;

        for (var i = 0; (node = SelectBox.cache[id][i]); i++) {

            node.displayed = 1;

            for (var j = 0; (token = tokens[j]); j++) {

                if (node.text.toLowerCase().indexOf(token) == -1) {

                    node.displayed = 0;

                }

            }

        }

        SelectBox.redisplay(id);

    },

    delete_from_cache: function(id, value) {

        var node, delete_index = null;

        for (var i = 0; (node = SelectBox.cache[id][i]); i++) {

            if (node.value == value) {

                delete_index = i;

                break;

            }

        }

        var j = SelectBox.cache[id].length - 1;

        for (var i = delete_index; i < j; i++) {

            SelectBox.cache[id][i] = SelectBox.cache[id][i+1];

        }

        SelectBox.cache[id].length--;

    },

    add_to_cache: function(id, option) {

        SelectBox.cache[id].push({ value: option.value, text: option.text, displayed: 1 });

    },

    cache_contains: function(id, value) {

        // Check if an item is contained in the cache

        var node;

        for (var i = 0; (node = SelectBox.cache[id][i]); i++) {

            if (node.value == value) {

                return true;

            }

        }

        return false;

    },

    move: function(from, to) {

        var from_box = document.getElementById(from);

        var to_box = document.getElementById(to);

        var option;

        for (var i = 0; (option = from_box.options[i]); i++) {

            if (option.selected && SelectBox.cache_contains(from, option.value)) {

                SelectBox.add_to_cache(to, { value: option.value, text: option.text, displayed: 1 });

                SelectBox.delete_from_cache(from, option.value);

            }

        }

        SelectBox.redisplay(from);

        SelectBox.redisplay(to);

    },

    move_all: function(from, to) {

        var from_box = document.getElementById(from);

        var to_box = document.getElementById(to);

        var option;

        for (var i = 0; (option = from_box.options[i]); i++) {

            SelectBox.add_to_cache(to, { value: option.value, text: option.text, displayed: 1 });

            SelectBox.delete_from_cache(from, option.value);

        }

        SelectBox.redisplay(from);

        SelectBox.redisplay(to);

    },

    sort: function(id) {

        SelectBox.cache[id].sort( function(a, b) {

            a = a.text.toLowerCase();

            b = b.text.toLowerCase();

            try {

                if (a > b) return 1;

                if (a < b) return -1;

            }

            catch (e) {

                // silently fail on IE 'unknown' exception

            }

            return 0;

        } );

    },

    select_all: function(id) {

        var box = document.getElementById(id);

        for (var i = 0; i < box.options.length; i++) {

            box.options[i].selected = 'selected';

        }

    }

}