/**
 * Provides a simple interface for creating, retrieving and clearing cookies.
 */
CookieManager = Class.create();
CookieManager.prototype =
{
    BROWSER_IS_IE:
        (document.all
         && window.ActiveXObject
         && navigator.userAgent.toLowerCase().indexOf("msie") > -1
         && navigator.userAgent.toLowerCase().indexOf("opera") == -1),

    /**
     * I hate navigator string based browser detection too, but when Opera alone
     * chokes on cookies containing double quotes...
     */
    BROWSER_IS_OPERA:
        (navigator.userAgent.toLowerCase().indexOf("opera") != -1),

    initialize: function(options)
    {
        this.options = Object.extend({
            shelfLife: 365,
            userData: false
        }, options || {}); 

        this.cookieShelfLife = this.options.shelfLife;
        this.userDataForIE = this.options.userData;

        // Internet Explorer has a cookie handling bug - if the *combined size*
        // of all cookies stored for a given domain is greater than 4096 bytes,
        // document.cookie will return an empty string. Until this is fixed, we
        // can fall back on IE's proprietary userData behaviour if necessary.
        if (this.BROWSER_IS_IE && this.userDataForIE)
        {
            this.IE_CACHE_NAME = "storage";
            if ($(this.IE_CACHE_NAME) == null)
            {
                var div = document.createElement("DIV");
                div.id = this.IE_CACHE_NAME;
                document.body.appendChild(div);
            }
            this.store = $(this.IE_CACHE_NAME);
            this.store.style.behavior = "url('#default#userData')";
        }
    },

    /**
     * Returns the value of a cookie with the given name, or <code>null</code>
     * if no such cookie exists.
     */
    getCookie: function(aCookieName)
    {
        var result = null;
        if (this.BROWSER_IS_IE && this.userDataForIE)
        {
            this.store.load(this.IE_CACHE_NAME);
            result = this.store.getAttribute(aCookieName);
        }
        else
        {
            for (var i = 0; i < document.cookie.split('; ').length; i++)
            {
                var crumb = document.cookie.split('; ')[i].split('=');
                if (crumb[0] == aCookieName && crumb[1] != null)
                {
                    result = crumb[1];
                    break;
                }
            }
        }

        if (this.BROWSER_IS_OPERA && result != null)
        {
            result = result.replace(/%22/g, '"');
        }
        return result;
    },

    /**
     * Sets a cookie with the given name and value.
     */
    setCookie: function(aCookieName, aCookieValue)
    {
        if (this.BROWSER_IS_IE && this.userDataForIE)
        {
            this.store.setAttribute(aCookieName, aCookieValue);
            this.store.save(this.IE_CACHE_NAME);
        }
        else
        {
            if (this.BROWSER_IS_OPERA)
            {
                aCookieValue = aCookieValue.replace(/"/g, "%22");
            }
            var date = new Date();
            date.setTime(date.getTime() + (this.cookieShelfLife * 24*60*60*1000));
            var expires = '; expires=' + date.toGMTString();
            document.cookie = aCookieName + '=' + aCookieValue + expires + '; path=/';
        }
    },

    /**
     * Clears the cookie with the given name.
     */
    clearCookie: function(aCookieName)
    {
        if (this.BROWSER_IS_IE && this.userDataForIE)
        {
            this.store.load(this.IE_CACHE_NAME);
            this.store.removeAttribute(aCookieName);
            this.store.save(this.IE_CACHE_NAME);
        }
        else
        {
            document.cookie =
                aCookieName + '=;expires=Thu, 01-Jan-1970 00:00:01 GMT; path=/';
        }
    }
}