<?php 
/**
 * Cookie Class.
 */
class clsCookie 
{

	/**
	 * @var  string  Magic salt to add to the cookie
	 */
	public static $salt = NULL;

	/**
	 * @var  integer  Number of seconds before the cookie expires
	 */
	public static $expiration = 0;

	/**
	 * @var  string  Restrict the path that the cookie is available to
	 */
	public static $path = '/';

	/**
	 * @var  string  Restrict the domain that the cookie is available to
	 */
	public static $domain = NULL;

	/**
	 * @var  boolean  Only transmit cookies over secure connections
	 */
	public static $secure = FALSE;

	/**
	 * @var  boolean  Only transmit cookies over HTTP, disabling Javascript access
	 */
	public static $httponly = FALSE;

	/**
	 * Gets the value of a signed cookie. Cookies without signatures will not
	 * be returned. If the cookie signature is present, but invalid, the cookie
	 * will be deleted.
	 *
	 *     // Get the "theme" cookie, or use "blue" if the cookie does not exist
	 *     $theme = clsCookie::get('theme', 'blue');
	 *
	 * @param   string  cookie name
	 * @param   mixed   default value to return
	 * @return  string
	 */
	public static function get($key, $default = NULL)
	{
		if ( ! isset($_COOKIE[$key]))
		{
			// The cookie does not exist
			return $default;
		}

		// Get the cookie value
		$cookie = $_COOKIE[$key];

		// Find the position of the split between salt and contents
		$split = strlen(clsCookie::salt($key, NULL));

		if (isset($cookie[$split]) AND $cookie[$split] === '~')
		{
			// Separate the salt and the value
			list ($hash, $value) = explode('~', $cookie, 2);

			if (clsCookie::salt($key, $value) === $hash)
			{
				// Cookie signature is valid
				return $value;
			}

			// The cookie signature is invalid, delete it
			clsCookie::delete($key);
		}

		return $default;
	}

	/**
	 * Sets a signed cookie. Note that all cookie values must be strings and no
	 * automatic serialization will be performed!
	 *
	 *     // Set the "theme" cookie
	 *     clsCookie::set('theme', 'red');
	 *
	 * @param   string   name of cookie
	 * @param   string   value of cookie
	 * @param   integer  lifetime in seconds
	 * @return  boolean
	 * @uses    clsCookie::salt
	 */
	public static function set($name, $value, $expiration = NULL)
	{
		if ($expiration === NULL)
		{
			// Use the default expiration
			$expiration = clsCookie::$expiration;
		}

		if ($expiration !== 0)
		{
			// The expiration is expected to be a UNIX timestamp
			$expiration += time();
		}

		// Add the salt to the cookie value
		$value = clsCookie::salt($name, $value).'~'.$value;

		return setcookie($name, $value, $expiration, clsCookie::$path, clsCookie::$domain, clsCookie::$secure, clsCookie::$httponly);
	}

	/**
	 * Deletes a cookie by making the value NULL and expiring it.
	 *
	 *     clsCookie::delete('theme');
	 *
	 * @param   string   cookie name
	 * @return  boolean
	 * @uses    clsCookie::set
	 */
	public static function delete($name)
	{
		// Remove the cookie
		unset($_COOKIE[$name]);

		// Nullify the cookie and make it expire
		return setcookie($name, NULL, -86400, clsCookie::$path, clsCookie::$domain, clsCookie::$secure, clsCookie::$httponly);
	}

	/**
	 * Generates a salt string for a cookie based on the name and value.
	 *
	 *     $salt = clsCookie::salt('theme', 'red');
	 *
	 * @param   string   name of cookie
	 * @param   string   value of cookie
	 * @return  string
	 */
	public static function salt($name, $value)
	{
		// Require a valid salt
		if ( ! clsCookie::$salt)
		{
			throw new expCore('A valid cookie salt is required. Please set '.clsCookie::$salt.'');
		}

		// Determine the user agent
		$agent = isset($_SERVER['HTTP_USER_AGENT']) ? strtolower($_SERVER['HTTP_USER_AGENT']) : 'unknown';

		return sha1($agent.$name.$value.clsCookie::$salt);
	}

} // End cookie
