class RulesLog

class RulesLog {
    const INFO = 1;
    const WARN = 2;
    const ERROR = 3;
    protected static $logger;
    
    /**
     * @return RulesLog
     *   Returns the rules logger instance.
     */
    public static function logger() {
        if (!isset(self::$logger)) {
            $class = __CLASS__;
            self::$logger = new $class(variable_get('rules_log_level', self::INFO));
        }
        return self::$logger;
    }
    protected $log = array();
    protected $logLevel;
    protected $line = 0;
    
    /**
     * This is a singleton.
     */
    protected function __construct($logLevel = self::WARN) {
        $this->logLevel = $logLevel;
    }
    public function __clone() {
        throw new Exception("Cannot clone the logger.");
    }
    
    /**
     * Logs a log message.
     *
     * @see rules_log()
     */
    public function log($msg, $args = array(), $logLevel = self::INFO, $scope = NULL, $path = NULL) {
        if ($logLevel >= $this->logLevel) {
            $this->log[] = array(
                $msg,
                $args,
                $logLevel,
                microtime(TRUE),
                $scope,
                $path,
            );
        }
    }
    
    /**
     * Gets an array of logged messages.
     */
    public function get() {
        return $this->log;
    }
    
    /**
     * Clears the logged messages.
     */
    public function clear() {
        $this->log = array();
    }
    
    /**
     * Checks the log and throws an exception if there were any problems.
     */
    public function checkLog($logLevel = self::WARN) {
        foreach ($this->log as $entry) {
            if ($entry[2] >= $logLevel) {
                throw new Exception($this->render());
            }
        }
    }
    
    /**
     * Checks the log for error messages.
     *
     * @param int $logLevel
     *   Lowest log level to return. Values lower than $logLevel will not be
     *   returned.
     *
     * @return bool
     *   Whether the an error has been logged.
     */
    public function hasErrors($logLevel = self::WARN) {
        foreach ($this->log as $entry) {
            if ($entry[2] >= $logLevel) {
                return TRUE;
            }
        }
        return FALSE;
    }
    
    /**
     * Renders the whole log.
     */
    public function render() {
        $line = 0;
        $output = array();
        while (isset($this->log[$line])) {
            $vars['head'] = t($this->log[$line][0], $this->log[$line][1]);
            $vars['log'] = $this->renderHelper($line);
            $output[] = theme('rules_debug_element', $vars);
            $line++;
        }
        return implode('', $output);
    }
    
    /**
     * Renders the log of one event invocation.
     */
    protected function renderHelper(&$line = 0) {
        $startTime = isset($this->log[$line][3]) ? $this->log[$line][3] : 0;
        $output = array();
        while ($line < count($this->log)) {
            if ($output && !empty($this->log[$line][4])) {
                // The next entry stems from another evaluated set, add in its log
                // messages here.
                $vars['head'] = t($this->log[$line][0], $this->log[$line][1]);
                if (isset($this->log[$line][5])) {
                    $vars['link'] = '[' . l(t('edit'), $this->log[$line][5]) . ']';
                }
                $vars['log'] = $this->renderHelper($line);
                $output[] = theme('rules_debug_element', $vars);
            }
            else {
                $formatted_diff = round(($this->log[$line][3] - $startTime) * 1000, 3) . ' ms';
                $msg = $formatted_diff . ' ' . t($this->log[$line][0], $this->log[$line][1]);
                if ($this->log[$line][2] >= RulesLog::WARN) {
                    $level = $this->log[$line][2] == RulesLog::WARN ? 'warn' : 'error';
                    $msg = '<span class="rules-debug-' . $level . '">' . $msg . '</span>';
                }
                if (isset($this->log[$line][5]) && !isset($this->log[$line][4])) {
                    $msg .= ' [' . l(t('edit'), $this->log[$line][5]) . ']';
                }
                $output[] = $msg;
                if (isset($this->log[$line][4]) && !$this->log[$line][4]) {
                    // This was the last log entry of this set.
                    return theme('item_list', array(
                        'items' => $output,
                    ));
                }
            }
            $line++;
        }
        return theme('item_list', array(
            'items' => $output,
        ));
    }

}