class Section

class Section {
    
    /**
     * @var StopwatchEvent[]
     */
    private $events = [];
    
    /**
     * @var null|float
     */
    private $origin;
    
    /**
     * @var string
     */
    private $id;
    
    /**
     * @var Section[]
     */
    private $children = [];
    
    /**
     * Constructor.
     *
     * @param float|null $origin Set the origin of the events in this section, use null to set their origin to their start time
     */
    public function __construct($origin = NULL) {
        $this->origin = is_numeric($origin) ? $origin : NULL;
    }
    
    /**
     * Returns the child section.
     *
     * @param string $id The child section identifier
     *
     * @return Section|null The child section or null when none found
     */
    public function get($id) {
        foreach ($this->children as $child) {
            if ($id === $child->getId()) {
                return $child;
            }
        }
        return NULL;
    }
    
    /**
     * Creates or re-opens a child section.
     *
     * @param string|null $id null to create a new section, the identifier to re-open an existing one.
     *
     * @return Section A child section
     */
    public function open($id) {
        if (NULL === ($session = $this->get($id))) {
            $session = $this->children[] = new self(microtime(TRUE) * 1000);
        }
        return $session;
    }
    
    /**
     * @return string The identifier of the section
     */
    public function getId() {
        return $this->id;
    }
    
    /**
     * Sets the session identifier.
     *
     * @param string $id The session identifier
     *
     * @return Section The current section
     */
    public function setId($id) {
        $this->id = $id;
        return $this;
    }
    
    /**
     * Starts an event.
     *
     * @param string $name The event name
     * @param string $category The event category
     *
     * @return StopwatchEvent The event
     */
    public function startEvent($name, $category) {
        if (!isset($this->events[$name])) {
            $this->events[$name] = new StopwatchEvent($this->origin ?: microtime(TRUE) * 1000, $category);
        }
        return $this->events[$name]
            ->start();
    }
    
    /**
     * Checks if the event was started
     *
     * @param string $name The event name
     *
     * @return bool
     */
    public function isEventStarted($name) {
        return isset($this->events[$name]) && $this->events[$name]
            ->isStarted();
    }
    
    /**
     * Stops an event.
     *
     * @param string $name The event name
     *
     * @return StopwatchEvent The event
     *
     * @throws \LogicException When the event has not been started
     */
    public function stopEvent($name) {
        if (!isset($this->events[$name])) {
            throw new \LogicException(sprintf('Event "%s" is not started.', $name));
        }
        return $this->events[$name]
            ->stop();
    }
    
    /**
     * Stops then restarts an event.
     *
     * @param string $name The event name
     *
     * @return StopwatchEvent The event
     *
     * @throws \LogicException When the event has not been started
     */
    public function lap($name) {
        return $this->stopEvent($name)
            ->start();
    }
    
    /**
     * Returns the events from this section.
     *
     * @return StopwatchEvent[] An array of StopwatchEvent instances
     */
    public function getEvents() {
        return $this->events;
    }

}