class Section

class Section {
  private $events = array();
  private $origin;
  private $id;
  private $children = array();

  /**
   * 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();
  }

  /**
   * 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 $this
      ->stop($name)
      ->start();
  }

  /**
   * Returns the events from this section.
   *
   * @return StopwatchEvent[] An array of StopwatchEvent instances
   */
  public function getEvents() {
    return $this->events;
  }

}