<?php
/** DomFramework
  * @package domframework
  * @author Dominique Fournier <dominique@fournier38.fr>
  */

/** This class allow to manage Server-Sent Events
  * The browser will be connected to a not ending loop. This loop will send
  * ping regularly. If the backend value change, it will be sent to the
  * browser.
  * The backend will be a file for each event name. Each line of the file will
  * be sent when it will be added
  * See https://developer.mozilla.org/fr/docs/Web/API/Server-sent_events/
  * The developper can use a handler to read/modify each event before it is
  * send to the user.
  */
class sse
{
  //////////////////////////
  ////    PROPERTIES    ////
  //////////////////////////
  // {{{
  /** The backend File to use
    */
  private $files;

  /** Set the time between each ping (in seconds). 30 by default
    */
  private $pingTime = 30;

  /** The filepointers storage
    */
  private $fps = array ();

  /** The handlers storage
    */
  private $handlers = array ();
  /** The handlers parameters
    */
  private $handlersParams = array ();
  // }}}

  //////////////////////////////
  ////    SETTER METHODS    ////
  //////////////////////////////
  /** The backend Files to use.
    * The backend directory used to store the files must exists and be readable
    * If array (namedEvent => filePath, "data" => dataFilePath);
    * If string dataFilePath
    * @param string|array $files The files to use
    * @return $this
    */
  final public function setBackendFiles ($files)
  // {{{
  {
    if (! is_array ($files))
      $files = array ("data" => $files);
    foreach ($files as $event => $file)
    {
      if (! file_exists (dirname ($file)))
        throw new \Exception (sprintf (dgettext ("domframework",
        "SSE : Can not use the backend file : ".
        "directory does not exists : %s"), dirname ($file)), 500);
      if (! is_readable (dirname ($file)))
        throw new \Exception (sprintf (dgettext ("domframework",
        "SSE : Can not use the backend file : ".
        "directory not readable : %s"), dirname ($file)), 500);
      if (! ctype_graph ($event))
        throw new \Exception (sprintf (dgettext ("domframework",
        "SSE : Can not create the backend file : ".
        "event name contains invalid chars : %s"), $event), 403);
    }
    $this->files = $files;
    return $this;
  }
  // }}}

  /** The pingTime to use. Must be positive. If null, the ping is disabled
    * @param integer|float $pingTime The time in seconds between two keepalive
    * pings
    */
  final public function setPingTime ($pingTime)
  // {{{
  {
    if (! is_float ($pingTime) && ! is_integer ($pingTime))
      throw new \Exception (sprintf (dgettext ("domframework",
      "SSE : Can not use requested pingTime : not a float : %s"),
      $pingTime), 500);
    if ($pingTime < 0)
      throw new \Exception (sprintf (dgettext ("domframework",
      "SSE : Can not use requested pingTime : not positive : %s"),
      $pingTime), 500);
    $this->pingTime = $pingTime;
    return $this;
  }
  // }}}

  /** The optional handler to use in DataOnly. Must be callable method
    * @param callable|null $handler
    * If callable is null, remove the handler for this event
    * @param mixed... $params The optional needed parameters
    */
  final public function setHandlerDataonly ($handler, $params = null)
  // {{{
  {
    if (! is_callable ($handler) && $handler !== null)
      throw new \Exception (dgettext ("domframework",
      "SSE : can not use handler : not callable"), 500);
    $this->handlers["data"] = $handler;
    $args = func_get_args ();
    array_shift ($args);
    $this->handlersParams["data"] = $args;
    return $this;
  }
  // }}}

  /** The optional handler to use in Events. Must be array of callable methods
    * @param array $handlers The handlers method, array[event=>callable]
    * @param array|mixed $params The parameters of the handlers
    * array[event=>callable]
    * If callable is null, remove the handler for this event
    * @param array|null $params The optional needed parameters
    * array(event=>array(params))
    * if event=>null is set, remove the parameters for the event
    */
  final public function setHandlersEvent ($handlers, $params = null)
  // {{{
  {
    if (! is_array ($handlers))
      throw new \Exception (dgettext ("domframework",
      "SSE : can not use handler : not array"), 500);
    if (! is_array ($params) && $params !== null)
      throw new \Exception (dgettext ("domframework",
      "SSE : can not use handler params : not array"), 500);
    foreach ($handlers as $event => $handler)
    {
      if ($handler === null && key_exists ($event, $this->handlers))
      {
        unset ($this->handlers[$event]);
        unset ($this->handlersParams[$event]);
        continue;
      }
      if (! is_callable ($handler))
        throw new \Exception (dgettext ("domframework",
        "SSE : can not use handler : not callable"), 500);
      $this->handlers[$event] = $handler;
    }
    if (is_array ($params))
    {
      foreach ($params as $event => $param)
      {
        if (! key_exists ($event, $this->handlers))
          throw new \Exception (dgettext ("domframework",
          "SSE : can not use parameter '$event' : no associated handler"), 500);
        if ($param === null)
          unset ($this->handlersParams[$event]);
        else
          $this->handlersParams[$event] = $param;
      }
    }
    return $this;
  }
  // }}}

  //////////////////////////////
  ////    PUBLIC METHODS    ////
  //////////////////////////////
  /** This method is called by the user's browser.
    * It send the "ping" each X second and send the backend content if it
    * is updated.
    * Never return !
    */
  final public function loop ()
  // {{{
  {
    if ($this->files === null)
      throw new \Exception (dgettext ("domframework",
      "SSE : Can not use the backend file : file is not defined"), 500);
    $this->backendInit();
    // The last ping in float
    $lastping = 0;
    @header ("Cache-Control: no-cache");        // Disable caching of response
    @header ("X-Accel-Buffering: no");          // Disable NGINX Buffering
    @header ("Content-Type: text/event-stream");
    // In tests, abort after 100ms * 50 = 5s. In production, never abort as the
    // counter is never decreased
    $testloop = 50;
    while ($testloop)
    {
      // Each $pingTime, send a comment ":ping" to keepalive the connection
      if ($this->pingTime > 0 && $lastping + $this->pingTime < microtime (true))
      {
        echo ": ping\n\n";
        $lastping = microtime (true);
      }

      // Try to get data from backends
      foreach ($this->files as $event => $filePath)
      {
        $data = $this->backendGet ($event);
        if ($data === false)
          continue;
        $data = rtrim ($data);
        if (key_exists ($event, $this->handlers) &&
             is_callable ($this->handlers[$event]))
        {
          $array = array ($data);
          if (key_exists ($event, $this->handlersParams))
            $array = array_merge ($array, $this->handlersParams[$event]);
          $data = call_user_func_array ($this->handlers[$event], $array);
        }
        if ($data === false)
          continue;
        // If the event is data, do not display "event:data", but data:
        // immediately
        if ($event !== "data")
        {
          echo "event: $event\n";
          $event = "data";
        }
        echo "$event: ".implode ("\n$event: ", explode ("\n", rtrim ($data))).
             "\n\n";
      }
      if (defined ("PHPUNIT"))
      {
        $testloop--;
        pcntl_signal_dispatch();
      }
      else
      {
        @ob_end_flush();
        @flush();
      }
      // Loop each 100ms if there is no data.
      usleep(100000);
    }
  }
  // }}}

  ///////////////////////////////
  ////    PRIVATE METHODS    ////
  ///////////////////////////////
  /** Initialize the backend : open all the files and go at the end
    */
  private function backendInit ()
  // {{{
  {
    if ($this->files === null)
      throw new \Exception (dgettext ("domframework",
      "SSE : Can not use the backend files : files are not defined"), 500);
    foreach ($this->files as $event => $filePath)
    {
      $this->backendInitEvent ($event, $filePath);
      if (key_exists ($event, $this->fps))
      {
        fseek ($this->fps[$event], 0, SEEK_END);
        stream_set_blocking ($this->fps[$event], false);
      }
    }
  }
  // }}}

  /** Get the pending lines from requested backend
    * @param string $event The event to get data
    * @return null if there is no new line pending
    * @return string the data lines stored in the lines
    */
  private function backendGet ($event)
  // {{{
  {
    // If the file was previously opened but doesn't exists anymore. Close it
    // and reopen it just after
    if (key_exists ($event, $this->fps) && (
        ! file_exists ($this->files[$event]) ||
        ! is_readable ($this->files[$event])))
    {
      @fclose ($this->fps[$event]);
      unset ($this->fps[$event]);
    }
    // If the file was not previously opened, try to open it. Abort if it
    // doesn't exists again
    if (! key_exists ($event, $this->fps))
    {
      if ($this->backendInitEvent ($event, $this->files[$event]) === false)
        return false;
    }
    $fp = $this->fps[$event];
    // If the file is truncated by an external action, must restart at 0
    if (fstat($fp)["size"] < ftell ($fp))
    {
      rewind ($fp);
    }
    $res = false;
    while (($line = stream_get_line ($fp, 10000, "\n")) !== false)
    {
      $res .= "$line\n";
    }
    return $res;
  }
  // }}}

  /** Initialize the backend for one specific file.
    * @param string $event The event to start
    * @param string $filePath The file path where the event data are stored
    * @return false if the file doesn't exists
    */
  private function backendInitEvent ($event, $filePath)
  // {{{
  {
    clearstatcache (true, $filePath);
    if (! file_exists (dirname ($filePath)))
      throw new \Exception (sprintf (dgettext ("domframework",
      "SSE : Backend directory no more exists : %s"), dirname ($filePath)),
      500);
    if (! is_readable (dirname ($filePath)))
      throw new \Exception (sprintf (dgettext ("domframework",
      "SSE : Backend directory no more readable : %s"), dirname ($filePath)),
      500);
    if (! file_exists ($filePath))
      return false;
    if (! is_readable ($filePath))
      throw new \Exception (sprintf (dgettext ("domframework",
      "SSE : Backend event file not readable : %s"), $filePath),
      500);
    $fp = fopen ($filePath, "r");
    if ($fp === false)
      throw new \Exception (sprintf (dgettext ("domframework",
      "SSE : Backend event file not openable : %s"), $filePath),
      500);
    $this->fps[$event] = $fp;
    return $this;
  }
  // }}}
}