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

//namespace Domframework;

/** This class allow a program to download a specific file from the filesystem,
  * without using too much memory. In also allow to manage the resuming of a
  * paused transfert by getting the range of download.
  */
class outputdl
{
  /** Allow or deny the resuming of the HTTP transferts
    */
  private $resumeAllow = true;

  /** The base dir used as root
    */
  private $base = "/";

  /** Store the headers to allow the unit tests to get them
    */
  private $headers = array ();

  /** Headers sent
    */
  private $headersSent = false;

  /** Get/Set Allow/Deny the resuming of transferts
    * @param boolean|null $resumeAllow True : resume OK, false : resume forbid
    * @return $this|boolean
    */
  public function resumeAllow ($resumeAllow = null)
  // {{{
  {
    if ($resumeAllow === null)
      return $this->resumeAllow;
    $this->resumeAllow = !! $resumeAllow;
    return $this;
  }
  // }}}

  /** Get/Set Base of filesystem
    * The base directory is use to secure the download. A user can not request
    * a file outside the base. Example : if the base is /var/lib/files, the
    * user can not request /etc/passwd file (out of scope). If not defined,
    * all the filesystem is allowed
    * @param string|null $base The filesystem base
    * @return $this|string
    */
  public function base ($base = null)
  // {{{
  {
    if ($base === null)
      return $this->base;
    $this->base = $base;
    return $this;
  }
  // }}}

  /** Get headers from headers list
    * The headers can be tested too
    * @return array
    */
  public function headers ()
  // {{{
  {
    return $this->headers;
  }
  // }}}

  /** Add a new header and send it if possible
    * @param string $header The header to send
    * @return $this
    */
  private function header ($header)
  // {{{
  {
    if (! headers_sent())
      header ($header);
    $this->headers[] = $header;
    return $this;
  }
  // }}}

  /** Download a file with management of Partial Download (like resume)
    * Manage the HTTP headers to allow to resume the download if it is allowed
    * Do not go throw the renderer, exit at end of transfert
    * @param string $path The path to download
    * @param string|null $filename The filename to send to the browser
    */
  public function downloadFile ($path, $filename = null)
  // {{{
  {
    if (!file_exists ($path))
      throw new \Exception (dgettext ("domframework",
        "Invalid file to download : file doesn't exists"), 404);
    if (is_link ($path) || is_dir ($path))
      throw new \Exception (dgettext ("domframework",
        "Invalid file to download : not a file"), 406);
    $path = realpath ($path);
    if (substr ($path, 0, strlen ($this->base)) !== $this->base)
      throw new \Exception (dgettext ("domframework",
        "Invalid file to download : out of base"), 406);
    if (! is_file ($path))
      throw new \Exception (dgettext ("domframework",
        "Invalid file to download : not a file"), 406);
    if (! is_readable ($path))
      throw new \Exception (dgettext ("domframework",
        "Invalid file to download : file not readable"), 406);
    ini_set ('display_errors', 0);
    ini_set ('display_startup_errors', 0);
    if (! defined ("PHPUNIT") && ob_get_level ())
      ob_end_clean ();

    if ($filename === null)
      $filename = basename ($path);
    $this->header ('Content-Description: File Transfer');
    $this->header ('Content-Type: application/octet-stream');
    $this->header ('Content-Disposition: attachment; filename="'.$filename.'"');
    $this->header ('Content-Transfer-Encoding: binary');
    //header ('Expires: 0');
    //header ('Cache-Control: must-revalidate, post-check=0, pre-check=0');
    //header ('Pragma: public');
    $filesize = filesize ($path);
    if (! $this->resumeAllow)
    {
      $this->header ('Accept-Ranges: none');
    }
    else
    {
      $this->header ('Accept-Ranges: bytes');
      if (isset ($_SERVER["HTTP_RANGE"]) &&
          strtolower (substr ($_SERVER["HTTP_RANGE"], 0, 6)) === "bytes=")
      {
        $boundary = "Qm91bmRhcnk=";
        $rangeTxt = trim (substr ($_SERVER["HTTP_RANGE"], 6));
        $ranges = explode (",", $rangeTxt);
        if (count ($ranges) > 1)
          $this->header (
            "Content-Type: multipart/byteranges; boundary=$boundary");
        foreach ($ranges as $nb => $range)
        {
          if (trim ($range) === "-")
            throw new \Exception ("Invalid range provided", 416);
          @list ($start, $stop) = explode ("-", trim ($range));
          if ($stop === null || $stop === "")
            $stop = $filesize;
          if ($stop && ($start === null || $start === ""))
          {
            $start = $filesize - $stop;
            $stop = $filesize;
          }
          $start = intval ($start);
          $stop = intval ($stop);
          if ($start > $stop)
            throw new \Exception ("Invalid range provided", 416);
          if ($start < 0 || $stop > $filesize || $start > $filesize)
            throw new \Exception ("Invalid range provided", 416);
          if (count ($ranges) > 1)
          {
            if ($nb > 0)
              echo "\r\n";
            echo "--".$boundary."\r\n";
            echo "Content-Range: bytes $start-$stop/$filesize\r\n";
            echo "Content-Type: application/octet-stream\r\n";
            echo "\r\n";
          }
          else
          {
            $this->header ("Content-Range: bytes $start-$stop/$filesize");
          }
          http_response_code (206);
          $this->downloadFileRange ($path, $start, $stop);

        }
        if (count ($ranges) > 1)
        {
          if ($nb > 0)
            echo "\r\n";
          echo "--".$boundary."--\r\n";
        }
        if (! defined ("PHPUNIT"))
          exit;
        return;
      }
    }
    // No range or error : send all the file
    $this->header ('Content-Length: '. $filesize);
    $this->downloadFileRange ($path, 0, $filesize);
    if (! defined ("PHPUNIT"))
      exit;
    return;
  }
  // }}}

  /** Download the file. Do not go through the renderer
    * @param string $path The path to download
    * @param integer $start The start range
    * @param integer $stop The stop range
    */
  private function downloadFileRange ($path, $start, $stop)
  // {{{
  {
    $file = realpath ($path);
    $chunksize = 10*1024*1024; // how many bytes per chunk
    $start = intval ($start);
    $stop = intval ($stop);
    $handle = fopen ($file, 'rb');
    if ($handle === false)
    {
      die ("error");
    }
    if (fseek ($handle, $start) === false)
      die ("Can not seek");
    $size = $start;
    while (! feof ($handle))
    {
      $block = fread ($handle, $chunksize);
      if ($size + $chunksize > $stop)
        $block = substr ($block, 0, $stop - $size + 1);
      $size += strlen ($block);
      echo $block;
      flush ();
      if ($size >= $stop)
        break;
    }
    fclose($handle);
  }
  // }}}
}