Format.php

<?php

/**
 * EasyRdf
 *
 * LICENSE
 *
 * Copyright (c) 2009-2012 Nicholas J Humfrey.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author 'Nicholas J Humfrey" may be used to endorse or
 *    promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * @package    EasyRdf
 * @copyright  Copyright (c) 2009-2012 Nicholas J Humfrey
 * @license    http://www.opensource.org/licenses/bsd-license.php
 * @version    $Id$
 */

/**
 * Class the represents an RDF file format.
 *
 * For each format, the name, label, URIs and associated MIME Types are
 * stored. A single parser and serialiser can also be registered to each
 * format.
 *
 * @package    EasyRdf
 * @copyright  Copyright (c) 2009-2012 Nicholas J Humfrey
 * @license    http://www.opensource.org/licenses/bsd-license.php
 */
class EasyRdf_Format {
  private static $formats = array();
  private $name = array();
  private $label = null;
  private $uri = null;
  private $mimeTypes = array();
  private $extensions = array();
  private $parserClass = null;
  private $serialiserClass = null;

  /** Get a list of format names
   *
   * @return array          An array of formats name
   */
  public static function getNames() {
    return array_keys(self::$formats);
  }

  /** Get a list of all the registered formats
   *
   * @return array          An array of format objects
   */
  public static function getFormats() {
    return self::$formats;
  }

  /** Generates an HTTP Accept header string
   *
   * The string will contain all of the MIME Types that we
   * are able to parse.
   *
   * It is also possible to specify additional MIME types
   * in the form array('text/plain' => 0.5) where 0.5 is the
   * q value for that type. The types are sorted by q value
   * before constructing the string.
   *
   * @param array $extraTypes    extra MIME types to add
   * @return string              list of supported MIME types
   */
  public static function getHttpAcceptHeader($extraTypes = array()) {
    $accept = $extraTypes;
    foreach (self::$formats as $format) {
      if ($format->parserClass and count($format->mimeTypes) > 0) {
        $accept = array_merge($accept, $format->mimeTypes);
      }
    }
    arsort($accept, SORT_NUMERIC);
    $acceptStr = '';
    foreach ($accept as $type => $q) {
      if ($acceptStr) {
        $acceptStr .= ',';
      }
      if ($q == 1.0) {
        $acceptStr .= $type;
      }
      else {
        $acceptStr .= sprintf("%s;q=%1.1f", $type, $q);
      }
    }
    return $acceptStr;
  }

  /** Check if a named graph exists
   *
   * @param string $name    the name of the format
   * @return boolean        true if the format exists
   */
  public static function formatExists($name) {
    return array_key_exists($name, self::$formats);
  }

  /** Get a EasyRdf_Format from a name, uri or mime type
   *
   * @param string $query   a query string to search for
   * @return object         the first EasyRdf_Format that matches the query
   * @throws EasyRdf_Exception  if no format is found
   */
  public static function getFormat($query) {
    if (!is_string($query) or $query == null or $query == '') {
      throw new InvalidArgumentException("\$query should be a string and cannot be null or empty");
    }
    foreach (self::$formats as $format) {
      if ($query == $format->name or $query == $format->uri or array_key_exists($query, $format->mimeTypes) or in_array($query, $format->extensions)) {
        return $format;
      }
    }

    # No match
    throw new EasyRdf_Exception("Format is not recognised: {$query}");
  }

  /** Register a new format
   *
   * @param  string  $name       The name of the format (e.g. ntriples)
   * @param  string  $label      The label for the format (e.g. N-Triples)
   * @param  string  $uri        The URI for the format
   * @param  string  $mimeTypes  One or more mime types for the format
   * @param  string  $extensions One or more extensions (file suffix)
   * @return object              The new EasyRdf_Format object
   */
  public static function register($name, $label = null, $uri = null, $mimeTypes = array(), $extensions = array()) {
    if (!is_string($name) or $name == null or $name == '') {
      throw new InvalidArgumentException("\$name should be a string and cannot be null or empty");
    }
    if (!array_key_exists($name, self::$formats)) {
      self::$formats[$name] = new EasyRdf_Format($name);
    }
    self::$formats[$name]
      ->setLabel($label);
    self::$formats[$name]
      ->setUri($uri);
    self::$formats[$name]
      ->setMimeTypes($mimeTypes);
    self::$formats[$name]
      ->setExtensions($extensions);
    return self::$formats[$name];
  }

  /** Remove a format from the registry
   *
   * @param  string  $name      The name of the format (e.g. ntriples)
   */
  public static function unregister($name) {
    unset(self::$formats[$name]);
  }

  /** Class method to register a parser class to a format name
   *
   * @param  string  $name   The name of the format (e.g. ntriples)
   * @param  string  $class  The name of the class (e.g. EasyRdf_Parser_Ntriples)
   */
  public static function registerParser($name, $class) {
    if (!self::formatExists($name)) {
      self::register($name);
    }
    self::getFormat($name)
      ->setParserClass($class);
  }

  /** Class method to register a serialiser class to a format name
   *
   * @param  string  $name   The name of the format (e.g. ntriples)
   * @param  string  $class  The name of the class (e.g. EasyRdf_Serialiser_Ntriples)
   */
  public static function registerSerialiser($name, $class) {
    if (!self::formatExists($name)) {
      self::register($name);
    }
    self::getFormat($name)
      ->setSerialiserClass($class);
  }

  /** Attempt to guess the document format from some content.
   *
   * If $filename is given, then the suffix is first used to guess the format.
   *
   * If the document format is not recognised, null is returned.
   *
   * @param  string $data     The document data
   * @param  string $filename Optional filename
   * @return object EasyRdf_Format The format object
   */
  public static function guessFormat($data, $filename = null) {
    if (is_array($data)) {

      # Data has already been parsed into RDF/PHP
      return self::getFormat('php');
    }

    // First try and identify by the filename
    if ($filename and preg_match("/\\.(\\w+)\$/", $filename, $matches)) {
      foreach (self::$formats as $format) {
        if (in_array($matches[1], $format->extensions)) {
          return $format;
        }
      }
    }

    // Then try and guess by the first 255 bytes of content
    $short = substr($data, 0, 255);
    if (preg_match("/^\\s*\\{/", $short)) {
      return self::getFormat('json');
    }
    elseif (preg_match("/<rdf:/i", $short)) {
      return self::getFormat('rdfxml');
    }
    elseif (preg_match("/@prefix\\s|@base\\s/", $short)) {
      return self::getFormat('turtle');
    }
    elseif (preg_match("/^\\s*<.+> <.+>/m", $short)) {
      return self::getFormat('ntriples');
    }
    elseif (preg_match("|http://www.w3.org/2005/sparql-results|", $short)) {
      return self::getFormat('sparql-xml');
    }
    elseif (preg_match("/\\WRDFa\\W/i", $short)) {
      return self::getFormat('rdfa');
    }
    elseif (preg_match("/<!DOCTYPE html|<html/i", $short)) {

      # We don't support any other microformats embedded in HTML
      return self::getFormat('rdfa');
    }
    else {
      return null;
    }
  }

  /**
   * This constructor is for internal use only.
   * To create a new format, use the register method.
   *
   * @param  string  $name    The name of the format
   * @see    EasyRdf_Format::register()
   * @ignore
   */
  public function __construct($name) {
    $this->name = $name;
    $this->label = $name;

    # Only a default
  }

  /** Get the name of a format object
   *
   * @return string The name of the format (e.g. rdfxml)
   */
  public function getName() {
    return $this->name;
  }

  /** Get the label for a format object
   *
   * @return string The format label (e.g. RDF/XML)
   */
  public function getLabel() {
    return $this->label;
  }

  /** Set the label for a format object
   *
   * @param  string $label  The new label for the format
   */
  public function setLabel($label) {
    if ($label) {
      if (!is_string($label)) {
        throw new InvalidArgumentException("\$label should be a string");
      }
      return $this->label = $label;
    }
    else {
      return $this->label = null;
    }
  }

  /** Get the URI for a format object
   *
   * @return string The format URI
   */
  public function getUri() {
    return $this->uri;
  }

  /** Set the URI for a format object
   *
   * @param string $uri  The new URI for the format
   */
  public function setUri($uri) {
    if ($uri) {
      if (!is_string($uri)) {
        throw new InvalidArgumentException("\$uri should be a string");
      }
      return $this->uri = $uri;
    }
    else {
      return $this->uri = null;
    }
  }

  /** Get the default registered mime type for a format object
   *
   * @return string The default mime type as a string.
   */
  public function getDefaultMimeType() {
    $types = array_keys($this->mimeTypes);
    return $types[0];
  }

  /** Get all the registered mime types for a format object
   *
   * @return array One or more MIME types in an array with
   *               the mime type as the key and q value as the value
   */
  public function getMimeTypes() {
    return $this->mimeTypes;
  }

  /** Set the MIME Types for a format object
   *
   * @param array $mimeTypes  One or more mime types
   */
  public function setMimeTypes($mimeTypes) {
    if ($mimeTypes) {
      if (!is_array($mimeTypes)) {
        $mimeTypes = array(
          $mimeTypes,
        );
      }
      $this->mimeTypes = $mimeTypes;
    }
    else {
      $this->mimeTypes = array();
    }
  }

  /** Get the default registered file extension (filename suffix) for a format object
   *
   * @return string The default extension as a string.
   */
  public function getDefaultExtension() {
    return $this->extensions[0];
  }

  /** Get all the registered file extensions (filename suffix) for a format object
   *
   * @return array One or more extensions as an array
   */
  public function getExtensions() {
    return $this->extensions;
  }

  /** Set the file format extensions (filename suffix) for a format object
   *
   * @param mixed $extensions  One or more file extensions
   */
  public function setExtensions($extensions) {
    if ($extensions) {
      if (!is_array($extensions)) {
        $extensions = array(
          $extensions,
        );
      }
      $this->extensions = $extensions;
    }
    else {
      $this->extensions = array();
    }
  }

  /** Set the parser to use for a format
   *
   * @param string $class  The name of the class
   */
  public function setParserClass($class) {
    if ($class) {
      if (!is_string($class)) {
        throw new InvalidArgumentException("\$class should be a string");
      }
      $this->parserClass = $class;
    }
    else {
      $this->parserClass = null;
    }
  }

  /** Get the name of the class to use to parse the format
   *
   * @return string The name of the class
   */
  public function getParserClass() {
    return $this->parserClass;
  }

  /** Create a new parser to parse this format
   *
   * @return object The new parser object
   */
  public function newParser() {
    $parserClass = $this->parserClass;
    if (!$parserClass) {
      throw new EasyRdf_Exception("No parser class available for format: " . $this
        ->getName());
    }
    return new $parserClass();
  }

  /** Set the serialiser to use for a format
   *
   * @param string $class  The name of the class
   */
  public function setSerialiserClass($class) {
    if ($class) {
      if (!is_string($class)) {
        throw new InvalidArgumentException("\$class should be a string");
      }
      $this->serialiserClass = $class;
    }
    else {
      $this->serialiserClass = null;
    }
  }

  /** Get the name of the class to use to serialise the format
   *
   * @return string The name of the class
   */
  public function getSerialiserClass() {
    return $this->serialiserClass;
  }

  /** Create a new serialiser to parse this format
   *
   * @return object The new serialiser object
   */
  public function newSerialiser() {
    $serialiserClass = $this->serialiserClass;
    if (!$serialiserClass) {
      throw new EasyRdf_Exception("No serialiser class available for format: " . $this
        ->getName());
    }
    return new $serialiserClass();
  }

  /** Magic method to return the name of the format when casted to string
   *
   * @return string The name of the format
   */
  public function __toString() {
    return $this->name;
  }

}

/*
   Register default set of supported formats
   NOTE: they are ordered by preference
*/
EasyRdf_Format::register('php', 'RDF/PHP', 'http://n2.talis.com/wiki/RDF_PHP_Specification');
EasyRdf_Format::register('json', 'RDF/JSON Resource-Centric', 'http://n2.talis.com/wiki/RDF_JSON_Specification', array(
  'application/json' => 1.0,
  'text/json' => 0.9,
  'application/rdf+json' => 0.9,
), array(
  'json',
));
EasyRdf_Format::register('ntriples', 'N-Triples', 'http://www.w3.org/TR/rdf-testcases/#ntriples', array(
  'text/plain' => 1.0,
  'text/ntriples' => 0.9,
  'application/ntriples' => 0.9,
  'application/x-ntriples' => 0.9,
), array(
  'nt',
));
EasyRdf_Format::register('turtle', 'Turtle Terse RDF Triple Language', 'http://www.dajobe.org/2004/01/turtle', array(
  'text/turtle' => 0.8,
  'application/turtle' => 0.7,
  'application/x-turtle' => 0.7,
), array(
  'ttl',
));
EasyRdf_Format::register('rdfxml', 'RDF/XML', 'http://www.w3.org/TR/rdf-syntax-grammar', array(
  'application/rdf+xml' => 0.8,
), array(
  'rdf',
  'xrdf',
));
EasyRdf_Format::register('dot', 'Graphviz', 'http://www.graphviz.org/doc/info/lang.html', array(
  'text/vnd.graphviz' => 0.8,
), array(
  'gv',
  'dot',
));
EasyRdf_Format::register('json-triples', 'RDF/JSON Triples');
EasyRdf_Format::register('n3', 'Notation3', 'http://www.w3.org/2000/10/swap/grammar/n3#', array(
  'text/n3' => 0.5,
  'text/rdf+n3' => 0.5,
), array(
  'n3',
));
EasyRdf_Format::register('rdfa', 'RDFa', 'http://www.w3.org/TR/rdfa-core/', array(
  'text/html' => 0.4,
  'application/xhtml+xml' => 0.4,
), array(
  'html',
));
EasyRdf_Format::register('sparql-xml', 'SPARQL XML Query Results', 'http://www.w3.org/TR/rdf-sparql-XMLres/', array(
  'application/sparql-results+xml' => 1.0,
));
EasyRdf_Format::register('sparql-json', 'SPARQL JSON Query Results', 'http://www.w3.org/TR/rdf-sparql-json-res/', array(
  'application/sparql-results+json' => 1.0,
));
EasyRdf_Format::register('png', 'Portable Network Graphics (PNG)', 'http://www.w3.org/TR/PNG/', array(
  'image/png' => 0.3,
), array(
  'png',
));
EasyRdf_Format::register('gif', 'Graphics Interchange Format (GIF)', 'http://www.w3.org/Graphics/GIF/spec-gif89a.txt', array(
  'image/gif' => 0.2,
), array(
  'gif',
));
EasyRdf_Format::register('svg', 'Scalable Vector Graphics (SVG)', 'http://www.w3.org/TR/SVG/', array(
  'image/svg+xml' => 0.3,
), array(
  'svg',
));

/*
   Register default set of parsers and serialisers
*/
EasyRdf_Format::registerParser('json', 'EasyRdf_Parser_Json');
EasyRdf_Format::registerParser('ntriples', 'EasyRdf_Parser_Ntriples');
EasyRdf_Format::registerParser('php', 'EasyRdf_Parser_RdfPhp');
EasyRdf_Format::registerParser('rdfxml', 'EasyRdf_Parser_RdfXml');
EasyRdf_Format::registerParser('turtle', 'EasyRdf_Parser_Turtle');
EasyRdf_Format::registerParser('rdfa', 'EasyRdf_Parser_Rdfa');
EasyRdf_Format::registerSerialiser('json', 'EasyRdf_Serialiser_Json');
EasyRdf_Format::registerSerialiser('n3', 'EasyRdf_Serialiser_Turtle');
EasyRdf_Format::registerSerialiser('ntriples', 'EasyRdf_Serialiser_Ntriples');
EasyRdf_Format::registerSerialiser('php', 'EasyRdf_Serialiser_RdfPhp');
EasyRdf_Format::registerSerialiser('rdfxml', 'EasyRdf_Serialiser_RdfXml');
EasyRdf_Format::registerSerialiser('turtle', 'EasyRdf_Serialiser_Turtle');
EasyRdf_Format::registerSerialiser('dot', 'EasyRdf_Serialiser_GraphViz');
EasyRdf_Format::registerSerialiser('gif', 'EasyRdf_Serialiser_GraphViz');
EasyRdf_Format::registerSerialiser('png', 'EasyRdf_Serialiser_GraphViz');
EasyRdf_Format::registerSerialiser('svg', 'EasyRdf_Serialiser_GraphViz');