<?php
/**
 * @file
 * The extension registry.
 */
namespace QueryPath;
/**
 * A registry for QueryPath extensions.
 *
 * QueryPath extensions should call the QueryPath::ExtensionRegistry::extend()
 * function to register their extension classes. The QueryPath library then
 * uses this information to determine what QueryPath extensions should be loaded and
 * executed.
 *
 * Extensions are attached to a Query object.
 *
 * To enable an extension (the easy way), use QueryPath::enable().
 *
 * This class provides lower-level interaction with the extension
 * mechanism.
 *
 * @ingroup querypath_extensions
 */
class ExtensionRegistry {
  /**
   * Internal flag indicating whether or not the registry should
   * be used for automatic extension loading. If this is false, then
   * implementations should not automatically load extensions.
   */
  public static $useRegistry = TRUE;
  /**
   * The extension registry. This should consist of an array of class
   * names.
   */
  protected static $extensionRegistry = array();
  protected static $extensionMethodRegistry = array();
  /**
   * Extend a Query with the given extension class.
   */
  public static function extend($classname) {
    self::$extensionRegistry[] = $classname;
    $class = new \ReflectionClass($classname);
    $methods = $class->getMethods();
    foreach ($methods as $method) {
      self::$extensionMethodRegistry[$method->getName()] = $classname;
    }
  }

  /**
   * Check to see if a method is known.
   * This checks to see if the given method name belongs to one of the
   * registered extensions. If it does, then this will return TRUE.
   *
   * @param string $name
   *  The name of the method to search for.
   * @return boolean
   *  TRUE if the method exists, false otherwise.
   */
  public static function hasMethod($name) {
    return isset(self::$extensionMethodRegistry[$name]);
  }

  /**
   * Check to see if the given extension class is registered.
   * Given a class name for a QueryPath::Extension class, this
   * will check to see if that class is registered. If so, it will return
   * TRUE.
   *
   * @param string $name
   *  The name of the class.
   * @return boolean
   *  TRUE if the class is registered, FALSE otherwise.
   */
  public static function hasExtension($name) {
    return in_array($name, self::$extensionRegistry);
  }

  /**
   * Get the class that a given method belongs to.
   * Given a method name, this will check all registered extension classes
   * to see if any of them has the named method. If so, this will return
   * the classname.
   *
   * Note that if two extensions are registered that contain the same
   * method name, the last one registred will be the only one recognized.
   *
   * @param string $name
   *  The name of the method.
   * @return string
   *  The name of the class.
   */
  public static function getMethodClass($name) {
    return self::$extensionMethodRegistry[$name];
  }

  /**
   * Get extensions for the given Query object.
   *
   * Given a Query object, this will return
   * an associative array of extension names to (new) instances.
   * Generally, this is intended to be used internally.
   *
   * @param Query $qp
   *  The Query into which the extensions should be registered.
   * @return array
   *  An associative array of classnames to instances.
   */
  public static function getExtensions(Query $qp) {
    $extInstances = array();
    foreach (self::$extensionRegistry as $ext) {
      $extInstances[$ext] = new $ext($qp);
    }
    return $extInstances;
  }

  public static function extensionNames() {
    return self::$extensionRegistry;
  }

  /**
   * Enable or disable automatic extension loading.
   *
   * If extension autoloading is disabled, then QueryPath will not
   * automatically load all registred extensions when a new Query
   * object is created using qp().
   */
  public static function autoloadExtensions($boolean = TRUE) {
    self::$useRegistry = $boolean;
  }
}