<?php

/*
 * This file is part of Twig.
 *
 * (c) 2011 Fabien Potencier
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

/**
 * Loads templates from other loaders.
 *
 * @author Fabien Potencier <fabien@symfony.com>
 */
class Twig_Loader_Chain implements Twig_LoaderInterface, Twig_ExistsLoaderInterface
{
  private $hasSourceCache = [];
  protected $loaders = [];

  /**
   * Constructor.
   *
   * @param Twig_LoaderInterface[] $loaders An array of loader instances
   */
  public function __construct(array $loaders = [])
  {
    foreach ($loaders as $loader) {
      $this->addLoader($loader);
    }
  }

  /**
   * Adds a loader instance.
   *
   * @param Twig_LoaderInterface $loader A Loader instance
   */
  public function addLoader(Twig_LoaderInterface $loader)
  {
    $this->loaders[] = $loader;
    $this->hasSourceCache = [];
  }

  /**
   * {@inheritdoc}
   */
  public function getSource($name)
  {
    $exceptions = [];
    foreach ($this->loaders as $loader) {
      if ($loader instanceof Twig_ExistsLoaderInterface && !$loader->exists($name)) {
        continue;
      }

      try {
        return $loader->getSource($name);
      } catch (Twig_Error_Loader $e) {
        $exceptions[] = $e->getMessage();
      }
    }

    throw new Twig_Error_Loader(sprintf('Template "%s" is not defined (%s).', $name, implode(', ', $exceptions)));
  }

  /**
   * {@inheritdoc}
   */
  public function exists($name)
  {
    $name = (string) $name;

    if (isset($this->hasSourceCache[$name])) {
      return $this->hasSourceCache[$name];
    }

    foreach ($this->loaders as $loader) {
      if ($loader instanceof Twig_ExistsLoaderInterface) {
        if ($loader->exists($name)) {
          return $this->hasSourceCache[$name] = true;
        }

        continue;
      }

      try {
        $loader->getSource($name);

        return $this->hasSourceCache[$name] = true;
      } catch (Twig_Error_Loader $e) {
      }
    }

    return $this->hasSourceCache[$name] = false;
  }

  /**
   * {@inheritdoc}
   */
  public function getCacheKey($name)
  {
    $exceptions = [];
    foreach ($this->loaders as $loader) {
      if ($loader instanceof Twig_ExistsLoaderInterface && !$loader->exists($name)) {
        continue;
      }

      try {
        return $loader->getCacheKey($name);
      } catch (Twig_Error_Loader $e) {
        $exceptions[] = get_class($loader) . ': ' . $e->getMessage();
      }
    }

    throw new Twig_Error_Loader(sprintf('Template "%s" is not defined (%s).', $name, implode(' ', $exceptions)));
  }

  /**
   * {@inheritdoc}
   */
  public function isFresh($name, $time)
  {
    $exceptions = [];
    foreach ($this->loaders as $loader) {
      if ($loader instanceof Twig_ExistsLoaderInterface && !$loader->exists($name)) {
        continue;
      }

      try {
        return $loader->isFresh($name, $time);
      } catch (Twig_Error_Loader $e) {
        $exceptions[] = get_class($loader) . ': ' . $e->getMessage();
      }
    }

    throw new Twig_Error_Loader(sprintf('Template "%s" is not defined (%s).', $name, implode(' ', $exceptions)));
  }
}
