<?php

namespace Drupal\Core\StreamWrapper;

/**
 * Defines a read-only Drupal stream wrapper base class for local files.
 *
 * This class extends the complete stream wrapper implementation in LocalStream.
 * URIs such as "public://example.txt" are expanded to a normal filesystem path
 * such as "sites/default/files/example.txt" and then PHP filesystem functions
 * are invoked.
 *
 * Drupal\Core\StreamWrapper\LocalReadOnlyStream implementations need to
 * implement at least the getDirectoryPath() and getExternalUrl() methods.
 */
abstract class LocalReadOnlyStream extends LocalStream {

  /**
   * {@inheritdoc}
   */
  public static function getType() {
    return StreamWrapperInterface::READ_VISIBLE | StreamWrapperInterface::LOCAL;
  }

  /**
   * {@inheritdoc}
   */
  public function stream_open($uri, $mode, $options, &$opened_path) {
    if (!in_array($mode, ['r', 'rb', 'rt'])) {
      if ($options & STREAM_REPORT_ERRORS) {
        trigger_error('stream_open() write modes not supported for read-only stream wrappers', E_USER_WARNING);
      }
      return FALSE;
    }
    return parent::stream_open($uri, $mode, $options, $opened_path);
  }

  /**
   * Support for flock().
   *
   * An exclusive lock attempt will be rejected, as this is a read-only stream
   * wrapper.
   *
   * @param int $operation
   *   One of the following:
   *   - LOCK_SH to acquire a shared lock (reader).
   *   - LOCK_EX to acquire an exclusive lock (writer).
   *   - LOCK_UN to release a lock (shared or exclusive).
   *   - LOCK_NB added as a bitmask if you don't want flock() to block while
   *     locking (not supported on Windows).
   *
   * @return bool
   *   Return FALSE for an exclusive lock (writer), as this is a read-only
   *   stream wrapper.  Return the result of flock() for other valid operations.
   *   Defaults to TRUE if an invalid operation is passed.
   *
   * @see http://php.net/manual/streamwrapper.stream-lock.php
   */
  public function stream_lock($operation) {
    // Disallow exclusive lock or non-blocking lock requests
    if (in_array($operation, [LOCK_EX, LOCK_EX | LOCK_NB])) {
      trigger_error('stream_lock() exclusive lock operations not supported for read-only stream wrappers', E_USER_WARNING);
      return FALSE;
    }
    if (in_array($operation, [LOCK_SH, LOCK_UN, LOCK_SH | LOCK_NB])) {
      return flock($this->handle, $operation);
    }

    return TRUE;
  }

  /**
   * Support for fwrite(), file_put_contents() etc.
   *
   * Data will not be written as this is a read-only stream wrapper.
   *
   * @param string $data
   *   The string to be written.
   *
   * @return bool
   *   FALSE as data will not be written.
   *
   * @see http://php.net/manual/streamwrapper.stream-write.php
   */
  public function stream_write($data) {
    trigger_error('stream_write() not supported for read-only stream wrappers', E_USER_WARNING);
    return FALSE;
  }

  /**
   * Support for fflush().
   *
   * Nothing will be output to the file, as this is a read-only stream wrapper.
   * However as stream_flush is called during stream_close we should not trigger
   * an error.
   *
   * @return bool
   *   FALSE, as no data will be stored.
   *
   * @see http://php.net/manual/streamwrapper.stream-flush.php
   */
  public function stream_flush() {
    return FALSE;
  }

  /**
   * {@inheritdoc}
   *
   * Does not change meta data as this is a read-only stream wrapper.
   */
  public function stream_metadata($uri, $option, $value) {
    trigger_error('stream_metadata() not supported for read-only stream wrappers', E_USER_WARNING);
    return FALSE;
  }

  /**
   * {@inheritdoc}
   */
  public function stream_truncate($new_size) {
    trigger_error('stream_truncate() not supported for read-only stream wrappers', E_USER_WARNING);
    return FALSE;
  }

  /**
   * Support for unlink().
   *
   * The file will not be deleted from the stream as this is a read-only stream
   * wrapper.
   *
   * @param string $uri
   *   A string containing the uri to the resource to delete.
   *
   * @return bool
   *   TRUE so that file_delete() will remove db reference to file. File is not
   *   actually deleted.
   *
   * @see http://php.net/manual/streamwrapper.unlink.php
   */
  public function unlink($uri) {
    trigger_error('unlink() not supported for read-only stream wrappers', E_USER_WARNING);
    return TRUE;
  }

  /**
   * Support for rename().
   *
   * The file will not be renamed as this is a read-only stream wrapper.
   *
   * @param string $from_uri
   *   The uri to the file to rename.
   * @param string $to_uri
   *   The new uri for file.
   *
   * @return bool
   *   FALSE as file will never be renamed.
   *
   * @see http://php.net/manual/streamwrapper.rename.php
   */
  public function rename($from_uri, $to_uri) {
    trigger_error('rename() not supported for read-only stream wrappers', E_USER_WARNING);
    return FALSE;
  }

  /**
   * Support for mkdir().
   *
   * Directory will never be created as this is a read-only stream wrapper.
   *
   * @param string $uri
   *   A string containing the URI to the directory to create.
   * @param int $mode
   *   Permission flags - see mkdir().
   * @param int $options
   *   A bit mask of STREAM_REPORT_ERRORS and STREAM_MKDIR_RECURSIVE.
   *
   * @return bool
   *   FALSE as directory will never be created.
   *
   * @see http://php.net/manual/streamwrapper.mkdir.php
   */
  public function mkdir($uri, $mode, $options) {
    trigger_error('mkdir() not supported for read-only stream wrappers', E_USER_WARNING);
    return FALSE;
  }

  /**
   * Support for rmdir().
   *
   * Directory will never be deleted as this is a read-only stream wrapper.
   *
   * @param string $uri
   *   A string containing the URI to the directory to delete.
   * @param int $options
   *   A bit mask of STREAM_REPORT_ERRORS.
   *
   * @return bool
   *   FALSE as directory will never be deleted.
   *
   * @see http://php.net/manual/streamwrapper.rmdir.php
   */
  public function rmdir($uri, $options) {
    trigger_error('rmdir() not supported for read-only stream wrappers', E_USER_WARNING);
    return FALSE;
  }

}