<?php

/**
 * @file
 * Module file for EXIF Orientation.
 */

use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\StreamWrapper\StreamWrapperManager;
use Drupal\file\FileInterface;

/**
 * Implements hook_file_presave().
 */
function exif_orientation_file_presave(EntityInterface $entity) {
  // Provide EXIF Orientation correction.
  _exif_orientation_rotate($entity);
}

/**
 * Implements hook_field_widget_single_element_form_alter().
 *
 * Add a custom validator before file_validate_image_resolution().
 * file_validate_image_resolution resizes the image if it's too large losing the
 * exif data in the process.
 */
function exif_orientation_field_widget_single_element_form_alter(&$element, FormStateInterface $form_state, $context) {
  if (isset($element['#upload_validators']['file_validate_image_resolution'])) {
    $element['#upload_validators'] = ['exif_orientation_validate_image_rotation' => []] + $element['#upload_validators'];
  }
}

/**
 * Ensures that image orientation is according to exif data.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity. This function may rotate the file.
 *
 * @return array
 *   An empty array.
 *
 * @see hook_file_validate()
 */
function exif_orientation_validate_image_rotation(FileInterface $file) {
  _exif_orientation_rotate($file);
  // This validator did not produce any errors.
  return [];
}

/**
 * Rotates an image to its EXIF Orientation.
 *
 * IPhone 4 and up save all images in landscape, relying on EXIF data to
 * set the orientation properly. This does not always translate well in the
 * browser or other devices.
 * See: http://www.daveperrett.com/articles/2012/07/28/exif-orientation-handling-is-a-ghetto/
 *
 * @param \Drupal\file\FileInterface $file
 *   File entity.
 */
function _exif_orientation_rotate(FileInterface $file) {
  $mime_types = ['image/jpeg', 'image/png'];

  if (function_exists('exif_read_data') && in_array($file->getMimeType(), $mime_types)) {

    $uri = $file->getFileUri();

    // Can't get stream wrapper if URI is without scheme.
    if (!StreamWrapperManager::getScheme($uri)) {
      $path = \Drupal::service('file_system')->realpath($uri);
    }
    else {
      /** @var \Drupal\Core\StreamWrapper\StreamWrapperInterface $wrapper */
      $wrapper = \Drupal::service('stream_wrapper_manager')->getViaUri($uri);
      $path = $wrapper->realpath();
      if (empty($path)) {
        $path = $wrapper->getExternalUrl();
      }
    }
    if (!$path) {
      return;
    }

    $file_exif = @exif_read_data($path);

    // Ensure that the Orientation key|value exists, otherwise leave.
    if (!is_array($file_exif) || !isset($file_exif['Orientation'])) {
      return;
    }

    // Orientation numbers and corresponding degrees.
    // @note: Odd numbers are flipped images, would need different process.
    switch ($file_exif['Orientation']) {
      case 3:
        $degrees = 180;
        break;

      case 6:
        $degrees = 90;
        break;

      case 8:
        $degrees = 270;
        break;

      default:
        $degrees = 0;
    }

    if ($degrees > 0) {
      $image = \Drupal::service('image.factory')->get($file->getFileUri());
      if ($image->rotate($degrees)) {
        $image->save();
      }
    }
  }
}