MDL-34290 repository API: add repository function to import referenced file

it must be independed from sync_external_file because sync often does not actually download contents, it is used just to retrieve
the size of the file. Besides the timeouts for get_file and sync requests are very different.

Also add option to send_stored_file() to ignore reference and send cached contents

lib/filelib.php

@@ -2326,7 +2326,7 @@ function send_stored_file($stored_file, $lifetime=86400 , $filter=0, $forcedownl
     }
 
     // handle external resource
-    if ($stored_file && $stored_file->is_external_file()) {
+    if ($stored_file && $stored_file->is_external_file() && !isset($options['sendcachedexternalfile'])) {
         $stored_file->send_file($lifetime, $filter, $forcedownload, $options);
         die;
     }

lib/filestorage/file_storage.php

@@ -1841,15 +1841,15 @@ class file_storage {
     /**
      * Convert file alias to local file
      *
+     * @throws moodle_exception if file could not be downloaded
+     *
      * @param stored_file $storedfile a stored_file instances
+     * @param int $maxbytes throw an exception if file size is bigger than $maxbytes (0 means no limit)
      * @return stored_file stored_file
      */
-    public function import_external_file(stored_file $storedfile) {
+    public function import_external_file(stored_file $storedfile, $maxbytes = 0) {
         global $CFG;
-        require_once($CFG->dirroot.'/repository/lib.php');
-        // sync external file
-        repository::sync_external_file($storedfile);
-        // Remove file references
+        $storedfile->import_external_file_contents($maxbytes);
         $storedfile->delete_reference();
         return $storedfile;
     }

lib/filestorage/stored_file.php

@@ -928,4 +928,16 @@ class stored_file {
     public function send_file($lifetime, $filter, $forcedownload, $options) {
         $this->repository->send_file($this, $lifetime, $filter, $forcedownload, $options);
     }
+
+    /**
+     * Imports the contents of an external file into moodle filepool.
+     *
+     * @throws moodle_exception if file could not be downloaded or is too big
+     * @param int $maxbytes throw an exception if file size is bigger than $maxbytes (0 means no limit)
+     */
+    public function import_external_file_contents($maxbytes = 0) {
+        if ($this->repository) {
+            $this->repository->import_external_file_contents($this, $maxbytes);
+        }
+    }
 }

repository/lib.php

@@ -1632,6 +1632,77 @@ abstract class repository {
         return array('path'=>$path, 'url'=>$url);
     }
 
+    /**
+     * Downloads the file from external repository and saves it in moodle filepool.
+     * This function is different from {@link repository::sync_external_file()} because it has
+     * bigger request timeout and always downloads the content.
+     *
+     * This function is invoked when we try to unlink the file from the source and convert
+     * a reference into a true copy.
+     *
+     * @throws exception when file could not be imported
+     *
+     * @param stored_file $file
+     * @param int $maxbytes throw an exception if file size is bigger than $maxbytes (0 means no limit)
+     */
+    public function import_external_file_contents(stored_file $file, $maxbytes = 0) {
+        if (!$file->is_external_file()) {
+            // nothing to import if the file is not a reference
+            return;
+        } else if ($file->get_repository_id() != $this->id) {
+            // error
+            debugging('Repository instance id does not match');
+            return;
+        } else if ($this->has_moodle_files()) {
+            // files that are references to local files are already in moodle filepool
+            // just validate the size
+            if ($maxbytes > 0 && $file->get_filesize() > $maxbytes) {
+                throw new file_exception('maxbytes');
+            }
+            return;
+        } else {
+            if ($maxbytes > 0 && $file->get_filesize() > $maxbytes) {
+                // note that stored_file::get_filesize() also calls synchronisation
+                throw new file_exception('maxbytes');
+            }
+            $fs = get_file_storage();
+            $contentexists = $fs->content_exists($file->get_contenthash());
+            if ($contentexists && $file->get_filesize() && $file->get_contenthash() === sha1('')) {
+                // even when 'file_storage::content_exists()' returns true this may be an empty
+                // content for the file that was not actually downloaded
+                $contentexists = false;
+            }
+            $now = time();
+            if ($file->get_referencelastsync() + $file->get_referencelifetime() >= $now &&
+                        !$file->get_status() &&
+                        $contentexists) {
+                // we already have the content in moodle filepool and it was synchronised recently.
+                // Repositories may overwrite it if they want to force synchronisation anyway!
+                return;
+            } else {
+                // attempt to get a file
+                try {
+                    $fileinfo = $this->get_file($file->get_reference());
+                    if (isset($fileinfo['path'])) {
+                        list($contenthash, $filesize, $newfile) = $fs->add_file_to_pool($fileinfo['path']);
+                        // set this file and other similar aliases synchronised
+                        $lifetime = $this->get_reference_file_lifetime($file->get_reference());
+                        $file->set_synchronized($contenthash, $filesize, 0, $lifetime);
+                    } else {
+                        throw new moodle_exception('errorwhiledownload', 'repository', '', '');
+                    }
+                } catch (Exception $e) {
+                    if ($contentexists) {
+                        // better something than nothing. We have a copy of file. It's sync time
+                        // has expired but it is still very likely that it is the last version
+                    } else {
+                        throw($e);
+                    }
+                }
+            }
+        }
+    }
+
     /**
      * Return size of a file in bytes.
      *