From 47da79bae9289103d02f2a3ff3e69f34d6f8888f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Dagef=C3=B6rde?=
 <jan.dagefoerde@ercis.uni-muenster.de>
Date: Fri, 1 Mar 2019 18:21:42 +0100
Subject: [PATCH] MDL-64243 nextcloud: Add support for offline download for
 Moodle Mobile

---
 .../access_controlled_link_manager.php        | 21 ++++++++++++++++++
 repository/nextcloud/lib.php                  | 22 +++++++++++++++----
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/repository/nextcloud/classes/access_controlled_link_manager.php b/repository/nextcloud/classes/access_controlled_link_manager.php
index f80f1ccc4d8..f9abc6f722b 100644
--- a/repository/nextcloud/classes/access_controlled_link_manager.php
+++ b/repository/nextcloud/classes/access_controlled_link_manager.php
@@ -26,6 +26,7 @@ namespace repository_nextcloud;
 use context;
 use \core\oauth2\api;
 use \core\notification;
+use repository_exception;
 
 defined('MOODLE_INTERNAL') || die();
 require_once($CFG->libdir . '/webdavlib.php');
@@ -453,4 +454,24 @@ class access_controlled_link_manager{
             'filetarget' => (string) $validfile->file_target
             ];
     }
+
+    /**
+     * Download a file from the system account for the purpose of offline usage.
+     * @param string $srcpath Name of a file owned by the system account
+     * @param string $targetpath Temporary filename in Moodle
+     * @throws repository_exception The download was unsuccessful, maybe the file does not exist.
+     */
+    public function download_for_offline_usage(string $srcpath, string $targetpath): void {
+        $this->systemwebdavclient->open();
+        $webdavendpoint = issuer_management::parse_endpoint_url('webdav', $this->issuer);
+        $srcpath = ltrim($srcpath, '/');
+        $sourcepath = $webdavendpoint['path'] . $srcpath;
+
+        // Write file into temp location.
+        if (!$this->systemwebdavclient->get_file($sourcepath, $targetpath)) {
+            $this->systemwebdavclient->close();
+            throw new repository_exception('cannotdownload', 'repository');
+        }
+        $this->systemwebdavclient->close();
+    }
 }
diff --git a/repository/nextcloud/lib.php b/repository/nextcloud/lib.php
index faae5fc5dab..e2ad61f27c7 100644
--- a/repository/nextcloud/lib.php
+++ b/repository/nextcloud/lib.php
@@ -427,11 +427,25 @@ class repository_nextcloud extends repository {
             throw new \repository_nextcloud\request_exception(array('instance' => $repositoryname, 'errormessage' => $details));
         }
 
+        // Download for offline usage. This is strictly read-only, so the file need not be shared.
+        if (!empty($options['offline'])) {
+            // Download from system account and provide the file to the user.
+            $linkmanager = new \repository_nextcloud\access_controlled_link_manager($this->ocsclient,
+                $this->get_system_oauth_client(), $this->get_system_ocs_client(), $this->issuer, $repositoryname);
+
+            // Create temp path, then download into it.
+            $filename = basename($reference->link);
+            $tmppath = make_request_directory() . '/' . $filename;
+            $linkmanager->download_for_offline_usage($reference->link, $tmppath);
+
+            // Output the obtained file to the user and remove it from disk.
+            send_temp_file($tmppath, $filename);
+
+            // That's all.
+            return;
+        }
+
         if (!$this->client->is_logged_in()) {
-            if (!empty($options['offline'])) {
-                // Right now, we can't download referenced files for offline if the client is not authenticated.
-                send_file_not_found();  // Use this function because it enforces a 404 error.
-            }
             $this->print_login_popup(['style' => 'margin-top: 250px'], $options['embed']);
             return;
         }