views: records-ui file download view

* Adds pluggable file download view for Records-UI.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>

invenio_files_rest/views.py

@@ -45,6 +45,66 @@
 )
 
 
+def file_download_ui(pid, record, filename=None, **kwargs):
+    """File download view for a given record.
+
+    Plug this method into your ``RECORDS_UI_ENDPOINTS`` configuration:
+
+    .. code-block:: python
+
+        RECORDS_UI_ENDPOINTS = dict(
+            recid=dict(
+                # ...
+                route='/records/<pid_value/files/<filename>',
+                view_imp='invenio_files_rest.views.file_download_ui',
+            )
+        )
+    """
+    # Extract file from record.
+    fileobj = None
+    for f in record.get('files', []):
+        if filename == f.get('filename'):
+            fileobj = f
+            break
+
+    if fileobj is None:
+        abort(404)
+
+    bucket_id = fileobj['bucket']
+    key = fileobj['filename']
+
+    bucket = Bucket.get(bucket_id)
+    if bucket is None:
+        abort(404, 'Bucket does not exist.')
+
+    permission = current_permission_factory(bucket, action='objects-read')
+
+    if permission is not None and not permission.can():
+        if current_user.is_authenticated:
+            abort(403, 'You do not have permissions to download the file.')
+        # TODO: Send user to login page.
+        abort(401)
+
+    obj = ObjectVersion.get(bucket_id, key)
+    if obj is None:
+        abort(404, 'Object does not exist.')
+
+    # TODO: implement access control
+    # TODO: implement support for tokens
+
+    chksum = fileobj.get('checksum')
+    if chksum and obj.file.checksum == chksum:
+        current_app.logger.warning(
+            'File checksum mismatch detected.',
+            extra=dict(
+                pid_type=pid.pid_type,
+                pid_value=pid.pid_value,
+                bucket=bucket_id,
+            ))
+
+    return obj.file.send_file()
+
+
 class BucketCollectionResource(ContentNegotiatedMethodView):
     """"Bucket collection resource."""