preview extractor

1 files changed, 19 insertions, 0 deletions

diff --git a/bsie/lib/naming_policy.py b/bsie/lib/naming_policy.py
index 360abde..131a70b 100644
--- a/bsie/lib/naming_policy.py
+++ b/bsie/lib/naming_policy.py
@@ -87,6 +87,8 @@ class DefaultNamingPolicy(NamingPolicy):
             return node
         if node.node_type == ns.bsfs.File:
             return self.name_file(node)
+        if node.node_type == ns.bsfs.Preview:
+            return self.name_preview(node)
         raise errors.ProgrammingError('no naming policy available for {node.node_type}')
 
     def name_file(self, node: Node) -> Node:
@@ -98,4 +100,21 @@ class DefaultNamingPolicy(NamingPolicy):
         node.uri = (self._prefix + 'file')[fragment]
         return node
 
+    def name_preview(self, node: Node) -> Node:
+        """Set a bsfs:Preview node's uri fragment to its ucid.
+        Uses its source fragment as fallback. Appends the size if provided.
+        """
+        fragment = None
+        if 'ucid' in node.hints: # content id
+            fragment = node.hints['ucid']
+        if fragment is None and 'source' in node.hints: # source id
+            self.handle_node(node.hints['source'])
+            fragment = node.hints['source'].uri.get('fragment', None)
+        if fragment is None: # random name
+            fragment = self._uuid()
+        if 'size' in node.hints: # append size
+            fragment += '_s' + str(node.hints['size'])
+        node.uri = (self._prefix + 'preview')[fragment]
+        return node
+
 ## EOF ##