1 files changed, 76 insertions, 0 deletions
diff --git a/bsie/matcher/default_matcher.py b/bsie/matcher/default_matcher.py
new file mode 100644
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+++ b/bsie/matcher/default_matcher.py
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+
+# standard imports
+import os
+import typing
+import urllib
+
+# bsie imports
+from bsie.utils import bsfs
+
+# inner-module imports
+from . import nodes
+from .matcher import Matcher
+
+# exports
+__all__: typing.Sequence[str] = (
+    'DefaultMatcher',
+    )
+
+
+## code ##
+
+class DefaultMatcher(Matcher):
+    """Compose URIs as <host/user/node_type#fragment>
+
+    What information is used as fragment depends on the node type.
+    Typically, the default is to use the "ucid" hint.
+    The fallback in all cases is to generate a random uuid.
+
+    Never changes previously assigned uris. Sets uris in-place.
+
+    """
+
+    def __init__(
+            self,
+            host: bsfs.URI,
+            user: str,
+            ):
+        self._prefix = bsfs.Namespace(os.path.join(host, user))
+
+    def match_node(self, node: nodes.Node) -> nodes.Node:
+        if node.uri is not None:
+            return node
+        if isinstance(node, nodes.Entity):
+            return self.match_entity(node)
+        if isinstance(node, nodes.Preview):
+            return self.match_preview(node)
+        if isinstance(node, nodes.Tag):
+            return self.match_tag(node)
+        if isinstance(node, nodes.Face):
+            return self.match_face(node)
+        raise ValueError(f'no matching policy available for bsfs.typename{node}')
+
+    def match_entity(self, node: nodes.Entity) -> nodes.Entity:
+        """Set a bsn:Entity node's uri fragment to its ucid."""
+        node.uri = getattr(self._prefix.file(), node.ucid)
+        return node
+
+    def match_preview(self, node: nodes.Preview) -> nodes.Preview:
+        """Set a bsn:Preview node's uri fragment to its ucid and size suffix."""
+        fragment = node.ucid + '_s' + str(node.size)
+        node.uri = getattr(self._prefix.preview(), fragment)
+        return node
+
+    def match_tag(self, node: nodes.Tag) -> nodes.Tag:
+        """Set a bsn:Tag node's uri to its label."""
+        # FIXME: match to existing tags in bsfs storage?!
+        fragment = urllib.parse.quote(node.label)
+        node.uri = getattr(self._prefix.tag(), fragment)
+        return node
+
+    def match_face(self, node: nodes.Face) -> nodes.Face:
+        """Set a bsn:Face node's uri to its ucid."""
+        node.uri = getattr(self._prefix.face(), node.ucid)
+        return node
+
+## EOF ##