1 files changed, 85 insertions, 0 deletions
diff --git a/lib/metadata.py b/lib/metadata.py
new file mode 100644
index 00000000..837fbf00
--- /dev/null
+++ b/lib/metadata.py
@@ -0,0 +1,85 @@
+import json
+import re
+from collections.abc import MutableMapping
+
+import inkex
+from lxml import etree
+
+from .utils.settings import DEFAULT_METADATA, global_settings
+
+
+def strip_namespace(tag):
+    """Remove xml namespace from a tag name.
+
+    >>> {http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd}namedview
+    <<< namedview
+    """
+
+    match = re.match(r'^\{[^}]+\}(.+)$', tag)
+
+    if match:
+        return match.group(1)
+    else:
+        return tag
+
+
+class InkStitchMetadata(MutableMapping):
+    """Helper class to get and set inkstitch-specific metadata attributes.
+
+    Operates on a document and acts like a dict.  Setting an item adds or
+    updates a metadata element in the document.  Getting an item retrieves
+    a metadata element's text contents or None if an element by that name
+    doesn't exist.
+    """
+
+    def __init__(self, document):
+        super().__init__()
+        self.document = document
+        self.metadata = document.metadata
+
+        for setting in DEFAULT_METADATA:
+            if self[setting] is None:
+                self[setting] = global_settings[f'default_{setting}']
+
+    # Because this class inherints from MutableMapping, all we have to do is
+    # implement these five methods and we get a full dict-like interface.
+    def __setitem__(self, name, value):
+        item = self._find_item(name)
+        item.text = json.dumps(value)
+
+    def _find_item(self, name, create=True):
+        tag = inkex.addNS(name, "inkstitch")
+        item = self.metadata.find(tag)
+        if item is None and create:
+            item = etree.SubElement(self.metadata, tag)
+
+        return item
+
+    def __getitem__(self, name):
+        item = self._find_item(name)
+
+        try:
+            return json.loads(item.text)
+        except (ValueError, TypeError):
+            return None
+
+    def __delitem__(self, name):
+        item = self._find_item(name, create=False)
+
+        if item is not None:
+            self.metadata.remove(item)
+
+    def __iter__(self):
+        for child in self.metadata:
+            if child.prefix == "inkstitch":
+                yield strip_namespace(child.tag)
+
+    def __len__(self):
+        i = 0
+        for i, item in enumerate(self):
+            pass
+
+        return i + 1
+
+    def __json__(self):
+        return dict(self)