Add support for footnotes

n2y/main.py

@@ -157,11 +157,23 @@ def main(raw_args, access_token):
     return 0
 
 
+def get_database_pages_and_prefetch_blocks(database):
+    pages = []
+    for page in database.children:
+        # We're doing this because plugins may need to do some preprocessing
+        # on blocks before they're rendred by to_pandoc(). Because page.block
+        # is a lazy-loaded property, we need to pre-fetch it to make sure all
+        # block contructors are called before all block to_pandoc() calls.
+        _ = page.block
+        pages.append(page)
+    return pages
+
+
 def export_database_as_markdown_files(database, options):
     os.makedirs(options.output, exist_ok=True)
     seen_file_names = set()
     counts = {'unnamed': 0, 'duplicate': 0}
-    for page in database.children:
+    for page in get_database_pages_and_prefetch_blocks(database):
         if page.filename:
             if page.filename not in seen_file_names:
                 seen_file_names.add(page.filename)

n2y/plugins/footnotes.py

@@ -0,0 +1,88 @@
+import re
+import logging
+
+from pandoc.types import Note, Str, Para
+
+from n2y.rich_text import TextRichText
+from n2y.blocks import ParagraphBlock
+from n2y.errors import UseNextClass
+
+
+plugin_data_key = "n2y.plugins.footnotes"
+
+logger = logging.getLogger(__name__)
+
+
+class ParagraphWithFootnoteBlock(ParagraphBlock):
+    def __init__(self, client, notion_data, page, get_children=True):
+        super().__init__(client, notion_data, page, get_children)
+        if self._is_footnote():
+            self._attach_footnote_data()
+        else:
+            raise UseNextClass()
+
+    def to_pandoc(self):
+        return None if self._is_footnote() else super().to_pandoc()
+
+    def _attach_footnote_data(self):
+        if plugin_data_key not in self.client.plugin_data:
+            self.client.plugin_data[plugin_data_key] = {}
+        if self._footnote() not in self.client.plugin_data[plugin_data_key]:
+            self.client.plugin_data[plugin_data_key][self._footnote()] = self._footnote_ast()
+        else:
+            msg = 'Multiple footnotes for "[%s]". Skipping latest (%s)'
+            logger.warning(msg, self._footnote(), self.notion_url)
+
+    def _is_footnote(self):
+        return self._footnote() is not None
+
+    def _footnote(self):
+        first_str = self.rich_text.to_plain_text().split(" ")[0]
+        footnotes = re.findall(r"\[(\d+)\]:", first_str)
+        if len(footnotes) != 1:
+            return None
+        return footnotes[0]
+
+    def _footnote_ast(self):
+        ast = super().to_pandoc()
+        return Para(ast[0][2:]) if not isinstance(ast, list) else [Para(ast[0][0][2:])] + ast[1:]
+
+
+class TextRichTextWithFootnoteRef(TextRichText):
+    def __init__(self, client, notion_data):
+        super().__init__(client, notion_data)
+        if not self._is_footnote():
+            raise UseNextClass()
+
+    def to_pandoc(self):
+        pandoc_ast = []
+        for token in super().to_pandoc():
+            ref = self._footnote_from_token(token)
+            if ref is None:
+                pandoc_ast.append(token)
+                continue
+            if ref not in self.client.plugin_data[plugin_data_key]:
+                pandoc_ast.append(token)
+                logger.warning('Missing footnote "[%s]". Rendering as plain text', ref)
+                continue
+            block = self.client.plugin_data[plugin_data_key][ref]
+            footnote = Note(block) if isinstance(block, list) else Note([block])
+            pandoc_ast.append(footnote)
+        return pandoc_ast
+
+    def _is_footnote(self):
+        return any(self._footnote_from_token(t) is not None for t in super().to_pandoc())
+
+    def _footnote_from_token(self, token):
+        if not isinstance(token, Str):
+            return None
+        refs = re.findall(r"\[\^(\d+)\]", token[0])
+        if len(refs) != 1:
+            return None
+        return refs[0]
+
+
+notion_classes = {
+    "blocks": {"paragraph": ParagraphWithFootnoteBlock},
+    "rich_texts": {"text": TextRichTextWithFootnoteRef},
+}