feat: add notion internal link plugin

n2y/plugins/internallinks.py

@@ -0,0 +1,64 @@
+import typing
+import uuid
+import urllib.parse
+
+from n2y.blocks import Block, ChildPageBlock
+from n2y.logger import logger
+from n2y.page import Page
+from n2y.rich_text import TextRichText
+from n2y.utils import header_id_from_text
+
+
+def get_notion_id_from_href(href: str) -> typing.Optional[str]:
+    """Extract the ID of a target block from a href"""
+    target_id = urllib.parse.urlparse(href, allow_fragments=True).fragment
+    if target_id is None:
+        return None
+    # Convert to UUID and back to ensure the format is correct
+    try:
+        return str(uuid.UUID(target_id))
+    except ValueError:
+        # fragment is not a Notion ID
+        return None
+
+
+def is_internal_link(href: str, notion_id: str) -> bool:
+    """Is the href fragment a link to a block on the same page?"""
+    return href is not None and href.startswith(f"/{notion_id.replace('-', '')}")
+
+
+def find_target_block(page: Page, target_id: str) -> Block:
+    try:
+        page_block: ChildPageBlock = page.block
+    except AttributeError:
+        logger.error(f"page block")
+        raise
+    try:
+        return next(
+            child for child in page_block.children if child.notion_id == target_id
+        )
+    except StopIteration:
+        logger.error(f"Page missing block with target id '{target_id}'")
+        raise
+
+
+class NotionInternalLink(TextRichText):
+
+    def to_pandoc(self):
+        if not is_internal_link(self.href, self.block.page.notion_id):
+            return super().to_pandoc()
+
+        target_id = get_notion_id_from_href(self.href)
+        if target_id is None:
+            logger.warning(
+                "Internal link missing; defaulting to link with no-op behavior"
+            )
+            return super().to_pandoc()
+
+        target_block = find_target_block(self.block.page, target_id)
+        header_id = header_id_from_text(target_block.rich_text.to_plain_text())
+        self.href = f"#{header_id}"
+        return super().to_pandoc()
+
+
+notion_classes = {"rich_texts": {"text": NotionInternalLink}}