First shot at supporting custom handler

app/customization.py

@@ -0,0 +1,112 @@
+from pathlib import Path
+from typing import Any
+from typing import Callable
+
+from fastapi import APIRouter
+from fastapi import Depends
+from fastapi import Request
+from starlette.responses import JSONResponse
+
+_DATA_DIR = Path().parent.resolve() / "data"
+_Handler = Callable[..., Any]
+
+
+class HTMLPage:
+    def __init__(
+        self,
+        title: str,
+        html_file: str,
+        show_in_navbar: bool,
+    ) -> None:
+        self.title = title
+        self.html_file = _DATA_DIR / html_file
+        self.show_in_navbar = show_in_navbar
+
+
+class RawHandler:
+    def __init__(
+        self,
+        title: str,
+        handler: Any,
+        show_in_navbar: bool,
+    ) -> None:
+        self.title = title
+        self.handler = handler
+        self.show_in_navbar = show_in_navbar
+
+
+_CUSTOM_ROUTES: dict[str, HTMLPage | RawHandler] = {}
+
+
+def register_html_page(
+    path: str,
+    *,
+    title: str,
+    html_file: str,
+    show_in_navbar: bool = True,
+) -> None:
+    if path in _CUSTOM_ROUTES:
+        raise ValueError(f"{path} is already registered")
+
+    _CUSTOM_ROUTES[path] = HTMLPage(title, html_file, show_in_navbar)
+
+
+def register_raw_handler(
+    path: str,
+    *,
+    title: str,
+    handler: _Handler,
+    show_in_navbar: bool = True,
+) -> None:
+    if path in _CUSTOM_ROUTES:
+        raise ValueError(f"{path} is already registered")
+
+    _CUSTOM_ROUTES[path] = RawHandler(title, handler, show_in_navbar)
+
+
+class ActivityPubResponse(JSONResponse):
+    media_type = "application/activity+json"
+
+
+def _custom_page_handler(path: str, html_page: HTMLPage) -> Any:
+    from app import templates
+    from app.actor import LOCAL_ACTOR
+    from app.config import is_activitypub_requested
+    from app.database import AsyncSession
+    from app.database import get_db_session
+
+    async def _handler(
+        request: Request,
+        db_session: AsyncSession = Depends(get_db_session),
+    ) -> templates.TemplateResponse | ActivityPubResponse:
+        if path == "/" and is_activitypub_requested(request):
+            return ActivityPubResponse(LOCAL_ACTOR.ap_actor)
+
+        return await templates.render_template(
+            db_session,
+            request,
+            "custom_page.html",
+            {
+                "page_content": html_page.html_file.read_text(),
+                "title": html_page.title,
+            },
+        )
+
+    return _handler
+
+
+def get_custom_router() -> APIRouter | None:
+    if not _CUSTOM_ROUTES:
+        return None
+
+    router = APIRouter()
+
+    for path, handler in _CUSTOM_ROUTES.items():
+        if isinstance(handler, HTMLPage):
+            router.add_api_route(
+                path, _custom_page_handler(path, handler), methods=["GET"]
+            )
+        else:
+            router.add_api_route(path, handler.handler)
+
+    return router