First shot at supporting custom handler

app/config.py

@@ -14,6 +14,7 @@ from itsdangerous import URLSafeTimedSerializer
 from loguru import logger
 from mistletoe import markdown  # type: ignore
 
+from app.customization import _CUSTOM_ROUTES
 from app.utils.emoji import _load_emojis
 from app.utils.version import get_version_commit
 
@@ -184,6 +185,31 @@ CODE_HIGHLIGHTING_THEME = CONFIG.code_highlighting_theme
 MOVED_TO = _get_moved_to()
 
 
+_NavBarItem = tuple[str, str]
+
+
+class NavBarItems:
+    EXTRA_NAVBAR_ITEMS: list[_NavBarItem] = []
+    INDEX_NAVBAR_ITEM: _NavBarItem | None = None
+    NOTES_PATH = "/"
+
+
+def load_custom_routes() -> None:
+    try:
+        from data import custom_routes  # type: ignore  # noqa: F401
+    except ImportError:
+        pass
+
+    for path, custom_handler in _CUSTOM_ROUTES.items():
+        # If a handler wants to replace the root, move the index to /notes
+        if path == "/":
+            NavBarItems.NOTES_PATH = "/notes"
+            NavBarItems.INDEX_NAVBAR_ITEM = (path, custom_handler.title)
+        else:
+            if custom_handler.show_in_navbar:
+                NavBarItems.EXTRA_NAVBAR_ITEMS.append((path, custom_handler.title))
+
+
 session_serializer = URLSafeTimedSerializer(
     CONFIG.secret,
     salt=f"{ID}.session",

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

app/main.py

@@ -63,6 +63,7 @@ from app.config import USER_AGENT
 from app.config import USERNAME
 from app.config import is_activitypub_requested
 from app.config import verify_csrf_token
+from app.customization import get_custom_router
 from app.database import AsyncSession
 from app.database import async_session
 from app.database import get_db_session
@@ -192,6 +193,9 @@ app.include_router(admin.unauthenticated_router, prefix="/admin")
 app.include_router(indieauth.router)
 app.include_router(micropub.router)
 app.include_router(webmentions.router)
+config.load_custom_routes()
+if custom_router := get_custom_router():
+    app.include_router(custom_router)
 
 # XXX: order matters, the proxy middleware needs to be last
 app.add_middleware(CustomMiddleware)
@@ -243,7 +247,7 @@ class ActivityPubResponse(JSONResponse):
     media_type = "application/activity+json"
 
 
-@app.get("/")
+@app.get(config.NavBarItems.NOTES_PATH)
 async def index(
     request: Request,
     db_session: AsyncSession = Depends(get_db_session),

app/templates.py

@@ -429,3 +429,4 @@ _templates.env.globals["CSS_HASH"] = config.CSS_HASH
 _templates.env.globals["BASE_URL"] = config.BASE_URL
 _templates.env.globals["HIDES_FOLLOWERS"] = config.HIDES_FOLLOWERS
 _templates.env.globals["HIDES_FOLLOWING"] = config.HIDES_FOLLOWING
+_templates.env.globals["NAVBAR_ITEMS"] = config.NavBarItems

app/templates/custom_page.html

@@ -0,0 +1,30 @@
+{%- import "utils.html" as utils with context -%}
+{% extends "layout.html" %}
+
+{% block head %}
+<title>{{ title }}</title>
+{% if request.url.path == "/" %}
+<link rel="indieauth-metadata" href="{{ url_for("well_known_authorization_server") }}">
+<link rel="authorization_endpoint" href="{{ url_for("indieauth_authorization_endpoint") }}">
+<link rel="token_endpoint" href="{{ url_for("indieauth_token_endpoint") }}">
+<link rel="micropub" href="{{ url_for("micropub_endpoint") }}">
+<link rel="alternate" href="{{ local_actor.url }}" title="ActivityPub profile"  type="application/activity+json">
+<meta content="profile" property="og:type" />
+<meta content="{{ local_actor.url }}" property="og:url" />
+<meta content="{{ local_actor.display_name }}'s microblog" property="og:site_name" />
+<meta content="Homepage" property="og:title" />
+<meta content="{{ local_actor.summary | html2text | trim }}" property="og:description" />
+<meta content="{{ local_actor.url }}" property="og:image" />
+<meta content="summary" property="twitter:card" />
+<meta content="{{ local_actor.handle }}" property="profile:username" />
+{% endif %}
+{% endblock %}
+
+{% block content %}
+{% include "header.html" %}
+
+<div class="box">
+    {{ page_content | safe }}
+</div>
+
+{% endblock %}

app/templates/header.html

@@ -29,9 +29,16 @@
 <a href="{{ url_for }}" {% if request.url.path == url_for %}class="active"{% endif %}>{{ text }}</a>
 {% endmacro %}
 
+{%- macro navbar_item_link(navbar_item) -%}
+<a href="{{ navbar_item[0] }}" {% if request.url.path == navbar_item[0] %}class="active"{% endif %}>{{ navbar_item[1] }}</a>
+{% endmacro %}
+
 <div class="public-top-menu">
 <nav class="flexbox">
     <ul>
+        {% if NAVBAR_ITEMS.INDEX_NAVBAR_ITEM %}
+        <li>{{ navbar_item_link(NAVBAR_ITEMS.INDEX_NAVBAR_ITEM) }}</li>
+        {% endif %}
         <li>{{ header_link("index", "Notes") }}</li>
         {% if articles_count %}
             <li>{{ header_link("articles", "Articles") }}</li>
@@ -43,6 +50,9 @@
         <li>{{ header_link("following", "Following") }} <span class="counter">{{ following_count }}</span></li>
         {% endif %}
         <li>{{ header_link("get_remote_follow", "Remote follow") }}</li>
+        {% for navbar_item in NAVBAR_ITEMS.EXTRA_NAVBAR_ITEMS %}
+            {{ navbar_item_link(navbar_item) }}
+        {% endfor %}
     </ul>
 </nav>
 </div>

app/utils/custom_index_handler.py

@@ -0,0 +1,32 @@
+from typing import Any
+from typing import Awaitable
+from typing import Callable
+
+from fastapi import Depends
+from fastapi import Request
+from fastapi.responses import JSONResponse
+
+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
+
+_Handler = Callable[[Request, AsyncSession], Awaitable[Any]]
+
+
+def build_custom_index_handler(handler: _Handler) -> _Handler:
+    async def custom_index(
+        request: Request,
+        db_session: AsyncSession = Depends(get_db_session),
+    ) -> Any:
+        # Serve the AP actor if requested
+        if is_activitypub_requested(request):
+            return JSONResponse(
+                LOCAL_ACTOR.ap_actor,
+                media_type="application/activity+json",
+            )
+
+        # Defer to the custom handler
+        return await handler(request, db_session)
+
+    return custom_index