port over base HTML layout from PHP to FastAPI+Jinja2

+ Mounted static files (at web/html) to /static.
+ Added AURWEB_VERSION to aurweb.config (this is used around HTML
  to refer back to aurweb's release on git.archlinux.org), so we
  need it easily accessible in the Python codebase.
+ Implemented basic Jinja2 partials to put together whole aurweb
  pages. This may be missing some things currently and is a WIP
  until this set is ready to be merged.
+ Added config [options] aurwebdir = YOUR_AUR_ROOT; this configuration
  option should specify the root directory of the aurweb project.
  It is used by various parts of the FastAPI codebase to target
  project directories.

Added routes via aurweb.routers.html:
    * POST /language: Set your session language.
    * GET /favicon.ico: Redirect to /static/images/favicon.ico.
        * Some browsers always look for $ROOT/favicon.ico to get an icon
          for the page being loaded, regardless of a specified "shortcut
          icon" given in a <link> directive.
    * GET /: Home page; WIP.

* Updated aurweb.routers.html.language passes query parameters to
  its next redirection.

When calling aurweb.templates.render_template, the context passed should
be formed via the aurweb.templates.make_context. See
aurweb.routers.html.index for an example of this.

Signed-off-by: Kevin Morris <kevr@0cost.org>

aurweb/asgi.py

@@ -2,13 +2,26 @@ import http
 
 from fastapi import FastAPI, HTTPException
 from fastapi.responses import HTMLResponse
+from fastapi.staticfiles import StaticFiles
 from starlette.middleware.sessions import SessionMiddleware
 
 import aurweb.config
 
-from aurweb.routers import sso
+from aurweb.routers import html, sso
 
+routes = set()
+
+# Setup the FastAPI app.
 app = FastAPI()
+app.mount("/static/css",
+          StaticFiles(directory="web/html/css"),
+          name="static_css")
+app.mount("/static/js",
+          StaticFiles(directory="web/html/js"),
+          name="static_js")
+app.mount("/static/images",
+          StaticFiles(directory="web/html/images"),
+          name="static_images")
 
 session_secret = aurweb.config.get("fastapi", "session_secret")
 if not session_secret:
@@ -17,6 +30,14 @@ if not session_secret:
 app.add_middleware(SessionMiddleware, secret_key=session_secret)
 
 app.include_router(sso.router)
+app.include_router(html.router)
+
+# NOTE: Always keep this dictionary updated with all routes
+# that the application contains. We use this to check for
+# parameter value verification.
+routes = {route.path for route in app.routes}
+routes.update({route.path for route in sso.router.routes})
+routes.update({route.path for route in html.router.routes})
 
 
 @app.exception_handler(HTTPException)

aurweb/config.py

@@ -1,6 +1,11 @@
 import configparser
 import os
 
+# Publicly visible version of aurweb. This is used to display
+# aurweb versioning in the footer and must be maintained.
+# Todo: Make this dynamic/automated.
+AURWEB_VERSION = "v5.0.0"
+
 _parser = None
 
 

aurweb/routers/html.py

@@ -0,0 +1,50 @@
+""" AURWeb's primary routing module. Define all routes via @app.app.{get,post}
+decorators in some way; more complex routes should be defined in their
+own modules and imported here. """
+from http import HTTPStatus
+from urllib.parse import unquote
+
+from fastapi import APIRouter, Form, Request
+from fastapi.responses import HTMLResponse, RedirectResponse
+
+from aurweb.templates import make_context, render_template
+
+router = APIRouter()
+
+
+@router.get("/favicon.ico")
+async def favicon(request: Request):
+    """ Some browsers attempt to find a website's favicon via root uri at
+    /favicon.ico, so provide a redirection here to our static icon. """
+    return RedirectResponse("/static/images/favicon.ico")
+
+
+@router.post("/language", response_class=RedirectResponse)
+async def language(request: Request,
+                   set_lang: str = Form(...),
+                   next: str = Form(...),
+                   q: str = Form(default=None)):
+    """ A POST route used to set a session's language.
+
+    Return a 303 See Other redirect to {next}?next={next}. If we are
+    setting the language on any page, we want to preserve query
+    parameters across the redirect.
+    """
+    from aurweb.asgi import routes
+    if unquote(next) not in routes:
+        return HTMLResponse(
+            b"Invalid 'next' parameter.",
+            status_code=400)
+
+    query_string = "?" + q if q else str()
+    response = RedirectResponse(url=f"{next}{query_string}",
+                                status_code=int(HTTPStatus.SEE_OTHER))
+    response.set_cookie("AURLANG", set_lang)
+    return response
+
+
+@router.get("/", response_class=HTMLResponse)
+async def index(request: Request):
+    """ Homepage route. """
+    context = make_context(request, "Home")
+    return render_template("index.html", context)

aurweb/templates.py

@@ -0,0 +1,57 @@
+import copy
+import os
+
+from datetime import datetime
+from http import HTTPStatus
+
+import jinja2
+
+from fastapi import Request
+from fastapi.responses import HTMLResponse
+
+import aurweb.config
+
+from aurweb import l10n
+
+# Prepare jinja2 objects.
+loader = jinja2.FileSystemLoader(os.path.join(
+    aurweb.config.get("options", "aurwebdir"), "templates"))
+env = jinja2.Environment(loader=loader, autoescape=True,
+                         extensions=["jinja2.ext.i18n"])
+
+# Add tr translation filter.
+env.filters["tr"] = l10n.tr
+
+
+def make_context(request: Request, title: str, next: str = None):
+    """ Create a context for a jinja2 TemplateResponse. """
+
+    return {
+        "request": request,
+        "language": l10n.get_request_language(request),
+        "languages": l10n.SUPPORTED_LANGUAGES,
+        "title": title,
+        # The 'now' context variable will not show proper datetimes
+        # until we've implemented timezone support here.
+        "now": datetime.now(),
+        "config": aurweb.config,
+        "next": next if next else request.url.path
+    }
+
+
+def render_template(path: str, context: dict, status_code=int(HTTPStatus.OK)):
+    """ Render a Jinja2 multi-lingual template with some context. """
+
+    # Create a deep copy of our jinja2 environment. The environment in
+    # total by itself is 48 bytes large (according to sys.getsizeof).
+    # This is done so we can install gettext translations on the template
+    # environment being rendered without installing them into a global
+    # which is reused in this function.
+    templates = copy.copy(env)
+
+    translator = l10n.get_raw_translator_for_request(context.get("request"))
+    templates.install_gettext_translations(translator)
+
+    template = templates.get_template(path)
+    rendered = template.render(context)
+    return HTMLResponse(rendered, status_code=status_code)