thermograph/app.py

94 lines
4.7 KiB
Python

"""SSR frontend service: server-rendered content pages (content.py), the
interactive tool's SPA shells, and every static asset. All climate data comes
from the backend's content API over HTTP (api_client.py) -- this process
holds no data of its own and does no polars/DB work.
Repo-split Stage 7a: frontend now owns static-asset + SPA-shell serving too
(moved from backend/web/app.py, which used to read them from a sibling
frontend/ directory -- a relationship that won't exist once backend and
frontend are separate repos). Backend keeps a single catch-all proxy route as
its Caddy-less fallback, so every real topology is unaffected; only which
process actually reads the files off disk changed.
"""
import hashlib
import mimetypes
import os
from fastapi import FastAPI, Request, Response
from fastapi.staticfiles import StaticFiles
import content
# content's own `paths` (not a fresh `import paths` here) -- in the test
# environment, conftest.py's sys.modules swap-then-restore trick means a
# top-level `import paths` in THIS module, executed later than content.py's,
# would bind to backend's paths module instead of frontend's own (they share
# the bare name "paths"). content.paths was bound correctly during the swap
# window and stays that way regardless of what sys.modules["paths"] points to
# later -- reusing it sidesteps the timing issue entirely, in tests and prod
# alike.
paths = content.paths
app = FastAPI(title="Thermograph SSR", version="0.1.0")
# The PWA manifest is served as a static file; register its media type so
# StaticFiles labels it correctly (not in Python's default mimetypes map).
mimetypes.add_type("application/manifest+json", ".webmanifest")
@app.get("/healthz")
def healthz():
"""Liveness probe: the process is up and serving. Deliberately does no I/O
-- no call to the backend -- so it stays cheap and reliable for a tight
healthcheck interval. Readiness (backend reachable) is a separate concern."""
return {"status": "ok"}
def _not_modified(request: Request, etag: str) -> bool:
inm = request.headers.get("if-none-match")
return inm is not None and inm == etag
def _page(name):
"""Route handler for one SPA-shell HTML page (the interactive tool's
calendar/day/score/compare/legend/alerts views). Serves the file with its
__ORIGIN__ placeholder (the link-preview/Open Graph tags) filled in --
preview crawlers need absolute URLs, and the host differs between LAN and
prod. Uses content._origin (not a simpler duplicate) since this route is
reached both directly (Caddy) and through backend's proxy fallback, and
only that version prefers X-Forwarded-Host over Host (repo-split Stage 5)
-- required for the proxied case to resolve the real browser-facing host
instead of this internal hop's own address."""
path = os.path.join(paths.STATIC_DIR, name)
def route(request: Request):
with open(path, encoding="utf-8") as f:
html = f.read()
html = html.replace("__ORIGIN__", f"{content._origin(request)}{content.BASE}")
# Search-engine verification <meta> tags (same source as the SSR content
# pages), so the interactive tool's own pages carry them too.
verify = content.head_verify_html()
if verify:
html = html.replace("<head>", f"<head>\n {verify}", 1)
etag = f'W/"{hashlib.sha1(html.encode()).hexdigest()[:20]}"'
if _not_modified(request, etag):
return Response(status_code=304, headers={"ETag": etag})
return Response(html, media_type="text/html", headers={"ETag": etag})
return route
# NOTE: "/" is not here -- the homepage is server-rendered by content.register().
content.register(app)
app.add_api_route(f"{content.BASE}/calendar", _page("calendar.html"), methods=["GET", "HEAD"], include_in_schema=False)
app.add_api_route(f"{content.BASE}/day", _page("day.html"), methods=["GET", "HEAD"], include_in_schema=False)
app.add_api_route(f"{content.BASE}/score", _page("score.html"), methods=["GET", "HEAD"], include_in_schema=False)
app.add_api_route(f"{content.BASE}/compare", _page("compare.html"), methods=["GET", "HEAD"], include_in_schema=False)
app.add_api_route(f"{content.BASE}/legend", _page("legend.html"), methods=["GET", "HEAD"], include_in_schema=False)
app.add_api_route(f"{content.BASE}/alerts", _page("subscriptions.html"), methods=["GET", "HEAD"], include_in_schema=False)
# Everything else under BASE (app.js, style.css, nav.js, manifest, favicons, …)
# is a static asset. Registered last so the explicit routes above win. Mounts
# must start with "/", so at the root (BASE == "") mount at "/" -- the
# earlier routes still win because Starlette matches in registration order.
app.mount(content.BASE or "/", StaticFiles(directory=paths.STATIC_DIR), name="static")