130 lines
4.4 KiB
Python
130 lines
4.4 KiB
Python
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"""FastAPI entrypoint for hmrc-sync.
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Endpoints:
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- GET /authorize — redirect to HMRC OAuth, primes refresh_token
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- GET /callback — OAuth callback; exchange code, persist token
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- POST /callback-metadata — browser-side session attributes (fraud headers)
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- POST /sync — pull latest HMRC figures for a given tax year
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- GET /healthz — readiness + queue depth
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"""
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from __future__ import annotations
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import logging
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import os
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import secrets
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import urllib.parse
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from contextlib import asynccontextmanager
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from typing import Any
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from fastapi import FastAPI, HTTPException, Request
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from fastapi.responses import HTMLResponse, RedirectResponse
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from prometheus_fastapi_instrumentator import Instrumentator
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from hmrc_sync import oauth
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from hmrc_sync.fraud_headers import SessionContext
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log = logging.getLogger(__name__)
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REQUIRED_ENV = [
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"HMRC_PROD_CLIENT_ID",
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"HMRC_PROD_CLIENT_SECRET",
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"HMRC_PROD_REDIRECT_URI",
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"DB_CONNECTION_STRING",
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]
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def _verify_env() -> None:
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missing = [k for k in REQUIRED_ENV if not os.environ.get(k)]
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if missing:
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raise RuntimeError(f"Missing required env vars: {', '.join(missing)}")
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@asynccontextmanager
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async def lifespan(app: FastAPI): # type: ignore[no-untyped-def]
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_verify_env()
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app.state.session_context = SessionContext(
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device_id=os.environ.get("HMRC_DEVICE_ID", ""),
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public_ip=os.environ.get("HMRC_VENDOR_PUBLIC_IP", ""),
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)
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app.state.oauth_states = {} # anti-CSRF state → expires_at
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yield
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app = FastAPI(title="HMRC Sync", lifespan=lifespan)
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Instrumentator().instrument(app).expose(app, endpoint="/metrics")
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@app.get("/healthz")
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async def healthz() -> dict[str, Any]:
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return {"status": "ok"}
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@app.get("/authorize")
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async def authorize() -> RedirectResponse:
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creds = oauth.load_creds_from_env()
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state = secrets.token_urlsafe(24)
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app.state.oauth_states[state] = True
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params = urllib.parse.urlencode({
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"response_type": "code",
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"client_id": creds.client_id,
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"scope": "read:self-assessment",
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"redirect_uri": creds.redirect_uri,
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"state": state,
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})
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return RedirectResponse(f"{oauth.PROD_BASE}/oauth/authorize?{params}")
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@app.get("/callback", response_class=HTMLResponse)
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async def callback(code: str, state: str) -> HTMLResponse:
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if state not in app.state.oauth_states:
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raise HTTPException(status_code=400, detail="unknown state (CSRF)")
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del app.state.oauth_states[state]
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creds = oauth.load_creds_from_env()
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token = await oauth.exchange_code(creds, code)
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oauth.persist_to_vault(token)
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# Serve a 1-page form that POSTs browser attributes to /callback-metadata
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# so we capture the per-session values HMRC wants in fraud headers.
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return HTMLResponse(_metadata_capture_html())
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@app.post("/callback-metadata")
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async def callback_metadata(request: Request) -> dict[str, str]:
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body = await request.json()
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session: SessionContext = app.state.session_context
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session.user_agent = str(body.get("user_agent", "") or "")
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session.screen_width = int(body.get("screen_width", 0) or 0)
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session.screen_height = int(body.get("screen_height", 0) or 0)
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session.screen_colour_depth = int(body.get("screen_colour_depth", 0) or 0)
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session.window_width = int(body.get("window_width", 0) or 0)
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session.window_height = int(body.get("window_height", 0) or 0)
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session.timezone_offset = int(body.get("timezone_offset", 0) or 0)
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return {"status": "captured"}
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@app.post("/sync")
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async def sync(tax_year: str | None = None) -> dict[str, Any]:
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"""Pull latest HMRC figures for `tax_year` (default: current fiscal year)."""
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raise HTTPException(status_code=501, detail="Sync not yet implemented — awaiting HMRC prod approval")
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def _metadata_capture_html() -> str:
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return """<!doctype html>
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<html><head><title>hmrc-sync — capturing session</title></head><body>
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<h2>Capturing session attributes for HMRC fraud headers...</h2>
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<script>
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fetch('/callback-metadata', {
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method: 'POST',
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headers: {'Content-Type': 'application/json'},
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body: JSON.stringify({
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user_agent: navigator.userAgent,
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screen_width: screen.width,
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screen_height: screen.height,
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screen_colour_depth: screen.colorDepth,
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window_width: window.innerWidth,
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window_height: window.innerHeight,
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timezone_offset: -new Date().getTimezoneOffset()
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})
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}).then(() => document.body.innerHTML = '<h2>Done. You can close this tab.</h2>');
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</script>
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</body></html>"""
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