FuelBoard Contributor
b315f4dc47
- Talks to the OFFICIAL GOV.UK Fuel Finder API instead of the public CSV mirror: OAuth token (/api/v1/oauth/generate_access_token), batched paging (500/page via batch-number) over /api/v1/pfs and /api/v1/pfs/fuel-prices, joined on node_id. - Price strings parsed to pence with pounds->pence correction (< 2.0); 50-500p sane band keeps junk out of the cheapest reference. - Fuel mapping: E5/E10 as-is; B7/B7_STANDARD/B7S/B7P/B10 -> DIESEL; HVO/SDV dropped (app tracks E5/E10/DIESEL only). - lat/lng parsed from nested location strings. - Output contract IDENTICAL to fuelboard-relay (/health + /api/v1/stations), so the app/widget/alerts work unchanged; switch = point app at :8789. - CSV mirror kept as automatic fallback (FUEL_SOURCE=auto) so the full path is testable before GOV.UK One Login creds exist. - 12 unit tests against documented API shapes (no network).
98 lines
4.2 KiB
Markdown
98 lines
4.2 KiB
Markdown
# FuelBoard Relay API
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Keyless proxy for the **official UK Fuel Finder API** (the OAuth-protected
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GOV.UK service). Sibling of `fuelboard-relay` (which reads the public CSV
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mirror): this one talks to the real API, joins the station-info and fuel-price
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endpoints on `node_id`, and normalises to the **same output shape** so the
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FuelBoard iOS app and widget work against either relay unchanged.
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Holds the GOV.UK OAuth 2.0 client credentials server-side so the app never
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embeds a secret (secrets inside an IPA are extractable by anyone).
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## Architecture
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```
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FuelBoard app / widget
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│ GET http://192.168.1.131:8789/api/v1/stations?fuel=e10&lat=..&lng=..
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▼
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FuelBoard Relay API (this repo, runs on the Mac Mini)
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│ POST /api/v1/oauth/generate_access_token (token cached ~1h)
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│ GET /api/v1/pfs?batch-number=N (station info, 500/page)
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│ GET /api/v1/pfs/fuel-prices?batch-number=N (prices, 500/page)
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▼
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UK Fuel Finder API (official gov.uk open data)
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```
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- Token refreshed automatically before expiry (60s buffer); reused across the
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two batched loops (docs: reuse tokens until near expiry).
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- Both endpoints paginated 500 records/page via `batch-number` until a short
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page is returned.
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- Prices arrive as **decimal strings in pence** (`"0120.0000"` = 120.0p); some
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stations report pounds (values < 2.0 are multiplied by 100). Out-of-band
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values are dropped (50–500p sane band) so a pounds-denominated column can't
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poison the nationwide cheapest reference.
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- Fuel types mapped: `E5`/`E10` → same, `B7`/`B7_STANDARD`/`B7S`/`B7P`/`B10` →
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`DIESEL`. Others (`HVO`, `SDV`, …) are ignored — the app tracks exactly
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E5/E10/DIESEL.
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- Station snapshot cached `FUEL_CACHE_TTL` (default 300s); stale cache is
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served on upstream failure so the app never sees a hard outage.
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- No credentials are exposed to clients — the app calls the relay keyless.
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## Setup
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```bash
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python3 -m venv .venv
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source .venv/bin/activate
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pip install -r requirements.txt
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pip install pytest # only needed for the test suite
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cp .env.example .env # then fill in FUEL_API_CLIENT_ID / FUEL_API_CLIENT_SECRET
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./scripts/run.sh # serves on FUEL_RELAY_PORT (default 8789)
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```
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Without credentials, `FUEL_SOURCE=auto` falls back to the public hourly CSV
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mirror (same parser as `fuelboard-relay`), so the full relay→app path is
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testable end-to-end before GOV.UK One Login creds exist. `/health` reports the
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active `source` (`csv` vs `api`).
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## Endpoints
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| Endpoint | Description |
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|---|---|
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| `GET /health` | Cache status, active source, last sync, failure counters |
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| `GET /api/v1/stations` | All stations with prices (keyless) |
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| `GET /api/v1/stations?fuel=e10&lat=53.72&lng=-1.85&radius=10&limit=10` | Filter by fuel, radius around a point, sorted nearest-first |
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| `GET /api/v1/stations?fuel=diesel` (no lat/lng) | Sorted cheapest-first |
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Fuel grades: `e10`, `e5`, `diesel`. Output contract identical to
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`fuelboard-relay` — the app can switch relays by changing the base URL only.
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## Getting credentials
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1. Sign in at <https://developer.fuel-finder.service.gov.uk/get-started-ifr/onelogin> with GOV.UK One Login.
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2. Register an application → get `client_id` + `client_secret`.
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3. Put them in `.env` (never in git, never in the app).
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## Fair use notes (from the Fuel Finder developer guideline)
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- Refresh at least every 5 minutes — we do (cron-style refresh on request + TTL cache).
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- Serve data unmodified — this relay only filters/sorts, never alters prices.
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- Keep timestamps — `price_updated` is passed through untouched.
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- Rate limits: ~100 rpm documented — batched loops issue ~2 requests per page
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(info + prices), comfortably inside the limit on a 5-minute cadence.
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## Tests
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```bash
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python -m pytest tests/ -q
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```
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Covers price-string parsing (pence, pounds, out-of-band), the node_id join,
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fuel-type mapping, and CSV-fallback parsing — against the documented API
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shapes, no network required.
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## Switching the app
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Point `Shared/FuelPriceProvider.swift`'s `RelayFuelProvider.baseURL` at
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`http://192.168.1.131:8789` (API relay) instead of `:8788` (CSV relay). No
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other app change needed — the station JSON is identical in shape.
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