rm-hull / next-departures-api / 25460597244

Pull #14

github

feat: add Traveline fallback for SIRI rate limits

Implement a fallback mechanism to fetch bus departures from Traveline
when the primary SIRI API exceeds its usage limits. This ensures service
availability even after the daily TransportAPI quota is exhausted.

-   Introduces `FallbackManager` to track rate-limit state.
-   Adds `TravelineClient` to scrape live departures from the Traveline
    website.
-   Includes a daily **CRON** job to reset the fallback state at
    midnight.
-   Updates `NextDepartures` route to automatically switch providers.

```mermaid
sequenceDiagram
    participant User
    participant API as API Server
    participant SIRI as SIRI API
    participant FM as Fallback Manager
    participant TVL as Traveline

    User->>API: GET /v1/next-departures/:id
    API->>FM: IsSiriRateLimited?
    alt No
        API->>SIRI: Request departures
        alt Success
            SIRI-->>API: Departure data
        else Rate Limited (429/403)
            SIRI-->>API: Limit Exceeded
            API->>FM: SetSiriRateLimited(true)
            API->>TVL: Scrape departures
            TVL-->>API: Fallback data
        end
    else Yes
        API->>TVL: Scrape departures
        TVL-->>API: Fallback data
    end
    API-->>User: JSON Response
```

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