1. API
2. Helsinki Transport API
3. Implementation

Implementation

The Helsinki developer-documentation available gives you pretty much everything you need to get started, including a simple interactive query-runner (the graphql console).

You can visit the GraphQL development console, and paste in the following contents:

{
  stop(id: "HSL:1160404") {
    name
    code
    desc
    stoptimesWithoutPatterns(numberOfDepartures:10) {
      scheduledArrival
      realtimeArrival
      realtime
      timepoint
      trip {
        route {
          id
          shortName
          longName
         }
      }
    }
  }
}

The only part that was hard was figuring out how to specify the number of departures - adding (numberOfDepartures:10) in the example above. I found that via sniffing the requests the public map-site made, via my browser extension.

Source Code

Source code for this API-proxy is available here.