I want to be able to use https://bikehopper.org in a way which lets me download the cycling directions in a fit file format by Garmin. This will allow me to put my phone away while I ride and use my cycling computer.

Approach

I have decided to take the following approach, which is to write a small backend service that will

1. Grab the route from the bikehopper backend
2. Convert that data to a fit course file via the Garmin SDK
3. Return that data so that the file can be downloaded via the front end

Tech stack

We use the following

• Kotlin (https://kotlinlang.org/)
• Javalin (https://javalin.io/)
• Garmin SDK (https://developer.garmin.com/fit/download/)
• ktor-client (https://ktor.io/docs)
• JUnit 5 testing (https://junit.org/)

General Data Flow

Basically What I'm doing is taking the exact query params that are passed to our backend from the web app and passing them to this fit file creator. The only difference is we now can pass an additional path parameter that tells the fit file server creator which path to use when creating the .fit file.

Here is a silly graph

   ┌─────────┐         ┌─────────┐
   │         │   get*  │         │
   │ Browser ├────────►│ Fit Svr │
   │         │         │         │
   └─────────┘         └─┬───────┘
       ▲                 │
       │ .fit file       │ sans (path param)
       │                 ▼
       │       ┌─────────────────┐
       │       │                 │
       └───────┤    Bikehopper   │
               │                 │
               └─────────────────┘

    * Matches with params sent to bikehopper backend

Using

To run this you must pull down this git repo and then make sure you have Java version 17.0.5-tem installed. Launch the app via intelli-j run or via cmd line ./gradlew run

Once launched the app listens on http://localhost:9001 via the /fit/ route.

An example request is as such.

localhost:9001/fit?locale=en-US&elevation=true&useMiles=false&layer=OpenStreetMap&profile=pt&optimize=true&pointsEncoded=false&pt.earliest_departure_time=2022-11-01T02:31:44.439Z&pt.connecting_profile=bike2&pt.arrive_by=false&details=cycleway&details=road_class&details=street_name&point=37.78306,-122.45867&point=37.78516,-122.46238&path=0

Testing

Functional testing can be run via the following ./gradlew test

This testing is quite minimal at the moment but does at the very least try to verify that the fit file created is an actual valid fit file. Additionally it is worth taking into consideration that currently the test that does this will fail if the bikehopper backend is currently unavailable.