Jokullbase

How to track how late buses are:

Download bus route data
Insert raw bus positions into timescaledb/postGIS table?
- "Fan-out" JSON responses into one DB row per datapoint.
Download routes.
- There is an endpoint called Timetable, which takes a route number (along with day of week etc).
- The timetable response includes a list of stops in the route, along with the route ID.
- There is an endpoint called BusLocationByStop, which takes a stop ID as a parameter.
  - This information has upcoming arrivals, included estimated arrival time, along with the current position of the bus.
- Record stop info every few minutes, notably the arrivals.
- This will be annoying to do only in DB since we have a trigger for bus positions.
Analyze actual arrival vs what the stop endpoint said about the arrival.
- Use PostGIS to compute "bus arrived" event: When bus is within X meters of a stop on its route, mark that as an arrival event.
- Once we have bus arrival events, we can compare them to arrivals throughout the day.
- We can then discard the raw bus position data, as it's not needed to store it: delete every raw data point between the last arrival and the newly computed one.

Arrival computation:

Can use edge functions for this?
Function takes a bus route number, start time, end time.
Cron in DB calls the edge functions, using state as function inputs.
- state = last interval end time, so we can properly calculate time interval to check.
- or rather use last ID in the raw table, so we don't skip entries.
Query DB to get raw bus positions in the interval.
Query DB to get all stops on the route (during the interval? some stops not in use sometimes)
For each bus ID, find the raw position where its lat,lon are X meters away from stop lat,lons.
These are arrival times for this bus ID, at each stop.
Insert into arrivals.
After all arrivals computed, drop all raw positions for this bus from DB.