transfer-generation.ts

const transfers = Map<Trip, Map<number, Transfer[]>>().asMutable();

// for each tripT
for (const tripT of trips) {
    const tripLine = this.lineRepository.lineForTrip(tripT);

    // for each stopQ of tripT after the first stop
    for (let i = 1; i < tripT.stops.length; i++) {

        // get stopQ for all stations connected to tripT.stops[i] by footpath.
        // note that the current stop (tripT.stops[i]) is included with interchange applied.
        for (const stopQ of this.footpathRepository.getConnectedStopsFor(tripT.stops[i])) {

            // return all lines that pass through stopQ.station and the index, j, of the point they stop
            for (const [j, line] of this.lineRepository.linesForStation(stopQ.station)) {
                // don't add transfers to a final destination, if tripT shares a stop we don't need a transfer
                if (j === line.stoppingStations().length -1) continue;

                // find the first trip on the line that we can board
                line.getEarliestTripAt(j, stopQ.arrivalTime).match({
                    none: () => {},
                    some: (tripU: Trip) => {
                        // add the transfer if:
                        // - the line of tripT is not the same as the line of tripU
                        // - tripU dominates tripT (arrives earlier)
                        // - we're transferring to an earlier stop on the same line
                        if (tripLine !== line || tripU.dominates(tripT) || j < i) {
                            const transfer = new Transfer(tripT, i, tripU, j);

                            // phase two of the algorithm, removing unnecessary u-turns
                            if (!transfer.isUTurn() || !transfer.canChangeEarlier(this.footpathRepository.getInterchangeAt(transfer.getStationPriorToTransfer()))) {
                                transfers.updateIn([transfer.tripT, transfer.stopI], [], prev => prev.concat(transfer));
                            }
                        }
                    }
                });
            }
        }
    }
}