| Code | What It Does | How It Does It |
| ▶ IMPORTS | | |
| import Foundation
import CoreLocation
import MapKit
import SwiftUI | Framework imports | Imports Foundation, CoreLocation, MapKit, SwiftUI. |
| ▶ MODEL | | |
| struct BusStop: Codable, Identifiable {
let id: String
let lat: Double
let lon: Double
let name: String
let routes: [String]
var coordinate: CLLocationCoordinate2D {
CLLocationCoordinate2D(latitude: lat, longitude: lon)
}
} | `BusStop` struct | Defines the `BusStop` struct. Conforms to Codable, Identifiable. |
| ▶ MAP ANNOTATION | | |
| final class BusStopAnnotation: NSObject, MKAnnotation {
let stop: BusStop
@objc dynamic var coordinate: CLLocationCoordinate2D { stop.coordinate }
var title: String? { stop.name }
init(_ stop: BusStop) { self.stop = stop }
} | `BusStopAnnotation` class | Defines the `BusStopAnnotation` class. Conforms to NSObject, MKAnnotation. |
| ▶ SERVICE | | |
| class BusStopService {
static let shared = BusStopService()
private var stops: [BusStop] = []
private(set) var isLoaded: Bool = false
private init() {}
// MARK: Load
func loadIfNeeded() {
guard !isLoaded else { return }
DispatchQueue.global(qos: .utility).async { [weak self] in
guard let self else { return }
guard let url = Bundle.main.url(forResource: "bus_stops", withExtension: "json"),
let data = try? Data(contentsOf: url),
let decoded = try? JSONDecoder().decode([BusStop].self, from: data)
else {
print("🚌 BusStopService: failed to load bus_stops.json")
return
}
self.stops = decoded // already lat-sorted by build script
self.isLoaded = true
print("🚌 BusStopService: loaded \(decoded.count) stops")
}
}
// MARK: Spatial query
/// Returns all stops within `radiusMeters` of `coordinate`, sorted by distance.
func stops(near coordinate: CLLocationCoordinate2D,
radiusMeters: Double = 400) -> [BusStop] {
guard isLoaded, !stops.isEmpty else { return [] }
let metersPerDegLat: Double = 111_320
let latDelta = radiusMeters / metersPerDegLat
let lo = lowerBound(lat: coordinate.latitude - latDelta)
let hi = upperBound(lat: coordinate.latitude + latDelta, from: lo)
let origin = CLLocation(latitude: coordinate.latitude, longitude: coordinate.longitude)
return stops[lo..<hi].filter { stop in
CLLocation(latitude: stop.lat, longitude: stop.lon).distance(from: origin) <= radiusMeters
}
.sorted {
CLLocation(latitude: $0.lat, longitude: $0.lon).distance(from: origin)
< CLLocation(latitude: $1.lat, longitude: $1.lon).distance(from: origin)
}
}
/// Returns the unique sorted route names served within `radiusMeters`.
func routes(near coordinate: CLLocationCoordinate2D,
radiusMeters: Double = 400) -> [String] {
var seen = Set<String>()
var result: [String] = []
for stop in stops(near: coordinate, radiusMeters: radiusMeters) {
for route in stop.routes where seen.insert(route).inserted {
result.append(route)
}
}
return result.sorted { busRouteSortKey($0) < busRouteSortKey($1) }
}
// MARK: Binary search helpers
private func lowerBound(lat: Double) -> Int {
var lo = 0, hi = stops.count
while lo < hi {
let mid = (lo + hi) / 2
if stops[mid].lat < lat { lo = mid + 1 } else { hi = mid }
}
return lo
}
private func upperBound(lat: Double, from start: Int) -> Int {
var lo = start, hi = stops.count
while lo < hi {
let mid = (lo + hi) / 2
if stops[mid].lat <= lat { lo = mid + 1 } else { hi = mid }
}
return lo
}
// MARK: Sort key ("M1" → "M001", "Bx12" → "Bx012")
private func busRouteSortKey(_ route: String) -> String {
let prefix = String(route.prefix(while: { $0.isLetter }))
let rest = String(route.dropFirst(prefix.count))
let num = String(rest.prefix(while: { $0.isNumber }))
let suffix = String(rest.dropFirst(num.count))
return "\(prefix)\(String(format: "%03d", Int(num) ?? 0))\(suffix)"
}
} | `BusStopService` class | Defines the `BusStopService` class. |
| ▶ BOROUGH COLOR PALETTE | | |
| /// Borough-keyed colors that match MTA's informal color scheme.
func busRouteColor(for route: String) -> Color {
let up = route.uppercased()
if up.hasPrefix("BX") { return Color(red: 0/255, green: 147/255, blue: 60/255) } // Bronx – green
if up.hasPrefix("M") { return Color(red: 0/255, green: 57/255, blue: 166/255) } // Manhattan – blue
if up.hasPrefix("B") && !up.hasPrefix("BX") { return Color(red: 255/255, green: 99/255, blue: 25/255) } // Brooklyn – orange
if up.hasPrefix("Q") { return Color(red: 185/255, green: 51/255, blue: 173/255) } // Queens – purple
if up.hasPrefix("S") { return Color(red: 128/255, green: 129/255, blue: 131/255) } // Staten Island – gray
return Color(red: 0/255, green: 57/255, blue: 166/255)
} | Documentation comment | Describes the following declaration. |
| ▶ BUS VEHICLE (REAL-TIME POSITION) | | |
| struct BusVehicle: Identifiable {
let id: String // VehicleRef e.g. "MTA NYCT_7812"
let route: String // cleaned label e.g. "M15"
let lineRef: String // full LineRef e.g. "MTA NYCT_M15"
let latitude: Double
let longitude: Double
let bearing: Double // degrees clockwise from north
let destination: String
let recordedAt: Date // RecordedAtTime from SIRI — used for dead-reckoning
} | `BusVehicle` struct | Defines the `BusVehicle` struct. Conforms to Identifiable. |
| ▶ BUS VEHICLE ANNOTATION | | |
| final class BusVehicleAnnotation: NSObject, MKAnnotation {
let vehicle: BusVehicle
@objc dynamic var coordinate: CLLocationCoordinate2D // set to dead-reckoned position at init
var title: String? { vehicle.route }
init(_ vehicle: BusVehicle, displayCoordinate: CLLocationCoordinate2D? = nil) {
self.vehicle = vehicle
self.coordinate = displayCoordinate
?? CLLocationCoordinate2D(latitude: vehicle.latitude, longitude: vehicle.longitude)
super.init()
}
} | `BusVehicleAnnotation` class | Defines the `BusVehicleAnnotation` class. Conforms to NSObject, MKAnnotation. |
| ▶ BUS VEHICLE SERVICE | | |
| struct BusVehicleService {
/// Fetches real-time vehicle positions via SIRI VehicleMonitoring.
/// Pass a lineRef (e.g. "MTA NYCT_M15") to limit to one route, or nil for all routes.
static func fetch(lineRef: String? = nil) async -> [BusVehicle] {
guard !BusArrivalsService.apiKey.isEmpty else { return [] }
var comps = URLComponents(string: "https://bustime.mta.info/api/siri/vehicle-monitoring.json")!
var queryItems = [
URLQueryItem(name: "key", value: BusArrivalsService.apiKey),
URLQueryItem(name: "OperatorRef", value: "MTA"),
URLQueryItem(name: "version", value: "2"),
]
if let lineRef { queryItems.append(URLQueryItem(name: "LineRef", value: lineRef)) }
comps.queryItems = queryItems
guard let url = comps.url else { return [] }
let cfg = URLSessionConfiguration.ephemeral
cfg.timeoutIntervalForRequest = 10
cfg.timeoutIntervalForResource = 15
let session = URLSession(configuration: cfg)
defer { session.invalidateAndCancel() }
guard
let (data, _) = try? await session.data(from: url),
let json = try? JSONSerialization.jsonObject(with: data) as? [String: Any],
let siri = json["Siri"] as? [String: Any],
let delivery = siri["ServiceDelivery"] as? [String: Any],
let vmdArray = delivery["VehicleMonitoringDelivery"] as? [[String: Any]],
let vmd = vmdArray.first,
let activities = vmd["VehicleActivity"] as? [[String: Any]]
else { return [] }
let isoParser: ISO8601DateFormatter = {
let f = ISO8601DateFormatter()
f.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
return f
}()
return activities.compactMap { activity -> BusVehicle? in
guard
let mvj = activity["MonitoredVehicleJourney"] as? [String: Any],
let loc = mvj["VehicleLocation"] as? [String: Any],
let lat = loc["Latitude"] as? Double,
let lon = loc["Longitude"] as? Double
else { return nil }
let vehicleRef = (mvj["VehicleRef"] as? String) ?? ""
let rawRoute = siriStringValue(mvj["PublishedLineName"]) ?? siriStringValue(mvj["LineRef"]) ?? lineRef ?? ""
let cleanRoute = rawRoute.firstIndex(of: "_").map { String(rawRoute[rawRoute.index(after: $0)...]) } ?? rawRoute
let destination = siriStringValue(mvj["DestinationName"]) ?? ""
let bearing = (mvj["Bearing"] as? Double) ?? 0
// RecordedAtTime is at the activity level, not inside MonitoredVehicleJourney
let recordedStr = activity["RecordedAtTime"] as? String ?? ""
let recordedAt = isoParser.date(from: recordedStr) ?? Date()
return BusVehicle(id: vehicleRef, route: cleanRoute, lineRef: lineRef ?? "",
latitude: lat, longitude: lon,
bearing: bearing, destination: destination,
recordedAt: recordedAt)
}
}
private static func siriStringValue(_ value: Any?) -> String? {
if let s = value as? String { return s.isEmpty ? nil : s }
if let a = value as? [String], let s = a.first { return s.isEmpty ? nil : s }
if let a = value as? [Any], let s = a.first as? String { return s.isEmpty ? nil : s }
return nil
}
} | `BusVehicleService` struct | Defines the `BusVehicleService` struct. |