fuelboard/FuelBoard/AlertsView.swift

import SwiftUI

/// Alerts tab — enables the cheapest-station proximity alerts. The fuel being
/// monitored is chosen HERE, independently of the Stations-tab selection:
/// users can browse any fuel without re-targeting their alerts (and vice
/// versa). The Live Activity section also lives here — it mirrors this page's
/// shape (toggle + fuel + distance) so the two "notify me while driving"
/// surfaces sit together. Geofence plumbing (count, 18-limit) lives in
/// Settings → Debug; the user-facing page keeps a plain-language explainer
/// plus a 0-stations hint.
struct AlertsView: View {
    @Binding var enabled: Bool
    @Binding var radius: Double   // stored in km (monitor + storage)
    @Binding var fuel: FuelType   // the fuel alerts monitor for
    /// Whether alerts mirror the Stations-tab search distance (capped at 8 mi).
    @Binding var followsSearch: Bool
    /// Whether the "cheapest nearby" Live Activity is shown on the Lock Screen
    /// / Dynamic Island. Tracks its OWN fuel + radius (below) — independent of
    /// the Stations tab.
    @Binding var liveActivityEnabled: Bool
    /// Fuel the Live Activity tracks (independent of the Stations tab).
    @Binding var liveActivityFuel: FuelType
    /// Search radius (miles, 5/10/15) the Live Activity uses.
    @Binding var liveActivityRadiusMiles: Int
    /// Whether the Live Activity mirrors the Stations-tab search distance.
    @Binding var liveActivityFollowsSearch: Bool
    /// Current Stations-tab search distance (miles) — the value "Follow search"
    /// mirrors.
    let stationLimit: Int
    let distanceUnit: DistanceUnit
    let monitoredCount: Int
    let lastAlert: String?

    /// The Stations-tab search distance shown in the user's unit, e.g.
    /// "5 miles" or "8 km" — for the "Follow search" rows.
    private var searchInUnitLabel: String {
        let shown = distanceUnit.displayMiles(stationLimit)   // stationLimit is always miles
        return "\(shown) \(distanceUnit.label(for: Double(shown)))"
    }

    /// A miles value (5/10/15) shown truthfully in the user's unit, e.g.
    /// "5 miles" (miles unit) or "8 km" (km unit) — picker labels must match
    /// what the option really means.
    private func distanceLabel(forMiles miles: Int) -> String {
        let shown = distanceUnit.displayMiles(miles)
        return "\(shown) \(distanceUnit.label(for: Double(shown)))"
    }

    private enum AlertRadiusChoice: Hashable {
        case followSearch
        case fixed(Int)
    }

    /// The radius picker works in the user's chosen unit; the stored value
    /// stays km so ProximityMonitor and persistence never change. Options are
    /// snapped to the nearest picker value so any stored radius still selects.
    /// "Follow search" mirrors the Stations-tab distance (capped at 8 miles).
    private var alertChoice: Binding<AlertRadiusChoice> {
        Binding(
            get: {
                if followsSearch { return .followSearch }
                let inUnit = distanceUnit.fromKM(radius)
                let snapped = FuelStore.alertRadiusOptions
                    .min(by: { abs(Double($0) - inUnit) < abs(Double($1) - inUnit) }) ?? 3
                return .fixed(snapped)
            },
            set: { choice in
                switch choice {
                case .followSearch:
                    followsSearch = true
                case .fixed(let value):
                    followsSearch = false
                    radius = distanceUnit.toKM(Double(value))
                }
            }
        )
    }

    private enum LADistanceChoice: Hashable {
        case followSearch
        case fixed(Int)
    }

    private var laChoice: Binding<LADistanceChoice> {
        Binding(
            get: {
                if liveActivityFollowsSearch { return .followSearch }
                return .fixed(liveActivityRadiusMiles)
            },
            set: { choice in
                switch choice {
                case .followSearch:
                    liveActivityFollowsSearch = true
                case .fixed(let miles):
                    liveActivityFollowsSearch = false
                    liveActivityRadiusMiles = miles
                }
            }
        )
    }

    var body: some View {
        NavigationStack {
            List {
                Section {
                    Toggle("Cheapest-station alerts", isOn: $enabled)
                    Picker("Fuel", selection: $fuel) {
                        ForEach(FuelType.allCases) { fuel in
                            Text(fuel.displayName).tag(fuel)
                        }
                    }
                    Picker("Radius", selection: alertChoice) {
                        Text("Follow search (\(searchInUnitLabel))").tag(AlertRadiusChoice.followSearch)
                        ForEach(FuelStore.alertRadiusOptions, id: \.self) { value in
                            Text("\(value) \(distanceUnit.label(for: Double(value)))").tag(AlertRadiusChoice.fixed(value))
                        }
                    }
                    if enabled && monitoredCount == 0 {
                        Text("No stations monitored yet — open the Stations tab to load prices first.")
                            .font(.caption)
                            .foregroundStyle(.secondary)
                    }
                } header: {
                    Text("Cheapest-station alerts")
                } footer: {
                    Text("When you approach a station that is the cheapest within the radius, FuelBoard sends a notification — even with the app closed. Nearby stations selling \(fuel.displayName.lowercased()) are watched — favourites get priority — and each station alerts at most once per hour. Follow search mirrors the Stations-tab distance, capped at 8 miles for reliable geofencing.")
                }

                if enabled, let lastAlert {
                    Section("Last alert") {
                        Label(lastAlert, systemImage: "bell.badge.fill")
                            .font(.footnote)
                    }
                }

                Section {
                    Toggle("Live Activity", isOn: $liveActivityEnabled)
                    Picker("Fuel", selection: $liveActivityFuel) {
                        ForEach(FuelType.allCases) { fuel in
                            Text(fuel.displayName).tag(fuel)
                        }
                    }
                    Picker("Distance", selection: laChoice) {
                        Text("Follow search (\(searchInUnitLabel))").tag(LADistanceChoice.followSearch)
                        ForEach(FuelStore.stationRadiusOptions, id: \.self) { miles in
                            Text(distanceLabel(forMiles: miles)).tag(LADistanceChoice.fixed(miles))
                        }
                    }
                } header: {
                    Text("Live Activity")
                } footer: {
                    Text("Shows the cheapest station for the fuel and distance you pick here on the Lock Screen and Dynamic Island — independent of the Stations tab (choose Follow search to mirror its distance instead). Updates as you drive; tap to open directions. Live Activities can be disabled in System Settings → Live Activities.")
                }
            }
            .navigationTitle("Alerts")
        }
    }
}