fuelboard/FuelBoard/AlertsView.swift

import SwiftUI

/// Alerts tab — enables the cheapest-station proximity alerts and shows what's
/// being monitored.
struct AlertsView: View {
    @Binding var enabled: Bool
    @Binding var radius: Double   // stored in km (monitor + storage)
    let distanceUnit: DistanceUnit
    let monitoredCount: Int
    let lastAlert: String?

    /// The radius slider works in the user's chosen unit; the stored value
    /// stays km so ProximityMonitor and persistence never change.
    private var radiusInUnit: Double { distanceUnit.fromKM(radius) }

    var body: some View {
        NavigationStack {
            List {
                Section {
                    Toggle("Cheapest-station alerts", isOn: $enabled)
                } footer: {
                    Text("When you approach a station that is the cheapest within the radius, FuelBoard sends a notification — even with the app closed.")
                }

                if enabled {
                    Section("Trigger radius") {
                        VStack(alignment: .leading, spacing: 8) {
                            HStack {
                                Text("Radius")
                                Spacer()
                                Text(String(format: "%.1f %@", radiusInUnit, distanceUnit.shortName))
                                    .foregroundStyle(.secondary)
                                    .monospacedDigit()
                            }
                            // 1–10 in the user's unit; convert back to km on change.
                            Slider(value: Binding(
                                get: { radiusInUnit },
                                set: { radius = distanceUnit.toKM($0) }
                            ), in: 1...10, step: distanceUnit == .kilometers ? 1 : 0.5)
                        }
                    }

                    Section("Monitoring") {
                        if monitoredCount == 0 {
                            Text("No stations monitored yet — open the Stations tab to load prices first.")
                                .font(.caption)
                                .foregroundStyle(.secondary)
                        } else {
                            LabeledContent("Geofenced stations", value: "\(monitoredCount)")
                            Text("Your favourites get priority, then the closest stations fill the rest (18 max, iOS region limit).")
                                .font(.caption)
                                .foregroundStyle(.secondary)
                            Text("Alerts are checked against the cheapest station within the trigger radius for the selected fuel. Each station alerts at most once per hour.")
                                .font(.caption)
                                .foregroundStyle(.secondary)
                        }
                    }

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