import SwiftUI
import StoreKit
import UserNotifications
import WidgetKit

/// Settings tab — distance units, onboarding replay, a tip jar, and an About
/// section. Test-notification buttons live in a Debug section that is hidden
/// unless the developer debug flag is on (tap the About → Version row five
/// times to toggle it — no user-facing switch). The first test button uses
/// REAL data (the actual cheapest station for the monitored fuel within the
/// radius, exactly like a live alert) via `onTestAlert`; the second fires
/// with no criteria at all. The Data source section (connection/stations/
/// freshness) is debug-only too — moved here so release builds don't expose
/// relay plumbing.
struct SettingsView: View {
    @Binding var distanceUnit: DistanceUnit
    @Binding var priceDisplayStyle: PriceDisplayStyle
    /// The fuel + radius currently configured for alerts (mirrors the Alerts
    /// tab) so the test notification matches what real alerts will say.
    var alertsFuel: FuelType = .e10
    var alertsRadiusKM: Double = 3.0
    /// Result line from the last real-data test alert (what it picked).
    var testAlertResult: String?
    /// Drives the real-data test — ContentView routes this to the live
    /// ProximityMonitor so the test uses its actual stations/fuel/radius.
    var onTestAlert: () -> Void = {}
    /// Drives the plain test (no criteria) — routed to the live monitor so it
    /// can carry a real station's name, price and coordinates.
    var onPlainTestAlert: () -> Void = {}
    /// Recomputes the debug location snapshot (coordinates + in-range count).
    var onRefreshDebugStatus: () -> Void = {}
    var onShowOnboarding: () -> Void = {}
    /// Live snapshot of the device fix + stations in range (from the monitor).
    var debugStatus: DebugLocationStatus?
    /// The app's own TOP-badge cheapest (selected fuel + stationLimit radius),
    /// passed in so the Debug section mirrors the app list exactly.
    var appCheapest: DebugAppCheapest?
    /// Last CoreLocation region-monitoring failure (monitor.lastRegionError).
    /// Shown in Debug so a silently-failed geofence registration is visible.
    var regionError: String?
    /// Live geofence count (monitor.monitoredStationIDs.count) — Debug-only
    /// status; the user-facing Alerts tab no longer exposes fence plumbing.
    var monitoredCount: Int = 0

    @StateObject private var tipStore = TipStore()
    @State private var showTipAlert = false
    @State private var tipAlertMessage = ""
    @State private var testAlertMessage: String?
    /// Hidden developer flag — the Debug section only appears when on. Toggled
    /// by tapping the About → Version row five times (NOT a user-facing switch).
    @State private var debugMode: Bool = FuelStore.loadDebugMode()
    @State private var versionTapCount = 0
    @State private var lastVersionTap = Date.distantPast
    /// Widget diagnostics: the extension's last makeEntry beacon PER intent
    /// type (keychain) + the installed-widget inventory from WidgetCenter.
    @State private var smallWidgetDiag: String?
    @State private var mediumWidgetDiag: String?
    @State private var installedWidgets: String = ""

    private func refreshWidgetDiag() {
        smallWidgetDiag = FuelStore.loadWidgetDiag(intentType: "FuelBoardSmallWidget")
        mediumWidgetDiag = FuelStore.loadWidgetDiag(intentType: "FuelBoardWidgetConfigurationIntent")
        WidgetCenter.shared.getCurrentConfigurations { result in
            let text: String
            switch result {
            case .success(let widgets):
                text = widgets.isEmpty
                    ? "No widgets installed"
                    : widgets.map { "\($0.kind) · \($0.family)" }.joined(separator: "\n")
            case .failure(let error):
                text = "Error: \(error.localizedDescription)"
            }
            Task { @MainActor in
                installedWidgets = text
            }
        }
    }

    var body: some View {
        NavigationStack {
            List {
                Section {
                    Picker("Distance", selection: $distanceUnit) {
                        ForEach(DistanceUnit.allCases) { unit in
                            Text(unit.displayName).tag(unit)
                        }
                    }
                    .pickerStyle(.segmented)
                    .onChange(of: distanceUnit) { _, newValue in
                        FuelStore.saveDistanceUnit(newValue)
                        WidgetCenter.shared.reloadAllTimelines()
                    }
                    Picker("Price display", selection: $priceDisplayStyle) {
                        ForEach(PriceDisplayStyle.allCases) { style in
                            Text(style.displayName).tag(style)
                        }
                    }
                    .pickerStyle(.segmented)
                    .onChange(of: priceDisplayStyle) { _, newValue in
                        FuelStore.savePriceDisplayStyle(newValue)
                        WidgetCenter.shared.reloadAllTimelines()
                    }
                } header: {
                    Text("Units")
                } footer: {
                    Text("Distances and search radii across the app, widget and alerts are shown in this unit. Prices can be shown as on a station sign (129.9) or in pounds and pence (£1.29⁹/L).")
                }

                Section {
                    Button {
                        onShowOnboarding()
                    } label: {
                        Label("Show introduction", systemImage: "sparkles")
                    }
                } footer: {
                    Text("Replay the welcome screen, including the location and notification permission prompts.")
                }

                if debugMode {
                    Section {
                        Button {
                            sendTestAlert()
                        } label: {
                            Label("Test alert notification (real data)", systemImage: "bell.badge.fill")
                        }
                        if let testAlertMessage {
                            Text(testAlertMessage)
                                .font(.footnote)
                                .foregroundStyle(.secondary)
                        }
                        if let testAlertResult {
                            Label(testAlertResult, systemImage: "checkmark.circle.fill")
                                .font(.footnote)
                                .foregroundStyle(.green)
                        }
                        if let regionError {
                            Label(regionError, systemImage: "exclamationmark.triangle.fill")
                                .font(.footnote)
                                .foregroundStyle(.red)
                        }
                        Button {
                            onPlainTestAlert()
                        } label: {
                            Label("Send plain test notification", systemImage: "bell.slash.fill")
                        }
                        debugLocationRows
                    } header: {
                        Text("Debug")
                    } footer: {
                        Text("The first button applies the real criteria — cheapest \(alertsFuel.displayName.lowercased()) station within \(distanceUnit.format(alertsRadiusKM)) of you — and sends the actual station's name, price and coordinates. The second fires with no criteria at all (nearest seller), still carrying a real station, just to verify a notification appears and tapping it opens directions. Cheapest in range mirrors the app list (selected fuel + distance); the in-range count mirrors the alert radius.")
                    }
                    .onAppear { onRefreshDebugStatus() }

                    Section {
                        Button {
                            refreshWidgetDiag()
                        } label: {
                            Label("Refresh widget diagnostics", systemImage: "arrow.clockwise")
                        }
                        if let smallWidgetDiag {
                            Text("SMALL: \(smallWidgetDiag)")
                                .font(.caption2)
                                .foregroundStyle(.secondary)
                                .textSelection(.enabled)
                        } else {
                            Text("SMALL: no beacon yet")
                                .font(.caption2)
                                .foregroundStyle(.secondary)
                        }
                        if let mediumWidgetDiag {
                            Text("MEDIUM: \(mediumWidgetDiag)")
                                .font(.caption2)
                                .foregroundStyle(.secondary)
                                .textSelection(.enabled)
                        } else {
                            Text("MEDIUM: no beacon yet")
                                .font(.caption2)
                                .foregroundStyle(.secondary)
                        }
                        Text(installedWidgets.isEmpty ? "No widgets installed" : installedWidgets)
                            .font(.caption2)
                            .foregroundStyle(.secondary)
                    } header: {
                        Text("Widget Diagnostics")
                    } footer: {
                        Text("Each beacon is written by the widget extension at the end of every timeline entry for that intent type (keychain, so it survives free-SideStore installs). A missing SMALL beacon after adding the small widget means its timeline never reaches the provider. Installed widgets come from WidgetCenter.")
                    }
                    .onAppear { refreshWidgetDiag() }

                    Section {
                        HStack {
                            Text("Connection")
                            Spacer()
                            Text(connectionText)
                                .foregroundStyle(.secondary)
                        }
                        HStack {
                            Text("Stations")
                            Spacer()
                            Text(stationCountText)
                                .foregroundStyle(.secondary)
                                .monospacedDigit()
                        }
                        HStack {
                            Text("Data updated")
                            Spacer()
                            Text(dataUpdatedText)
                                .foregroundStyle(.secondary)
                                .monospacedDigit()
                        }
                    } header: {
                        Text("Data source")
                    } footer: {
                        Text("Connection shows whether prices come from the official Fuel Finder API or the CSV mirror. Data updated is the latest price change reported by the GOV.UK server itself.")
                    }

                    Section {
                        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("Favourites for \(alertsFuel.displayName.lowercased()) get priority, then the closest stations selling that fuel fill the rest (18 max, iOS region limit). Each station alerts at most once per hour.")
                            .font(.caption)
                            .foregroundStyle(.secondary)
                    } header: {
                        Text("Geofence monitoring")
                    }
                }

                Section {
                    Button {
                        Task { await tipStore.purchase() }
                    } label: {
                        HStack {
                            Label("Leave a tip", systemImage: "heart.fill")
                                .foregroundStyle(.pink)
                            Spacer()
                            Text(tipStore.displayPrice)
                                .foregroundStyle(.secondary)
                                .monospacedDigit()
                        }
                    }
                    .disabled(tipStore.purchaseInProgress)
                } header: {
                    Text("Support FuelBoard")
                } footer: {
                    Text("A small tip helps keep the data relay and app development going. Thank you!")
                }

                Section {
                    HStack {
                        Text("Version")
                        Spacer()
                        Text(appVersion)
                            .foregroundStyle(.secondary)
                            .monospacedDigit()
                            .contentShape(Rectangle())
                            .onTapGesture { handleVersionTap() }
                    }
                } header: {
                    Text("About")
                }

                if let message = tipStore.message {
                    Section {
                        Text(message)
                            .font(.footnote)
                            .foregroundStyle(.secondary)
                    }
                }
            }
            .navigationTitle("Settings")
            .onAppear {
                Task { await tipStore.load() }
            }
        }
    }

    /// Debug location block: device coordinates + fix age, then the in-range
    /// indicator. "Cheapest in range" mirrors the app list (selected fuel +
    /// stationLimit radius) via `appCheapest`; the "In range" count mirrors
    /// the alert prediction (alert fuel + alert radius).
    @ViewBuilder
    private var debugLocationRows: some View {
        Divider()
        if let status = debugStatus {
            HStack {
                Label("Device", systemImage: "location.fill")
                Spacer()
                if let coord = status.coordinate {
                    Text(String(format: "%.5f, %.5f", coord.lat, coord.lng))
                        .font(.footnote)
                        .monospacedDigit()
                        .foregroundStyle(.secondary)
                } else {
                    Text("No fix")
                        .foregroundStyle(.secondary)
                }
            }
            if let age = status.fixAge {
                HStack {
                    Label("Fix age", systemImage: "clock.fill")
                    Spacer()
                    Text(ageText(age))
                        .font(.footnote)
                        .foregroundStyle(.secondary)
                }
            }
            HStack {
                Label("In range", systemImage: "location.circle.fill")
                Spacer()
                HStack(spacing: 6) {
                    if let coord = status.coordinate {
                        Circle()
                            .fill(inRangeColor(status.inRangeCount))
                            .frame(width: 10, height: 10)
                    } else {
                        Circle()
                            .fill(.gray)
                            .frame(width: 10, height: 10)
                    }
                    Text(inRangeText(status))
                        .font(.footnote)
                        .foregroundStyle(.secondary)
                }
            }
            if let cheapest = appCheapest {
                HStack {
                    Label("Cheapest in range", systemImage: "fuelpump.fill")
                    Spacer()
                    Text(cheapestText(cheapest.station, fuel: cheapest.fuel, distance: cheapest.distanceKM))
                        .font(.footnote)
                        .monospacedDigit()
                        .foregroundStyle(.secondary)
                }
            } else if let cheapest = status.cheapestInRange {
                // Fallback when the app view hasn't resolved yet — show the
                // alert-prediction cheapest rather than nothing.
                HStack {
                    Label("Cheapest in range", systemImage: "fuelpump.fill")
                    Spacer()
                    Text(cheapestText(cheapest, fuel: status.fuel, distance: status.cheapestDistanceKM))
                        .font(.footnote)
                        .monospacedDigit()
                        .foregroundStyle(.secondary)
                }
            }
        } else {
            HStack {
                Label("Device", systemImage: "location.fill")
                Spacer()
                Text("—")
                    .foregroundStyle(.secondary)
            }
        }
    }

    private func inRangeColor(_ count: Int) -> Color {
        count > 0 ? .green : .red
    }

    private func inRangeText(_ status: DebugLocationStatus) -> String {
        guard status.coordinate != nil else { return NSLocalizedString("waiting for fix", comment: "") }
        let fuelName = status.fuel.displayName.lowercased()
        if status.inRangeCount == 1 {
            return String(format: NSLocalizedString("1 %@ station within %@", comment: ""), fuelName, distanceUnit.format(status.radiusKM))
        }
        return String(format: NSLocalizedString("%lld %@ stations within %@", comment: ""), status.inRangeCount, fuelName, distanceUnit.format(status.radiusKM))
    }

    private func cheapestText(_ station: FuelStation, fuel: FuelType, distance: Double?) -> String {
        let price = station.prices[fuel].map { String(format: "%.1fp", $0) } ?? "—"
        if let distance {
            return "\(station.name) · \(distanceUnit.format(distance)) · \(price)"
        }
        return "\(station.name) · \(price)"
    }

    private func ageText(_ age: TimeInterval) -> String {
        if age < 60 { return String(format: NSLocalizedString("%llds ago", comment: ""), Int(age)) }
        if age < 3600 { return String(format: NSLocalizedString("%lldm %llds ago", comment: ""), Int(age / 60), Int(age.truncatingRemainder(dividingBy: 60))) }
        return String(format: NSLocalizedString("%lldh %lldm ago", comment: ""), Int(age / 3600), Int((age.truncatingRemainder(dividingBy: 3600)) / 60))
    }

    private var appVersion: String {
        let version = Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String ?? "1.0"
        let build = Bundle.main.object(forInfoDictionaryKey: "CFBundleVersion") as? String ?? "1"
        return "\(version) (\(build))"
    }

    /// "API" when the relay is serving the official Fuel Finder API, "CSV"
    /// when it fell back to the public mirror, "—" when unknown/never fetched.
    private var connectionText: String {
        switch FuelStore.loadRelaySource()?.lowercased() {
        case "api": return "API"
        case "csv": return "CSV"
        default: return "—"
        }
    }

    private var stationCountText: String {
        guard let count = FuelStore.loadStationCount() else { return "—" }
        return count.formatted()
    }

    /// GOV.UK server's own dataset update timestamp (ISO 8601 from the API,
    /// e.g. 2026-08-12T10:23:00.000Z). Shown as a local date/time — it is the
    /// data's own freshness, not the relay's sync time.
    private var dataUpdatedText: String {
        guard let raw = FuelStore.loadDataUpdated(), !raw.isEmpty else { return "—" }
        let iso = ISO8601DateFormatter()
        iso.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
        if let date = iso.date(from: raw) {
            return date.formatted(date: .abbreviated, time: .shortened)
        }
        // Some sources send "YYYY-MM-DDTHH:MM:SS" without fractional seconds
        // or timezone — try the plain form before showing the raw string.
        iso.formatOptions = [.withInternetDateTime]
        if let date = iso.date(from: raw) {
            return date.formatted(date: .abbreviated, time: .shortened)
        }
        return raw
    }

    /// Hidden debug-mode toggle: five taps on the Version row flips the flag.
    /// Nothing in the UI advertises this — the Debug section simply appears or
    /// disappears. Deliberately NOT a visible switch so end users never see it.
    private func handleVersionTap() {
        let now = Date()
        if now.timeIntervalSince(lastVersionTap) > 0.6 {
            versionTapCount = 0
        }
        lastVersionTap = now
        versionTapCount += 1
        if versionTapCount >= 5 {
            versionTapCount = 0
            debugMode.toggle()
            FuelStore.saveDebugMode(debugMode)
        }
    }

    private func sendTestAlert() {
        UNUserNotificationCenter.current().getNotificationSettings { settings in
            Task { @MainActor in
                switch settings.authorizationStatus {
                case .authorized, .provisional, .ephemeral:
                    onTestAlert()
                case .denied:
                    testAlertMessage = NSLocalizedString("Notifications are turned off for FuelBoard. Enable them in Settings → Notifications → FuelBoard, then try again.", comment: "")
                default:
                    // First time — ask, then fire if granted.
                    UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .sound, .badge]) { granted, _ in
                        Task { @MainActor in
                            if granted {
                                onTestAlert()
                            } else {
                                testAlertMessage = NSLocalizedString("Notifications weren't allowed, so no test alert was sent.", comment: "")
                            }
                        }
                    }
                }
            }
        }
    }
}

/// Loads the £4.99 tip product and drives its purchase.
@MainActor
final class TipStore: ObservableObject {
    /// Product ID for the £4.99 tip (App Store Connect — consumable).
    static let productID = "com.apt.fuelboard.tip499"

    @Published private(set) var product: Product?
    @Published private(set) var purchaseInProgress = false
    @Published private(set) var message: String?

    var displayPrice: String {
        product?.displayPrice ?? "£4.99"
    }

    func load() async {
        // Refreshes product state on every visit so a newly-approved product
        // (or a restored transaction) is picked up.
        do {
            let products = try await Product.products(for: [Self.productID])
            product = products.first
        } catch {
            // No product yet (sideloaded build) — the button still shows the
            // intended price and reports the purchase attempt gracefully.
            product = nil
        }
    }

    func purchase() async {
        guard !purchaseInProgress else { return }
        purchaseInProgress = true
        defer { purchaseInProgress = false }

        // If the product hasn't loaded (e.g. not configured in App Store
        // Connect yet), still allow the attempt so the user sees a clear
        // outcome rather than a dead button.
        guard let product else {
            message = NSLocalizedString("The tip isn't available in this build yet — check back after an App Store release.", comment: "")
            return
        }

        do {
            let result = try await product.purchase()
            switch result {
            case .success(let verification):
                switch verification {
                case .verified:
                    message = NSLocalizedString("Thank you! Your tip has been received. ⛽", comment: "")
                case .unverified:
                    message = NSLocalizedString("The purchase couldn't be verified. Please try again.", comment: "")
                }
            case .userCancelled:
                message = nil   // silent — the user just closed the sheet
            case .pending:
                message = NSLocalizedString("Your tip is pending approval. It'll finish automatically.", comment: "")
            @unknown default:
                message = nil
            }
        } catch {
            message = String(format: NSLocalizedString("The tip couldn't be completed: %@", comment: ""), error.localizedDescription)
        }
    }
}