import SwiftUI
#if canImport(UIKit)
import UIKit
#endif

/// Der Ausrichtungs-Assistent: begleitet das Rangieren und sagt, ob es besser
/// oder schlechter wird und wo es am besten stand.
struct AlignmentAssistantView: View {
    let device: ConfiguredDevice
    let profile: Profile?

    @Environment(BluetoothManager.self) private var bluetooth
    @Environment(\.dismiss) private var dismiss

    @State private var assistant = AlignmentAssistant()
    @State private var didAnnounceTarget = false

    private var state: LevelState { bluetooth.levelStates[device.id] ?? LevelState() }

    var body: some View {
        NavigationStack {
            ScrollView {
                VStack(spacing: 24) {
                    LevelBubble(pitch: state.pitch, roll: state.roll)
                        .frame(maxWidth: 320)
                        .padding(.top, 8)

                    adviceBanner

                    readings

                    if let best = assistant.best, let gain = assistant.improvementAtBest,
                       let seconds = assistant.timeSinceBest {
                        bestPointCard(best: best, gain: gain, seconds: seconds)
                    }

                    wedgeSection

                    Button("Neu beginnen", systemImage: "arrow.counterclockwise") {
                        assistant.reset()
                        didAnnounceTarget = false
                    }
                    .buttonStyle(.bordered)
                    .padding(.bottom, 24)
                }
                .padding(.horizontal)
                .frame(maxWidth: .infinity)
            }
            .background(Color(.systemGroupedBackground))
            .navigationTitle("Ausrichtungs-Assistent")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .confirmationAction) {
                    Button("Fertig") { dismiss() }
                }
            }
        }
        .onChange(of: state) { _, new in
            guard let pitch = new.pitch, let roll = new.roll else { return }
            assistant.add(pitch: pitch, roll: roll)
            announceIfReached()
        }
        .onAppear {
            // Den anliegenden Wert gleich übernehmen. Sonst stünde bis zur
            // nächsten Messung "Warte auf Messwerte", obwohl längst welche da
            // sind – die Ansicht wirkt dann tot.
            if let pitch = state.pitch, let roll = state.roll {
                assistant.add(pitch: pitch, roll: roll)
            }
            // Beim Rangieren schaut man immer wieder aufs Display; es darf
            // dabei nicht dunkel werden.
            #if canImport(UIKit)
            UIApplication.shared.isIdleTimerDisabled = true
            #endif
        }
        .onDisappear {
            #if canImport(UIKit)
            UIApplication.shared.isIdleTimerDisabled = false
            #endif
        }
    }

    // MARK: - Bausteine

    private var adviceBanner: some View {
        HStack(spacing: 12) {
            Image(systemName: assistant.hasReachedTarget
                  ? "checkmark.circle.fill" : assistant.trend.symbol)
                .font(.title)
                .foregroundStyle(assistant.hasReachedTarget ? Color.green : Color.accentColor)
            Text(assistant.advice)
                .font(.title3.weight(.medium))
                .frame(maxWidth: .infinity, alignment: .leading)
        }
        .padding()
        .background(assistant.hasReachedTarget ? Color.green.opacity(0.15)
                                               : Color(.secondarySystemGroupedBackground),
                    in: .rect(cornerRadius: 16))
    }

    private var readings: some View {
        HStack(spacing: 12) {
            reading("Längs", state.pitch)
            reading("Quer", state.roll)
            reading("Gesamt", assistant.current?.deviation)
        }
    }

    private func reading(_ title: String, _ value: Double?) -> some View {
        VStack(spacing: 4) {
            Text(value.map { String(format: "%.1f°", $0) } ?? "–")
                .font(.title2.weight(.semibold).monospacedDigit())
            Text(title)
                .font(.caption)
                .foregroundStyle(.secondary)
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, 12)
        .background(Color(.secondarySystemGroupedBackground), in: .rect(cornerRadius: 12))
    }

    private func bestPointCard(best: AlignmentAssistant.Sample,
                               gain: Double,
                               seconds: TimeInterval) -> some View {
        VStack(alignment: .leading, spacing: 6) {
            Label("Bester Punkt", systemImage: "flag.checkered")
                .font(.headline)
            Text(String(format: "Vor %.0f Sekunden stand das Fahrzeug %.1f° flacher (%.1f° statt %.1f°).",
                        seconds.rounded(), gain, best.deviation,
                        assistant.current?.deviation ?? 0))
                .font(.callout)
                .foregroundStyle(.secondary)
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding()
        .background(Color(.secondarySystemGroupedBackground), in: .rect(cornerRadius: 16))
    }

    @ViewBuilder
    private var wedgeSection: some View {
        let across = profile?.trackWidth.flatMap { width in
            state.roll.flatMap { LevelingWedge.across(roll: $0, trackWidth: width) }
        }
        let along = profile?.wheelbase.flatMap { base in
            state.pitch.flatMap { LevelingWedge.along(pitch: $0, wheelbase: base) }
        }

        VStack(alignment: .leading, spacing: 10) {
            Label("Auffahrkeile", systemImage: "triangle.fill")
                .font(.headline)

            if profile?.trackWidth == nil && profile?.wheelbase == nil {
                Text("Für die Keilhöhe fehlen Spurweite und Radstand. Beides lässt "
                     + "sich beim Fahrzeug hinterlegen.")
                    .font(.callout)
                    .foregroundStyle(.secondary)
            } else if across == nil && along == nil {
                Text("Keine Keile nötig.")
                    .font(.callout)
                    .foregroundStyle(.secondary)
            } else {
                ForEach([across, along].compactMap { $0 }, id: \.side) { wedge in
                    HStack {
                        Text(wedge.side.text.capitalized)
                        Spacer()
                        Text(String(format: "%.0f cm", wedge.heightInCentimetres))
                            .font(.title3.weight(.semibold).monospacedDigit())
                    }
                }
                Text("Höhe unter die tieferstehende Seite, damit das Fahrzeug eben steht.")
                    .font(.caption)
                    .foregroundStyle(.secondary)
            }
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding()
        .background(Color(.secondarySystemGroupedBackground), in: .rect(cornerRadius: 16))
    }

    /// Einmal spürbar melden, wenn die Waage erreicht ist – man schaut beim
    /// Rangieren nicht dauernd aufs Display.
    private func announceIfReached() {
        guard assistant.hasReachedTarget else {
            didAnnounceTarget = false
            return
        }
        guard !didAnnounceTarget else { return }
        didAnnounceTarget = true
        #if canImport(UIKit)
        UINotificationFeedbackGenerator().notificationOccurred(.success)
        #endif
    }
}

extension LevelingWedge.Side: Hashable {}