import SwiftUI
import WidgetKit
import UIKit

struct HeimView: View {
    @Environment(AuthSession.self) private var auth
    @Environment(ActiveDogStore.self) private var activeDog

    @State private var dashboard: DashboardSnapshot?
    @State private var cachedPhotoUrl: String?
    @State private var isLoading = false

    private var photoCacheKey: String? {
        guard let userId = auth.profile?.id,
              let dogId = activeDog.activeDog?.id else { return nil }
        let f = DateFormatter()
        f.dateFormat = "yyyy-MM-dd"
        return "heimPhoto_\(userId)_\(dogId)_\(f.string(from: .now))"
    }

    private var greeting: String {
        let hour = Calendar.current.component(.hour, from: .now)
        let name = auth.profile?.name ?? auth.userName ?? ""
        let salute: String = {
            switch hour {
            case 5..<11: return "Guten Morgen"
            case 11..<14: return "Hallo"
            case 14..<18: return "Hallo"
            case 18..<22: return "Guten Abend"
            default: return "Gute Nacht"
            }
        }()
        return name.isEmpty ? salute : "\(salute), \(name)"
    }

    var body: some View {
        NavigationStack {
            ZStack {
                background
                    .ignoresSafeArea()

                ScrollView {
                    VStack(spacing: 16) {
                        Spacer(minLength: 250) // breathing room for the photo
                        header
                        dogPickerCard
                        if let dashboard {
                            dashboardCards(dashboard)
                        }
                        quickActions
                        Spacer(minLength: 24)
                    }
                    .padding(.horizontal)
                }
                .refreshable { await load() }
            }
            .navigationBarTitleDisplayMode(.inline)
            .toolbar(.hidden, for: .navigationBar)
            .task {
                if activeDog.dogs.isEmpty { await activeDog.loadDogs() }
                await load()
            }
            .onChange(of: activeDog.activeDogId) { _, _ in
                Task { await load() }
            }
        }
    }

    @ViewBuilder
    private var background: some View {
        ZStack {
            Color.accentColor.opacity(0.08).ignoresSafeArea()
            if let path = dashboard?.randomPhoto?.url ?? cachedPhotoUrl,
               let url = URL(string: "https://banyaro.app\(path)") {
                AsyncImage(url: url) { phase in
                    switch phase {
                    case .success(let img):
                        img.resizable().scaledToFill()
                    default:
                        Color.clear
                    }
                }
                .frame(maxWidth: .infinity, maxHeight: 320, alignment: .top)
                .clipped()
                .frame(maxHeight: .infinity, alignment: .top)
            }
        }
    }

    private var header: some View {
        VStack(spacing: 4) {
            Text(greeting)
                .font(.title2.bold())
                .multilineTextAlignment(.center)
                .shadow(color: .black.opacity(0.4), radius: 3, y: 1)
            if let dog = activeDog.activeDog {
                Text("Was machst du heute mit \(dog.name)?")
                    .font(.subheadline)
                    .foregroundStyle(.secondary)
                    .multilineTextAlignment(.center)
            }
        }
        .frame(maxWidth: .infinity)
        .padding(.bottom, 6)
    }

    private var dogPickerCard: some View {
        Group {
            if activeDog.dogs.isEmpty {
                EmptyView()
            } else {
                Menu {
                    ForEach(activeDog.dogs) { dog in
                        Button {
                            activeDog.setActive(dog.id)
                        } label: {
                            if dog.id == activeDog.activeDogId {
                                Label(dog.name, systemImage: "checkmark")
                            } else {
                                Text(dog.name)
                            }
                        }
                    }
                } label: {
                    HStack(spacing: 12) {
                        dogAvatar
                            .frame(width: 48, height: 48)
                            .clipShape(Circle())
                        VStack(alignment: .leading) {
                            Text(activeDog.activeDog?.name ?? "Hund wählen")
                                .font(.headline)
                                .foregroundStyle(.primary)
                            if let rasse = activeDog.activeDog?.rasse, !rasse.isEmpty {
                                Text(rasse)
                                    .font(.caption)
                                    .foregroundStyle(.secondary)
                            }
                        }
                        Spacer()
                        Image(systemName: "chevron.up.chevron.down")
                            .font(.caption)
                            .foregroundStyle(.secondary)
                    }
                    .padding(14)
                    .background(.thinMaterial, in: RoundedRectangle(cornerRadius: 16))
                }
            }
        }
    }

    @ViewBuilder
    private var dogAvatar: some View {
        if let path = activeDog.activeDog?.fotoUrl,
           let url = URL(string: "https://banyaro.app\(path)") {
            AsyncImage(url: url) { phase in
                switch phase {
                case .success(let img): img.resizable().scaledToFill()
                default: avatarFallback
                }
            }
        } else {
            avatarFallback
        }
    }

    private var avatarFallback: some View {
        ZStack {
            Color.accentColor.opacity(0.2)
            Image(systemName: "pawprint.fill")
                .foregroundStyle(Color.accentColor)
        }
    }

    private func dashboardCards(_ snap: DashboardSnapshot) -> some View {
        VStack(spacing: 10) {
            if let appt = snap.nextAppointment, let bez = appt.bezeichnung {
                infoCard(
                    icon: "calendar",
                    title: "Nächster Termin",
                    value: bez,
                    detail: appt.naechstes.map(DiaryUtil.format) ?? ""
                )
            }
        }
    }

    private func infoCard(icon: String, title: String, value: String, detail: String) -> some View {
        HStack(spacing: 12) {
            Image(systemName: icon)
                .font(.title3)
                .foregroundStyle(Color.accentColor)
                .frame(width: 28)
            VStack(alignment: .leading, spacing: 2) {
                Text(title).font(.caption).foregroundStyle(.secondary)
                Text(value).font(.subheadline.bold())
                if !detail.isEmpty {
                    Text(detail).font(.caption2).foregroundStyle(.tertiary)
                }
            }
            Spacer()
        }
        .padding(14)
        .background(.thinMaterial, in: RoundedRectangle(cornerRadius: 14))
    }

    private var quickActions: some View {
        VStack(spacing: 10) {
            NavigationLink {
                TagebuchView()
            } label: {
                actionRow(icon: "book.fill", title: "Tagebuch", subtitle: "Eintrag anlegen oder lesen")
            }
            NavigationLink {
                WetterView()
            } label: {
                actionRow(icon: "cloud.sun.fill", title: "Wetter", subtitle: "Vorhersage für heute")
            }
            NavigationLink {
                ErsteHilfeView()
            } label: {
                actionRow(icon: "cross.case.fill", title: "Erste Hilfe", subtitle: "Notfall-Anleitung — offline")
            }
        }
    }

    private func actionRow(icon: String, title: String, subtitle: String) -> some View {
        HStack(spacing: 12) {
            Image(systemName: icon)
                .font(.title3)
                .foregroundStyle(.white)
                .frame(width: 36, height: 36)
                .background(Color.accentColor, in: RoundedRectangle(cornerRadius: 10))
            VStack(alignment: .leading, spacing: 2) {
                Text(title).font(.subheadline.bold()).foregroundStyle(.primary)
                Text(subtitle).font(.caption).foregroundStyle(.secondary)
            }
            Spacer()
            Image(systemName: "chevron.right")
                .font(.caption.bold())
                .foregroundStyle(.tertiary)
        }
        .padding(14)
        .background(.thinMaterial, in: RoundedRectangle(cornerRadius: 14))
    }

    private func load() async {
        guard let dog = activeDog.activeDog else { return }

        // Cache als Fallback, falls Backend offline. Nicht als Vorzug —
        // sonst klebt eine tote URL (gelöschtes Bild) über den ganzen Tag.
        cachedPhotoUrl = photoCacheKey.flatMap { UserDefaults.standard.string(forKey: $0) }

        isLoading = true
        defer { isLoading = false }
        dashboard = try? await APIClient.shared.get("/api/dogs/\(dog.id)/welcome-dashboard")

        // Backend ist Source-of-Truth: wenn es ein Foto liefert, ist das
        // aktuell und im Server-Cache stabil. Lokal denselben Wert ablegen.
        if let fresh = dashboard?.randomPhoto?.url, let key = photoCacheKey {
            if fresh != cachedPhotoUrl {
                UserDefaults.standard.set(fresh, forKey: key)
            }
            cachedPhotoUrl = fresh
        }

        await updateWidgetSnapshot(dog: dog)
    }

    /// Schreibt einen Snapshot (kleines Foto + nächster Termin) in die App Group
    /// fürs Home-Screen-Widget und triggert ein Widget-Reload.
    private func updateWidgetSnapshot(dog: Dog) async {
        var photoJPEG: Data?
        if let path = dashboard?.randomPhoto?.previewUrl ?? dashboard?.randomPhoto?.url,
           let url = URL(string: "https://banyaro.app\(path)"),
           let (data, _) = try? await URLSession.shared.data(from: url) {
            photoJPEG = Self.widgetThumbnail(from: data)
        }
        let appt: String? = {
            guard let a = dashboard?.nextAppointment, let bez = a.bezeichnung, !bez.isEmpty else { return nil }
            if let date = a.naechstes { return "\(bez) · \(DiaryUtil.format(date))" }
            return bez
        }()
        HomeWidgetStore.save(HomeWidgetData(
            dogName: dog.name,
            photoJPEG: photoJPEG,
            nextAppointment: appt,
            diaryCount: dashboard?.diaryCount,
            updatedAt: Date()
        ))
        WidgetCenter.shared.reloadAllTimelines()
    }

    private static func widgetThumbnail(from data: Data, max: CGFloat = 600) -> Data? {
        guard let img = UIImage(data: data) else { return nil }
        let longest = Swift.max(img.size.width, img.size.height)
        let scale = longest > max ? max / longest : 1
        let size = CGSize(width: img.size.width * scale, height: img.size.height * scale)
        let rendered = UIGraphicsImageRenderer(size: size).image { _ in
            img.draw(in: CGRect(origin: .zero, size: size))
        }
        return rendered.jpegData(compressionQuality: 0.7)
    }
}