import SwiftUI

/// Persönliches Tagebuch — alle eigenen Posts, auch die anonymen.
/// Bleibt für immer. Das ist der Retention-Hook.
struct DiaryView: View {
    @StateObject private var viewModel = DiaryViewModel()
    @EnvironmentObject var appState: AppState

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

                if viewModel.groupedPosts.isEmpty && !viewModel.isLoading {
                    DiaryEmptyView()
                } else {
                    ScrollView {
                        LazyVStack(alignment: .leading, spacing: 0) {
                            // "Vor genau einem Jahr" — Memory
                            if let memory = viewModel.yearAgoPost {
                                MemoryBanner(post: memory)
                                    .padding(.bottom, 4)
                            }

                            ForEach(viewModel.groupedPosts, id: \.nightLabel) { group in
                                // Nacht-Header
                                DiaryNightHeader(label: group.nightLabel, count: group.posts.count)

                                ForEach(group.posts) { post in
                                    DiaryPostRow(post: post) {
                                        Task { await viewModel.deletePost(post) }
                                    }
                                    Divider().background(Color.nightBorder).padding(.leading, 16)
                                }
                            }
                            Color.clear.frame(height: 100)
                        }
                    }
                    .refreshable { await viewModel.load() }
                }
            }
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .principal) {
                    HStack(spacing: 7) {
                        Image(systemName: "book.closed.fill")
                            .foregroundColor(.nightPurple)
                        Text("tagebuch")
                            .font(.nightTitle(17))
                            .foregroundColor(.nightPrimary)
                    }
                }
            }
        }
        .task { await viewModel.load() }
    }
}

// MARK: - Memory Banner

struct MemoryBanner: View {
    let post: Post
    @State private var show = true

    var body: some View {
        if show {
            VStack(alignment: .leading, spacing: 10) {
                HStack(spacing: 8) {
                    Image(systemName: "clock.arrow.circlepath")
                        .foregroundColor(.nightPurpleSoft)
                        .font(.system(size: 14))
                    Text("vor genau einem jahr")
                        .font(.nightLabel(12, weight: .semibold))
                        .foregroundColor(.nightPurpleSoft)
                        .kerning(0.5)
                    Spacer()
                    Button { withAnimation { show = false } } label: {
                        Image(systemName: "xmark")
                            .font(.system(size: 12))
                            .foregroundColor(.nightTertiary)
                    }
                }

                Text(post.content)
                    .font(.nightBody(15))
                    .foregroundColor(.nightPrimary.opacity(0.85))
                    .lineSpacing(4)

                HStack(spacing: 5) {
                    if let mood = post.mood {
                        Text(mood.emoji).font(.nightMono(11))
                        Text(mood.label).font(.nightLabel(11))
                    }
                    Text("·")
                    Text(post.formattedTime)
                        .font(.nightMono(11))
                }
                .foregroundColor(.nightTertiary)
            }
            .padding(16)
            .background(
                ZStack {
                    RoundedRectangle(cornerRadius: 0)
                        .fill(Color.nightPurple.opacity(0.06))
                    RoundedRectangle(cornerRadius: 0)
                        .fill(
                            LinearGradient(
                                colors: [Color.nightPurple.opacity(0.08), .clear],
                                startPoint: .topLeading,
                                endPoint: .bottomTrailing
                            )
                        )
                }
            )
            .overlay(
                Rectangle().fill(Color.nightBorder).frame(height: 1),
                alignment: .bottom
            )
        }
    }
}

// MARK: - Night Group Header

struct DiaryNightHeader: View {
    let label: String
    let count: Int

    var body: some View {
        HStack {
            Text(label)
                .font(.nightLabel(12, weight: .semibold))
                .foregroundColor(.nightSecondary)
                .kerning(0.5)
            Text("·  \(count) Gedanke\(count == 1 ? "" : "n")")
                .font(.nightLabel(12))
                .foregroundColor(.nightTertiary)
            Spacer()
        }
        .padding(.horizontal, 16)
        .padding(.vertical, 10)
        .background(Color.nightSurface)
    }
}

// MARK: - Diary Post Row

struct DiaryPostRow: View {
    let post: Post
    let onDelete: () -> Void
    @State private var confirmDelete = false

    var body: some View {
        HStack(alignment: .top, spacing: 0) {
            Rectangle()
                .fill(post.mood?.color ?? Color.nightTertiary)
                .frame(width: 2)
                .padding(.vertical, 14)

            VStack(alignment: .leading, spacing: 8) {
                HStack {
                    Text(post.formattedTime)
                        .font(.nightMono(12))
                        .foregroundColor(.nightTertiary)

                    if post.isAnonymous {
                        Text("· anonym")
                            .font(.nightLabel(11))
                            .foregroundColor(.nightTertiary)
                            .italic()
                    }

                    if let mood = post.mood {
                        Text("· \(mood.emoji) \(mood.label)")
                            .font(.nightLabel(11))
                            .foregroundColor(mood.color.opacity(0.7))
                    }

                    Spacer()

                    if post.resonanceCount > 0 {
                        HStack(spacing: 3) {
                            Image(systemName: "heart.fill")
                                .font(.system(size: 10))
                            Text("\(post.resonanceCount)")
                                .font(.nightLabel(11))
                        }
                        .foregroundColor(.nightRed.opacity(0.7))
                    }
                }

                Text(post.content)
                    .font(.nightBody(16))
                    .foregroundColor(.nightPrimary.opacity(0.88))
                    .lineSpacing(5)
                    .fixedSize(horizontal: false, vertical: true)
            }
            .padding(.horizontal, 14)
            .padding(.vertical, 14)
            .contextMenu {
                Button(role: .destructive) {
                    confirmDelete = true
                } label: {
                    Label("Löschen", systemImage: "trash")
                }
            }
        }
        .confirmationDialog(
            "Post löschen?",
            isPresented: $confirmDelete,
            titleVisibility: .visible
        ) {
            Button("Löschen", role: .destructive) { onDelete() }
        } message: {
            Text("Der Post wird aus dem Feed entfernt, bleibt aber in deinem Tagebuch-Archiv.")
        }
    }
}

// MARK: - Empty State

struct DiaryEmptyView: View {
    var body: some View {
        VStack(spacing: 18) {
            Image(systemName: "book.closed")
                .font(.system(size: 48))
                .foregroundColor(.nightTertiary)
            Text("noch nichts hier")
                .font(.nightTitle(18))
                .foregroundColor(.nightPrimary)
            Text("Deine Posts landen hier.\nIn einem Jahr kannst du nachlesen, was dich\nmitten in der Nacht beschäftigt hat.")
                .font(.nightBody(15))
                .foregroundColor(.nightSecondary)
                .multilineTextAlignment(.center)
                .lineSpacing(4)
        }
        .padding(40)
    }
}

// MARK: - ViewModel

@MainActor
class DiaryViewModel: ObservableObject {
    struct NightGroup { let nightLabel: String; let posts: [Post] }

    @Published var groupedPosts: [NightGroup] = []
    @Published var yearAgoPost: Post? = nil
    @Published var isLoading = false

    func load() async {
        isLoading = true
        defer { isLoading = false }

        do {
            let posts = try await supabase.getDiary()

            // Gruppiere nach Nacht (Datum - 2h, damit 2–5 Uhr zur selben Nacht gehört)
            let grouped = Dictionary(grouping: posts) { post -> String in
                let nightDate = post.createdAt.addingTimeInterval(-2 * 3600)
                let f = DateFormatter()
                f.locale = Locale(identifier: "de_DE")
                f.dateFormat = "EEEE, d. MMMM yyyy"
                return f.string(from: nightDate)
            }

            groupedPosts = grouped
                .sorted { $0.key > $1.key }
                .map { NightGroup(nightLabel: $0.key, posts: $0.value) }

            // Memory: Post von vor genau einem Jahr
            let oneYearAgo = Calendar.current.date(byAdding: .year, value: -1, to: Date())!
            yearAgoPost = posts.first { post in
                Calendar.current.isDate(post.createdAt, equalTo: oneYearAgo, toGranularity: .day)
            }
        } catch {
            #if DEBUG
            groupedPosts = [NightGroup(nightLabel: "gestern", posts: Post.previews)]
            #endif
        }
    }

    func deletePost(_ post: Post) async {
        try? await supabase.softDeletePost(id: post.id)
        await load()
    }
}