import ManaCore
import SwiftData
import SwiftUI

/// Detail-View für ein Public-Deck. Subscribe-Button löst Auto-Fork
/// serverseitig aus und navigiert anschließend zur eigenen Deck-Detail.
struct PublicDeckView: View {
    let slug: String

    @Environment(AuthClient.self) private var auth
    @Environment(\.modelContext) private var context
    @State private var detail: PublicDeckDetail?
    @State private var isLoading = false
    @State private var isSubscribing = false
    @State private var errorMessage: String?
    @State private var subscribed: SubscribeResponse?

    var body: some View {
        ZStack {
            CardsTheme.background.ignoresSafeArea()
            content
        }
        .navigationTitle(detail?.deck.title ?? "Deck")
        #if os(iOS)
            .navigationBarTitleDisplayMode(.inline)
        #endif
            .task(id: slug) {
                await load()
            }
    }

    @ViewBuilder
    private var content: some View {
        if isLoading, detail == nil {
            ProgressView()
                .tint(CardsTheme.primary)
        } else if let detail {
            ScrollView {
                VStack(alignment: .leading, spacing: 16) {
                    header(detail: detail)
                    Divider().background(CardsTheme.border)
                    metadata(detail: detail)
                    Divider().background(CardsTheme.border)
                    subscribeSection(detail: detail)
                    if let errorMessage {
                        Text(errorMessage)
                            .font(.caption)
                            .foregroundStyle(CardsTheme.error)
                            .padding(.horizontal, 16)
                    }
                }
                .padding(.vertical, 16)
            }
        } else if let errorMessage {
            ContentUnavailableView(
                "Deck nicht gefunden",
                systemImage: "questionmark.folder",
                description: Text(errorMessage)
            )
            .foregroundStyle(CardsTheme.foreground)
        }
    }

    private func header(detail: PublicDeckDetail) -> some View {
        VStack(alignment: .leading, spacing: 8) {
            HStack {
                Text(detail.deck.title)
                    .font(.title.bold())
                    .foregroundStyle(CardsTheme.foreground)
                if detail.deck.isFeatured {
                    Image(systemName: "star.fill")
                        .foregroundStyle(CardsTheme.warning)
                }
            }
            if let description = detail.deck.description, !description.isEmpty {
                Text(description)
                    .foregroundStyle(CardsTheme.mutedForeground)
            }
        }
        .padding(.horizontal, 16)
    }

    private func metadata(detail: PublicDeckDetail) -> some View {
        VStack(alignment: .leading, spacing: 8) {
            if let owner = detail.owner {
                HStack(spacing: 6) {
                    Image(systemName: "person.crop.circle")
                        .foregroundStyle(CardsTheme.mutedForeground)
                    Text(owner.displayName)
                        .foregroundStyle(CardsTheme.foreground)
                    if owner.verifiedMana {
                        Image(systemName: "checkmark.seal.fill")
                            .font(.caption)
                            .foregroundStyle(CardsTheme.primary)
                    }
                }
                .font(.subheadline)
            }
            HStack(spacing: 16) {
                if let version = detail.latestVersion {
                    Label("v\(version.semver)", systemImage: "tag")
                    Label("\(version.cardCount) Karten", systemImage: "rectangle.stack")
                }
                Label(detail.deck.license, systemImage: "doc.text")
                if let language = detail.deck.language {
                    Label(language.uppercased(), systemImage: "globe")
                }
            }
            .font(.caption)
            .foregroundStyle(CardsTheme.mutedForeground)

            if let changelog = detail.latestVersion?.changelog, !changelog.isEmpty {
                Text("Changelog")
                    .font(.caption.weight(.semibold))
                    .foregroundStyle(CardsTheme.mutedForeground)
                    .padding(.top, 8)
                Text(changelog)
                    .font(.caption)
                    .foregroundStyle(CardsTheme.foreground)
            }
        }
        .padding(.horizontal, 16)
    }

    @ViewBuilder
    private func subscribeSection(detail: PublicDeckDetail) -> some View {
        VStack(spacing: 12) {
            if let subscribed {
                Label("Abonniert — dein Fork ist in deiner Bibliothek", systemImage: "checkmark.circle.fill")
                    .foregroundStyle(CardsTheme.success)
                    .padding()
                    .frame(maxWidth: .infinity)
                    .background(CardsTheme.success.opacity(0.1), in: RoundedRectangle(cornerRadius: 10))
                NavigationLink(value: subscribed.privateDeckId) {
                    Label("Zum eigenen Deck", systemImage: "arrow.right.circle")
                        .frame(maxWidth: .infinity)
                        .padding(.vertical, 10)
                        .background(CardsTheme.primary, in: RoundedRectangle(cornerRadius: 10))
                        .foregroundStyle(CardsTheme.primaryForeground)
                }
                .buttonStyle(.plain)
            } else if detail.deck.isTakedown {
                Label("Dieses Deck wurde entfernt", systemImage: "exclamationmark.triangle")
                    .foregroundStyle(CardsTheme.error)
            } else if detail.deck.latestVersionId == nil {
                Label("Noch keine Version veröffentlicht", systemImage: "clock")
                    .foregroundStyle(CardsTheme.mutedForeground)
            } else {
                Button {
                    Task { await subscribe(detail: detail) }
                } label: {
                    HStack {
                        if isSubscribing {
                            ProgressView()
                                .controlSize(.small)
                                .tint(CardsTheme.primaryForeground)
                        }
                        Text(detail.deck.priceCredits > 0
                             ? "Abonnieren (\(detail.deck.priceCredits) Credits)"
                             : "Abonnieren")
                            .fontWeight(.semibold)
                    }
                    .frame(maxWidth: .infinity)
                    .padding(.vertical, 14)
                    .background(CardsTheme.primary, in: RoundedRectangle(cornerRadius: 10))
                    .foregroundStyle(CardsTheme.primaryForeground)
                }
                .buttonStyle(.plain)
                .disabled(isSubscribing)
            }
        }
        .padding(.horizontal, 16)
    }

    private func load() async {
        isLoading = true
        defer { isLoading = false }
        let api = CardsAPI(auth: auth)
        do {
            detail = try await api.publicDeck(slug: slug)
        } catch {
            errorMessage = (error as? LocalizedError)?.errorDescription ?? String(describing: error)
        }
    }

    private func subscribe(detail: PublicDeckDetail) async {
        isSubscribing = true
        errorMessage = nil
        defer { isSubscribing = false }
        let api = CardsAPI(auth: auth)
        do {
            let response = try await api.subscribe(slug: slug)
            subscribed = response
            // Cache neu laden, damit der Fork in der Liste auftaucht
            let store = DeckListStore(auth: auth, context: context)
            await store.refresh()
        } catch {
            errorMessage = (error as? LocalizedError)?.errorDescription ?? String(describing: error)
        }
    }
}