import ManaCore
import SwiftUI

/// Deck-Create und Deck-Edit in einer View. `existing == nil` → Create-
/// Modus mit "Erstellen"-Button. Sonst Edit-Modus mit "Speichern".
struct DeckEditorView: View {
    enum Mode: Sendable {
        case create
        case edit(deckId: String)
    }

    let mode: Mode
    let onSaved: (Deck) -> Void

    @Environment(AuthClient.self) private var auth
    @Environment(\.dismiss) private var dismiss

    @State private var name: String
    @State private var description: String
    @State private var color: String
    @State private var category: DeckCategory?
    @State private var visibility: DeckVisibility
    @State private var isSubmitting = false
    @State private var errorMessage: String?

    /// Vorgefüllte Farbpalette aus dem forest-Theme. User können
    /// freie Hex-Werte später via Picker setzen (β-3-extension).
    private static let presetColors: [String] = [
        "#10803D", // forest primary light
        "#1E3A2F", // forest dark
        "#D97706", // amber
        "#DC2626", // red
        "#2563EB", // blue
        "#7C3AED", // violet
        "#0D9488", // teal
        "#737373", // neutral
    ]

    init(mode: Mode, existing: CachedDeck? = nil, onSaved: @escaping (Deck) -> Void) {
        self.mode = mode
        self.onSaved = onSaved
        _name = State(initialValue: existing?.name ?? "")
        _description = State(initialValue: existing?.deckDescription ?? "")
        _color = State(initialValue: existing?.color ?? Self.presetColors[0])
        _category = State(initialValue: existing?.category)
        _visibility = State(initialValue: DeckVisibility(rawValue: existing?.visibilityRaw ?? "private") ?? .private)
    }

    var body: some View {
        Form {
            Section("Name") {
                TextField("Deck-Name", text: $name)
                    .textInputAutocapitalization(.sentences)
            }

            Section("Beschreibung") {
                TextField("optional", text: $description, axis: .vertical)
                    .lineLimit(2 ... 4)
            }

            Section("Farbe") {
                ScrollView(.horizontal, showsIndicators: false) {
                    HStack(spacing: 10) {
                        ForEach(Self.presetColors, id: \.self) { hex in
                            colorSwatch(hex)
                        }
                    }
                    .padding(.vertical, 4)
                }
            }

            Section("Kategorie") {
                Picker("Kategorie", selection: $category) {
                    Text("Keine").tag(DeckCategory?.none)
                    ForEach(DeckCategory.allCases, id: \.self) { cat in
                        Text(cat.label).tag(DeckCategory?.some(cat))
                    }
                }
            }

            Section("Sichtbarkeit") {
                Picker("Sichtbarkeit", selection: $visibility) {
                    Text("Privat").tag(DeckVisibility.private)
                    Text("Space").tag(DeckVisibility.space)
                    Text("Öffentlich").tag(DeckVisibility.public)
                }
                .pickerStyle(.segmented)
            }

            if let errorMessage {
                Section {
                    Text(errorMessage)
                        .font(.footnote)
                        .foregroundStyle(CardsTheme.error)
                }
            }
        }
        .navigationTitle(isCreate ? "Neues Deck" : "Deck bearbeiten")
        #if os(iOS)
            .navigationBarTitleDisplayMode(.inline)
        #endif
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("Abbrechen") { dismiss() }
                }
                ToolbarItem(placement: .confirmationAction) {
                    Button(isCreate ? "Erstellen" : "Speichern") {
                        Task { await submit() }
                    }
                    .disabled(name.trimmingCharacters(in: .whitespaces).isEmpty || isSubmitting)
                }
            }
    }

    private var isCreate: Bool {
        if case .create = mode { return true }
        return false
    }

    @ViewBuilder
    private func colorSwatch(_ hex: String) -> some View {
        let isSelected = color == hex
        Circle()
            .fill(Color.swatchFromHex(hex))
            .frame(width: 36, height: 36)
            .overlay(
                Circle()
                    .stroke(isSelected ? CardsTheme.foreground : CardsTheme.border, lineWidth: isSelected ? 3 : 1)
            )
            .onTapGesture { color = hex }
    }

    private func submit() async {
        isSubmitting = true
        errorMessage = nil
        defer { isSubmitting = false }
        let api = CardsAPI(auth: auth)

        do {
            switch mode {
            case .create:
                let body = DeckCreateBody(
                    name: name.trimmingCharacters(in: .whitespaces),
                    description: nonEmpty(description),
                    color: color,
                    category: category,
                    visibility: visibility
                )
                let deck = try await api.createDeck(body)
                onSaved(deck)
                dismiss()
            case let .edit(deckId):
                let body = DeckUpdateBody(
                    name: name.trimmingCharacters(in: .whitespaces),
                    description: nonEmpty(description),
                    color: color,
                    category: category,
                    visibility: visibility
                )
                let deck = try await api.updateDeck(id: deckId, body: body)
                onSaved(deck)
                dismiss()
            }
        } catch {
            errorMessage = (error as? LocalizedError)?.errorDescription ?? String(describing: error)
        }
    }

    private func nonEmpty(_ s: String) -> String? {
        let trimmed = s.trimmingCharacters(in: .whitespaces)
        return trimmed.isEmpty ? nil : trimmed
    }
}

extension Color {
    static func swatchFromHex(_ hex: String) -> Color {
        var trimmed = hex.trimmingCharacters(in: .whitespacesAndNewlines)
        if trimmed.hasPrefix("#") { trimmed = String(trimmed.dropFirst()) }
        guard let rgb = UInt32(trimmed, radix: 16) else {
            return CardsTheme.primary
        }
        let r = Double((rgb >> 16) & 0xFF) / 255.0
        let g = Double((rgb >> 8) & 0xFF) / 255.0
        let b = Double(rgb & 0xFF) / 255.0
        return Color(red: r, green: g, blue: b)
    }
}