import ManaCore
import PhotosUI
import SwiftUI

#if canImport(UIKit)
import UIKit
#endif

/// Card-Create-View. Type-Picker oben, type-spezifische Felder unten.
/// Deckt alle 7 Card-Types ab.
struct CardEditorView: View {
    let deckId: String
    let onCreated: (Card) -> Void

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

    @State private var type: CardType = .basic
    @State private var front: String = ""
    @State private var back: String = ""
    @State private var clozeText: String = ""
    @State private var typingAnswer: String = ""
    @State private var multipleChoiceAnswer: String = ""
    @State private var isSubmitting = false
    @State private var errorMessage: String?

    // Image-Occlusion-State
    @State private var imagePickerItem: PhotosPickerItem?
    @State private var occlusionImage: PlatformImage?
    @State private var occlusionImageData: Data?
    @State private var occlusionMimeType: String = "image/jpeg"
    @State private var occlusionRegions: [MaskRegion] = []
    @State private var occlusionNote: String = ""

    // Audio-Front-State
    @State private var audioFileURL: URL?
    @State private var showAudioPicker = false

    private static let supportedTypes: [CardType] = [
        .basic, .basicReverse, .cloze, .typing, .multipleChoice,
        .imageOcclusion, .audioFront,
    ]

    var body: some View {
        Form {
            Section("Card-Type") {
                Picker("Typ", selection: $type) {
                    ForEach(Self.supportedTypes, id: \.self) { t in
                        Text(label(for: t)).tag(t)
                    }
                }
                .pickerStyle(.menu)
            }

            typeFields

            if let errorMessage {
                Section {
                    Text(errorMessage)
                        .font(.footnote)
                        .foregroundStyle(CardsTheme.error)
                }
            }
        }
        .navigationTitle("Neue Karte")
        #if os(iOS)
            .navigationBarTitleDisplayMode(.inline)
        #endif
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("Abbrechen") { dismiss() }
                }
                ToolbarItem(placement: .confirmationAction) {
                    Button("Erstellen") { Task { await submit() } }
                        .disabled(!canSubmit || isSubmitting)
                }
            }
    }

    @ViewBuilder
    private var typeFields: some View {
        switch type {
        case .basic, .basicReverse:
            Section("Vorderseite") {
                TextField("Front", text: $front, axis: .vertical)
                    .lineLimit(2 ... 6)
            }
            Section("Rückseite") {
                TextField("Back", text: $back, axis: .vertical)
                    .lineLimit(2 ... 6)
            }
            if type == .basicReverse {
                Section {
                    Text("Beide Richtungen werden gelernt — front→back und back→front.")
                        .font(.caption)
                        .foregroundStyle(CardsTheme.mutedForeground)
                }
            }

        case .cloze:
            Section("Cloze-Text") {
                TextField("Beispiel: Die Hauptstadt von {{c1::Frankreich}} ist {{c2::Paris}}.",
                          text: $clozeText, axis: .vertical)
                    .lineLimit(3 ... 8)
                    .autocorrectionDisabled()
                    .textInputAutocapitalization(.sentences)
                    .monospaced()
            }
            Section {
                let count = Cloze.subIndexCount(clozeText)
                if count > 0 {
                    Label("\(count) Lücken erkannt → \(count) Reviews", systemImage: "checkmark.circle.fill")
                        .font(.caption)
                        .foregroundStyle(CardsTheme.success)
                } else {
                    Label("Mindestens ein Cluster `{{c1::...}}` erforderlich", systemImage: "exclamationmark.circle")
                        .font(.caption)
                        .foregroundStyle(CardsTheme.warning)
                }
                Text("Mit Hint: `{{c1::Berlin::Hauptstadt von DE}}`")
                    .font(.caption2)
                    .foregroundStyle(CardsTheme.mutedForeground)
            }

        case .typing:
            Section("Frage") {
                TextField("Front", text: $front, axis: .vertical)
                    .lineLimit(2 ... 4)
            }
            Section("Erwartete Antwort") {
                TextField("Answer", text: $typingAnswer)
            }

        case .multipleChoice:
            Section("Frage") {
                TextField("Front", text: $front, axis: .vertical)
                    .lineLimit(2 ... 4)
            }
            Section("Richtige Antwort") {
                TextField("Answer", text: $multipleChoiceAnswer)
            }
            Section {
                Text("Distractor-Optionen werden zur Lernzeit automatisch aus anderen Karten desselben Decks gezogen.")
                    .font(.caption)
                    .foregroundStyle(CardsTheme.mutedForeground)
            }

        case .imageOcclusion:
            imageOcclusionFields

        case .audioFront:
            audioFrontFields
        }
    }

    /// Extrahiert in eine eigene Property, weil PhotosPickers Label-Closure
    /// unter Swift-6-Strict-Concurrency den direkten Zugriff auf
    /// `@State`-Properties als Sendable-Verletzung markiert. Indirektion
    /// über eine MainActor-isolierte computed Property löst das.
    private var pickerLabel: some View {
        Group {
            if occlusionImage == nil {
                Label("Bild auswählen", systemImage: "photo")
            } else {
                Label("Bild ersetzen", systemImage: "arrow.triangle.2.circlepath")
            }
        }
    }

    @ViewBuilder
    private var imageOcclusionFields: some View {
        Section("Bild") {
            PhotosPicker(selection: $imagePickerItem, matching: .images) {
                pickerLabel
            }
            .onChange(of: imagePickerItem) { _, newItem in
                Task { await loadPickedImage(newItem) }
            }
        }

        if let image = occlusionImage {
            Section("Masken") {
                MaskEditorView(image: image, regions: $occlusionRegions)
            }
        }

        Section("Hinweis (optional)") {
            TextField("z.B. Kurz-Erklärung", text: $occlusionNote, axis: .vertical)
                .lineLimit(1 ... 3)
        }

        Section {
            if occlusionImage == nil {
                Label("Erst Bild wählen", systemImage: "info.circle")
                    .font(.caption)
                    .foregroundStyle(CardsTheme.mutedForeground)
            } else if occlusionRegions.isEmpty {
                Label("Mindestens eine Maske nötig", systemImage: "exclamationmark.circle")
                    .font(.caption)
                    .foregroundStyle(CardsTheme.warning)
            } else {
                Label("\(occlusionRegions.count) Masken → \(occlusionRegions.count) Reviews",
                      systemImage: "checkmark.circle.fill")
                    .font(.caption)
                    .foregroundStyle(CardsTheme.success)
            }
        }
    }

    @ViewBuilder
    private var audioFrontFields: some View {
        Section("Audio-Datei") {
            Button {
                showAudioPicker = true
            } label: {
                if let audioFileURL {
                    Label(audioFileURL.lastPathComponent, systemImage: "waveform")
                } else {
                    Label("Audio auswählen", systemImage: "waveform.badge.plus")
                }
            }
            .fileImporter(
                isPresented: $showAudioPicker,
                allowedContentTypes: [.audio, .mp3, .wav, .mpeg4Audio],
                allowsMultipleSelection: false
            ) { result in
                if case let .success(urls) = result, let first = urls.first {
                    audioFileURL = first
                }
            }
        }
        Section("Antwort") {
            TextField("Was zu hören ist", text: $back, axis: .vertical)
                .lineLimit(2 ... 4)
        }
    }

    private func loadPickedImage(_ item: PhotosPickerItem?) async {
        guard let item else { return }
        do {
            guard let data = try await item.loadTransferable(type: Data.self) else { return }
            occlusionImageData = data
            occlusionMimeType = inferMimeType(from: data)
            if let img = PlatformImage(data: data) {
                occlusionImage = img
                occlusionRegions = [] // neue Bildauswahl resetet Masken
            }
        } catch {
            errorMessage = "Bild konnte nicht geladen werden: \(error.localizedDescription)"
        }
    }

    private func inferMimeType(from data: Data) -> String {
        // Schneller Magic-Byte-Check für die häufigsten Formate
        guard data.count > 4 else { return "image/jpeg" }
        let bytes = Array(data.prefix(8))
        if bytes.starts(with: [0xFF, 0xD8, 0xFF]) { return "image/jpeg" }
        if bytes.starts(with: [0x89, 0x50, 0x4E, 0x47]) { return "image/png" }
        if bytes.starts(with: [0x47, 0x49, 0x46, 0x38]) { return "image/gif" }
        // WebP: starts with "RIFF" + 4 bytes size + "WEBP"
        if bytes.count >= 8,
           bytes[0 ... 3] == [0x52, 0x49, 0x46, 0x46] {
            return "image/webp"
        }
        return "image/jpeg"
    }

    private func audioMimeType(for url: URL) -> String {
        switch url.pathExtension.lowercased() {
        case "mp3": "audio/mpeg"
        case "wav": "audio/wav"
        case "m4a", "mp4": "audio/mp4"
        case "ogg", "oga": "audio/ogg"
        default: "audio/mpeg"
        }
    }

    private var canSubmit: Bool {
        switch type {
        case .basic, .basicReverse:
            !front.trimmed.isEmpty && !back.trimmed.isEmpty
        case .cloze:
            Cloze.subIndexCount(clozeText) > 0
        case .typing:
            !front.trimmed.isEmpty && !typingAnswer.trimmed.isEmpty
        case .multipleChoice:
            !front.trimmed.isEmpty && !multipleChoiceAnswer.trimmed.isEmpty
        case .imageOcclusion:
            occlusionImageData != nil && !occlusionRegions.isEmpty
        case .audioFront:
            audioFileURL != nil && !back.trimmed.isEmpty
        }
    }

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

        do {
            let fields: [String: String]
            var mediaRefs: [String]? = nil
            switch type {
            case .basic, .basicReverse:
                fields = CardFieldsBuilder.basic(front: front.trimmed, back: back.trimmed)
            case .cloze:
                fields = CardFieldsBuilder.cloze(text: clozeText.trimmed)
            case .typing:
                fields = CardFieldsBuilder.typing(front: front.trimmed, answer: typingAnswer.trimmed)
            case .multipleChoice:
                fields = CardFieldsBuilder.multipleChoice(front: front.trimmed, answer: multipleChoiceAnswer.trimmed)
            case .imageOcclusion:
                guard let data = occlusionImageData else { return }
                let media = try await api.uploadMedia(
                    data: data,
                    filename: "occlusion.\(occlusionMimeType.contains("png") ? "png" : "jpg")",
                    mimeType: occlusionMimeType
                )
                fields = CardFieldsBuilder.imageOcclusion(
                    imageRef: media.id,
                    regions: occlusionRegions,
                    note: occlusionNote.trimmed.isEmpty ? nil : occlusionNote.trimmed
                )
                mediaRefs = [media.id]
            case .audioFront:
                guard let url = audioFileURL else { return }
                let didStart = url.startAccessingSecurityScopedResource()
                defer { if didStart { url.stopAccessingSecurityScopedResource() } }
                let data = try Data(contentsOf: url)
                let media = try await api.uploadMedia(
                    data: data,
                    filename: url.lastPathComponent,
                    mimeType: audioMimeType(for: url)
                )
                fields = CardFieldsBuilder.audioFront(audioRef: media.id, back: back.trimmed)
                mediaRefs = [media.id]
            }

            let body = CardCreateBody(deckId: deckId, type: type, fields: fields, mediaRefs: mediaRefs)
            let card = try await api.createCard(body)
            onCreated(card)
            dismiss()
        } catch {
            errorMessage = (error as? LocalizedError)?.errorDescription ?? String(describing: error)
        }
    }

    private func label(for type: CardType) -> String {
        switch type {
        case .basic: "Einfach (Vorder/Rück)"
        case .basicReverse: "Beidseitig"
        case .cloze: "Lückentext"
        case .typing: "Eintippen"
        case .multipleChoice: "Multiple Choice"
        case .imageOcclusion: "Bild-Verdeckung"
        case .audioFront: "Audio"
        }
    }
}

private extension String {
    var trimmed: String {
        trimmingCharacters(in: .whitespacesAndNewlines)
    }
}