import ManaCore
import SwiftUI

/// Card-Create und Card-Edit in einer View.
///
/// - `.create(deckId:)` zeigt Type-Picker + leere Felder.
/// - `.edit(card:)` blendet Type-Picker aus (Server-seitig immutable),
///   pre-fillt alle Felder, und PATCHt auf Submit.
struct CardEditorView: View {
    enum Mode {
        case create(deckId: String)
        case edit(card: Card)
    }

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

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

    @State private var type: CardType
    @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?

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

    init(mode: Mode, onSaved: @escaping (Card) -> Void) {
        self.mode = mode
        self.onSaved = onSaved

        let initialType: CardType
        var initialFront = ""
        var initialBack = ""
        var initialCloze = ""
        var initialTyping = ""
        var initialMC = ""

        switch mode {
        case .create:
            initialType = .basic
        case let .edit(card):
            initialType = card.type
            switch card.type {
            case .basic, .basicReverse:
                initialFront = card.fields["front"] ?? ""
                initialBack = card.fields["back"] ?? ""
            case .cloze:
                initialCloze = card.fields["text"] ?? ""
            case .typing:
                initialFront = card.fields["front"] ?? ""
                initialTyping = card.fields["answer"] ?? ""
            case .multipleChoice:
                initialFront = card.fields["front"] ?? ""
                initialMC = card.fields["answer"] ?? ""
            }
        }

        _type = State(initialValue: initialType)
        _front = State(initialValue: initialFront)
        _back = State(initialValue: initialBack)
        _clozeText = State(initialValue: initialCloze)
        _typingAnswer = State(initialValue: initialTyping)
        _multipleChoiceAnswer = State(initialValue: initialMC)
    }

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

            typeFields

            if let errorMessage {
                Section {
                    Text(errorMessage)
                        .font(.footnote)
                        .foregroundStyle(WordeckTheme.error)
                }
            }
        }
        .disabled(isSubmitting)
        .navigationTitle(isCreate ? "Neue Karte" : "Karte 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(!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(WordeckTheme.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(WordeckTheme.success)
                } else {
                    Label("Mindestens ein Cluster `{{c1::...}}` erforderlich", systemImage: "exclamationmark.circle")
                        .font(.caption)
                        .foregroundStyle(WordeckTheme.warning)
                }
                Text("Mit Hint: `{{c1::Berlin::Hauptstadt von DE}}`")
                    .font(.caption2)
                    .foregroundStyle(WordeckTheme.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(WordeckTheme.mutedForeground)
            }
        }
    }

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

    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
        }
    }

    private func buildFields() -> [String: String] {
        switch type {
        case .basic, .basicReverse:
            CardFieldsBuilder.basic(front: front.trimmed, back: back.trimmed)
        case .cloze:
            CardFieldsBuilder.cloze(text: clozeText.trimmed)
        case .typing:
            CardFieldsBuilder.typing(front: front.trimmed, answer: typingAnswer.trimmed)
        case .multipleChoice:
            CardFieldsBuilder.multipleChoice(
                front: front.trimmed,
                answer: multipleChoiceAnswer.trimmed
            )
        }
    }

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

        do {
            let card: Card = switch mode {
            case let .create(deckId):
                try await api.createCard(CardCreateBody(
                    deckId: deckId,
                    type: type,
                    fields: fields
                ))
            case let .edit(existing):
                try await api.updateCard(id: existing.id, body: CardUpdateBody(fields: fields))
            }
            onSaved(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"
        }
    }
}

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