cards-native/Sources/Features/Study/MultipleChoiceCardView.swift

import ManaCore
import SwiftUI

/// Multiple-Choice-Karten-View: zeigt 4 shuffled Optionen (1 richtige
/// + 3 Distractors vom Server). User-Tap markiert Wahl, beim Flip
/// werden richtige Antwort + Wahl hervorgehoben.
///
/// Web-Vorbild: `cards/apps/web/src/lib/components/MultipleChoiceView.svelte`.
struct MultipleChoiceCardView: View {
    let card: ReviewCard
    let isFlipped: Bool

    @Environment(AuthClient.self) private var auth
    @State private var options: [String] = []
    @State private var selected: String?
    @State private var phase: LoadPhase = .loading

    enum LoadPhase: Sendable {
        case loading
        case ready
        case tooFew   // < 1 Distractor → manueller Modus
        case failed
    }

    var body: some View {
        VStack(alignment: .leading, spacing: 16) {
            text(card.fields["front"] ?? "")
                .font(.title3)
                .foregroundStyle(CardsTheme.foreground)

            switch phase {
            case .loading:
                ProgressView()
                    .tint(CardsTheme.primary)
                    .frame(maxWidth: .infinity)
                    .padding(.top, 12)

            case .ready:
                ForEach(options, id: \.self) { option in
                    optionRow(option)
                }

            case .tooFew:
                if isFlipped {
                    answerOnlyView
                } else {
                    Text("Nicht genug andere Karten im Deck für Multiple-Choice — tippe auf »Antwort anzeigen«.")
                        .font(.caption)
                        .foregroundStyle(CardsTheme.mutedForeground)
                }

            case .failed:
                Text("Distractors konnten nicht geladen werden.")
                    .font(.caption)
                    .foregroundStyle(CardsTheme.error)
            }
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .task(id: card.id) {
            await loadOptions()
        }
    }

    /// Option-Row mit dynamischem Highlight: vor Flip nur Selected-Hint,
    /// nach Flip wird richtige Antwort grün, falsche-aber-gewählte rot.
    @ViewBuilder
    private func optionRow(_ option: String) -> some View {
        let isCorrect = option == card.fields["answer"]
        let isSelected = option == selected

        Button {
            if selected == nil { selected = option }
        } label: {
            HStack(alignment: .top, spacing: 12) {
                statusIcon(isCorrect: isCorrect, isSelected: isSelected)
                    .frame(width: 22)
                Text(option)
                    .font(.subheadline)
                    .foregroundStyle(CardsTheme.foreground)
                    .multilineTextAlignment(.leading)
                Spacer(minLength: 0)
            }
            .padding(.vertical, 12)
            .padding(.horizontal, 14)
            .background(background(isCorrect: isCorrect, isSelected: isSelected), in: RoundedRectangle(cornerRadius: 10, style: .continuous))
            .overlay(
                RoundedRectangle(cornerRadius: 10, style: .continuous)
                    .stroke(border(isCorrect: isCorrect, isSelected: isSelected), lineWidth: 1)
            )
        }
        .buttonStyle(.plain)
        .disabled(isFlipped || selected != nil)
    }

    @ViewBuilder
    private func statusIcon(isCorrect: Bool, isSelected: Bool) -> some View {
        if isFlipped {
            if isCorrect {
                Image(systemName: "checkmark.circle.fill")
                    .foregroundStyle(CardsTheme.success)
            } else if isSelected {
                Image(systemName: "xmark.circle.fill")
                    .foregroundStyle(CardsTheme.error)
            } else {
                Image(systemName: "circle")
                    .foregroundStyle(CardsTheme.mutedForeground.opacity(0.4))
            }
        } else if isSelected {
            Image(systemName: "largecircle.fill.circle")
                .foregroundStyle(CardsTheme.primary)
        } else {
            Image(systemName: "circle")
                .foregroundStyle(CardsTheme.mutedForeground.opacity(0.4))
        }
    }

    private func background(isCorrect: Bool, isSelected: Bool) -> Color {
        if isFlipped {
            if isCorrect { return CardsTheme.success.opacity(0.12) }
            if isSelected { return CardsTheme.error.opacity(0.10) }
            return CardsTheme.surfaceHover
        }
        return isSelected
            ? CardsTheme.primary.opacity(0.10)
            : CardsTheme.surface
    }

    private func border(isCorrect: Bool, isSelected: Bool) -> Color {
        if isFlipped {
            if isCorrect { return CardsTheme.success.opacity(0.55) }
            if isSelected { return CardsTheme.error.opacity(0.55) }
            return CardsTheme.border
        }
        return isSelected ? CardsTheme.primary.opacity(0.5) : CardsTheme.border
    }

    /// Fallback wenn nicht genug Distractors: zeigt die Antwort
    /// direkt nach Flip, ohne Auswahl-Spiel.
    private var answerOnlyView: some View {
        VStack(alignment: .leading, spacing: 6) {
            Divider().background(CardsTheme.border)
            Text(card.fields["answer"] ?? "")
                .font(.title3)
                .foregroundStyle(CardsTheme.primary)
                .padding(.top, 4)
        }
    }

    private func text(_ markdown: String) -> some View {
        let attributed = (try? AttributedString(
            markdown: markdown,
            options: AttributedString.MarkdownParsingOptions(
                interpretedSyntax: .inlineOnlyPreservingWhitespace
            )
        )) ?? AttributedString(markdown)
        return Text(attributed)
            .multilineTextAlignment(.leading)
    }

    private func loadOptions() async {
        phase = .loading
        selected = nil
        let api = CardsAPI(auth: auth)
        let answer = card.fields["answer"] ?? ""

        var distractors: [String] = []
        // Erst answer-Feld versuchen, dann back-Feld als Fallback
        // (Decks mit basic/basic-reverse-Karten daneben).
        for field in ["answer", "back"] {
            if distractors.count >= 3 { break }
            if let result = try? await api.distractors(
                deckId: card.deckId,
                cardId: card.id,
                field: field,
                count: 3
            ) {
                let filtered = result.filter { $0 != answer && !distractors.contains($0) }
                distractors.append(contentsOf: filtered)
            }
        }

        // Fallback aus statischem distractor_pool-Field (Web-Pattern)
        if distractors.count < 3, let pool = card.fields["distractor_pool"] {
            let poolItems = pool
                .split(separator: "\n")
                .map { $0.trimmingCharacters(in: .whitespaces) }
                .filter { !$0.isEmpty && $0 != answer && !distractors.contains($0) }
            distractors.append(contentsOf: poolItems)
        }

        if distractors.isEmpty {
            phase = .tooFew
            return
        }
        let finalDistractors = Array(distractors.prefix(3))
        options = ([answer] + finalDistractors).shuffled()
        phase = .ready
    }
}