import SwiftUI

/// Rendert die Karten-Inhalte je nach `CardType`. Front-/Back-Seite
/// werden über `isFlipped` gesteuert.
///
/// β-2 deckt `basic`, `basic-reverse`, `cloze` ab. Restliche Typen
/// zeigen einen Placeholder mit Hinweis auf die kommende Phase.
struct CardRenderer: View {
    let card: ReviewCard
    let subIndex: Int
    let isFlipped: Bool

    var body: some View {
        Group {
            switch card.type {
            case .basic:
                basicView(front: "front", back: "back")
            case .basicReverse:
                // sub_index 0 = front→back, sub_index 1 = back→front
                if subIndex == 0 {
                    basicView(front: "front", back: "back")
                } else {
                    basicView(front: "back", back: "front")
                }
            case .cloze:
                clozeView
            case .imageOcclusion:
                imageOcclusionView
            case .audioFront:
                audioFrontView
            case .multipleChoice:
                MultipleChoiceCardView(card: card, isFlipped: isFlipped)
            case .typing:
                TypingCardView(card: card, isFlipped: isFlipped)
            }
        }
        .padding(24)
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }

    private func basicView(front frontKey: String, back backKey: String) -> some View {
        VStack(spacing: 16) {
            text(card.fields[frontKey] ?? "")
                .font(.title2)
                .foregroundStyle(CardsTheme.foreground)
            if isFlipped {
                Divider().background(CardsTheme.border)
                text(card.fields[backKey] ?? "")
                    .font(.title3)
                    .foregroundStyle(CardsTheme.mutedForeground)
            }
        }
    }

    @ViewBuilder
    private var clozeView: some View {
        let raw = card.fields["text"] ?? ""
        let clusterId = Cloze.clusterId(for: raw, subIndex: subIndex) ?? 1
        let rendered = isFlipped
            ? Cloze.renderAnswer(raw, activeClusterId: clusterId)
            : Cloze.renderPrompt(raw, activeClusterId: clusterId)
        VStack(spacing: 12) {
            text(rendered)
                .font(.title3)
                .foregroundStyle(CardsTheme.foreground)
        }
    }

    @ViewBuilder
    private var imageOcclusionView: some View {
        let imageRef = card.fields["image_ref"] ?? ""
        let maskJSON = card.fields["mask_regions"] ?? "[]"
        let regions = MaskRegions.parse(maskJSON)
        let activeRegion = regions.indices.contains(subIndex) ? regions[subIndex] : nil

        VStack(spacing: 12) {
            GeometryReader { geo in
                ZStack(alignment: .topLeading) {
                    RemoteImage(mediaId: imageRef, contentMode: .fit)
                        .frame(width: geo.size.width, height: geo.size.height)
                    ForEach(regions) { region in
                        let isActive = region.id == activeRegion?.id
                        // Front: aktive Maske opak, andere transparent.
                        // Back: alle Masken transparent (Bild komplett sichtbar).
                        if !isFlipped, isActive {
                            Rectangle()
                                .fill(CardsTheme.primary.opacity(0.92))
                                .frame(
                                    width: region.w * geo.size.width,
                                    height: region.h * geo.size.height
                                )
                                .offset(x: region.x * geo.size.width, y: region.y * geo.size.height)
                                .overlay(
                                    Text(region.label?.isEmpty == false ? region.label! : "?")
                                        .font(.caption.weight(.bold))
                                        .foregroundStyle(CardsTheme.primaryForeground)
                                        .offset(x: region.x * geo.size.width, y: region.y * geo.size.height),
                                    alignment: .topLeading
                                )
                        }
                    }
                }
            }
            .aspectRatio(4 / 3, contentMode: .fit)

            if isFlipped, let label = activeRegion?.label, !label.isEmpty {
                Text(label)
                    .font(.title3.weight(.semibold))
                    .foregroundStyle(CardsTheme.primary)
            }
            if let note = card.fields["note"], !note.isEmpty {
                Text(note)
                    .font(.caption)
                    .foregroundStyle(CardsTheme.mutedForeground)
            }
        }
    }

    @ViewBuilder
    private var audioFrontView: some View {
        let audioRef = card.fields["audio_ref"] ?? ""
        VStack(spacing: 16) {
            AudioPlayerButton(mediaId: audioRef)
            if isFlipped {
                Divider().background(CardsTheme.border)
                text(card.fields["back"] ?? "")
                    .font(.title3)
                    .foregroundStyle(CardsTheme.foreground)
            }
        }
    }

    private var placeholderView: some View {
        VStack(spacing: 8) {
            Image(systemName: "questionmark.square.dashed")
                .font(.largeTitle)
                .foregroundStyle(CardsTheme.mutedForeground)
            Text("Card-Type »\(card.type.rawValue)« kommt in einer späteren Phase")
                .font(.caption)
                .multilineTextAlignment(.center)
                .foregroundStyle(CardsTheme.mutedForeground)
        }
    }

    /// Markdown-Bold (`**...**`) wird auf SwiftUI's AttributedString gemappt.
    private func text(_ markdown: String) -> some View {
        let attributed = (try? AttributedString(
            markdown: markdown,
            options: AttributedString.MarkdownParsingOptions(
                interpretedSyntax: .inlineOnlyPreservingWhitespace
            )
        )) ?? AttributedString(markdown)
        return Text(attributed)
            .multilineTextAlignment(.center)
    }
}