import SwiftUI

/// Gemeinsame Karten-Tile mit Fan-Stack-Hintergrund-Layern.
/// Basis für `DeckStackTile` (eigene Decks) und `PublicDeckCard`
/// (Marketplace-Decks). Web-Vorbild:
/// `cards/apps/web/src/lib/components/DeckStack.svelte` und
/// `MarketplaceDeckStack.svelte` — selbe Größe, selbes Stack-Visual,
/// nur der Footer variiert.
struct DeckCoverTile<Footer: View>: View {
    let title: String
    let description: String?
    let category: DeckCategory?
    let seed: String
    let colorAccentHex: String?
    let isFeatured: Bool
    @ViewBuilder let footer: () -> Footer

    init(
        title: String,
        description: String? = nil,
        category: DeckCategory? = nil,
        seed: String,
        colorAccentHex: String? = nil,
        isFeatured: Bool = false,
        @ViewBuilder footer: @escaping () -> Footer
    ) {
        self.title = title
        self.description = description
        self.category = category
        self.seed = seed
        self.colorAccentHex = colorAccentHex
        self.isFeatured = isFeatured
        self.footer = footer
    }

    var body: some View {
        ZStack {
            ForEach(Array(layers.enumerated()), id: \.offset) { _, layer in
                RoundedRectangle(cornerRadius: 14, style: .continuous)
                    .fill(CardsTheme.surface)
                    .overlay(
                        RoundedRectangle(cornerRadius: 14, style: .continuous)
                            .stroke(CardsTheme.border, lineWidth: 1)
                    )
                    .opacity(layer.opacity)
                    .rotationEffect(.degrees(layer.tilt))
                    .offset(x: layer.dx, y: layer.dy)
                    .shadow(color: CardsTheme.foreground.opacity(0.05), radius: 2, y: 1)
            }

            CardSurface(size: .md, elevation: .standard, colorAccentHex: colorAccentHex) {
                cardContent
            }
        }
        .aspectRatio(5.0 / 7.0, contentMode: .fit)
        .frame(maxWidth: 280)
    }

    private var cardContent: some View {
        VStack(alignment: .leading, spacing: 6) {
            HStack(alignment: .top) {
                if isFeatured {
                    Image(systemName: "star.fill")
                        .font(.caption)
                        .foregroundStyle(CardsTheme.warning)
                }
                Spacer()
                Image(systemName: category?.systemImageName ?? "rectangle.stack")
                    .font(.title2)
                    .foregroundStyle(CardsTheme.primary.opacity(0.85))
            }

            Spacer(minLength: 0)

            VStack(alignment: .leading, spacing: 6) {
                Text(title)
                    .font(.system(size: 17, weight: .semibold))
                    .foregroundStyle(CardsTheme.foreground)
                    .lineLimit(3)

                if let description, !description.isEmpty {
                    Text(description)
                        .font(.caption)
                        .foregroundStyle(CardsTheme.mutedForeground)
                        .lineLimit(2)
                }
            }

            Spacer(minLength: 0)

            footer()
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .topLeading)
    }

    private var layers: [DeckCoverStackLayer] {
        var hash = UInt64(0)
        for byte in seed.utf8 {
            hash = hash &* 31 &+ UInt64(byte)
        }
        return (0 ..< 3).map { index in
            let seedHash = hash &+ UInt64(index) &* 17
            let tiltRaw = Double((seedHash >> 8) & 0xFF) / 255.0 - 0.5
            let xRaw = Double((seedHash >> 16) & 0xFF) / 255.0 - 0.5
            let yRaw = Double((seedHash >> 24) & 0xFF) / 255.0 - 0.5
            let depth = Double(index + 1)
            return DeckCoverStackLayer(
                tilt: tiltRaw * 4.0,
                dx: xRaw * 6.0,
                dy: depth * 3.0 + yRaw * 2.0,
                opacity: 0.7 - depth * 0.18
            )
        }
    }
}

private struct DeckCoverStackLayer {
    let tilt: Double
    let dx: Double
    let dy: Double
    let opacity: Double
}