import SwiftUI

#if canImport(UIKit)
    import UIKit
#endif

/// Vier Rating-Buttons mit emphasis auf "Good" (full-width primary).
/// Web-Vorbild: `cards/apps/web/src/routes/study/[deckId]/+page.svelte`
/// — `.grade.again/.hard/.good/.easy`-Klassen.
struct RatingBar: View {
    let onRate: (Rating) -> Void

    var body: some View {
        HStack(spacing: 8) {
            ForEach(Rating.allCases, id: \.self) { rating in
                Button {
                    triggerHaptic(for: rating)
                    onRate(rating)
                } label: {
                    HStack(spacing: 6) {
                        Text(rating.label)
                            .font(.subheadline.weight(.semibold))
                        Text(rating.shortcut)
                            .font(.caption2.weight(.semibold))
                            .padding(.horizontal, 5)
                            .padding(.vertical, 1)
                            .background(kbdBackground(for: rating), in: RoundedRectangle(cornerRadius: 4))
                            .foregroundStyle(kbdForeground(for: rating))
                    }
                    .frame(maxWidth: .infinity)
                    .padding(.vertical, 14)
                    .background(background(for: rating), in: RoundedRectangle(cornerRadius: 10, style: .continuous))
                    .foregroundStyle(foreground(for: rating))
                    .overlay(
                        RoundedRectangle(cornerRadius: 10, style: .continuous)
                            .stroke(borderColor(for: rating), lineWidth: rating == .good ? 0 : 1)
                    )
                }
                .buttonStyle(.plain)
            }
        }
        .padding(.horizontal, 16)
    }

    /// `good` ist die Hero-Action (primary full background) — analog
    /// zum Web-Default-Klick. Andere bekommen subtle tinted borders.
    private func background(for rating: Rating) -> Color {
        switch rating {
        case .again: CardsTheme.error.opacity(0.06)
        case .hard: CardsTheme.warning.opacity(0.06)
        case .good: CardsTheme.primary
        case .easy: CardsTheme.success.opacity(0.06)
        }
    }

    private func foreground(for rating: Rating) -> Color {
        switch rating {
        case .again: CardsTheme.error
        case .hard: CardsTheme.warning
        case .good: CardsTheme.primaryForeground
        case .easy: CardsTheme.success
        }
    }

    private func borderColor(for rating: Rating) -> Color {
        switch rating {
        case .again: CardsTheme.error.opacity(0.4)
        case .hard: CardsTheme.warning.opacity(0.4)
        case .good: .clear
        case .easy: CardsTheme.success.opacity(0.4)
        }
    }

    private func kbdBackground(for rating: Rating) -> Color {
        rating == .good
            ? CardsTheme.primaryForeground.opacity(0.18)
            : CardsTheme.muted
    }

    private func kbdForeground(for rating: Rating) -> Color {
        rating == .good
            ? CardsTheme.primaryForeground.opacity(0.85)
            : CardsTheme.mutedForeground
    }

    private func triggerHaptic(for rating: Rating) {
        #if canImport(UIKit)
            let style: UIImpactFeedbackGenerator.FeedbackStyle =
                rating == .easy ? .heavy : .medium
            UIImpactFeedbackGenerator(style: style).impactOccurred()
        #endif
    }
}