import SwiftUI

struct ProductScreen: View {
    @EnvironmentObject var appState: AppState
    @Environment(\.dismiss) private var dismiss
    let product: Product

    @State private var isFavorite = false
    @State private var showAlternatives = false
    @State private var isLoadingFavorite = false

    var body: some View {
        ScrollView {
            VStack(spacing: 20) {
                // Product Image
                if let imageURL = product.imageURL {
                    AsyncImage(url: imageURL) { phase in
                        switch phase {
                        case .success(let image):
                            image
                                .resizable()
                                .aspectRatio(contentMode: .fit)
                        case .failure:
                            productPlaceholder
                        default:
                            ProgressView()
                        }
                    }
                    .frame(height: 200)
                    .background(Color(.systemGray6))
                    .cornerRadius(16)
                } else {
                    productPlaceholder
                        .frame(height: 200)
                }

                // Product Info
                VStack(spacing: 8) {
                    Text(product.brand)
                        .font(.subheadline)
                        .foregroundColor(.secondary)

                    Text(product.name)
                        .font(.title2.bold())
                        .multilineTextAlignment(.center)
                }

                // Score and NOVA
                HStack(spacing: 30) {
                    ScoreRing(score: product.score)

                    NOVABadge(novaGroup: product.novaGroup)
                }
                .padding(.vertical)

                // Dietary Tags
                if !product.dietaryTags.isEmpty {
                    DietaryPills(tags: product.dietaryTags)
                }

                // Nutrition Section
                NutritionSection(product: product)

                // Ingredients Section
                IngredientsSection(ingredients: product.ingredients)

                // See Alternatives Button
                Button {
                    showAlternatives = true
                } label: {
                    HStack {
                        Image(systemName: "arrow.triangle.2.circlepath")
                        Text("See Healthier Alternatives")
                    }
                    .font(.headline)
                    .foregroundColor(.black)
                    .frame(maxWidth: .infinity)
                    .padding()
                    .background(Color.green)
                    .cornerRadius(12)
                }
                .padding(.top)
            }
            .padding()
        }
        .background(Color(.systemBackground))
        .navigationBarTitleDisplayMode(.inline)
        .toolbar {
            ToolbarItem(placement: .navigationBarTrailing) {
                if appState.isAuthenticated {
                    Button {
                        toggleFavorite()
                    } label: {
                        if isLoadingFavorite {
                            ProgressView()
                        } else {
                            Image(systemName: isFavorite ? "heart.fill" : "heart")
                                .foregroundColor(isFavorite ? .red : .primary)
                        }
                    }
                }
            }
        }
        .navigationDestination(isPresented: $showAlternatives) {
            AlternativesScreen(product: product)
                .environmentObject(appState)
        }
    }

    private var productPlaceholder: some View {
        ZStack {
            Color(.systemGray5)
            Image(systemName: "carrot.fill")
                .font(.system(size: 50))
                .foregroundColor(.gray)
        }
        .cornerRadius(16)
    }

    private func toggleFavorite() {
        isLoadingFavorite = true
        Task {
            do {
                if isFavorite {
                    try await APIService.shared.removeFavorite(productId: product.id)
                } else {
                    try await APIService.shared.addFavorite(productId: product.id)
                }
                await MainActor.run {
                    isFavorite.toggle()
                    isLoadingFavorite = false
                }
            } catch {
                await MainActor.run {
                    isLoadingFavorite = false
                    appState.showError(error.localizedDescription)
                }
            }
        }
    }
}