import Foundation
import SwiftUI

struct CartView: View {
    @Binding var appState: AppState
    @State var openCheckout = false
    @State var couponCode = ""
    @State var appliedCouponCode: String? = nil
    @State var discountValue: Double = 0
    @State var deliveryFee: Double = 5

    var body: some View {
        ScrollView(showsIndicators: false) {
            VStack(spacing: 16) {
                Text("Meu Carrinho")
                    .font(AppTypography.heading1)
                    .foregroundStyle(AppColors.textPrimary)
                    .frame(maxWidth: .infinity, alignment: .center)
                    .padding(.top, 20)

                if appState.cart.items.isEmpty {
                    VStack(spacing: 10) {
                        Text("Seu carrinho está vazio")
                            .font(AppTypography.heading3)
                            .foregroundStyle(AppColors.textPrimary)
                        Text("Adicione produtos para continuar.")
                            .font(AppTypography.body)
                            .foregroundStyle(AppColors.textMuted)
                    }
                    .frame(maxWidth: .infinity, minHeight: 280, alignment: .center)
                } else {
                    VStack(spacing: 12) {
                        ForEach(appState.cart.items) { item in
                            cartItemRow(item)
                        }
                    }
                    .padding(.horizontal, 20)

                    couponSection
                        .padding(.horizontal, 20)

                    summarySection
                        .padding(.horizontal, 20)
                }
            }
            .padding(.bottom, 120)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .background(AppColors.backgroundLight)
        .navigationDestination(isPresented: $openCheckout) {
            CheckoutView(appState: $appState)
        }
    }

    private var subtotalValue: Double {
        appState.cart.items.reduce(0) { $0 + (Double($1.quantity) * $1.unitPrice) }
    }

    private var totalValue: Double {
        max(0, subtotalValue + deliveryFee - discountValue)
    }

    private var couponSection: some View {
        VStack(alignment: .leading, spacing: 10) {
            Text("Cupom de Desconto")
                .font(AppTypography.heading2)
                .foregroundStyle(AppColors.textPrimary)

            HStack(spacing: 10) {
                HStack(spacing: 8) {
                    Image(systemName: "ticket")
                        .foregroundStyle(AppColors.textMuted)
                    TextField("Inserir cupom", text: $couponCode)
                        .appNoAutoCap()
                }
                .padding(.horizontal, 12)
                .frame(height: 50)
                .background(AppColors.surface)
                .overlay(
                    RoundedRectangle(cornerRadius: AppLayout.radiusLG, style: .continuous)
                        .stroke(AppColors.brandSoft, lineWidth: 1)
                )
                .clipShape(RoundedRectangle(cornerRadius: AppLayout.radiusLG, style: .continuous))

                Button("Aplicar") {
                    applyCoupon()
                }
                .font(AppTypography.heading3)
                .foregroundStyle(AppColors.textInverse)
                .frame(width: 120, height: 50)
                .background(AppColors.brandDark)
                .clipShape(RoundedRectangle(cornerRadius: AppLayout.radiusLG, style: .continuous))
                .buttonStyle(.plain)
            }

            if let appliedCouponCode {
                Text("Cupom aplicado: \(appliedCouponCode)")
                    .font(.caption)
                    .foregroundStyle(AppColors.primary)
            }
        }
    }

    private var summarySection: some View {
        VStack(alignment: .leading, spacing: 12) {
            Text("Resumo de Valores")
                .font(AppTypography.heading2)
                .foregroundStyle(AppColors.textPrimary)

            summaryRow(title: "Subtotal", value: formatCurrency(subtotalValue))
            summaryRow(title: "Taxa de Entrega", value: formatCurrency(deliveryFee))
            summaryRow(title: "Desconto", value: "-\(formatCurrency(discountValue))", valueColor: Color.red)

            Divider()

            summaryRow(title: "Total", value: formatCurrency(totalValue), highlighted: true)

            Button {
                openCheckout = true
            } label: {
                HStack(spacing: 10) {
                    Text("Ir para o Pagamento")
                        .font(AppTypography.heading2)
                    Image(systemName: "arrow.right")
                        .font(.system(size: 18, weight: .bold))
                }
                .foregroundStyle(AppColors.textInverse)
                .frame(maxWidth: .infinity, minHeight: 54)
                .background(AppColors.primary)
                .clipShape(RoundedRectangle(cornerRadius: AppLayout.radiusLG, style: .continuous))
            }
            .buttonStyle(.plain)
        }
        .padding(16)
        .background(AppColors.surface)
        .clipShape(RoundedRectangle(cornerRadius: AppLayout.radiusXL, style: .continuous))
    }

    private func summaryRow(title: String, value: String, valueColor: Color? = nil, highlighted: Bool = false) -> some View {
        HStack {
            Text(title)
                .font(highlighted ? AppTypography.heading2 : AppTypography.body)
                .foregroundStyle(AppColors.textMuted)
            Spacer()
            Text(value)
                .font(highlighted ? AppTypography.heading1 : AppTypography.heading3)
                .foregroundStyle(valueColor ?? AppColors.textPrimary)
        }
    }

    private func cartItemRow(_ item: CartItemState) -> some View {
        HStack(spacing: 14) {
            AsyncStoreImage(imageURL: item.imageURL)
                .frame(width: 78, height: 78)
                .clipShape(RoundedRectangle(cornerRadius: AppLayout.radiusLG, style: .continuous))

            VStack(alignment: .leading, spacing: 6) {
                Text(item.name)
                    .font(AppTypography.heading3)
                    .foregroundStyle(AppColors.textPrimary)
                    .lineLimit(1)
                if let details = item.details, details.isEmpty == false {
                    Text(details)
                        .font(.caption)
                        .foregroundStyle(AppColors.textMuted)
                        .lineLimit(2)
                }
                Text(formatCurrency(item.unitPrice))
                    .font(AppTypography.body)
                    .foregroundStyle(AppColors.textMuted)
            }

            Spacer()

            HStack(spacing: 10) {
                Button(action: { appState.cart.decrement(itemId: item.id) }) {
                    Image(systemName: "minus")
                        .font(.system(size: 13, weight: .bold))
                        .foregroundStyle(AppColors.textPrimary)
                        .frame(width: 32, height: 32)
                        .background(AppColors.backgroundLight)
                        .clipShape(Circle())
                }
                .buttonStyle(.plain)

                Text("\(item.quantity)")
                    .font(AppTypography.heading3)
                    .foregroundStyle(AppColors.textPrimary)
                    .frame(minWidth: 18)

                Button(action: { appState.cart.increment(itemId: item.id) }) {
                    Image(systemName: "plus")
                        .font(.system(size: 13, weight: .bold))
                        .foregroundStyle(AppColors.textPrimary)
                        .frame(width: 32, height: 32)
                        .background(AppColors.tertiary)
                        .clipShape(Circle())
                }
                .buttonStyle(.plain)
            }
            .padding(.horizontal, 8)
            .padding(.vertical, 6)
            .background(AppColors.backgroundLight)
            .clipShape(Capsule())
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 12)
        .background(AppColors.surface)
        .clipShape(RoundedRectangle(cornerRadius: AppLayout.radiusLG, style: .continuous))
    }

    private func applyCoupon() {
        let normalized = couponCode.trimmingCharacters(in: .whitespacesAndNewlines).uppercased()
        guard normalized.isEmpty == false else {
            appliedCouponCode = nil
            discountValue = 0
            return
        }

        if normalized == "DESCONTO10" {
            appliedCouponCode = normalized
            discountValue = min(subtotalValue, subtotalValue * 0.1)
            return
        }

        appliedCouponCode = nil
        discountValue = 0
    }

    private func formatCurrency(_ value: Double) -> String {
        String(format: "R$ %.2f", value).replacingOccurrences(of: ".", with: ",")
    }
}