import SwiftUI

struct ScanScreen: View {
    @EnvironmentObject var appState: AppState
    @StateObject private var scanner = BarcodeScanner()
    @State private var showManualEntry = false
    @State private var isLoading = false
    @State private var showProduct = false

    var body: some View {
        NavigationStack {
            ZStack {
                Color.black.ignoresSafeArea()

                if scanner.isScanning {
                    CameraPreviewView(scanner: scanner)
                        .ignoresSafeArea()

                    // Scan overlay
                    VStack {
                        Spacer()

                        // Scan region indicator
                        RoundedRectangle(cornerRadius: 20)
                            .strokeBorder(Color.green, lineWidth: 3)
                            .frame(width: 280, height: 180)
                            .overlay {
                                Text("Position barcode here")
                                    .font(.caption)
                                    .foregroundColor(.white.opacity(0.7))
                            }

                        Spacer()

                        // Manual entry button
                        Button {
                            showManualEntry = true
                        } label: {
                            HStack {
                                Image(systemName: "keyboard")
                                Text("Enter Manually")
                            }
                            .font(.headline)
                            .foregroundColor(.white)
                            .padding()
                            .background(Color.white.opacity(0.2))
                            .cornerRadius(12)
                        }
                        .padding(.bottom, 40)
                    }
                } else if isLoading {
                    VStack(spacing: 20) {
                        ProgressView()
                            .scaleEffect(1.5)
                            .tint(.white)
                        Text("Looking up product...")
                            .foregroundColor(.white)
                    }
                } else {
                    // Start scan prompt
                    VStack(spacing: 30) {
                        Image(systemName: "barcode.viewfinder")
                            .font(.system(size: 80))
                            .foregroundColor(.green)

                        Text("Scan a Barcode")
                            .font(.title)
                            .foregroundColor(.white)

                        Text("Point your camera at a food product barcode to see its health rating and find healthier alternatives.")
                            .font(.body)
                            .foregroundColor(.gray)
                            .multilineTextAlignment(.center)
                            .padding(.horizontal, 40)

                        Button {
                            Task {
                                let hasPermission = await scanner.checkPermission()
                                if hasPermission {
                                    scanner.startScanning()
                                }
                            }
                        } label: {
                            Text("Start Scanning")
                                .font(.headline)
                                .foregroundColor(.black)
                                .frame(maxWidth: .infinity)
                                .padding()
                                .background(Color.green)
                                .cornerRadius(12)
                        }
                        .padding(.horizontal, 40)

                        Button {
                            showManualEntry = true
                        } label: {
                            Text("Enter Barcode Manually")
                                .font(.subheadline)
                                .foregroundColor(.green)
                        }
                    }
                }
            }
            .navigationTitle("Scan")
            .navigationBarTitleDisplayMode(.inline)
            .toolbarColorScheme(.dark, for: .navigationBar)
            .toolbar {
                ToolbarItem(placement: .navigationBarTrailing) {
                    if scanner.isScanning {
                        Button("Cancel") {
                            scanner.stopScanning()
                        }
                        .foregroundColor(.white)
                    }
                }
            }
            .sheet(isPresented: $showManualEntry) {
                ManualEntrySheet { barcode in
                    lookupProduct(barcode: barcode)
                }
            }
            .navigationDestination(isPresented: $showProduct) {
                if let product = appState.currentProduct {
                    ProductScreen(product: product)
                        .environmentObject(appState)
                }
            }
            .onChange(of: scanner.scannedCode) { newCode in
                if let code = newCode {
                    lookupProduct(barcode: code)
                }
            }
        }
    }

    private func lookupProduct(barcode: String) {
        isLoading = true
        scanner.stopScanning()

        Task {
            do {
                let product = try await APIService.shared.lookupProduct(barcode: barcode)
                await MainActor.run {
                    appState.setCurrentProduct(product)
                    isLoading = false
                    showProduct = true

                    // Add to history if authenticated
                    if appState.isAuthenticated {
                        Task {
                            try? await APIService.shared.addToHistory(productId: product.id)
                        }
                    }
                }
            } catch {
                await MainActor.run {
                    isLoading = false
                    appState.showError(error.localizedDescription)
                    scanner.reset()
                }
            }
        }
    }
}