import SwiftUI
import LocalAuthentication
import SVGKit

struct LoginView: View {
    var onLoginSuccess: (String, Int) -> Void

    @State private var otpUuid: String?
    @State private var phone = ""
    @State private var otp = ""
    @State private var isLoading = false
    @State private var errorMessage: String?
    @State private var showPhoneInput = false
    @State private var showOtpInput = false
    @State private var hasCheckedAuth = false

    var body: some View {
        ScrollView {
            VStack(spacing: 24) {
                Spacer(minLength: 80)

                // SVG Logo
                SVGLogoView(width: 200)
                    .frame(width: 200, height: 117)

                Text("Payfrit Beacon")
                    .font(.title2.bold())
                    .foregroundColor(.payfritGreen)

                if isLoading {
                    ProgressView()
                        .padding()
                }

                if let error = errorMessage {
                    Text(error)
                        .foregroundColor(.errorRed)
                        .font(.callout)
                        .multilineTextAlignment(.center)
                        .padding(.horizontal)
                }

                if showPhoneInput {
                    VStack(spacing: 12) {
                        TextField("Phone number", text: $phone)
                            .keyboardType(.phonePad)
                            .textContentType(.telephoneNumber)
                            .foregroundColor(.primary)
                            .padding()
                            .background(Color(.systemGray6))
                            .cornerRadius(8)
                            .padding(.horizontal)

                        Button(action: sendOtp) {
                            Text("Send Code")
                                .frame(maxWidth: .infinity)
                                .padding()
                                .background(Color.payfritGreen)
                                .foregroundColor(.white)
                                .cornerRadius(8)
                        }
                        .disabled(isLoading)
                        .padding(.horizontal)
                    }
                }

                if showOtpInput {
                    VStack(spacing: 12) {
                        Text("Please enter the 6-digit code sent to your phone")
                            .font(.callout)
                            .foregroundColor(.secondary)
                            .multilineTextAlignment(.center)
                            .padding(.horizontal)

                        TextField("Verification code", text: $otp)
                            .keyboardType(.numberPad)
                            .textContentType(.oneTimeCode)
                            .foregroundColor(.primary)
                            .padding()
                            .background(Color(.systemGray6))
                            .cornerRadius(8)
                            .padding(.horizontal)

                        Button(action: verifyOtp) {
                            Text("Verify")
                                .frame(maxWidth: .infinity)
                                .padding()
                                .background(Color.payfritGreen)
                                .foregroundColor(.white)
                                .cornerRadius(8)
                        }
                        .disabled(isLoading)
                        .padding(.horizontal)
                    }
                }

                Spacer(minLength: 40)
            }
            .frame(maxWidth: .infinity)
        }
        .onAppear {
            guard !hasCheckedAuth else { return }
            hasCheckedAuth = true
            checkSavedAuth()
        }
    }

    private func checkSavedAuth() {
        let defaults = UserDefaults.standard
        let savedToken = defaults.string(forKey: "token")
        let savedUserId = defaults.integer(forKey: "userId")

        if let token = savedToken, !token.isEmpty, savedUserId > 0 {
            if canUseBiometrics() {
                showBiometricPrompt(token: token, userId: savedUserId)
            } else {
                loginSuccess(token: token, userId: savedUserId)
            }
        } else {
            showPhoneInput = true
        }
    }

    private func canUseBiometrics() -> Bool {
        let context = LAContext()
        var error: NSError?
        return context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error)
    }

    private func showBiometricPrompt(token: String, userId: Int) {
        let context = LAContext()
        context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics,
                               localizedReason: "Sign in to Payfrit Beacon") { success, _ in
            DispatchQueue.main.async {
                if success {
                    loginSuccess(token: token, userId: userId)
                } else {
                    showPhoneInput = true
                }
            }
        }
    }

    private func sendOtp() {
        let trimmed = phone.trimmingCharacters(in: .whitespacesAndNewlines)
        guard trimmed.count >= 10 else {
            errorMessage = "Enter a valid phone number"
            return
        }

        isLoading = true
        errorMessage = nil

        Task {
            do {
                let response = try await Api.shared.sendLoginOtp(phone: trimmed)
                otpUuid = response.uuid

                showPhoneInput = false
                showOtpInput = true
                isLoading = false
            } catch {
                errorMessage = error.localizedDescription
                isLoading = false
            }
        }
    }

    private func verifyOtp() {
        guard let uuid = otpUuid else { return }
        let trimmed = otp.trimmingCharacters(in: .whitespacesAndNewlines)
        guard trimmed.count >= 4 else {
            errorMessage = "Enter the verification code"
            return
        }

        isLoading = true
        errorMessage = nil

        Task {
            do {
                let response = try await Api.shared.verifyLoginOtp(uuid: uuid, otp: trimmed)

                let defaults = UserDefaults.standard
                defaults.set(response.token, forKey: "token")
                defaults.set(response.userId, forKey: "userId")
                defaults.set(response.userFirstName, forKey: "firstName")

                loginSuccess(token: response.token, userId: response.userId)
            } catch {
                errorMessage = error.localizedDescription
                isLoading = false
            }
        }
    }

    private func loginSuccess(token: String, userId: Int) {
        Api.shared.setAuthToken(token)
        onLoginSuccess(token, userId)
    }
}

// MARK: - SVG Logo UIKit wrapper

struct SVGLogoView: UIViewRepresentable {
    var width: CGFloat = 200

    func makeUIView(context: Context) -> UIView {
        let container = UIView()
        container.clipsToBounds = true

        let svgPath = Bundle.main.path(forResource: "payfrit-favicon-light-outlines", ofType: "svg") ?? ""
        guard let svgImage = SVGKImage(contentsOfFile: svgPath) else { return container }

        // Scale SVG proportionally based on width
        let nativeW = svgImage.size.width
        let nativeH = svgImage.size.height
        let scale = width / nativeW
        svgImage.size = CGSize(width: width, height: nativeH * scale)

        let imageView = SVGKLayeredImageView(svgkImage: svgImage) ?? UIImageView()
        imageView.translatesAutoresizingMaskIntoConstraints = false
        container.addSubview(imageView)

        NSLayoutConstraint.activate([
            imageView.widthAnchor.constraint(equalToConstant: svgImage.size.width),
            imageView.heightAnchor.constraint(equalToConstant: svgImage.size.height),
            imageView.centerXAnchor.constraint(equalTo: container.centerXAnchor),
            imageView.centerYAnchor.constraint(equalTo: container.centerYAnchor),
        ])

        return container
    }

    func updateUIView(_ uiView: UIView, context: Context) {}
}