import SwiftUI
import Security

// MARK: - Keychain
enum Keychain {
    @discardableResult
    static func save(key: String, value: String) -> Bool {
        guard let data = value.data(using: .utf8) else { return false }
        let deleteQuery: [CFString: Any] = [
            kSecClass: kSecClassGenericPassword,
            kSecAttrAccount: key
        ]
        SecItemDelete(deleteQuery as CFDictionary)
        let addQuery: [CFString: Any] = [
            kSecClass: kSecClassGenericPassword,
            kSecAttrAccount: key,
            kSecValueData: data,
            kSecAttrAccessible: kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly
        ]
        return SecItemAdd(addQuery as CFDictionary, nil) == errSecSuccess
    }

    static func load(key: String) -> String? {
        let query: [CFString: Any] = [
            kSecClass: kSecClassGenericPassword,
            kSecAttrAccount: key,
            kSecReturnData: kCFBooleanTrue!,
            kSecMatchLimit: kSecMatchLimitOne
        ]
        var result: AnyObject?
        guard SecItemCopyMatching(query as CFDictionary, &result) == errSecSuccess,
              let data = result as? Data else { return nil }
        return String(data: data, encoding: .utf8)
    }

    @discardableResult
    static func delete(key: String) -> Bool {
        let query: [CFString: Any] = [
            kSecClass: kSecClassGenericPassword,
            kSecAttrAccount: key
        ]
        return SecItemDelete(query as CFDictionary) == errSecSuccess
    }
}

// MARK: - AuthView
struct AuthView: View {
    var onAuthenticated: (String) -> Void

    @State private var isLoginMode = true
    @State private var email        = ""
    @State private var password     = ""
    @State private var displayName  = ""
    @State private var nativeLanguage = "EN"
    @State private var isLoading    = false
    @State private var errorMessage = ""

    private let nativeLangs = ["EN", "FR", "ES", "PT", "IT", "DE", "ZH", "JA"]

    // Design tokens — identical to ContentView
    let accentColor  = Color(hex: "#f59e0b")
    let bgColor      = Color(hex: "#080d14")
    let surfaceColor = Color(hex: "#0d1421")
    let borderColor  = Color(hex: "#1a2535")
    let textColor    = Color(hex: "#cbd5e1")
    let mutedColor   = Color(hex: "#475569")
    let errorColor   = Color(hex: "#ef4444")

    var body: some View {
        ZStack {
            bgColor.ignoresSafeArea()

            VStack(spacing: 0) {

                // ── Wordmark ──────────────────────────────────────────
                VStack(spacing: 6) {
                    Text("MIMIO")
                        .font(.system(size: 26, weight: .bold, design: .monospaced))
                        .foregroundColor(accentColor)
                        .tracking(8)
                    Text("hear yourself, clearer")
                        .font(.system(size: 11, design: .monospaced))
                        .foregroundColor(mutedColor)
                        .tracking(2)
                }
                .padding(.top, 72)
                .padding(.bottom, 48)

                VStack(spacing: 14) {

                    // ── Mode toggle ───────────────────────────────────
                    HStack(spacing: 0) {
                        modeToggleButton("LOGIN",    selected: isLoginMode)  { switchMode(true)  }
                        modeToggleButton("REGISTER", selected: !isLoginMode) { switchMode(false) }
                    }
                    .background(surfaceColor)
                    .overlay(
                        RoundedRectangle(cornerRadius: 8)
                            .stroke(borderColor, lineWidth: 1)
                    )
                    .cornerRadius(8)

                    // ── Display name + native language (register only) ──
                    if !isLoginMode {
                        authField("Display name", text: $displayName, keyboard: .default)
                            .transition(.opacity.combined(with: .move(edge: .top)))

                        VStack(alignment: .leading, spacing: 8) {
                            Text("I SPEAK…")
                                .font(.system(size: 10, weight: .bold, design: .monospaced))
                                .foregroundColor(mutedColor)
                                .tracking(2)
                            ScrollView(.horizontal, showsIndicators: false) {
                                HStack(spacing: 8) {
                                    ForEach(nativeLangs, id: \.self) { lang in
                                        Button { nativeLanguage = lang } label: {
                                            Text(lang)
                                                .font(.system(size: 11, weight: .bold, design: .monospaced))
                                                .tracking(1)
                                                .foregroundColor(nativeLanguage == lang ? bgColor : mutedColor)
                                                .padding(.horizontal, 13)
                                                .padding(.vertical, 6)
                                                .background(nativeLanguage == lang ? accentColor : Color.clear)
                                                .overlay(
                                                    RoundedRectangle(cornerRadius: 12)
                                                        .stroke(nativeLanguage == lang ? accentColor : borderColor, lineWidth: 1)
                                                )
                                                .cornerRadius(12)
                                        }
                                    }
                                }
                            }
                        }
                        .transition(.opacity.combined(with: .move(edge: .top)))
                    }

                    // ── Email ─────────────────────────────────────────
                    authField("Email", text: $email, keyboard: .emailAddress)
                        .autocorrectionDisabled()
                        .textInputAutocapitalization(.never)

                    // ── Password ──────────────────────────────────────
                    SecureField("Password", text: $password)
                        .font(.system(size: 14, design: .monospaced))
                        .foregroundColor(textColor)
                        .padding(14)
                        .background(surfaceColor)
                        .overlay(
                            RoundedRectangle(cornerRadius: 8)
                                .stroke(borderColor, lineWidth: 1)
                        )
                        .cornerRadius(8)

                    // ── Error ─────────────────────────────────────────
                    if !errorMessage.isEmpty {
                        HStack(spacing: 6) {
                            Image(systemName: "exclamationmark.triangle")
                                .font(.system(size: 10))
                            Text(errorMessage)
                                .font(.system(size: 11, design: .monospaced))
                        }
                        .foregroundColor(errorColor)
                        .frame(maxWidth: .infinity, alignment: .leading)
                        .transition(.opacity)
                    }

                    // ── Submit ────────────────────────────────────────
                    Button { submit() } label: {
                        HStack(spacing: 8) {
                            if isLoading {
                                ProgressView()
                                    .tint(Color(hex: "#080d14"))
                                    .scaleEffect(0.8)
                            }
                            Text(isLoading
                                 ? (isLoginMode ? "Logging in..." : "Creating account...")
                                 : (isLoginMode ? "LOGIN" : "CREATE ACCOUNT"))
                                .font(.system(size: 13, weight: .bold, design: .monospaced))
                                .tracking(2)
                        }
                        .foregroundColor(Color(hex: "#080d14"))
                        .frame(maxWidth: .infinity)
                        .padding(.vertical, 14)
                        .background(isLoading ? accentColor.opacity(0.65) : accentColor)
                        .cornerRadius(8)
                    }
                    .disabled(isLoading)
                    .padding(.top, 4)
                }
                .padding(.horizontal, 24)
                .animation(.easeInOut(duration: 0.18), value: isLoginMode)
                .animation(.easeInOut(duration: 0.18), value: errorMessage)

                Spacer()

                // ── Footer ────────────────────────────────────────────
                Text("v1.0  ·  mimio")
                    .font(.system(size: 9, design: .monospaced))
                    .foregroundColor(mutedColor.opacity(0.5))
                    .tracking(2)
                    .padding(.bottom, 32)
            }
        }
    }

    // MARK: - Sub-views

    @ViewBuilder
    private func modeToggleButton(_ label: String, selected: Bool, action: @escaping () -> Void) -> some View {
        Button(action: action) {
            Text(label)
                .font(.system(size: 11, weight: .bold, design: .monospaced))
                .tracking(2)
                .foregroundColor(selected ? Color(hex: "#080d14") : mutedColor)
                .frame(maxWidth: .infinity)
                .padding(.vertical, 10)
                .background(selected ? accentColor : Color.clear)
                .cornerRadius(7)
                .padding(2)
        }
    }

    @ViewBuilder
    private func authField(
        _ placeholder: String,
        text: Binding<String>,
        keyboard: UIKeyboardType
    ) -> some View {
        TextField(placeholder, text: text)
            .font(.system(size: 14, design: .monospaced))
            .foregroundColor(textColor)
            .keyboardType(keyboard)
            .padding(14)
            .background(surfaceColor)
            .overlay(
                RoundedRectangle(cornerRadius: 8)
                    .stroke(borderColor, lineWidth: 1)
            )
            .cornerRadius(8)
    }

    // MARK: - Logic

    private func switchMode(_ login: Bool) {
        isLoginMode = login
        errorMessage = ""
    }

    private func submit() {
        errorMessage = ""

        // Basic client-side validation
        guard !email.trimmingCharacters(in: .whitespaces).isEmpty else {
            errorMessage = "Email is required."
            return
        }
        guard !password.isEmpty else {
            errorMessage = "Password is required."
            return
        }
        if !isLoginMode && displayName.trimmingCharacters(in: .whitespaces).isEmpty {
            errorMessage = "Display name is required."
            return
        }

        let endpoint = isLoginMode ? "login" : "register"
        guard let url = URL(string: "https://coach.cubecast.app/\(endpoint)") else { return }

        var body: [String: String] = [
            "email":    email.trimmingCharacters(in: .whitespaces),
            "password": password
        ]
        if !isLoginMode {
            body["name"] = displayName.trimmingCharacters(in: .whitespaces)
            body["native_language"] = nativeLanguage
        }

        guard let payload = try? JSONSerialization.data(withJSONObject: body) else { return }

        var req = URLRequest(url: url)
        req.httpMethod = "POST"
        req.setValue("application/json", forHTTPHeaderField: "Content-Type")
        req.httpBody = payload
        req.timeoutInterval = 15

        isLoading = true
        URLSession.shared.dataTask(with: req) { data, response, error in
            DispatchQueue.main.async {
                isLoading = false

                if let error = error {
                    errorMessage = error.localizedDescription
                    return
                }

                guard let httpResponse = response as? HTTPURLResponse,
                      let data = data else {
                    errorMessage = "No response from server."
                    return
                }

                guard let json = try? JSONSerialization.jsonObject(with: data) as? [String: Any] else {
                    errorMessage = "Unexpected server response."
                    return
                }

                // Success path — expect { "token": "...", "user_id": ... }
                if (200...299).contains(httpResponse.statusCode),
                   let token = json["token"] as? String {
                    Keychain.save(key: "mimio_token", value: token)

                    if let userId = json["user_id"] as? Int {
                        UserDefaults.standard.set(userId, forKey: "mimio_user_id")
                    } else if let userId = json["user_id"] as? String {
                        UserDefaults.standard.set(userId, forKey: "mimio_user_id")
                    }

                    // Save native language — from picker on register, or from server on login
                    if !isLoginMode {
                        UserDefaults.standard.set(nativeLanguage, forKey: "mimio_native_language")
                    } else if let lang = json["native_language"] as? String {
                        UserDefaults.standard.set(lang, forKey: "mimio_native_language")
                    } else {
                        UserDefaults.standard.set(nativeLanguage, forKey: "mimio_native_language")
                    }

                    onAuthenticated(token)
                    return
                }

                // Error path — try common error keys
                if let msg = json["error"] as? String, !msg.isEmpty {
                    errorMessage = msg
                } else if let msg = json["message"] as? String, !msg.isEmpty {
                    errorMessage = msg
                } else if let msg = json["detail"] as? String, !msg.isEmpty {
                    errorMessage = msg
                } else {
                    errorMessage = httpResponse.statusCode == 401
                        ? "Invalid email or password."
                        : "Something went wrong (HTTP \(httpResponse.statusCode))."
                }
            }
        }.resume()
    }
}