import SwiftUI

// MARK: - Auth Manager (shared state)

@MainActor
final class AuthManager: ObservableObject {
    @Published var token: String
    @Published var nickname: String
    @Published var userID: String
    @Published var showingRegister = false
    @Published var showingSSO = false
    @Published var showingPhoneBinding = false
    @Published var ssoPendingToken: String?
    @Published var ssoPendingUserId = ""

    init() {
        let defaults = UserDefaults.standard
        token = defaults.string(forKey: "oral_trainer_token") ?? ""
        nickname = defaults.string(forKey: "oral_trainer_nickname") ?? ""
        let userID = defaults.string(forKey: "oral_trainer_user_id") ?? ""
        AppConfig.currentUserId = userID
        self.userID = userID
        AppConfig.authToken = token
    }

    var isLoggedIn: Bool { !token.isEmpty }

    func saveSession(_ session: AuthSession) {
        token = session.token
        nickname = session.user.nickname
        AppConfig.authToken = session.token
        userID = session.user.id
        AppConfig.currentUserId = session.user.id
        let defaults = UserDefaults.standard
        defaults.set(session.token, forKey: "oral_trainer_token")
        defaults.set(session.user.nickname, forKey: "oral_trainer_nickname")
        defaults.set(session.user.id, forKey: "oral_trainer_user_id")
    }

    func logout() {
        token = ""
        nickname = ""
        AppConfig.authToken = ""
        userID = ""
        AppConfig.currentUserId = ""
        showingRegister = false
        showingSSO = false
        showingPhoneBinding = false
        ssoPendingToken = nil
        ssoPendingUserId = ""
        let defaults = UserDefaults.standard
        defaults.removeObject(forKey: "oral_trainer_token")
        defaults.removeObject(forKey: "oral_trainer_nickname")
        defaults.removeObject(forKey: "oral_trainer_user_id")
    }
}

// MARK: - Auth View (root auth screen)

struct AuthView: View {
    @ObservedObject var auth: AuthManager
    @State private var username = ""
    @State private var password = ""
    @State private var statusText = ""
    @State private var isLoading = false
    var onLoginSuccess: () -> Void

    var body: some View {
        VStack(alignment: .leading, spacing: 0) {
            Spacer()
            Text("八哥口语")
                .font(.system(size: 32, weight: .bold))
                .foregroundColor(.white)
            Text("请先注册或登录后开始学习")
                .font(.system(size: 15))
                .foregroundColor(Theme.textMuted)
                .padding(.top, 6)
                .padding(.bottom, 24)

            TextField("用户名", text: $username)
                .textFieldStyle(.plain)
                .autocorrectionDisabled()
                .textInputAutocapitalization(.never)
                .padding(12)
                .background(Theme.surface)
                .clipShape(RoundedRectangle(cornerRadius: 8))
                .overlay(RoundedRectangle(cornerRadius: 8).stroke(Theme.border, lineWidth: 1))

            SecureField("密码（至少 8 位）", text: $password)
                .textFieldStyle(.plain)
                .padding(12)
                .padding(.top, 8)
                .background(Theme.surface)
                .clipShape(RoundedRectangle(cornerRadius: 8))
                .overlay(RoundedRectangle(cornerRadius: 8).stroke(Theme.border, lineWidth: 1))

            Button {
                Task { await login() }
            } label: {
                Text(isLoading ? "登录中..." : "登录")
                    .frame(maxWidth: .infinity)
                    .frame(height: 44)
                    .background(Theme.accent)
                    .foregroundColor(.white)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
            }
            .padding(.top, 20)
            .disabled(isLoading)

            Button {
                auth.showingRegister = true
            } label: {
                Text("注册")
                    .frame(maxWidth: .infinity)
                    .frame(height: 44)
                    .background(Theme.surface)
                    .foregroundColor(.white)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
            }
            .padding(.top, 8)

            Text("── 或 ──")
                .font(.system(size: 13))
                .foregroundColor(Theme.textMuted)
                .frame(maxWidth: .infinity)
                .padding(.top, 12)

            Button {
                auth.showingSSO = true
            } label: {
                Text("第一课堂一键登录")
                    .frame(maxWidth: .infinity)
                    .frame(height: 44)
                    .background(Theme.buttonBlue)
                    .foregroundColor(.white)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
            }
            .padding(.top, 8)

            if !statusText.isEmpty {
                Text(statusText)
                    .font(.system(size: 13))
                    .foregroundColor(Theme.accentLight)
                    .padding(.top, 14)
            }
            Spacer()
        }
        .padding(.horizontal, 28)
        .background(Theme.background.ignoresSafeArea())
        .fullScreenCover(isPresented: $auth.showingRegister) {
            RegisterView(auth: auth) {
                onLoginSuccess()
            }
        }
        .fullScreenCover(isPresented: $auth.showingSSO) {
            SSOWebView(auth: auth) {
                onLoginSuccess()
            }
        }
        .fullScreenCover(isPresented: $auth.showingPhoneBinding) {
            PhoneBindingView(auth: auth) {
                onLoginSuccess()
            }
        }
    }

    private func login() async {
        guard !username.isEmpty, !password.isEmpty else {
            statusText = "请填写用户名和密码"
            return
        }
        isLoading = true
        statusText = "登录中..."
        defer { isLoading = false }
        do {
            let session = try await AuthAPI.login(username: username, password: password)
            auth.saveSession(session)
            onLoginSuccess()
        } catch {
            statusText = "失败：\(error.localizedDescription)"
        }
    }
}

// MARK: - Register View

struct RegisterView: View {
    @ObservedObject var auth: AuthManager
    @Environment(\.dismiss) private var dismiss
    @State private var username = ""
    @State private var password = ""
    @State private var nickname = ""
    @State private var phone = ""
    @State private var statusText = ""
    @State private var isLoading = false
    var onLoginSuccess: () -> Void

    var body: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 0) {
                Text("注册账号")
                    .font(.system(size: 28, weight: .bold))
                    .foregroundColor(.white)
                Text("填写以下信息完成注册")
                    .font(.system(size: 14))
                    .foregroundColor(Theme.textMuted)
                    .padding(.top, 6)
                    .padding(.bottom, 24)

                fieldLabel("用户名")
                TextField("3-50 位字母、数字或下划线", text: $username)
                    .textFieldStyle(.plain)
                    .autocorrectionDisabled()
                    .textInputAutocapitalization(.never)
                    .padding(12)
                    .background(Theme.surface)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
                    .overlay(RoundedRectangle(cornerRadius: 8).stroke(Theme.border, lineWidth: 1))

                fieldLabel("密码")
                SecureField("至少 8 位", text: $password)
                    .textFieldStyle(.plain)
                    .padding(12)
                    .background(Theme.surface)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
                    .overlay(RoundedRectangle(cornerRadius: 8).stroke(Theme.border, lineWidth: 1))

                fieldLabel("姓名")
                TextField("你的真实姓名或昵称", text: $nickname)
                    .textFieldStyle(.plain)
                    .padding(12)
                    .background(Theme.surface)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
                    .overlay(RoundedRectangle(cornerRadius: 8).stroke(Theme.border, lineWidth: 1))

                fieldLabel("手机号")
                TextField("请输入 11 位手机号", text: $phone)
                    .textFieldStyle(.plain)
                    .keyboardType(.phonePad)
                    .padding(12)
                    .background(Theme.surface)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
                    .overlay(RoundedRectangle(cornerRadius: 8).stroke(Theme.border, lineWidth: 1))

                Button {
                    Task { await register() }
                } label: {
                    Text(isLoading ? "注册中..." : "注册")
                        .frame(maxWidth: .infinity)
                        .frame(height: 48)
                        .background(Theme.accent)
                        .foregroundColor(.white)
                        .clipShape(RoundedRectangle(cornerRadius: 8))
                }
                .padding(.top, 20)
                .disabled(isLoading)

                Button {
                    dismiss()
                } label: {
                    Text("返回登录")
                        .frame(maxWidth: .infinity)
                        .frame(height: 44)
                        .background(Theme.surface)
                        .foregroundColor(.white)
                        .clipShape(RoundedRectangle(cornerRadius: 8))
                }
                .padding(.top, 8)

                if !statusText.isEmpty {
                    Text(statusText)
                        .font(.system(size: 13))
                        .foregroundColor(Theme.accentLight)
                        .padding(.top, 14)
                }
            }
            .padding(.horizontal, 28)
            .padding(.top, 60)
        }
        .background(Theme.background.ignoresSafeArea())
    }

    private func fieldLabel(_ text: String) -> some View {
        Text(text)
            .font(.system(size: 13))
            .foregroundColor(Theme.textMuted)
            .padding(.top, 12)
            .padding(.bottom, 4)
    }

    private func register() async {
        guard username.count >= 3 else { statusText = "用户名至少 3 个字符"; return }
        guard password.count >= 8 else { statusText = "密码至少 8 位"; return }
        guard !nickname.isEmpty else { statusText = "请填写姓名"; return }
        let cleanedPhone = phone.trimmingCharacters(in: .whitespaces)
        guard cleanedPhone.range(of: "^1[3-9]\\d{9}$", options: .regularExpression) != nil else {
            statusText = "请输入有效的 11 位手机号"
            return
        }

        isLoading = true
        statusText = "注册中..."
        defer { isLoading = false }
        do {
            let session = try await AuthAPI.register(
                username: username, password: password, nickname: nickname, phone: cleanedPhone
            )
            auth.saveSession(session)
            dismiss()
            onLoginSuccess()
        } catch {
            statusText = "注册失败：\(error.localizedDescription)"
        }
    }
}

// MARK: - SSO WebView

import WebKit

struct SSOWebView: View {
    @ObservedObject var auth: AuthManager
    @Environment(\.dismiss) private var dismiss
    var onLoginSuccess: () -> Void

    var body: some View {
        VStack(spacing: 0) {
            Button {
                dismiss()
            } label: {
                Text("取消登录")
                    .frame(maxWidth: .infinity)
                    .frame(height: 44)
                    .background(Theme.surface)
                    .foregroundColor(.white)
            }

            SSOWebViewRepresentable()

            Button {
                readJwtAndLogin()
            } label: {
                Text("已登录，点击继续")
                    .frame(maxWidth: .infinity)
                    .frame(height: 48)
                    .background(Theme.accent)
                    .foregroundColor(.white)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
            }
            .padding(8)
        }
        .background(Theme.background.ignoresSafeArea())
    }

    private func readJwtAndLogin() {
        // Read JWT from WKWebView's localStorage via JavaScript
        SSOWebViewHolder.shared.readToken { jwt in
            guard let jwt = jwt, !jwt.isEmpty, jwt != "null" else {
                DispatchQueue.main.async {
                    // Toast
                }
                return
            }
            Task {
                await exchangeJwt(jwt)
            }
        }
    }

    private func exchangeJwt(_ jwt: String) async {
        do {
            let result = try await AuthAPI.ssoExchange(jwtToken: jwt)
            await MainActor.run {
                dismiss()
                if !result.phoneBound {
                    auth.ssoPendingToken = result.token
                    auth.ssoPendingUserId = result.user.id
                    auth.showingPhoneBinding = true
                } else {
                    auth.saveSession(AuthSession(token: result.token, user: result.user))
                    onLoginSuccess()
                }
            }
        } catch {
            await MainActor.run {
                dismiss()
            }
        }
    }
}

// MARK: - SSO WebView Representable

struct SSOWebViewRepresentable: UIViewRepresentable {
    func makeUIView(context: Context) -> WKWebView {
        let config = WKWebViewConfiguration()
        config.websiteDataStore = .default()
        let webView = WKWebView(frame: .zero, configuration: config)
        webView.navigationDelegate = context.coordinator
        SSOWebViewHolder.shared.webView = webView
        if let url = URL(string: "https://d1kt.cn/login") {
            webView.load(URLRequest(url: url))
        }
        return webView
    }

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

    func makeCoordinator() -> Coordinator {
        Coordinator()
    }

    class Coordinator: NSObject, WKNavigationDelegate {
        func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
            decisionHandler(.allow)
        }
    }
}

// MARK: - Holder for WebView reference

final class SSOWebViewHolder {
    static let shared = SSOWebViewHolder()
    weak var webView: WKWebView?

    func readToken(completion: @escaping (String?) -> Void) {
        guard let webView = webView else {
            completion(nil)
            return
        }
        webView.evaluateJavaScript(
            "(function(){ try { return localStorage.getItem('token') || sessionStorage.getItem('token') || ''; } catch(e) { return ''; } })()"
        ) { result, _ in
            let token = (result as? String) ?? ""
            completion(token.isEmpty || token == "null" ? nil : token)
        }
    }
}

// MARK: - Phone Binding View

struct PhoneBindingView: View {
    @ObservedObject var auth: AuthManager
    @Environment(\.dismiss) private var dismiss
    @State private var phone = ""
    @State private var statusText = ""
    @State private var isLoading = false
    var onLoginSuccess: () -> Void

    var body: some View {
        VStack(alignment: .leading, spacing: 0) {
            Text("绑定手机号")
                .font(.system(size: 28, weight: .bold))
                .foregroundColor(.white)
            Text("已通过第一课堂登录，请绑定手机号后继续")
                .font(.system(size: 14))
                .foregroundColor(Theme.textMuted)
                .padding(.top, 6)
                .padding(.bottom, 24)

            fieldLabel("手机号")
            TextField("请输入 11 位手机号", text: $phone)
                .textFieldStyle(.plain)
                .keyboardType(.phonePad)
                .padding(12)
                .background(Theme.surface)
                .clipShape(RoundedRectangle(cornerRadius: 8))
                .overlay(RoundedRectangle(cornerRadius: 8).stroke(Theme.border, lineWidth: 1))

            Button {
                Task { await bindPhone() }
            } label: {
                Text(isLoading ? "绑定中..." : "绑定并继续")
                    .frame(maxWidth: .infinity)
                    .frame(height: 48)
                    .background(Theme.accent)
                    .foregroundColor(.white)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
            }
            .padding(.top, 20)
            .disabled(isLoading)

            if !statusText.isEmpty {
                Text(statusText)
                    .font(.system(size: 13))
                    .foregroundColor(Theme.accentLight)
                    .padding(.top, 14)
            }
            Spacer()
        }
        .padding(.horizontal, 28)
        .padding(.top, 60)
        .background(Theme.background.ignoresSafeArea())
    }

    private func fieldLabel(_ text: String) -> some View {
        Text(text)
            .font(.system(size: 13))
            .foregroundColor(Theme.textMuted)
            .padding(.bottom, 4)
    }

    private func bindPhone() async {
        let cleaned = phone.trimmingCharacters(in: .whitespaces)
        guard cleaned.range(of: "^1[3-9]\\d{9}$", options: .regularExpression) != nil else {
            statusText = "请输入有效的 11 位手机号"
            return
        }
        guard let token = auth.ssoPendingToken else {
            statusText = "登录状态已过期，请重新登录"
            return
        }
        isLoading = true
        statusText = "绑定中..."
        defer { isLoading = false }
        do {
            try await AuthAPI.ssoBindPhone(token: token, phone: cleaned)
            auth.showingPhoneBinding = false
            auth.ssoPendingToken = nil
            let userID = auth.ssoPendingUserId
            auth.saveSession(
                AuthSession(
                    token: token,
                    user: AuthUser(id: userID, username: "", nickname: "")
                )
            )
            dismiss()
            onLoginSuccess()
        } catch {
            statusText = "绑定失败：\(error.localizedDescription)"
        }
    }
}