import { useEffect, useState } from "react";

import { platformApiClient, setPlatformApiAuthFailureHandler, setPlatformApiSessionToken } from "../api/client";
import type {
  AuthSessionResponse,
  CurrentUserResponse,
  LoginRequest,
  RegisterRequest,
  UserProfileUpdateRequest,
  UserThemePreferenceRequest,
  UserThemePreferenceResponse
} from "../api/types";
import type { CurrentUserView } from "../contracts/workspace";
import { capabilitiesForRoles, rolesFromBackendRoles } from "../contracts/workspace";
import { readWebRuntimeEnv } from "../schemas/env";
import { defaultThemeBackgroundId, defaultThemePaletteId, loadThemeState } from "../theme/tokens";

const sessionTokenStorageKey = "platform-web.session.apiToken";
const localFallbackEnabled = readWebRuntimeEnv().enableLocalAuthFallback;

export const localFallbackUser: CurrentUserView = {
  id: "local-server-operator",
  displayName: "Local Server Operator",
  email: "local.server@example.test",
  status: "active",
  roles: ["serverAdmin"],
  capabilities: capabilitiesForRoles(["serverAdmin"]),
  profile: {
    phone: "",
    qq: "",
    contactNote: "本地开发回退账号，仅限服务器工作台"
  },
  source: "local"
};

export interface AuthFormState {
  mode: "login" | "register";
  pending: boolean;
  error?: string;
  success?: string;
}

export interface SessionState {
  user?: CurrentUserView;
  loaded: boolean;
  authenticated: boolean;
  authUnavailable: boolean;
  localFallbackAvailable: boolean;
  auth: AuthFormState;
  login: (request: LoginRequest) => Promise<void>;
  register: (request: RegisterRequest) => Promise<void>;
  logout: () => Promise<void>;
  continueWithLocalFallback: () => void;
  switchAuthMode: (mode: AuthFormState["mode"]) => void;
  updateProfile: (request: UserProfileUpdateRequest) => Promise<CurrentUserView>;
  updateThemePreference: (request: UserThemePreferenceRequest) => Promise<UserThemePreferenceResponse>;
}

export async function loadCurrentUser(): Promise<CurrentUserView | null> {
  const storedToken = readStoredSessionToken();
  setPlatformApiSessionToken(storedToken);
  try {
    const response = await platformApiClient.getCurrentUser();
    return currentUserFromResponse(response, "api");
  } catch {
    persistSessionToken(null);
    setPlatformApiSessionToken(null);
    return null;
  }
}

export function useSession(): SessionState {
  const [user, setUser] = useState<CurrentUserView | undefined>();
  const [loaded, setLoaded] = useState(false);
  const [authUnavailable, setAuthUnavailable] = useState(false);
  const [auth, setAuth] = useState<AuthFormState>({ mode: "login", pending: false });

  useEffect(() => {
    let cancelled = false;
    void loadCurrentUser().then((currentUser) => {
      if (cancelled) {
        return;
      }
      setUser(currentUser ?? undefined);
      setAuthUnavailable(!currentUser);
      setLoaded(true);
    });
    return () => {
      cancelled = true;
    };
  }, []);

  useEffect(() => {
    setPlatformApiAuthFailureHandler(() => {
      persistSessionToken(null);
      setUser(undefined);
      setAuthUnavailable(false);
      setAuth({ mode: "login", pending: false, error: "会话已失效，请重新登录。" });
    });
    return () => setPlatformApiAuthFailureHandler(null);
  }, []);

  async function login(request: LoginRequest) {
    setAuth({ mode: "login", pending: true });
    try {
      const response = await platformApiClient.login(request);
      finishAuth(response, "登录成功");
    } catch (error) {
      setAuth({
        mode: "login",
        pending: false,
        error: error instanceof Error ? error.message : "登录失败，请重试。"
      });
    }
  }

  async function register(request: RegisterRequest) {
    setAuth({ mode: "register", pending: true });
    try {
      const response = await platformApiClient.register(request);
      const nextUser = currentUserFromResponse(response.user, "api");
      if (response.status === "authenticated") {
        setUser(nextUser);
        persistSessionToken(response.sessionId ?? null);
        setPlatformApiSessionToken(response.sessionId ?? null);
      }
      setAuth({
        mode: response.status === "authenticated" ? "login" : "register",
        pending: false,
        success: response.message ?? (response.status === "authenticated" ? "注册成功，已进入工作台。" : "注册申请已提交，等待平台管理员审核。")
      });
    } catch (error) {
      setAuth({
        mode: "register",
        pending: false,
        error: error instanceof Error ? error.message : "注册失败，请稍后重试。"
      });
    }
  }

  async function logout() {
    try {
      await platformApiClient.logout();
    } catch {
      // Local fallback logout still clears the visible session.
    }
    persistSessionToken(null);
    setPlatformApiSessionToken(null);
    setUser(undefined);
    setAuthUnavailable(false);
    setAuth({ mode: "login", pending: false, success: "已退出登录。" });
  }

  function continueWithLocalFallback() {
    if (!localFallbackEnabled) {
      setAuth({ mode: "login", pending: false, error: "本地回退未启用，请使用真实账号登录。" });
      return;
    }
    setUser(localFallbackUser);
    setAuthUnavailable(false);
    setAuth({ mode: "login", pending: false, success: "已进入本地回退工作台。" });
  }

  function switchAuthMode(mode: AuthFormState["mode"]) {
    setAuth({ mode, pending: false });
  }

  async function updateProfile(request: UserProfileUpdateRequest): Promise<CurrentUserView> {
    const current = user ?? localFallbackUser;
    try {
      const response = await platformApiClient.updateCurrentUserProfile(request);
      const nextUser = currentUserFromResponse(response, "api");
      setUser(nextUser);
      return nextUser;
    } catch {
      const nextUser: CurrentUserView = {
        ...current,
        displayName: request.displayName,
        profile: {
          avatarUrl: request.avatarUrl,
          phone: request.phone,
          qq: request.qq,
          contactNote: request.contactNote
        },
        source: "local"
      };
      setUser(nextUser);
      return nextUser;
    }
  }

  async function updateThemePreference(request: UserThemePreferenceRequest): Promise<UserThemePreferenceResponse> {
    const current = user ?? localFallbackUser;
    try {
      const response = await platformApiClient.updateCurrentUserTheme(request);
      setUser({ ...current, themePreference: response, source: "api" });
      return response;
    } catch {
      const response: UserThemePreferenceResponse = {
        ...request,
        userId: current.id,
        persistence: "local",
        updatedAt: new Date().toISOString()
      };
      const nextUser = { ...current, themePreference: response, source: "local" as const };
      setUser(nextUser);
      return response;
    }
  }

  function finishAuth(response: AuthSessionResponse, fallbackMessage: string) {
    const nextUser = currentUserFromResponse(response.user, "api");
    setUser(nextUser);
    persistSessionToken(response.sessionId ?? null);
    setPlatformApiSessionToken(response.sessionId ?? null);
    setAuthUnavailable(false);
    setAuth({ mode: "login", pending: false, success: response.message ?? fallbackMessage });
  }

  return {
    user,
    loaded,
    authenticated: Boolean(user),
    authUnavailable,
    localFallbackAvailable: localFallbackEnabled,
    auth,
    login,
    register,
    logout,
    continueWithLocalFallback,
    switchAuthMode,
    updateProfile,
    updateThemePreference
  };
}

export function currentUserFromResponse(response: CurrentUserResponse, source: CurrentUserView["source"]): CurrentUserView {
  const roles = rolesFromBackendRoles(response.roles);
  const themeState = loadThemeState();
  return {
    id: response.id,
    displayName: response.displayName,
    email: response.email,
    status: response.status ?? "active",
    roles,
    capabilities: response.capabilities?.length ? (response.capabilities as CurrentUserView["capabilities"]) : capabilitiesForRoles(roles),
    profile: response.profile ?? {},
    themePreference:
      response.themePreference ??
      (source === "local"
        ? {
            userId: response.id,
            paletteId: themeState.paletteId || defaultThemePaletteId,
            backgroundPresetId: themeState.backgroundPresetId || defaultThemeBackgroundId,
            backgroundImage: themeState.backgroundImage,
            persistence: "local",
            updatedAt: new Date().toISOString()
          }
        : undefined),
    source
  };
}

function readStoredSessionToken(): string | null {
  if (typeof window === "undefined") {
    return null;
  }
  try {
    return window.localStorage.getItem(sessionTokenStorageKey);
  } catch {
    return null;
  }
}

function persistSessionToken(token: string | null) {
  if (typeof window === "undefined") {
    return;
  }
  try {
    if (token) {
      window.localStorage.setItem(sessionTokenStorageKey, token);
    } else {
      window.localStorage.removeItem(sessionTokenStorageKey);
    }
  } catch {
    // Storage can be unavailable; the in-memory session remains usable.
  }
}