import { createAsyncThunk, createSlice, type PayloadAction } from "@reduxjs/toolkit";
import { ApiError } from "../services/api";
import { changePassword as changePasswordRequest, getAuthStatus, getSession, login as loginRequest, logout as logoutRequest } from "../services/auth";
import type { Admin, AuthStatus, ChangePasswordInput, LoginCredentials } from "../types/auth";

export type SessionStatus = "idle" | "loading" | "authenticated" | "unauthenticated" | "error";

export interface SessionState {
  status: SessionStatus;
  admin: Admin | null;
  initialized: boolean | null;
  timezone: string;
  error: string | null;
  bootstrapRequestId: string | null;
}

const initialState: SessionState = {
  status: "idle",
  admin: null,
  initialized: null,
  timezone: "Asia/Shanghai",
  error: null,
  bootstrapRequestId: null,
};

/** Only the initial session check should replace the auth surface with a
 * full-page bootstrap indicator. Login and password requests keep their form
 * mounted so their controls can show progress in place. */
export function isSessionBootstrapping(state: Pick<SessionState, "status" | "initialized" | "bootstrapRequestId">): boolean {
  return state.status === "idle"
    || (state.status === "loading" && (state.initialized === null || state.bootstrapRequestId !== null));
}

export const bootstrapSession = createAsyncThunk("session/bootstrap", async () => {
  const authStatus = await getAuthStatus();
  try {
    const session = await getSession();
    return { ...authStatus, admin: session.admin };
  } catch (error) {
    if (error instanceof ApiError && error.status === 401) return { ...authStatus, admin: null };
    throw error;
  }
});

export const loginThunk = createAsyncThunk("session/login", async (credentials: LoginCredentials) => {
  const result = await loginRequest(credentials);
  return result.admin;
});

export const changePasswordThunk = createAsyncThunk("session/changePassword", async (input: ChangePasswordInput) => {
  const result = await changePasswordRequest(input);
  return result.admin;
});

export const logoutThunk = createAsyncThunk("session/logout", async () => {
  await logoutRequest();
});

// Friendly aliases keep page code terse while the *Thunk suffix remains explicit at call sites.
export const restoreSession = bootstrapSession;
export const login = loginThunk;
export const changePassword = changePasswordThunk;
export const logout = logoutThunk;

const sessionSlice = createSlice({
  name: "session",
  initialState,
  reducers: {
    clearSessionError(state) {
      state.error = null;
    },
    sessionExpired(state, action: PayloadAction<string | undefined>) {
      state.bootstrapRequestId = null;
      state.status = "unauthenticated";
      state.admin = null;
      state.error = action.payload ?? null;
    },
    setTimezone(state, action: PayloadAction<string>) {
      state.timezone = action.payload;
    },
  },
  extraReducers: (builder) => {
    builder
      .addCase(bootstrapSession.pending, (state, action) => {
        state.status = "loading";
        state.error = null;
        state.bootstrapRequestId = action.meta.requestId;
      })
      .addCase(bootstrapSession.fulfilled, (state, action) => {
        if (state.bootstrapRequestId !== action.meta.requestId) return;
        state.bootstrapRequestId = null;
        state.status = action.payload.admin ? "authenticated" : "unauthenticated";
        state.admin = action.payload.admin;
        state.initialized = action.payload.initialized;
        state.timezone = action.payload.timezone || state.timezone;
      })
      .addCase(bootstrapSession.rejected, (state, action) => {
        if (state.bootstrapRequestId !== action.meta.requestId) return;
        state.bootstrapRequestId = null;
        state.status = "error";
        state.error = action.error.message ?? "无法读取登录状态";
      })
      .addCase(loginThunk.pending, (state) => {
        state.bootstrapRequestId = null;
        state.status = "loading";
        state.error = null;
      })
      .addCase(loginThunk.fulfilled, (state, action: PayloadAction<Admin>) => {
        state.bootstrapRequestId = null;
        state.status = "authenticated";
        state.admin = action.payload;
        state.initialized = true;
        state.error = null;
      })
      .addCase(loginThunk.rejected, (state, action) => {
        state.bootstrapRequestId = null;
        state.status = "unauthenticated";
        state.error = action.error.message ?? "登录失败";
      })
      .addCase(changePasswordThunk.pending, (state) => {
        state.bootstrapRequestId = null;
        state.status = "loading";
        state.error = null;
      })
      .addCase(changePasswordThunk.fulfilled, (state, action: PayloadAction<Admin>) => {
        state.bootstrapRequestId = null;
        state.status = "authenticated";
        state.admin = action.payload;
        state.error = null;
      })
      .addCase(changePasswordThunk.rejected, (state, action) => {
        state.bootstrapRequestId = null;
        state.status = "authenticated";
        state.error = action.error.message ?? "密码更新失败";
      })
      .addCase(logoutThunk.pending, (state) => {
        state.bootstrapRequestId = null;
        state.status = "loading";
      })
      .addCase(logoutThunk.fulfilled, (state) => {
        state.bootstrapRequestId = null;
        state.status = "unauthenticated";
        state.admin = null;
        state.error = null;
      })
      .addCase(logoutThunk.rejected, (state, action) => {
        state.bootstrapRequestId = null;
        state.status = "unauthenticated";
        state.admin = null;
        state.error = action.error.message ?? "退出登录失败";
      });
  },
});

export const { clearSessionError, sessionExpired, setTimezone } = sessionSlice.actions;
export default sessionSlice.reducer;