import { useState } from "react";
import { Alert, Button, Checkbox, Form } from "tdesign-react";
import { useAppDispatch, useAppSelector, clearSessionError, loginThunk } from "../../store";
import type { Admin } from "../../types/auth";
import { LoginUserIcon, StarterPasswordInput } from "./StarterAuth";
import AccessibleInput from "../../components/AccessibleInput";

const REMEMBERED_USERNAME_KEY = "tallynote.login.username";

export interface LoginPageProps {
  notice?: string;
  onSuccess?: (admin: Admin) => void;
}

function getRememberedUsername(): string {
  if (typeof window === "undefined") return "";
  try {
    return window.localStorage.getItem(REMEMBERED_USERNAME_KEY) ?? "";
  } catch {
    return "";
  }
}

export default function LoginPage({ notice, onSuccess }: LoginPageProps) {
  const dispatch = useAppDispatch();
  const { status, error } = useAppSelector((state) => state.session);
  const [username, setUsername] = useState(getRememberedUsername);
  const [password, setPassword] = useState("");
  const [rememberAccount, setRememberAccount] = useState(Boolean(username));
  const [fieldErrors, setFieldErrors] = useState<{ username?: string; password?: string }>({});
  const busy = status === "loading";

  const updateUsername = (value: string) => {
    setUsername(value);
    setFieldErrors(current => ({ ...current, username: undefined }));
    if (error) dispatch(clearSessionError());
  };

  const updatePassword = (value: string) => {
    setPassword(value);
    setFieldErrors(current => ({ ...current, password: undefined }));
    if (error) dispatch(clearSessionError());
  };

  const submit = async () => {
    const normalizedUsername = username.trim();
    const nextErrors: { username?: string; password?: string } = {};
    if (!normalizedUsername) nextErrors.username = "请输入用户名";
    if (!password) nextErrors.password = "请输入密码";
    if (Object.keys(nextErrors).length) {
      setFieldErrors(nextErrors);
      const focusInvalid = () => document.querySelector<HTMLElement>("[aria-invalid='true'], [aria-invalid='true'] input, [aria-invalid='true'] textarea")?.focus();
      requestAnimationFrame(focusInvalid);
      window.setTimeout(focusInvalid, 60);
      return;
    }
    setFieldErrors({});
    try {
      if (rememberAccount) {
        window.localStorage.setItem(REMEMBERED_USERNAME_KEY, normalizedUsername);
      } else {
        window.localStorage.removeItem(REMEMBERED_USERNAME_KEY);
      }
    } catch {
      // Private browsing or a locked-down browser may reject localStorage.
    }
    try {
      const admin = await dispatch(loginThunk({ username: normalizedUsername, password })).unwrap();
      onSuccess?.(admin);
    } catch {
      // The rejected thunk exposes its server message through session.error.
    }
  };

  return (
    <main className="tn-login-page" data-page="login">
      <section className="tn-login-container" aria-labelledby="login-title">
        <div className="tn-login-heading">
          <h1 id="login-title" className="tn-login-title">登录 <span className="tn-login-title-brand">TallyNote</span> 工作台</h1>
        </div>

        <Form
          className="tn-login-form"
          labelWidth={0}
          onSubmit={(context) => { context.e?.preventDefault(); void submit(); }}
        >
          {notice && <div role="status" aria-live="polite"><Alert className="tn-login-alert" theme="info" message={notice} /></div>}
          {error && <div role="alert" aria-live="assertive"><Alert className="tn-login-alert" theme="error" message={error} /></div>}
          <Form.FormItem label="用户名" requiredMark={false} name="username" status={fieldErrors.username ? "error" : undefined} help={fieldErrors.username}>
            <AccessibleInput
              inputAriaLabel="用户名"
              inputAriaInvalid={Boolean(fieldErrors.username)}
              inputAriaDescribedby={fieldErrors.username ? "login-username-error" : undefined}
              size="large"
              value={username}
              onChange={(value) => updateUsername(String(value))}
              clearable
              disabled={busy}
              autocomplete="username"
              autofocus
              prefixIcon={<LoginUserIcon />}
              placeholder="请输入用户名"
            />
            {fieldErrors.username && <span id="login-username-error" className="tn-sr-only">{fieldErrors.username}</span>}
          </Form.FormItem>
          <Form.FormItem label="密码" requiredMark={false} name="password" status={fieldErrors.password ? "error" : undefined} help={fieldErrors.password}>
            <StarterPasswordInput
              ariaLabel="密码"
              ariaInvalid={Boolean(fieldErrors.password)}
              ariaDescribedby={fieldErrors.password ? "login-password-error" : undefined}
              value={password}
              onChange={updatePassword}
              autocomplete="current-password"
              disabled={busy}
              placeholder="请输入登录密码"
            />
            {fieldErrors.password && <span id="login-password-error" className="tn-sr-only">{fieldErrors.password}</span>}
          </Form.FormItem>
          <div className="tn-login-options"><Checkbox checked={rememberAccount} onChange={setRememberAccount} disabled={busy}>记住账号</Checkbox></div>
          <Form.FormItem className="tn-login-submit">
            <Button block size="large" theme="primary" type="submit" loading={busy} disabled={busy}>登录</Button>
          </Form.FormItem>
        </Form>

      </section>
    </main>
  );
}