import VisibilityOffOutlined from "@mui/icons-material/VisibilityOffOutlined";
import VisibilityOutlined from "@mui/icons-material/VisibilityOutlined";
import Alert from "@mui/material/Alert";
import Box from "@mui/material/Box";
import Button from "@mui/material/Button";
import Card from "@mui/material/Card";
import CardContent from "@mui/material/CardContent";
import CircularProgress from "@mui/material/CircularProgress";
import IconButton from "@mui/material/IconButton";
import InputAdornment from "@mui/material/InputAdornment";
import Stack from "@mui/material/Stack";
import TextField from "@mui/material/TextField";
import Typography from "@mui/material/Typography";
import { useEffect, useState } from "react";
import { useLocation, useNavigate } from "react-router-dom";
import { useExternalAuth } from "../auth/ExternalAuthProvider.jsx";
import { LanguageSwitcher } from "../i18n/LanguageSwitcher.jsx";
import { useExternalI18n } from "../i18n/ExternalI18nProvider.jsx";
import { translateExternalError } from "../i18n/errors.js";

export default function LoginPage() {
  const { initializing, login, session } = useExternalAuth();
  const { t } = useExternalI18n();
  const [form, setForm] = useState({ account: "", password: "" });
  const [error, setError] = useState("");
  const [submitting, setSubmitting] = useState(false);
  const [showPassword, setShowPassword] = useState(false);
  const navigate = useNavigate();
  const location = useLocation();

  useEffect(() => {
    // 登录前没有可信 App 上下文；使用通用标题并清掉上次认证遗留的图标，避免误导用户所属 App。
    globalThis.document.title = t("app.title");
    globalThis.document.head.querySelector('link[data-external-app-favicon="true"]')?.remove();
  }, [t]);

  useEffect(() => {
    if (!initializing && session) {
      // Password rotation is optional. An authenticated session always returns to the
      // requested business page, including sessions created by older server versions.
      const destination = location.state?.from?.pathname || "/overview";
      navigate(destination, { replace: true });
    }
  }, [initializing, location.state, navigate, session]);

  const handleSubmit = async (event) => {
    event.preventDefault();
    if (!form.account.trim() || !form.password) {
      setError(t("auth.fillAccountPassword"));
      return;
    }
    setSubmitting(true);
    setError("");
    try {
      await login(form);
      navigate("/overview", { replace: true });
    } catch (requestError) {
      // Every login 401 uses one generic credential message so unknown, disabled and locked accounts cannot be distinguished.
      setError(requestError?.status === 401 ? t("auth.invalidCredentials") : translateExternalError(requestError, t, "auth.loginFailed"));
    } finally {
      setSubmitting(false);
    }
  };

  return (
    <Box className="external-login-page">
      <Card className="external-login-card" elevation={0}>
        <CardContent>
          <Stack sx={{ alignItems: "flex-end" }}><LanguageSwitcher /></Stack>
          <Stack spacing={1.5} sx={{ alignItems: "center" }}>
            <Typography className="external-login-title" component="h1" variant="h5">{t("app.title")}</Typography>
          </Stack>
          <Stack component="form" spacing={2.25} onSubmit={handleSubmit}>
            {error ? <Alert severity="error">{error}</Alert> : null}
            <TextField autoComplete="username" disabled={submitting} label={t("auth.account")} required value={form.account} onChange={(event) => setForm({ ...form, account: event.target.value })} />
            <TextField
              autoComplete="current-password"
              disabled={submitting}
              label={t("auth.password")}
              required
              type={showPassword ? "text" : "password"}
              value={form.password}
              onChange={(event) => setForm({ ...form, password: event.target.value })}
              slotProps={{ input: { endAdornment: <InputAdornment position="end"><IconButton aria-label={showPassword ? t("auth.hidePassword") : t("auth.showPassword")} edge="end" onClick={() => setShowPassword((current) => !current)}>{showPassword ? <VisibilityOffOutlined /> : <VisibilityOutlined />}</IconButton></InputAdornment> } }}
            />
            <Button disabled={submitting} size="large" type="submit" variant="contained">
              {submitting ? <CircularProgress color="inherit" size={20} /> : t("auth.login")}
            </Button>
          </Stack>
        </CardContent>
      </Card>
    </Box>
  );
}
