import { useEffect, useState } from "react";
import { Navigate, useNavigate } from "react-router-dom";
import { useTranslation } from "react-i18next";
import { useAuth } from "../auth";
import { api } from "../api";
import { useToast } from "../toast";
import { useConfirm } from "../confirm";
import Icon from "../components/Icon";
import PasswordInput from "../components/PasswordInput";

/** Codeliste als Textdatei sichern – Zwischenablage ist nicht überall erlaubt. */
function codesSichern(codes, benutzer) {
  const inhalt =
    `Certain Finance – Wiederherstellungscodes für ${benutzer}\n` +
    `Jeder Code funktioniert genau einmal. Sicher aufbewahren.\n\n` +
    codes.join("\n") + "\n";
  const url = URL.createObjectURL(new Blob([inhalt], { type: "text/plain;charset=utf-8" }));
  const link = document.createElement("a");
  link.href = url;
  link.download = `certain-finance_wiederherstellungscodes_${benutzer}.txt`;
  document.body.appendChild(link);
  link.click();
  link.remove();
  URL.revokeObjectURL(url);
}

/** Anzeige der frisch erzeugten Codes – sie sind danach nicht mehr abrufbar. */
function CodeListe({ codes, benutzer, onFertig }) {
  const { t } = useTranslation();
  const toast = useToast();

  async function kopieren() {
    try {
      await navigator.clipboard.writeText(codes.join("\n"));
      toast(t("twofactor.copied"));
    } catch {
      // Ohne sicheren Kontext (http) gibt es keine Zwischenablage – dann
      // bleibt der Download, und markieren geht ohnehin.
      codesSichern(codes, benutzer);
    }
  }

  return (
    <div className="card" style={{ maxWidth: 520, marginTop: "var(--sp-4)", borderColor: "var(--warn)" }}>
      <h2 style={{ marginTop: 0 }}>{t("twofactor.codesTitle")}</h2>
      <p className="muted small">{t("twofactor.codesHint")}</p>
      <div className="tfa-codes selectable">
        {codes.map((c) => <span key={c}>{c}</span>)}
      </div>
      <div className="btn-pair">
        <button className="btn" onClick={kopieren}>
          <Icon name="copy" size={15} /> {t("twofactor.copy")}
        </button>
        <button className="btn" onClick={() => codesSichern(codes, benutzer)}>
          <Icon name="download" size={15} /> {t("twofactor.download")}
        </button>
        <button className="btn primary" onClick={onFertig}>{t("twofactor.codesSaved")}</button>
      </div>
    </div>
  );
}

export default function TwoFactor() {
  const { user, aktualisieren } = useAuth();
  const { t } = useTranslation();
  const toast = useToast();
  const confirm = useConfirm();
  const navigate = useNavigate();

  const [status, setStatus] = useState(null);
  const [policy, setPolicy] = useState(null);
  const [setup, setSetup] = useState(null);   // { secret, otpauth_uri, qr_png }
  const [code, setCode] = useState("");
  const [codes, setCodes] = useState(null);   // frisch erzeugte Wiederherstellungscodes
  const [fehler, setFehler] = useState(null);
  const [busy, setBusy] = useState(false);

  async function laden() {
    try {
      const [s, p] = await Promise.all([api.twoFactorStatus(), api.getPolicy()]);
      setStatus(s);
      setPolicy(p);
    } catch (err) {
      setFehler(err.message);
    }
  }
  useEffect(() => { laden(); }, []);

  if (!user) return <Navigate to="/login" replace />;
  // Erst Passwort wechseln, dann zweiter Faktor – dieselbe Reihenfolge, die
  // der Server erzwingt.
  if (user.must_change_password) return <Navigate to="/passwort-aendern" replace />;

  const pflicht = Boolean(policy?.mfa_required);
  const erzwungen = pflicht && !status?.enabled;

  async function starten() {
    setFehler(null);
    setBusy(true);
    try {
      setSetup(await api.twoFactorSetup());
    } catch (err) {
      setFehler(err.message);
    } finally {
      setBusy(false);
    }
  }

  async function aktivieren(e) {
    e.preventDefault();
    setFehler(null);
    setBusy(true);
    try {
      const res = await api.twoFactorActivate(code.trim());
      setCodes(res.codes);
      setSetup(null);
      setCode("");
      // Die Sperre „MFA einrichten" fällt damit weg – Benutzer neu laden.
      aktualisieren(await api.me());
      await laden();
    } catch (err) {
      setFehler(err.message);
    } finally {
      setBusy(false);
    }
  }

  async function abschalten() {
    const passwort = await confirm({
      title: t("twofactor.disableTitle"),
      message: t("twofactor.disableHint"),
      confirmLabel: t("twofactor.disable"),
      danger: true,
      prompt: true,
      inputType: "password",
    });
    if (!passwort) return;
    try {
      aktualisieren(await api.twoFactorDisable(passwort));
      toast(t("twofactor.disabled"));
      await laden();
    } catch (err) {
      setFehler(err.message);
    }
  }

  async function codesErneuern() {
    const passwort = await confirm({
      title: t("twofactor.newCodesTitle"),
      message: t("twofactor.newCodesHint"),
      confirmLabel: t("twofactor.newCodes"),
      prompt: true,
      inputType: "password",
    });
    if (!passwort) return;
    try {
      const res = await api.newRecoveryCodes(passwort);
      setCodes(res.codes);
      await laden();
    } catch (err) {
      setFehler(err.message);
    }
  }

  return (
    <>
      <h1>{t("twofactor.title")}</h1>

      {fehler && (
        <div className="alert error" style={{ maxWidth: 520, marginBottom: "var(--sp-4)" }}>
          <Icon name="alert" size={16} />
          <span>{fehler}</span>
        </div>
      )}
      {erzwungen && (
        <div className="alert warn" style={{ maxWidth: 520, marginBottom: "var(--sp-4)" }}>
          <Icon name="shield" size={16} />
          <span>{t("twofactor.requiredHint")}</span>
        </div>
      )}

      <div className="card" style={{ maxWidth: 520 }}>
        <h2 style={{ marginTop: 0, display: "flex", alignItems: "center", gap: "var(--sp-2)" }}>
          <Icon name="shield" size={18} />
          {status?.enabled ? t("twofactor.on") : t("twofactor.off")}
        </h2>
        <p className="muted small">{t("twofactor.intro")}</p>

        {status?.enabled ? (
          <>
            <p className="small">
              {t("twofactor.codesLeft", { n: status.recovery_codes_left })}
            </p>
            <div className="btn-pair">
              <button className="btn" onClick={codesErneuern}>
                <Icon name="refresh-ccw" size={15} /> {t("twofactor.newCodes")}
              </button>
              {!pflicht && (
                <button className="btn danger" onClick={abschalten}>
                  {t("twofactor.disable")}
                </button>
              )}
            </div>
          </>
        ) : setup ? (
          <form onSubmit={aktivieren}>
            <p className="small">{t("twofactor.scan")}</p>
            <img className="tfa-qr" src={setup.qr_png} alt={t("twofactor.qrAlt")} />
            <p className="muted small" style={{ marginTop: "var(--sp-3)" }}>
              {t("twofactor.manual")}
            </p>
            <code className="tfa-secret selectable">{setup.secret}</code>

            <label className="field" style={{ marginTop: "var(--sp-4)" }}>
              <span>{t("twofactor.code")}</span>
              <input value={code} onChange={(e) => setCode(e.target.value)} required
                     inputMode="numeric" maxLength={6} autoComplete="one-time-code"
                     placeholder="123456" />
            </label>
            <div className="btn-pair" style={{ marginTop: "var(--sp-3)" }}>
              <button className="btn primary" type="submit" disabled={busy}>
                {busy ? t("common.loading") : t("twofactor.activate")}
              </button>
              <button className="btn ghost" type="button" onClick={() => { setSetup(null); setCode(""); }}>
                {t("common.cancel")}
              </button>
            </div>
          </form>
        ) : (
          <button className="btn primary" onClick={starten} disabled={busy}>
            <Icon name="smartphone" size={15} /> {t("twofactor.start")}
          </button>
        )}
      </div>

      {codes && (
        <CodeListe
          codes={codes}
          benutzer={user.username}
          onFertig={() => { setCodes(null); if (erzwungen) navigate("/"); }}
        />
      )}
    </>
  );
}