"use client";

import { authClient } from "@/lib/auth-client";
import { useRouter } from "next/navigation";
import { useRef, useState } from "react";

const OTP_STEP_STORAGE_KEY = "hellthhub_login_step_otp";

function clearOtpStep() {
  try {
    window.localStorage.removeItem(OTP_STEP_STORAGE_KEY);
  } catch {
    // ignore storage access issues
  }
}

export default function OtpLoginPage() {
  const router = useRouter();
  const inputRef = useRef<HTMLInputElement>(null);
  const [method, setMethod] = useState<"totp" | "backup">("totp");
  const [error, setError] = useState<string | null>(null);
  const [loading, setLoading] = useState(false);

  async function handleSubmit(e: React.FormEvent) {
    e.preventDefault();
    setError(null);
    setLoading(true);

    try {
      const code = inputRef.current?.value?.trim() ?? "";
      const normalizedCode = method === "totp" ? code.replace(/\D/g, "") : code;

      if (method === "totp" && normalizedCode.length !== 6) {
        setError("Bitte den 6-stelligen OTP-Code eingeben.");
        return;
      }
      if (method === "backup" && normalizedCode.length < 6) {
        setError("Bitte einen gültigen Backup-Code eingeben.");
        return;
      }

      const verifyResult =
        method === "totp"
          ? await authClient.twoFactor.verifyTotp({ code: normalizedCode })
          : await authClient.twoFactor.verifyBackupCode({ code: normalizedCode });
      if (verifyResult.error) {
        const message =
          verifyResult.error.message ??
          (method === "totp"
            ? "OTP-Code ungültig. Bitte erneut prüfen."
            : "Backup-Code ungültig. Bitte erneut prüfen.");

        if (
          message.includes("session") ||
          message.includes("Session") ||
          message.includes("expired")
        ) {
          setError(
            "OTP-Sitzung abgelaufen. Bitte erneut mit E-Mail und Passwort anmelden.",
          );
          return;
        }

        setError(
          method === "totp"
            ? "OTP-Code ungültig. Bitte erneut prüfen."
            : "Backup-Code ungültig. Bitte erneut prüfen.",
        );
        return;
      }

      clearOtpStep();
      if (inputRef.current) {
        inputRef.current.value = "";
      }
      router.push("/");
    } catch {
      setError("2FA-Prüfung derzeit nicht möglich. Bitte erneut versuchen.");
    } finally {
      setLoading(false);
    }
  }

  return (
    <div className="min-h-screen flex items-center justify-center bg-[#F9F9F9]">
      <div className="w-full max-w-sm">
        <div className="flex flex-col items-center mb-8">
          <div className="mb-4 flex h-14 w-14 items-center justify-center rounded-xl bg-[#0F766E] text-lg font-bold text-white shadow-sm">
            HH
          </div>
          <h1 className="text-xl font-bold text-[#333333]">Hellth Hub</h1>
          <p className="text-sm text-gray-500 mt-2">OTP-Verifizierung</p>
        </div>

        <form
          onSubmit={handleSubmit}
          className="bg-white rounded-xl shadow-sm border border-gray-100 p-6 space-y-4"
        >
          <div className="grid grid-cols-2 gap-2 rounded-lg bg-gray-100 p-1">
            <button
              type="button"
              onClick={() => {
                setMethod("totp");
                setError(null);
                if (inputRef.current) inputRef.current.value = "";
              }}
              className={`rounded-md px-3 py-2 text-sm font-medium transition-colors ${
                method === "totp" ? "bg-white text-gray-900 shadow-sm" : "text-gray-600"
              }`}
            >
              Authenticator-Code
            </button>
            <button
              type="button"
              onClick={() => {
                setMethod("backup");
                setError(null);
                if (inputRef.current) inputRef.current.value = "";
              }}
              className={`rounded-md px-3 py-2 text-sm font-medium transition-colors ${
                method === "backup" ? "bg-white text-gray-900 shadow-sm" : "text-gray-600"
              }`}
            >
              Backup-Code
            </button>
          </div>

          {error && (
            <div className="flex items-center gap-2 text-sm text-red-600 bg-[#ECFDF5] border border-red-100 px-3 py-2.5 rounded-lg">
              <span className="w-4 h-4 text-[#0F766E] shrink-0">!</span>
              {error}
            </div>
          )}

          <div>
            <label className="block text-sm font-medium text-[#333333] mb-1.5">
              {method === "totp" ? "OTP-Code (6-stellig)" : "Backup-Code"}
            </label>
            <input
              ref={inputRef}
              type="text"
              required
              autoFocus
              suppressHydrationWarning
              name={method === "totp" ? "one-time-code" : "backup-code"}
              autoComplete={method === "totp" ? "one-time-code" : "off"}
              inputMode={method === "totp" ? "numeric" : "text"}
              pattern={method === "totp" ? "[0-9]{6}" : undefined}
              maxLength={method === "totp" ? 6 : 64}
              onInput={(e) => {
                const input = e.currentTarget;
                if (method === "totp") {
                  input.value = input.value.replace(/\D/g, "").slice(0, 6);
                }
              }}
              placeholder={method === "totp" ? "123456" : "z. B. ABCD-EFGH"}
              className="w-full px-3 py-2.5 border border-gray-200 rounded-lg text-sm text-[#333333] placeholder-gray-300 focus:outline-none focus:ring-2 focus:ring-[#0F766E] focus:border-transparent transition-shadow"
            />
            {method === "backup" && (
              <p className="mt-1 text-xs text-gray-500">
                Jeder Backup-Code ist nur einmal gültig.
              </p>
            )}
          </div>

          <button
            type="submit"
            disabled={loading}
            className="w-full py-2.5 bg-[#0F766E] text-white text-sm font-semibold rounded-lg hover:bg-[#115E59] transition-colors disabled:opacity-50 disabled:cursor-not-allowed mt-2"
          >
            {loading ? "Prüfen..." : method === "totp" ? "OTP prüfen" : "Backup-Code prüfen"}
          </button>

          <button
            type="button"
            onClick={() => {
              clearOtpStep();
              router.replace("/login");
            }}
            className="w-full py-2.5 bg-white text-[#333333] text-sm font-semibold rounded-lg border border-gray-200 hover:bg-gray-50 transition-colors"
          >
            Zurück zu Login
          </button>
        </form>
      </div>
    </div>
  );
}