import { useState } from 'react';
import { useApp } from '../context/AppContext.js';
import { themeVars } from '../components/reader/readerThemes.js';
import { loginUser, registerUser, verifyMfaLogin, logoutUser } from '../syncService.js';

export default function AuthPage() {
  const { signIn, readerTheme } = useApp();
  const shell = { style: themeVars(readerTheme) };
  const [authMode, setAuthMode] = useState('login'); // 'login' | 'register'
  const [authForm, setAuthForm] = useState({ email: '', password: '' });
  const [authError, setAuthError] = useState('');
  const [authBusy, setAuthBusy] = useState(false);
  const [authMfaPending, setAuthMfaPending] = useState(false); // password ok, waiting on TOTP/backup code
  const [authMfaCode, setAuthMfaCode] = useState('');
  const [authMfaUseBackup, setAuthMfaUseBackup] = useState(false);

  const submitAuth = async (e) => {
    e.preventDefault();
    setAuthError('');
    setAuthBusy(true);
    const action = authMode === 'login' ? loginUser : registerUser;
    const result = await action(authForm.email.trim(), authForm.password);
    setAuthBusy(false);
    if (!result.ok) {
      setAuthError(result.error ?? 'Something went wrong.');
      return;
    }
    if (result.data?.mfaRequired) {
      setAuthMfaPending(true);
      return;
    }
    signIn(result.data);
  };

  const submitMfa = async (e) => {
    e.preventDefault();
    setAuthError('');
    setAuthBusy(true);
    const result = await verifyMfaLogin(
      authMfaUseBackup ? { backupCode: authMfaCode.trim() } : { token: authMfaCode.trim() },
    );
    setAuthBusy(false);
    if (!result.ok) {
      setAuthError(result.error ?? 'Invalid code.');
      return;
    }
    setAuthMfaPending(false);
    setAuthMfaCode('');
    signIn(result.data);
  };

  if (authMfaPending) {
    return (
      <div {...shell} className="flex min-h-dvh items-center justify-center bg-[var(--r-bg)] px-4 text-[var(--r-text)]">
        <div className="w-full max-w-sm rounded-2xl border border-[var(--r-line)] bg-[var(--r-bar)] p-8">
          <p className="text-sm uppercase tracking-[0.24em] text-[var(--r-sub)]">Bible Study Project</p>
          <h1 className="mt-2 text-xl font-medium text-[var(--r-text)]">Two-factor verification</h1>
          <p className="mt-2 text-sm text-[var(--r-sub)]">
            {authMfaUseBackup
              ? 'Enter one of your saved backup codes.'
              : 'Enter the 6-digit code from your authenticator app.'}
          </p>
          <form onSubmit={submitMfa} className="mt-6 space-y-4">
            <input
              type="text"
              required
              autoFocus
              inputMode={authMfaUseBackup ? 'text' : 'numeric'}
              placeholder={authMfaUseBackup ? 'xxxxxxxxxx' : '123456'}
              value={authMfaCode}
              onChange={(e) => setAuthMfaCode(e.target.value)}
              className="block w-full rounded-xl border border-[var(--r-line)] bg-[var(--r-bg)] px-3 py-2 text-[var(--r-text)] text-center text-lg tracking-widest focus:outline-none focus:ring-2 focus:ring-[var(--r-line)]"
            />
            {authError && <p className="text-sm text-[var(--r-danger,#b42318)]">{authError}</p>}
            <button
              type="submit"
              disabled={authBusy}
              className="w-full rounded-full bg-[var(--r-accent)] px-4 py-2.5 text-sm font-medium text-[var(--r-on)] transition hover:opacity-90 disabled:cursor-not-allowed disabled:opacity-50"
            >
              {authBusy ? 'Verifying…' : 'Verify'}
            </button>
          </form>
          <button
            type="button"
            onClick={() => {
              setAuthMfaUseBackup((v) => !v);
              setAuthMfaCode('');
              setAuthError('');
            }}
            className="mt-4 w-full text-center text-sm text-[var(--r-sub)] underline hover:text-[var(--r-text)]"
          >
            {authMfaUseBackup ? 'Use your authenticator app instead' : "Lost your device? Use a backup code"}
          </button>
          <button
            type="button"
            onClick={async () => {
              await logoutUser();
              setAuthMfaPending(false);
              setAuthMfaCode('');
              setAuthError('');
            }}
            className="mt-2 w-full text-center text-sm text-[var(--r-sub)] underline hover:text-[var(--r-sub)]"
          >
            Cancel
          </button>
        </div>
      </div>
    );
  }

  return (
    <div {...shell} className="flex min-h-dvh items-center justify-center bg-[var(--r-bg)] px-4 py-12 text-[var(--r-text)]">
      <div className="grid w-full max-w-5xl items-center gap-16 lg:grid-cols-2">
        {/* Branding / feature panel — hidden on small screens to keep the form front and center there */}
        <div className="hidden lg:block">
          <p className="text-sm uppercase tracking-[0.24em] text-[var(--r-sub)]">Bible Study Project</p>
          <h1 className="mt-4 text-3xl font-semibold leading-tight text-[var(--r-text)]">
            Deep Bible study,<br />one chunk at a time.
          </h1>
          <p className="mt-4 max-w-sm text-[var(--r-sub)]">
            Read Scripture in six translations, follow a reading plan into the text, and study a passage one chunk
            at a time with commentary, word studies, and cross-references beside it.
          </p>
          <ul className="mt-8 space-y-3 text-sm text-[var(--r-sub)]">
            <li>Read in BSB, ESV, NLT, CSB, NASB, or NET, with audio and search</li>
            <li>Reading plans that open straight into the Reader</li>
            <li>Observe, Interpret, Apply notes with Greek &amp; Hebrew word studies</li>
            <li>Turn your notes into a script, then export or share</li>
            <li>Your studies stay private to your account, with optional 2FA</li>
          </ul>
          <blockquote className="mt-8 border-l-2 border-[var(--r-line)] pl-4 text-sm italic text-[var(--r-sub)]">
            "Make every effort to present yourself approved to God, an unashamed workman who accurately
            handles the word of truth."
            <footer className="mt-1 not-italic text-[var(--r-sub)]">— 2 Timothy 2:15 (BSB)</footer>
          </blockquote>
        </div>

        {/* Sign in / register form */}
        <div className="flex justify-center lg:justify-start">
        <div className="w-full max-w-sm rounded-2xl border border-[var(--r-line)] bg-[var(--r-bar)] p-8">
          <p className="text-sm uppercase tracking-[0.24em] text-[var(--r-sub)] lg:hidden">Bible Study Project</p>
          <h1 className="mt-2 text-xl font-medium text-[var(--r-text)]">
            {authMode === 'login' ? 'Sign in' : 'Create an account'}
          </h1>
          <form onSubmit={submitAuth} className="mt-6 space-y-4">
            <label className="block text-sm">
              Email
              <input
                type="email"
                required
                autoComplete="email"
                value={authForm.email}
                onChange={(e) => setAuthForm((f) => ({ ...f, email: e.target.value }))}
                className="mt-1 block w-full rounded-xl border border-[var(--r-line)] bg-[var(--r-bg)] px-3 py-2 text-[var(--r-text)] text-sm focus:outline-none focus:ring-2 focus:ring-[var(--r-line)]"
              />
            </label>
            <label className="block text-sm font-medium text-[var(--r-text)]">
              Password
              <input
                type="password"
                required
                minLength={8}
                autoComplete={authMode === 'login' ? 'current-password' : 'new-password'}
                value={authForm.password}
                onChange={(e) => setAuthForm((f) => ({ ...f, password: e.target.value }))}
                className="mt-1 block w-full rounded-xl border border-[var(--r-line)] bg-[var(--r-bg)] px-3 py-2 text-[var(--r-text)] text-sm focus:outline-none focus:ring-2 focus:ring-[var(--r-line)]"
              />
            </label>
            {authError && <p className="text-sm text-[var(--r-danger,#b42318)]">{authError}</p>}
            <button
              type="submit"
              disabled={authBusy}
              className="w-full rounded-full bg-[var(--r-accent)] px-4 py-2.5 text-sm font-medium text-[var(--r-on)] transition hover:opacity-90 disabled:cursor-not-allowed disabled:opacity-50"
            >
              {authBusy ? 'Please wait…' : authMode === 'login' ? 'Sign in' : 'Create account'}
            </button>
          </form>
          <button
            type="button"
            onClick={() => {
              setAuthMode((m) => (m === 'login' ? 'register' : 'login'));
              setAuthError('');
            }}
            className="mt-4 w-full text-center text-sm text-[var(--r-sub)] underline hover:text-[var(--r-text)]"
          >
            {authMode === 'login' ? "Need an account? Sign up" : 'Already have an account? Sign in'}
          </button>
        </div>
        </div>
      </div>
    </div>
  );
}