import { useState, FormEvent } from 'react';
import { Link, useNavigate } from 'react-router-dom';
import { Shield } from 'lucide-react';
import api from '../lib/api';
import { useAuthStore } from '../lib/store';
import { deriveKeyFromPassword, decryptMasterKey } from '../crypto';
import { socket } from '../lib/ws';

export default function LoginPage() {
  const navigate = useNavigate();
  const { setAuth, setMasterKey, setUsername } = useAuthStore();
  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [totpCode, setTotpCode] = useState('');
  const [require2fa, setRequire2fa] = useState(false);
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState('');

  async function submit(e: FormEvent) {
    e.preventDefault();
    setError('');
    setLoading(true);

    try {
      const res = await api.post('/auth/login', {
        email,
        password,
        ...(totpCode ? { totpCode } : {}),
      });

      if (res.data.require2fa) {
        setRequire2fa(true);
        setLoading(false);
        return;
      }

      const { accessToken, refreshToken, userId, kdfSalt, encryptedMasterKey, username } =
        res.data;

      // Derive key from password — never leaves the browser
      const derived = await deriveKeyFromPassword(password, kdfSalt);
      const masterKey = await decryptMasterKey(encryptedMasterKey, derived);

      setAuth({ accessToken, refreshToken, userId });
      setMasterKey(masterKey);
      setUsername(username);

      socket.connect(accessToken);
      navigate('/messages');
    } catch (err: any) {
      setError(err.response?.data?.error || 'Login failed');
    } finally {
      setLoading(false);
    }
  }

  return (
    <div className="min-h-screen flex items-center justify-center p-4">
      <div className="w-full max-w-sm">
        <div className="flex flex-col items-center mb-8">
          <Shield className="w-12 h-12 text-accent mb-3" />
          <h1 className="text-2xl font-bold">CloudLink</h1>
          <p className="text-slate-400 text-sm mt-1">End-to-end encrypted</p>
        </div>

        <form onSubmit={submit} className="bg-surface-1 rounded-xl p-6 space-y-4 border border-slate-700">
          <h2 className="font-semibold text-lg">Sign in</h2>

          {error && <p className="text-red-400 text-sm">{error}</p>}

          {!require2fa ? (
            <>
              <Field label="Email" type="email" value={email} onChange={setEmail} />
              <Field label="Password" type="password" value={password} onChange={setPassword} />
            </>
          ) : (
            <div>
              <label className="block text-sm text-slate-400 mb-1">Authenticator code</label>
              <input
                className="input w-full"
                type="text"
                inputMode="numeric"
                maxLength={6}
                placeholder="000000"
                value={totpCode}
                onChange={(e) => setTotpCode(e.target.value)}
                autoFocus
              />
            </div>
          )}

          <button
            type="submit"
            disabled={loading}
            className="btn-primary w-full"
          >
            {loading ? 'Signing in…' : require2fa ? 'Verify' : 'Sign in'}
          </button>
        </form>

        <p className="text-center text-sm text-slate-400 mt-4">
          No account?{' '}
          <Link to="/register" className="text-accent hover:underline">
            Register
          </Link>
        </p>
      </div>
    </div>
  );
}

function Field({
  label,
  type,
  value,
  onChange,
}: {
  label: string;
  type: string;
  value: string;
  onChange: (v: string) => void;
}) {
  return (
    <div>
      <label className="block text-sm text-slate-400 mb-1">{label}</label>
      <input
        className="input w-full"
        type={type}
        value={value}
        onChange={(e) => onChange(e.target.value)}
        required
      />
    </div>
  );
}