import { useState, useEffect } from 'react';
import {
  Center,
  Container,
  Paper,
  Text,
  TextInput,
  PasswordInput,
  Button,
  Anchor,
  Stack,
  Alert,
  Divider,
  Group,
  PinInput,
} from '@mantine/core';
import { useForm } from '@mantine/form';
import {
  IconAlertCircle,
  IconBrandGoogle,
  IconBrandWindows,
  IconFingerprint,
  IconShieldLock,
} from '@tabler/icons-react';
import { useNavigate, Link } from 'react-router-dom';
import { startAuthentication } from '@simplewebauthn/browser';
import api from '../../services/api';
import { useAuthStore } from '../../stores/authStore';
import { usePreferencesStore } from '../../stores/preferencesStore';
import logoSrc from '../../assets/logo.png';

type LoginState = 'credentials' | 'mfa';

export function LoginPage() {
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState('');
  const [loginState, setLoginState] = useState<LoginState>('credentials');
  const [mfaToken, setMfaToken] = useState('');
  const [mfaCode, setMfaCode] = useState('');
  const [useRecovery, setUseRecovery] = useState(false);
  const [recoveryCode, setRecoveryCode] = useState('');
  const [ssoProviders, setSsoProviders] = useState<{ google: boolean; azure: boolean }>({
    google: false,
    azure: false,
  });
  const [passkeySupported, setPasskeySupported] = useState(false);

  const navigate = useNavigate();
  const setAuth = useAuthStore((s) => s.setAuth);
  const isDark = usePreferencesStore((s) => s.colorScheme) === 'dark';

  const form = useForm({
    initialValues: { email: '', password: '' },
    validate: {
      email: (v) => (/^\S+@\S+$/.test(v) ? null : 'Invalid email'),
      password: (v) => (v.length >= 1 ? null : 'Password required'),
    },
  });

  // Fetch SSO providers & check passkey support on mount
  useEffect(() => {
    api
      .get('/auth/sso/providers')
      .then(({ data }) => setSsoProviders(data))
      .catch(() => {});

    if (
      window.PublicKeyCredential &&
      typeof window.PublicKeyCredential === 'function'
    ) {
      setPasskeySupported(true);
    }
  }, []);

  const handleLoginSuccess = (data: any) => {
    setAuth(data.accessToken, data.user, data.organizations);
    if (data.user?.isSuperadmin && data.organizations.length === 0) {
      navigate('/admin');
    } else if (data.organizations.length >= 1) {
      navigate('/select-org');
    } else {
      navigate('/');
    }
  };

  const handleSubmit = async (values: typeof form.values) => {
    setLoading(true);
    setError('');
    try {
      const { data } = await api.post('/auth/login', values);
      if (data.mfaRequired) {
        setMfaToken(data.mfaToken);
        setLoginState('mfa');
      } else {
        handleLoginSuccess(data);
      }
    } catch (err: any) {
      setError(err.response?.data?.message || 'Login failed');
    } finally {
      setLoading(false);
    }
  };

  const handleMfaVerify = async () => {
    setLoading(true);
    setError('');
    try {
      const token = useRecovery ? recoveryCode : mfaCode;
      const { data } = await api.post('/auth/mfa/verify', {
        mfaToken,
        token,
        isRecoveryCode: useRecovery,
      });
      handleLoginSuccess(data);
    } catch (err: any) {
      setError(err.response?.data?.message || 'MFA verification failed');
    } finally {
      setLoading(false);
    }
  };

  const handlePasskeyLogin = async () => {
    setLoading(true);
    setError('');
    try {
      // Get authentication options
      const { data: options } = await api.post('/auth/passkeys/login-options', {
        email: form.values.email || undefined,
      });

      // Trigger browser WebAuthn prompt
      const credential = await startAuthentication({ optionsJSON: options });

      // Verify with server
      const { data } = await api.post('/auth/passkeys/login', {
        response: credential,
        challenge: options.challenge,
      });
      handleLoginSuccess(data);
    } catch (err: any) {
      if (err.name === 'NotAllowedError') {
        setError('Passkey authentication was cancelled');
      } else {
        setError(err.response?.data?.message || err.message || 'Passkey login failed');
      }
    } finally {
      setLoading(false);
    }
  };

  const hasSso = ssoProviders.google || ssoProviders.azure;

  // MFA verification screen
  if (loginState === 'mfa') {
    return (
      <Container size={420} my={80}>
        <Center>
          <img
            src={logoSrc}
            alt="HOA LedgerIQ"
            style={{
              height: 60,
              ...(isDark
                ? {
                    filter:
                      'drop-shadow(0 0 1px rgba(255,255,255,0.8)) drop-shadow(0 0 2px rgba(255,255,255,0.4))',
                  }
                : {}),
            }}
          />
        </Center>

        <Paper withBorder shadow="md" p={30} mt={30} radius="md">
          <Stack>
            <Group gap="xs" justify="center">
              <IconShieldLock size={24} />
              <Text fw={600} size="lg">
                Two-Factor Authentication
              </Text>
            </Group>

            {error && (
              <Alert icon={<IconAlertCircle size={16} />} color="red" variant="light">
                {error}
              </Alert>
            )}

            {!useRecovery ? (
              <>
                <Text size="sm" c="dimmed" ta="center">
                  Enter the 6-digit code from your authenticator app
                </Text>
                <Center>
                  <PinInput
                    length={6}
                    type="number"
                    value={mfaCode}
                    onChange={setMfaCode}
                    oneTimeCode
                    autoFocus
                    size="lg"
                  />
                </Center>
                <Button
                  fullWidth
                  loading={loading}
                  onClick={handleMfaVerify}
                  disabled={mfaCode.length !== 6}
                >
                  Verify
                </Button>
                <Anchor
                  size="sm"
                  ta="center"
                  onClick={() => {
                    setUseRecovery(true);
                    setError('');
                  }}
                  style={{ cursor: 'pointer' }}
                >
                  Use a recovery code instead
                </Anchor>
              </>
            ) : (
              <>
                <Text size="sm" c="dimmed" ta="center">
                  Enter one of your recovery codes
                </Text>
                <TextInput
                  placeholder="xxxxxxxx"
                  value={recoveryCode}
                  onChange={(e) => setRecoveryCode(e.currentTarget.value)}
                  autoFocus
                  ff="monospace"
                />
                <Button
                  fullWidth
                  loading={loading}
                  onClick={handleMfaVerify}
                  disabled={!recoveryCode.trim()}
                >
                  Verify Recovery Code
                </Button>
                <Anchor
                  size="sm"
                  ta="center"
                  onClick={() => {
                    setUseRecovery(false);
                    setError('');
                  }}
                  style={{ cursor: 'pointer' }}
                >
                  Use authenticator code instead
                </Anchor>
              </>
            )}

            <Anchor
              size="sm"
              ta="center"
              onClick={() => {
                setLoginState('credentials');
                setMfaToken('');
                setMfaCode('');
                setRecoveryCode('');
                setError('');
              }}
              style={{ cursor: 'pointer' }}
            >
              ← Back to login
            </Anchor>
          </Stack>
        </Paper>
      </Container>
    );
  }

  // Main login form
  return (
    <Container size={420} my={80}>
      <Center>
        <img
          src={logoSrc}
          alt="HOA LedgerIQ"
          style={{
            height: 60,
            ...(isDark
              ? {
                  filter:
                    'drop-shadow(0 0 1px rgba(255,255,255,0.8)) drop-shadow(0 0 2px rgba(255,255,255,0.4))',
                }
              : {}),
          }}
        />
      </Center>
      <Text c="dimmed" size="sm" ta="center" mt={5}>
        Don&apos;t have an account?{' '}
        <Anchor component={Link} to="/register" size="sm">
          Register
        </Anchor>
      </Text>

      <Paper withBorder shadow="md" p={30} mt={30} radius="md">
        <form onSubmit={form.onSubmit(handleSubmit)}>
          <Stack>
            {error && (
              <Alert icon={<IconAlertCircle size={16} />} color="red" variant="light">
                {error}
              </Alert>
            )}
            <TextInput
              label="Email"
              placeholder="your@email.com"
              required
              {...form.getInputProps('email')}
            />
            <PasswordInput
              label="Password"
              placeholder="Your password"
              required
              {...form.getInputProps('password')}
            />
            <Button type="submit" fullWidth loading={loading}>
              Sign in
            </Button>
          </Stack>
        </form>

        {/* Passkey login */}
        {passkeySupported && (
          <>
            <Divider label="or" labelPosition="center" my="md" />
            <Button
              variant="light"
              fullWidth
              leftSection={<IconFingerprint size={18} />}
              onClick={handlePasskeyLogin}
              loading={loading}
            >
              Sign in with Passkey
            </Button>
          </>
        )}

        {/* SSO providers */}
        {hasSso && (
          <>
            <Divider label="or continue with" labelPosition="center" my="md" />
            <Group grow>
              {ssoProviders.google && (
                <Button
                  variant="default"
                  leftSection={<IconBrandGoogle size={18} color="#4285F4" />}
                  onClick={() => {
                    window.location.href = '/api/auth/google';
                  }}
                >
                  Google
                </Button>
              )}
              {ssoProviders.azure && (
                <Button
                  variant="default"
                  leftSection={<IconBrandWindows size={18} color="#0078D4" />}
                  onClick={() => {
                    window.location.href = '/api/auth/azure';
                  }}
                >
                  Microsoft
                </Button>
              )}
            </Group>
          </>
        )}
      </Paper>
    </Container>
  );
}