import { useEffect, useState } from 'react';
import {
  Container, Paper, Title, Text, TextInput, PasswordInput,
  Button, Stack, Alert, Center, Loader, Progress, Anchor,
} from '@mantine/core';
import { useForm } from '@mantine/form';
import { IconAlertCircle, IconCheck, IconShieldCheck } from '@tabler/icons-react';
import { useSearchParams, useNavigate, Link } from 'react-router-dom';
import api from '../../services/api';
import { useAuthStore } from '../../stores/authStore';
import logoSrc from '../../assets/logo.png';

function getPasswordStrength(pw: string): number {
  let score = 0;
  if (pw.length >= 8) score += 25;
  if (pw.length >= 12) score += 15;
  if (/[A-Z]/.test(pw)) score += 20;
  if (/[a-z]/.test(pw)) score += 10;
  if (/[0-9]/.test(pw)) score += 15;
  if (/[^A-Za-z0-9]/.test(pw)) score += 15;
  return Math.min(score, 100);
}

function strengthColor(s: number): string {
  if (s < 40) return 'red';
  if (s < 70) return 'orange';
  return 'green';
}

export function ActivatePage() {
  const [searchParams] = useSearchParams();
  const navigate = useNavigate();
  const setAuth = useAuthStore((s) => s.setAuth);
  const token = searchParams.get('token');

  const [validating, setValidating] = useState(true);
  const [tokenInfo, setTokenInfo] = useState<any>(null);
  const [error, setError] = useState('');
  const [loading, setLoading] = useState(false);

  const form = useForm({
    initialValues: { fullName: '', password: '', confirmPassword: '' },
    validate: {
      fullName: (v) => (v.trim().length >= 2 ? null : 'Name is required'),
      password: (v) => (v.length >= 8 ? null : 'Password must be at least 8 characters'),
      confirmPassword: (v, values) => (v === values.password ? null : 'Passwords do not match'),
    },
  });

  useEffect(() => {
    if (!token) {
      setError('No activation token provided');
      setValidating(false);
      return;
    }

    api.get(`/auth/activate?token=${token}`)
      .then(({ data }) => {
        setTokenInfo(data);
        setValidating(false);
      })
      .catch((err) => {
        setError(err.response?.data?.message || 'Invalid or expired activation link');
        setValidating(false);
      });
  }, [token]);

  const handleSubmit = async (values: typeof form.values) => {
    setLoading(true);
    setError('');
    try {
      const { data } = await api.post('/auth/activate', {
        token,
        password: values.password,
        fullName: values.fullName,
      });
      setAuth(data.accessToken, data.user, data.organizations);
      navigate('/onboarding');
    } catch (err: any) {
      setError(err.response?.data?.message || 'Activation failed');
    } finally {
      setLoading(false);
    }
  };

  const passwordStrength = getPasswordStrength(form.values.password);

  if (validating) {
    return (
      <Container size={420} my={80}>
        <Center><Loader size="lg" /></Center>
        <Text ta="center" mt="md" c="dimmed">Validating activation link...</Text>
      </Container>
    );
  }

  if (error && !tokenInfo) {
    return (
      <Container size={420} my={80}>
        <Center>
          <img src={logoSrc} alt="HOA LedgerIQ" style={{ height: 50 }} />
        </Center>
        <Paper withBorder shadow="md" p={30} mt={30} radius="md">
          <Alert icon={<IconAlertCircle size={16} />} color="red" variant="light" mb="md">
            {error}
          </Alert>
          <Stack>
            <Anchor component={Link} to="/login" size="sm" ta="center">
              Go to Login
            </Anchor>
          </Stack>
        </Paper>
      </Container>
    );
  }

  return (
    <Container size={420} my={80}>
      <Center>
        <img src={logoSrc} alt="HOA LedgerIQ" style={{ height: 50 }} />
      </Center>
      <Text ta="center" mt={5} c="dimmed" size="sm">
        Activate your account for <strong>{tokenInfo?.orgName || 'your organization'}</strong>
      </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="Full Name"
              placeholder="John Doe"
              required
              {...form.getInputProps('fullName')}
            />

            <div>
              <PasswordInput
                label="Password"
                placeholder="Create a strong password"
                required
                {...form.getInputProps('password')}
              />
              {form.values.password && (
                <Progress
                  value={passwordStrength}
                  color={strengthColor(passwordStrength)}
                  size="xs"
                  mt={4}
                />
              )}
            </div>

            <PasswordInput
              label="Confirm Password"
              placeholder="Confirm your password"
              required
              {...form.getInputProps('confirmPassword')}
            />

            <Button
              type="submit"
              fullWidth
              loading={loading}
              leftSection={<IconShieldCheck size={16} />}
            >
              Activate Account
            </Button>
          </Stack>
        </form>
      </Paper>
    </Container>
  );
}