'use client';

import React, { useState } from 'react';
import {
  Box,
  TextField,
  Button,
  Typography,
  Paper,
  InputAdornment,
  IconButton,
  Alert,
  CircularProgress,
  Link as MuiLink,
  Checkbox,
  FormControlLabel,
} from '@mui/material';
import { Visibility, VisibilityOff } from '@mui/icons-material';
import { useForm } from 'react-hook-form';
import { zodResolver } from '@hookform/resolvers/zod';
import { motion } from 'framer-motion';
import * as z from 'zod';
import { useAuth } from '@/lib/auth/AuthContext';
import Link from 'next/link';
import { useTheme } from '@mui/material/styles';

const registerSchema = z.object({
  name: z.string().min(2, 'Name must be at least 2 characters'),
  email: z.string().email('Invalid email address'),
  password: z.string()
    .min(8, 'Password must be at least 8 characters')
    .regex(/[A-Z]/, 'Password must contain at least one uppercase letter')
    .regex(/[a-z]/, 'Password must contain at least one lowercase letter')
    .regex(/[0-9]/, 'Password must contain at least one number'),
  confirmPassword: z.string(),
  dateOfBirth: z.string().min(1, 'Date of birth is required'),
  parentalEmail: z.string().email('Invalid email address').optional().or(z.literal('')),
  agreeToTerms: z.boolean().refine(val => val === true, {
    message: 'You must agree to the Terms of Service',
  }),
  agreeToPrivacy: z.boolean().refine(val => val === true, {
    message: 'You must agree to the Privacy Policy',
  }),
  coppaConsent: z.boolean().optional(),
}).refine((data) => data.password === data.confirmPassword, {
  message: 'Passwords do not match',
  path: ['confirmPassword'],
}).refine((data) => {
  // Check if user is under 18 and requires parental consent
  const birthDate = new Date(data.dateOfBirth);
  const today = new Date();
  const age = today.getFullYear() - birthDate.getFullYear() -
    (today.getMonth() < birthDate.getMonth() ||
     (today.getMonth() === birthDate.getMonth() && today.getDate() < birthDate.getDate()) ? 1 : 0);

  if (age < 13) {
    return false; // Users under 13 cannot register (COPPA compliance)
  }

  if (age >= 13 && age < 18) {
    // Users 13-17 need parental email and consent
    return !!data.parentalEmail && data.parentalEmail.length > 0 && data.coppaConsent === true;
  }

  return true;
}, {
  message: 'Users under 13 cannot create an account. Users 13-17 require parental consent and email.',
  path: ['dateOfBirth'],
});

type RegisterFormData = z.infer<typeof registerSchema>;

export default function RegisterPage() {
  const theme = useTheme();
  const [showPassword, setShowPassword] = useState(false);
  const [showConfirmPassword, setShowConfirmPassword] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const [isLoading, setIsLoading] = useState(false);
  const [userAge, setUserAge] = useState<number | null>(null);
  const [requiresParentalConsent, setRequiresParentalConsent] = useState(false);
  const { register: registerUser } = useAuth();

  const {
    register,
    handleSubmit,
    watch,
    formState: { errors },
  } = useForm<RegisterFormData>({
    resolver: zodResolver(registerSchema),
    defaultValues: {
      agreeToTerms: false,
      agreeToPrivacy: false,
      coppaConsent: false,
    },
  });

  // Watch date of birth to calculate age and show parental consent if needed
  const dateOfBirth = watch('dateOfBirth');

  // Calculate age when date of birth changes
  const calculateAge = (dob: string): number | null => {
    if (!dob) return null;
    const birthDate = new Date(dob);
    const today = new Date();
    const age = today.getFullYear() - birthDate.getFullYear() -
      (today.getMonth() < birthDate.getMonth() ||
       (today.getMonth() === birthDate.getMonth() && today.getDate() < birthDate.getDate()) ? 1 : 0);
    return age;
  };

  // Update age and parental consent requirement when DOB changes
  React.useEffect(() => {
    if (dateOfBirth) {
      const age = calculateAge(dateOfBirth);
      setUserAge(age);
      setRequiresParentalConsent(age !== null && age >= 13 && age < 18);
    } else {
      setUserAge(null);
      setRequiresParentalConsent(false);
    }
  }, [dateOfBirth]);

  const onSubmit = async (data: RegisterFormData) => {
    setError(null);
    setIsLoading(true);

    try {
      await registerUser({
        name: data.name,
        email: data.email,
        password: data.password,
        dateOfBirth: data.dateOfBirth,
        parentalEmail: data.parentalEmail || undefined,
        coppaConsentGiven: data.coppaConsent || false,
      });
      // Navigation to onboarding is handled in the register function
    } catch (err: any) {
      setError(err.message || 'Failed to register. Please try again.');
    } finally {
      setIsLoading(false);
    }
  };

  return (
    <Box
      sx={{
        minHeight: '100vh',
        display: 'flex',
        flexDirection: 'column',
        justifyContent: 'center',
        px: 3,
        py: 6,
        background: `linear-gradient(135deg, ${theme.palette.primary.light} 0%, ${theme.palette.secondary.light} 100%)`,
      }}
    >
      <motion.div
        initial={{ opacity: 0, y: 20 }}
        animate={{ opacity: 1, y: 0 }}
        transition={{ duration: 0.5 }}
      >
        <Paper
          elevation={0}
          sx={{
            p: 4,
            borderRadius: 4,
            maxWidth: 440,
            mx: 'auto',
            background: 'rgba(255, 255, 255, 0.95)',
            backdropFilter: 'blur(10px)',
          }}
        >
          <Typography
            variant="h4"
            gutterBottom
            align="center"
            fontWeight="600"
            color="primary.main"
          >
            Create Account ✨
          </Typography>
          <Typography
            variant="body2"
            align="center"
            color="text.secondary"
            sx={{ mb: 3 }}
          >
            Start your journey to organized parenting
          </Typography>

          {error && (
            <Alert severity="error" sx={{ mb: 3, borderRadius: 2 }}>
              {error}
            </Alert>
          )}

          <Box component="form" onSubmit={handleSubmit(onSubmit)} noValidate>
            <TextField
              fullWidth
              label="Full Name"
              margin="normal"
              error={!!errors.name}
              helperText={errors.name?.message}
              {...register('name')}
              disabled={isLoading}
              required
              inputProps={{
                'aria-required': 'true',
                'aria-invalid': !!errors.name,
                'aria-describedby': errors.name ? 'name-error' : undefined,
              }}
              InputProps={{
                sx: { borderRadius: 3 },
              }}
              FormHelperTextProps={{
                id: errors.name ? 'name-error' : undefined,
                role: errors.name ? 'alert' : undefined,
              }}
            />

            <TextField
              fullWidth
              label="Email"
              type="email"
              margin="normal"
              error={!!errors.email}
              helperText={errors.email?.message}
              {...register('email')}
              disabled={isLoading}
              required
              inputProps={{
                autoComplete: 'username',
                'aria-required': 'true',
                'aria-invalid': !!errors.email,
                'aria-describedby': errors.email ? 'email-error' : undefined,
              }}
              InputProps={{
                sx: { borderRadius: 3 },
              }}
              FormHelperTextProps={{
                id: errors.email ? 'email-error' : undefined,
                role: errors.email ? 'alert' : undefined,
              }}
            />

            <TextField
              fullWidth
              label="Password"
              type={showPassword ? 'text' : 'password'}
              margin="normal"
              error={!!errors.password}
              helperText={errors.password?.message}
              {...register('password')}
              disabled={isLoading}
              required
              inputProps={{
                autoComplete: 'new-password',
                'aria-required': 'true',
                'aria-invalid': !!errors.password,
                'aria-describedby': errors.password ? 'password-error' : undefined,
              }}
              InputProps={{
                sx: { borderRadius: 3 },
                endAdornment: (
                  <InputAdornment position="end">
                    <IconButton
                      onClick={() => setShowPassword(!showPassword)}
                      edge="end"
                      disabled={isLoading}
                      aria-label={showPassword ? 'Hide password' : 'Show password'}
                    >
                      {showPassword ? <VisibilityOff /> : <Visibility />}
                    </IconButton>
                  </InputAdornment>
                ),
              }}
              FormHelperTextProps={{
                id: errors.password ? 'password-error' : undefined,
                role: errors.password ? 'alert' : undefined,
              }}
            />

            <TextField
              fullWidth
              label="Confirm Password"
              type={showConfirmPassword ? 'text' : 'password'}
              margin="normal"
              error={!!errors.confirmPassword}
              helperText={errors.confirmPassword?.message}
              {...register('confirmPassword')}
              disabled={isLoading}
              required
              inputProps={{
                autoComplete: 'new-password',
                'aria-required': 'true',
                'aria-invalid': !!errors.confirmPassword,
                'aria-describedby': errors.confirmPassword ? 'confirm-password-error' : undefined,
              }}
              InputProps={{
                sx: { borderRadius: 3 },
                endAdornment: (
                  <InputAdornment position="end">
                    <IconButton
                      onClick={() => setShowConfirmPassword(!showConfirmPassword)}
                      edge="end"
                      disabled={isLoading}
                      aria-label={showConfirmPassword ? 'Hide password' : 'Show password'}
                    >
                      {showConfirmPassword ? <VisibilityOff /> : <Visibility />}
                    </IconButton>
                  </InputAdornment>
                ),
              }}
              FormHelperTextProps={{
                id: errors.confirmPassword ? 'confirm-password-error' : undefined,
                role: errors.confirmPassword ? 'alert' : undefined,
              }}
            />

            <TextField
              fullWidth
              label="Date of Birth"
              type="date"
              margin="normal"
              error={!!errors.dateOfBirth}
              helperText={errors.dateOfBirth?.message || 'Required for COPPA compliance (users under 13 cannot register)'}
              {...register('dateOfBirth')}
              disabled={isLoading}
              required
              InputLabelProps={{
                shrink: true,
              }}
              inputProps={{
                'aria-required': 'true',
                'aria-invalid': !!errors.dateOfBirth,
                'aria-describedby': errors.dateOfBirth ? 'dob-error' : 'dob-helper',
              }}
              InputProps={{
                sx: { borderRadius: 3 },
              }}
              FormHelperTextProps={{
                id: errors.dateOfBirth ? 'dob-error' : 'dob-helper',
                role: errors.dateOfBirth ? 'alert' : undefined,
              }}
            />

            {userAge !== null && userAge < 13 && (
              <Alert severity="error" sx={{ mt: 2 }}>
                Users under 13 years old cannot create an account per COPPA regulations.
              </Alert>
            )}

            {requiresParentalConsent && (
              <Box sx={{ mt: 2 }}>
                <Alert severity="info" sx={{ mb: 2 }}>
                  As you are under 18, parental consent is required to create an account.
                </Alert>
                <TextField
                  fullWidth
                  label="Parent/Guardian Email"
                  type="email"
                  margin="normal"
                  error={!!errors.parentalEmail}
                  helperText={errors.parentalEmail?.message || 'We will send a consent email to your parent/guardian'}
                  {...register('parentalEmail')}
                  disabled={isLoading}
                  required
                  inputProps={{
                    'aria-required': 'true',
                    'aria-invalid': !!errors.parentalEmail,
                    'aria-describedby': errors.parentalEmail ? 'parental-email-error' : 'parental-email-helper',
                  }}
                  InputProps={{
                    sx: { borderRadius: 3 },
                  }}
                  FormHelperTextProps={{
                    id: errors.parentalEmail ? 'parental-email-error' : 'parental-email-helper',
                    role: errors.parentalEmail ? 'alert' : undefined,
                  }}
                />
                <FormControlLabel
                  control={
                    <Checkbox
                      {...register('coppaConsent')}
                      disabled={isLoading}
                      required
                      inputProps={{
                        'aria-required': 'true',
                        'aria-invalid': !!errors.coppaConsent,
                        'aria-describedby': errors.coppaConsent ? 'coppa-consent-error' : undefined,
                      } as any}
                    />
                  }
                  label={
                    <Typography variant="body2" color="text.secondary">
                      I confirm that I have my parent/guardian&apos;s permission to create this account
                    </Typography>
                  }
                  sx={{ mt: 1 }}
                />
                {errors.coppaConsent && (
                  <Typography variant="caption" color="error" sx={{ display: 'block', mt: 1 }} id="coppa-consent-error" role="alert">
                    Parental consent is required for users under 18
                  </Typography>
                )}
              </Box>
            )}

            <Box sx={{ mt: 2 }}>
              <FormControlLabel
                control={
                  <Checkbox
                    {...register('agreeToTerms')}
                    disabled={isLoading}
                    inputProps={{
                      'aria-required': 'true',
                      'aria-invalid': !!errors.agreeToTerms,
                      'aria-describedby': errors.agreeToTerms ? 'terms-error' : undefined,
                    } as any}
                  />
                }
                label={
                  <Typography variant="body2" color="text.secondary" component="span">
                    I agree to the{' '}
                    <MuiLink href="/terms" target="_blank" underline="hover">
                      Terms of Service
                    </MuiLink>
                    {' '}<Typography component="span" color="error.main">*</Typography>
                  </Typography>
                }
                sx={{ alignItems: 'flex-start', mb: 1 }}
              />
              {errors.agreeToTerms && (
                <Typography variant="caption" color="error" sx={{ display: 'block', mt: 0.5, ml: 4 }} id="terms-error" role="alert">
                  {errors.agreeToTerms.message}
                </Typography>
              )}

              <FormControlLabel
                control={
                  <Checkbox
                    {...register('agreeToPrivacy')}
                    disabled={isLoading}
                    inputProps={{
                      'aria-required': 'true',
                      'aria-invalid': !!errors.agreeToPrivacy,
                      'aria-describedby': errors.agreeToPrivacy ? 'privacy-error' : undefined,
                    } as any}
                  />
                }
                label={
                  <Typography variant="body2" color="text.secondary" component="span">
                    I agree to the{' '}
                    <MuiLink href="/privacy" target="_blank" underline="hover">
                      Privacy Policy
                    </MuiLink>
                    {' '}<Typography component="span" color="error.main">*</Typography>
                  </Typography>
                }
                sx={{ alignItems: 'flex-start', mb: 1 }}
              />
              {errors.agreeToPrivacy && (
                <Typography variant="caption" color="error" sx={{ display: 'block', mt: 0.5, ml: 4 }} id="privacy-error" role="alert">
                  {errors.agreeToPrivacy.message}
                </Typography>
              )}
            </Box>

            <Button
              fullWidth
              type="submit"
              variant="contained"
              size="large"
              disabled={isLoading}
              sx={{ mt: 3, mb: 2 }}
            >
              {isLoading ? (
                <CircularProgress size={24} color="inherit" />
              ) : (
                'Create Account'
              )}
            </Button>
          </Box>

          <Box sx={{ mt: 3, textAlign: 'center' }}>
            <Typography variant="body2" color="text.secondary">
              Already have an account?{' '}
              <MuiLink component={Link} href="/login" sx={{ cursor: 'pointer', fontWeight: 600 }}>
                Sign in
              </MuiLink>
            </Typography>
          </Box>
        </Paper>
      </motion.div>
    </Box>
  );
}
