useForm Hook

import { useState, ChangeEvent } from 'react';

type ValidationRules<T> = {
  [K in keyof T]?: (value: T[K]) => string | null;
};

type FormErrors<T> = { [K in keyof T]?: string };

function useForm<T>(
  initialValues: T,
  validationRules?: ValidationRules<T>
) {
  const [values, setValues] = useState<T>(initialValues);
  const [errors, setErrors] = useState<FormErrors<T>>({});

  const handleChange = (e: ChangeEvent<HTMLInputElement | HTMLSelectElement | HTMLTextAreaElement>) => {
    const { name, value } = e.target;
    setValues(prev => ({ ...prev, [name]: value }));
  };

  const validate = (): boolean => {
    __TOKEN_21__ (!validationRules) return true;
    const newErrors: FormErrors<T> = {};
    Object.entries(validationRules).forEach(([key, rule]) => {
      __TOKEN_24__ (rule) {
        const error = rule(values[key as keyof T]);
        __TOKEN_26__ (error) newErrors[key as keyof T] = error;
      }
    });
    setErrors(newErrors);
    return Object.keys(newErrors).length === 0;
  };

  const reset = () => setValues(initialValues);

  return { values, errors, handleChange, validate, reset };
}

// Usage example
// const { values, errors, handleChange, validate, reset } = useForm({
//   email: '',
//   password: ''
// }, {
//   email: (val) => !val ? 'Email is required' : !/^\S+@\S+\.\S+$/.test(val) ? 'Invalid email' : null,
//   password: (val) => !val ? 'Password is required' : val.length < 6 ? 'Min 6 chars' : null
// });