frontend/src/components/ui/form.tsx

import * as React from 'react';
import {
  Controller,
  FormProvider,
  useFormContext,
  useFormState,
  type ControllerProps,
  type FieldPath,
  type FieldValues,
} from 'react-hook-form';
import * as LabelPrimitive from '@radix-ui/react-label';
import { Slot } from '@radix-ui/react-slot';
import { cn } from '@/lib/utils';
import { Label } from '@/components/ui/label';

const Form = FormProvider;

type FormFieldContextValue<
  TFieldValues extends FieldValues = FieldValues,
  TName extends FieldPath<TFieldValues> = FieldPath<TFieldValues>,
> = {
  name: TName;
};

const FormFieldContext = React.createContext<FormFieldContextValue>({} as FormFieldContextValue);

const FormField = <TFieldValues extends FieldValues = FieldValues, TName extends FieldPath<TFieldValues> = FieldPath<TFieldValues>>({
  ...props
}: ControllerProps<TFieldValues, TName>) => {
  return (
    <FormFieldContext.Provider value={{ name: props.name }}>
      <Controller {...props} />
    </FormFieldContext.Provider>
  );
};

const useFormField = () => {
  const fieldContext = React.useContext(FormFieldContext);
  const itemContext = React.useContext(FormItemContext);
  const { getFieldState } = useFormContext();
  const formState = useFormState({ name: fieldContext.name });
  const fieldState = getFieldState(fieldContext.name, formState);

  if (!fieldContext) {
    throw new Error('useFormField should be used within <FormField>');
  }

  const { id } = itemContext;

  return {
    id,
    name: fieldContext.name,
    formItemId: `${id}-form-item`,
    formDescriptionId: `${id}-form-item-description`,
    formMessageId: `${id}-form-item-message`,
    ...fieldState,
  };
};

type FormItemContextValue = {
  id: string;
};

const FormItemContext = React.createContext<FormItemContextValue>({} as FormItemContextValue);

function FormItem({ className, ...props }: React.ComponentProps<'div'>) {
  const id = React.useId();

  return (
    <FormItemContext.Provider value={{ id }}>
      <div data-slot='form-item' className={cn('grid gap-2', className)} {...props} />
    </FormItemContext.Provider>
  );
}

function FormLabel({ className, ...props }: React.ComponentProps<typeof LabelPrimitive.Root>) {
  const { error, formItemId } = useFormField();

  return (
    <Label
      data-slot='form-label'
      data-error={!!error}
      className={cn('data-[error=true]:text-destructive', className)}
      htmlFor={formItemId}
      {...props}
    />
  );
}

function FormControl({ ...props }: React.ComponentProps<typeof Slot>) {
  const { error, formItemId, formDescriptionId, formMessageId } = useFormField();

  return (
    <Slot
      data-slot='form-control'
      id={formItemId}
      aria-describedby={!error ? `${formDescriptionId}` : `${formDescriptionId} ${formMessageId}`}
      aria-invalid={!!error}
      {...props}
    />
  );
}

function FormDescription({ className, asChild, ...props }: React.ComponentProps<'p'> & { asChild?: boolean }) {
  const { formDescriptionId } = useFormField();
  const Comp = asChild ? Slot : 'p';

  return <Comp data-slot='form-description' id={formDescriptionId} className={cn('text-muted-foreground text-sm', className)} {...props} />;
}

function FormMessage({ className, ...props }: React.ComponentProps<'p'>) {
  const { error, formMessageId } = useFormField();
  const body = error ? String(error?.message ?? '') : props.children;

  if (!body) {
    return null;
  }

  return (
    <p data-slot='form-message' id={formMessageId} {...props} className={cn('text-destructive text-sm', className)}>
      {body}
    </p>
  );
}

export { useFormField, Form, FormItem, FormLabel, FormControl, FormDescription, FormMessage, FormField };