snippet-pastebin/src/components/ui/form.tsx

import { ComponentProps, createContext, useContext, useId } from "react"
import {
  Controller,
  FormProvider,
  useFormContext,
  useFormState,
  type ControllerProps,
  type FieldPath,
  type FieldValues,
} from "react-hook-form"
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 = 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 = useContext(FormFieldContext)
  const itemContext = 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 = createContext<FormItemContextValue>(
  {} as FormItemContextValue
)

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

  return (
    <FormItemContext.Provider value={{ id }}>
      <div className={cn("mat-mdc-form-field", className)} {...props} />
    </FormItemContext.Provider>
  )
}

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

  return (
    <Label
      className={cn(error && "mat-error", className)}
      htmlFor={formItemId}
      {...props}
    />
  )
}

function FormControl({ className, ...props }: ComponentProps<"div">) {
  const { error, formItemId, formDescriptionId, formMessageId } = useFormField()

  return (
    <div
      id={formItemId}
      aria-describedby={
        !error
          ? `${formDescriptionId}`
          : `${formDescriptionId} ${formMessageId}`
      }
      aria-invalid={!!error}
      className={className}
      {...props}
    />
  )
}

function FormDescription({ className, ...props }: ComponentProps<"p">) {
  const { formDescriptionId } = useFormField()

  return (
    <p
      id={formDescriptionId}
      className={cn("mat-mdc-form-field-hint", className)}
      {...props}
    />
  )
}

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

  if (!body) {
    return null
  }

  return (
    <p
      id={formMessageId}
      className={cn("mat-mdc-form-field-error", className)}
      {...props}
    >
      {body}
    </p>
  )
}

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