react/components/utils/use-context-state/create-geist-context.tsx

import React, { useImperativeHandle } from 'react'
import useContextState, {
  ContextHandler,
  ContextHandlerWhere,
  ContextStateFilter,
  ContextStateOnChange,
  ContextStates,
} from './use-context-state'
import { capitalize } from '../collections'

const makeVirtualValues = <S,>(values: S): ContextStates<S> => {
  const keys = Object.keys(values) as Array<keyof S>
  const handlers = keys.reduce<ContextHandler<S>>((pre, current) => {
    const updateHandler = {
      // eslint-disable-next-line @typescript-eslint/no-unused-vars
      [`set${capitalize(current)}`]: (_next: S[typeof current]) => {},
    }
    return { ...pre, ...updateHandler }
  }, {} as ContextHandler<S>)
  // eslint-disable-next-line @typescript-eslint/no-unused-vars
  const update: ContextHandlerWhere<S> = (_key, _next) => {}
  return {
    update,
    ...values,
    ...handlers,
  }
}

export type GeistNamedContext<T, N> = {
  [key in string as `use${Capitalize<string & N>}Context`]: () => T
}

export type GeistNamedProvider<T, N> = {
  [key in string as `${Capitalize<string & N>}Provider`]: T
}

export const createGeistContext = <S extends Record<string, unknown>, N extends string>(
  name: N,
  initialStates: S,
) => {
  const virtualValues = makeVirtualValues(initialStates)
  const Context = React.createContext<ContextStates<S>>(virtualValues)

  type GeistContextProps = {
    defaultValues?: Partial<S> | (() => Partial<S>)
    onChange?: ContextStateOnChange<S>
    onChangeBefore?: ContextStateFilter<S>
  }

  const GeistContext = React.forwardRef<S, React.PropsWithChildren<GeistContextProps>>(
    ({ defaultValues, children, onChange, onChangeBefore }, ref) => {
      const initialValues =
        typeof defaultValues === 'function' ? (defaultValues as () => S)() : defaultValues
      const mergedValues = {
        ...initialStates,
        ...initialValues,
      } as Required<S>
      const [states, , statesRef] = useContextState(mergedValues, {
        onChange: onChange ? onChange : () => {},
        filter: onChangeBefore ? onChangeBefore : () => true,
      })

      useImperativeHandle(ref, () => statesRef.current, [statesRef.current])

      return <Context.Provider value={states}>{children}</Context.Provider>
    },
  )

  type ResultType = GeistNamedProvider<typeof GeistContext, N> &
    GeistNamedContext<ContextStates<S>, N>

  return {
    [`${capitalize(name)}Provider`]: GeistContext,
    [`use${capitalize(name)}Context`]: () => React.useContext<ContextStates<S>>(Context),
  } as ResultType
}