enum.ts

import { createFail, setupInternalRuntype, Runtype } from './runtype'
import { debugValue } from './runtypeError'

type EnumObject = { [key: string]: string | number }

/**
 * Any value defined in the enumObject.
 */
function enumRuntype<T extends EnumObject, S extends keyof T>(
  enumObject: T,
): Runtype<T[S]> {
  return setupInternalRuntype(
    (v, failOrThrow) => {
      // use the fast reverse lookup of number enums to check whether v is a
      // value of the enum
      if (
        typeof v === 'number' &&
        (enumObject as any)[v as any] !== undefined
      ) {
        return (v as unknown) as T[S]
      }

      if (Object.values(enumObject).indexOf(v as any) !== -1) {
        return v as T[S]
      }

      return createFail(
        failOrThrow,
        `expected a value that belongs to the enum ${debugValue(enumObject)}`,
        v,
      )
    },
    { isPure: true },
  )
}

export { enumRuntype as enum }