5821-maptypes.ts

/**
 * 5821 - MapTypes
 *
 * Implement `MapTypes<T, R>` which will transform types in object T to different types defined by type R which has the following structure
 *
 * ```ts
 * type StringToNumber = {
 *   mapFrom: string; // value of key which value is string
 *   mapTo: number; // will be transformed for number
 * }
 * ```
 *
 * ## Examples:
 *
 * ```ts
 * type StringToNumber = { mapFrom: string; mapTo: number;}
 * MapTypes<{iWillBeANumberOneDay: string}, StringToNumber> // gives { iWillBeANumberOneDay: number; }
 * ```
 *
 * Be aware that user can provide a union of types:
 * ```ts
 * type StringToNumber = { mapFrom: string; mapTo: number;}
 * type StringToDate = { mapFrom: string; mapTo: Date;}
 * MapTypes<{iWillBeNumberOrDate: string}, StringToDate | StringToNumber> // gives { iWillBeNumberOrDate: number | Date; }
 * ```
 *
 * If the type doesn't exist in our map, leave it as it was:
 * ```ts
 * type StringToNumber = { mapFrom: string; mapTo: number;}
 * MapTypes<{iWillBeANumberOneDay: string, iWillStayTheSame: Function}, StringToNumber> // // gives { iWillBeANumberOneDay: number, iWillStayTheSame: Function }
 * ```
 *
 *
 */

/* _____________ Your Code Here _____________ */

type Option<From = any, To = any> = { mapFrom: From, mapTo: To };

type MapTypes<T, R extends Option<any, any>> = {
  [Key in keyof T]: (R extends Option<T[Key]> ? R['mapTo'] : never) extends infer Val
    ? [Val] extends [never]
      ? T[Key]
      : Val
    : never
}


/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<MapTypes<{ stringToArray: string }, { mapFrom: string, mapTo: [] }>, { stringToArray: [] }>>,
  Expect<Equal<MapTypes<{ stringToNumber: string }, { mapFrom: string, mapTo: number }>, { stringToNumber: number }>>,
  Expect<Equal<MapTypes<{ stringToNumber: string, skipParsingMe: boolean }, { mapFrom: string, mapTo: number }>, { stringToNumber: number, skipParsingMe: boolean }>>,
  Expect<Equal<MapTypes<{ date: string }, { mapFrom: string, mapTo: Date } | { mapFrom: string, mapTo: null }>, { date: null | Date }>>,
  Expect<Equal<MapTypes<{ date: string }, { mapFrom: string, mapTo: Date | null }>, { date: null | Date }>>,
  Expect<Equal<MapTypes<{ fields: Record<string, boolean> }, { mapFrom: Record<string, boolean>, mapTo: string[] }>, { fields: string[] }>>,
  Expect<Equal<MapTypes<{ name: string }, { mapFrom: boolean, mapTo: never }>, { name: string }>>,
  Expect<Equal<MapTypes<{ name: string, date: Date }, { mapFrom: string, mapTo: boolean } | { mapFrom: Date, mapTo: string }>, { name: boolean, date: string }>>,
]