/*
  9 - Deep Readonly
  -------
  by Anthony Fu (@antfu) #medium #readonly #object-keys #deep
  
  ### Question
  
  Implement a generic `DeepReadonly<T>` which make every parameter of an object - and its sub-objects recursively - readonly.
  
  You can assume that we are only dealing with Objects in this challenge. Arrays, Functions, Classes and so on are no need to take into consideration. However, you can still challenge your self by covering different cases as many as possbile.
  
  For example
  
  ```ts
  type X = { 
    x: { 
      a: 1
      b: 'hi'
    }
    y: 'hey'
  }
  
  type Expected = { 
    readonly x: { 
      readonly a: 1
      readonly b: 'hi'
    }
    readonly y: 'hey' 
  }
  
  const todo: DeepReadonly<X> // should be same as `Expected`

View on GitHub: https://tsch.js.org/9 */

/* _____________ Your Code Here _____________ */

type DeepReadonly<T> = any

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

type cases = [ Expect<Equal<DeepReadonly<X>, Expected>>, ]

type X = { a: () => 22 b: string c: { d: boolean e: { g: { h: { i: true j: 'string' } k: 'hello' } } } }

type Expected = { readonly a: () => 22 readonly b: string readonly c: { readonly d: boolean readonly e: { readonly g: { readonly h: { readonly i: true readonly j: 'string' } readonly k: 'hello' } } } }

/* _____________ Further Steps _____________ / /

Share your solutions: https://tsch.js.org/9/answer View solutions: https://tsch.js.org/9/solutions More Challenges: https://tsch.js.org */

재귀가 필요한 문제이다.

```tsx
type DeepReadonly<T> = keyof T extends never
  ? T
  : { readonly [k in keyof T]: DeepReadonly<T[k]> };

더이상 접근할 프로퍼티가 없으면 T 현재 값을 그대로 리턴하고 아니면 readonly로 만드는데 재귀적으로 동작시킨다.