// ============= Test Cases =============
import type { Equal, Expect } from './test-utils'

interface User {
  name: string
  age: number
  address: string
}

interface UserPartialName {
  name?: string
  age: number
  address: string
}

interface UserPartialNameAndAge {
  name?: string
  age?: number
  address: string
}

type A1 = PartialByKeys<User, 'name'>;
type B1 = UserPartialName;
type C1 = Expect<Equal<A1, B1>>;

type A2 = PartialByKeys<User, 'name' | 'age'>;
type B2 = UserPartialNameAndAge;
type C2 = Expect<Equal<A2, B2>>;

type A3 = PartialByKeys<User>;
type B3 = Partial<User>;
type C3 = Expect<Equal<A3, B3>>;

// @ts-expect-error(2344)
type E1 = PartialByKeys<User, 'name' | 'unknown'>;

// ============= Your Code Here =============
type MergeIntersection<T> = {
  [P in keyof T]: T[P];
}
type PartialByKeys<
  T,
  K extends keyof T = keyof T
> = MergeIntersection<{
  [P in keyof T as P extends K ? P : never]?: T[P]
} & {
  [P in keyof T as P extends K ? never : P]: T[P]
}>

// ============== Alternatives ==============
type Copy<T> = Pick<T, keyof T>;
type PartialByKeys<
  T,
  K extends keyof T = keyof T
> =
  Copy<
    Partial<Pick<T, K>>
    & Omit<T, K>
  >;