leetcode-hire-writeup-typescript.ts

// LeetCode Hire Writeup

interface Action<T> {
  payload?: T;
  type: string;
}

class EffectModule {
  count = 1;
  message = "hello!";

  delay(input: Promise<number>) {
    return input.then(i => ({
      payload: `hello ${i}!`,
      type: 'delay'
    }));
  }

  setMessage(action: Action<Date>) {
    return {
      payload: action.payload!.getMilliseconds(),
      type: "set-message"
    };
  }
}

type FuncName<T> = { [P in keyof T]: T[P] extends Function ? P : never }[keyof T];
type ParamType<T> = T extends (param: infer P) => any ? P : T;
type PromiseType<T> = T extends Promise<infer U> ? U : T;
type PickParam<T> = T extends Promise<infer U> ? U : (T extends Action<infer V> ? V : T);

type Connect = (module: EffectModule) => {
  [T in FuncName<EffectModule>]: (x: PickParam<ParamType<EffectModule[T]>>) => PromiseType<ReturnType<EffectModule[T]>>
};

const connect: Connect = m => ({
  delay: (input: number) => ({
    type: 'delay',
    payload: `hello ${input}`
  }),
  setMessage: (input: Date) => ({
    type: "set-message",
    payload: input.getMilliseconds()
  })
});

type Connected = {
  delay(input: number): Action<string>;
  setMessage(action: Date): Action<number>;
};

export const connected: Connected = connect(new EffectModule());