applicatives.ts

type Add = (a: number) => (b: number) => (c: number) => number;
const add: Add = a => b => c => a + b + c;

const r = succeed(4).map(add).ap(fail(['err1'])).ap(fail(['err2']));
// const r = succeed(add).ap(succeed(4)).ap(succeed(1)).ap(succeed(2));
// console.log(r);



type Person = {
  firstname: string,
  lastname: string,
  age: number,
}

type CreatePerson = (firstname: string) => (lastname: string) => (age: number) => Person;
const createPerson: CreatePerson = firstname => lastname => age => ({
  firstname,
  lastname,
  age,
});

function createAge(age: number): Result<number, string[]> {
  if (age < 0) {
    return fail(["Age must be positive"]);
  } else if (age > 100) {
    return fail(["Age must be positive"]);
  } else {
    return succeed(age);
  }
}


function createFirstname(firstname: string): Result<string, string[]> {
  if (firstname.length > 10) {
    return fail(["invalid firstname"])
  } else {
    return succeed(firstname);
  }
}

function createLastname(lastname: string): Result<string, string[]> {
  if (lastname.length > 10) {
    return fail(["invalid lastname"])
  } else {
    return succeed(lastname);
  }
}

function validatePerson(firstname: string, lastname: string, age: number): Result<Person, string[]>{
  const firstnameRes = createFirstname(firstname);
  const lastnameRes = createLastname(lastname);
  const ageRes = createAge(age);

  return firstnameRes.map(createPerson).ap(firstnameRes).ap(lastnameRes).ap(ageRes);
}

console.log(validatePerson('Vincent', 'Cordobes', -14))