Add the ability to serialize types about io-ts HOT 3 CLOSED

import * as t from 'io-ts'
import { pathReporterFailure } from 'io-ts/lib/reporters/default'
import { Option, none, some } from 'fp-ts/lib/Option'

// given a runtime type for T returns a runtime type for Option<T>
export function createOption<A>(type: t.Type<A | null | undefined>): t.Type<Option<A>> {
  return t.mapWithName(v => (v === null ? none : some(v)), type, `Option<${type.name}>`)
}

const Id = createOption(t.number)

const T = t.interface({
  id: Id
})

// helper for this demo
function validate<A>(value: any, type: t.Type<A>): A {
  return t.validate(value, type).fold(errors => {
    throw new Error(pathReporterFailure(errors).join('\n'))
  }, x => x)
}

console.log(validate('wrong', T)) // Invalid value "wrong" supplied to : { id: Option<number> }
console.log(validate({}, T)) // Invalid value undefined supplied to : { id: Option<number> }/id: Option<number>
console.log(validate({ id: 'wrong' }, T)) // Invalid value "wrong" supplied to : { id: Option<number> }/id: Option<number>
console.log(validate({ id: 1 }, T)) // { id: Some(1) }

console.log(JSON.stringify({ id: some(1) })) // {"id":{"value":1,"_tag":"Some"}}

// module augmentation
declare module 'fp-ts/lib/Option' {
  interface None<A> {
    toJSON(): A | null
  }
  interface Some<A> {
    toJSON(): A | null
  }
}

None.prototype.toJSON = () => null
Some.prototype.toJSON = function<A>(this: Some<A>): A {
  return this.value
}

console.log(JSON.stringify({ id: none })) // {"id":null}
console.log(JSON.stringify({ id: some(1) })) // {"id":1}

console.log(validate(JSON.parse(JSON.stringify({ id: some(1) })), T)) // { id: Some(1) }