import { Algebra, Monad } from './interfaces.js'

/** @import { Apply, Chain, Fn, Functor, Morphism } from './types.js' */

/** @template {Fn} T */
export class IO extends Algebra(Monad) {
  _effect

  /**
   * @param {T} effect
   */
  constructor(effect) {
    super()
    this._effect = effect
  }

  /**
   * @template {Fn} T
   * @param {T} a
   */
  static of(a) {
    return new IO(() => a)
  }

  /**
   * @template {Fn} U
   * @type {Chain<T>['chain']}
   * @param {Morphism<T, IO<U>>} f
   * @returns {IO<U>}
   */
  chain(f) {
    return /** @type {IO<U>} */ (IO.of(() => f(this.run()).run()))
  }

  /**
   * @template {Fn} U
   * @type {Functor<T>['map']}
   * @param {Morphism<T, U>} f
   * @returns {IO<U>}
   */
  map(f) {
    return /** @type {IO<U>} */ (IO.of(() => f(this.run())))
  }

  /**
   * @template {Fn} U
   * @type {Apply<T>['ap']}
   * @param {IO<Morphism<T, U>>} other
   * @returns {IO<U>}
   */
  ap(other) {
    return /** @type {IO<U>} */ (IO.of((() => other.run()(this.run()))))
  }

  run() {
    return this._effect()
  }

  toString() {
    return `IO(${this._effect})`
  }
}