Apply.ts

/**
 * The `Apply` class provides the `ap` which is used to apply a function to an argument under a type constructor.
 *
 * `Apply` can be used to lift functions of two or more arguments to work on values wrapped with the type constructor
 * `f`.
 *
 * Instances must satisfy the following law in addition to the `Functor` laws:
 *
 * 1. Associative composition: `F.ap(F.ap(F.map(fbc, bc => ab => a => bc(ab(a))), fab), fa) = F.ap(fbc, F.ap(fab, fa))`
 *
 * Formally, `Apply` represents a strong lax semi-monoidal endofunctor.
 *
 * @since 2.0.0
 */
import { Functor, Functor1, Functor2, Functor2C, Functor3, Functor4, Functor3C } from './Functor'
import { HKT, Kind, Kind2, Kind3, Kind4, URIS, URIS2, URIS3, URIS4 } from './HKT'
import { tuple } from './function'

/**
 * @since 2.0.0
 */
export interface Apply<F> extends Functor<F> {
  readonly ap: <A, B>(fab: HKT<F, (a: A) => B>, fa: HKT<F, A>) => HKT<F, B>
}

/**
 * @since 2.0.0
 */
export interface Apply1<F extends URIS> extends Functor1<F> {
  readonly ap: <A, B>(fab: Kind<F, (a: A) => B>, fa: Kind<F, A>) => Kind<F, B>
}

/**
 * @since 2.0.0
 */
export interface Apply2<F extends URIS2> extends Functor2<F> {
  readonly ap: <E, A, B>(fab: Kind2<F, E, (a: A) => B>, fa: Kind2<F, E, A>) => Kind2<F, E, B>
}

/**
 * @since 2.0.0
 */
export interface Apply2C<F extends URIS2, E> extends Functor2C<F, E> {
  readonly ap: <A, B>(fab: Kind2<F, E, (a: A) => B>, fa: Kind2<F, E, A>) => Kind2<F, E, B>
}

/**
 * @since 2.0.0
 */
export interface Apply3<F extends URIS3> extends Functor3<F> {
  readonly ap: <R, E, A, B>(fab: Kind3<F, R, E, (a: A) => B>, fa: Kind3<F, R, E, A>) => Kind3<F, R, E, B>
}

/**
 * @since 2.2.0
 */
export interface Apply3C<F extends URIS3, E> extends Functor3C<F, E> {
  readonly ap: <R, A, B>(fab: Kind3<F, R, E, (a: A) => B>, fa: Kind3<F, R, E, A>) => Kind3<F, R, E, B>
}

/**
 * @since 2.0.0
 */
export interface Apply4<F extends URIS4> extends Functor4<F> {
  readonly ap: <S, R, E, A, B>(fab: Kind4<F, S, R, E, (a: A) => B>, fa: Kind4<F, S, R, E, A>) => Kind4<F, S, R, E, B>
}

function curried(f: Function, n: number, acc: Array<unknown>) {
  return function(x: unknown) {
    const combined = acc.concat([x])
    return n === 0 ? f.apply(null, combined) : curried(f, n - 1, combined)
  }
}

const tupleConstructors: Record<number, (a: unknown) => unknown> = {}

function getTupleConstructor(len: number): (a: unknown) => any {
  if (!tupleConstructors.hasOwnProperty(len)) {
    tupleConstructors[len] = curried(tuple, len - 1, [])
  }
  return tupleConstructors[len]
}

/**
 * Tuple sequencing, i.e., take a tuple of monadic actions and does them from left-to-right, returning the resulting tuple.
 *
 * @example
 * import { sequenceT } from 'fp-ts/lib/Apply'
 * import { option, some, none } from 'fp-ts/lib/Option'
 *
 * const sequenceTOption = sequenceT(option)
 * assert.deepStrictEqual(sequenceTOption(some(1)), some([1]))
 * assert.deepStrictEqual(sequenceTOption(some(1), some('2')), some([1, '2']))
 * assert.deepStrictEqual(sequenceTOption(some(1), some('2'), none), none)
 *
 * @since 2.0.0
 */
export function sequenceT<F extends URIS4>(
  F: Apply4<F>
): <S, R, E, T extends Array<Kind4<F, S, R, E, any>>>(
  ...t: T & { 0: Kind4<F, S, R, E, any> }
) => Kind4<F, S, R, E, { [K in keyof T]: [T[K]] extends [Kind4<F, S, R, E, infer A>] ? A : never }>
export function sequenceT<F extends URIS3>(
  F: Apply3<F>
): <R, E, T extends Array<Kind3<F, R, E, any>>>(
  ...t: T & { 0: Kind3<F, R, E, any> }
) => Kind3<F, R, E, { [K in keyof T]: [T[K]] extends [Kind3<F, R, E, infer A>] ? A : never }>
export function sequenceT<F extends URIS3, E>(
  F: Apply3C<F, E>
): <R, T extends Array<Kind3<F, R, E, any>>>(
  ...t: T & { 0: Kind3<F, R, E, any> }
) => Kind3<F, R, E, { [K in keyof T]: [T[K]] extends [Kind3<F, R, E, infer A>] ? A : never }>
export function sequenceT<F extends URIS2>(
  F: Apply2<F>
): <E, T extends Array<Kind2<F, E, any>>>(
  ...t: T & { 0: Kind2<F, E, any> }
) => Kind2<F, E, { [K in keyof T]: [T[K]] extends [Kind2<F, E, infer A>] ? A : never }>
export function sequenceT<F extends URIS2, E>(
  F: Apply2C<F, E>
): <T extends Array<Kind2<F, E, any>>>(
  ...t: T & { 0: Kind2<F, E, any> }
) => Kind2<F, E, { [K in keyof T]: [T[K]] extends [Kind2<F, E, infer A>] ? A : never }>

export function sequenceT<F extends URIS>(
  F: Apply1<F>
): <T extends Array<Kind<F, any>>>(
  ...t: T & { 0: Kind<F, any> }
) => Kind<F, { [K in keyof T]: [T[K]] extends [Kind<F, infer A>] ? A : never }>
export function sequenceT<F>(
  F: Apply<F>
): <T extends Array<HKT<F, any>>>(
  ...t: T & { 0: HKT<F, any> }
) => HKT<F, { [K in keyof T]: [T[K]] extends [HKT<F, infer A>] ? A : never }>
export function sequenceT<F>(F: Apply<F>): any {
  return <A>(...args: Array<HKT<F, A>>) => {
    const len = args.length
    const f = getTupleConstructor(len)
    let fas = F.map(args[0], f)
    for (let i = 1; i < len; i++) {
      fas = F.ap(fas, args[i])
    }
    return fas
  }
}

type EnforceNonEmptyRecord<R> = keyof R extends never ? never : R

function getRecordConstructor(keys: Array<string>) {
  const len = keys.length
  return curried(
    (...args: Array<unknown>) => {
      const r: Record<string, unknown> = {}
      for (let i = 0; i < len; i++) {
        r[keys[i]] = args[i]
      }
      return r
    },
    len - 1,
    []
  )
}

/**
 * Like `Apply.sequenceT` but works with structs instead of tuples.
 *
 * @example
 * import { either, right, left } from 'fp-ts/lib/Either'
 * import { sequenceS } from 'fp-ts/lib/Apply'
 *
 * const ado = sequenceS(either)
 *
 * assert.deepStrictEqual(
 *   ado({
 *     a: right(1),
 *     b: right(true)
 *   }),
 *   right({ a: 1, b: true })
 * )
 * assert.deepStrictEqual(
 *   ado({
 *     a: right(1),
 *     b: left('error')
 *   }),
 *   left('error')
 * )
 *
 * @since 2.0.0
 */
export function sequenceS<F extends URIS4>(
  F: Apply4<F>
): <S, R, E, NER extends Record<string, Kind4<F, S, R, E, any>>>(
  r: EnforceNonEmptyRecord<NER> & Record<string, Kind4<F, S, R, E, any>>
) => Kind4<F, S, R, E, { [K in keyof NER]: [NER[K]] extends [Kind4<F, any, any, any, infer A>] ? A : never }>
export function sequenceS<F extends URIS3>(
  F: Apply3<F>
): <R, E, NER extends Record<string, Kind3<F, R, E, any>>>(
  r: EnforceNonEmptyRecord<NER> & Record<string, Kind3<F, R, E, any>>
) => Kind3<F, R, E, { [K in keyof NER]: [NER[K]] extends [Kind3<F, any, any, infer A>] ? A : never }>
export function sequenceS<F extends URIS3, E>(
  F: Apply3C<F, E>
): <R, NER extends Record<string, Kind3<F, R, E, any>>>(
  r: EnforceNonEmptyRecord<NER> & Record<string, Kind3<F, R, E, any>>
) => Kind3<F, R, E, { [K in keyof NER]: [NER[K]] extends [Kind3<F, any, any, infer A>] ? A : never }>
export function sequenceS<F extends URIS2>(
  F: Apply2<F>
): <E, NER extends Record<string, Kind2<F, E, any>>>(
  r: EnforceNonEmptyRecord<NER> & Record<string, Kind2<F, E, any>>
) => Kind2<F, E, { [K in keyof NER]: [NER[K]] extends [Kind2<F, any, infer A>] ? A : never }>
export function sequenceS<F extends URIS2, E>(
  F: Apply2C<F, E>
): <NER extends Record<string, Kind2<F, E, any>>>(
  r: EnforceNonEmptyRecord<NER>
) => Kind2<F, E, { [K in keyof NER]: [NER[K]] extends [Kind2<F, any, infer A>] ? A : never }>
export function sequenceS<F extends URIS>(
  F: Apply1<F>
): <NER extends Record<string, Kind<F, any>>>(
  r: EnforceNonEmptyRecord<NER>
) => Kind<F, { [K in keyof NER]: [NER[K]] extends [Kind<F, infer A>] ? A : never }>
export function sequenceS<F>(
  F: Apply<F>
): <NER extends Record<string, HKT<F, any>>>(
  r: EnforceNonEmptyRecord<NER>
) => HKT<F, { [K in keyof NER]: [NER[K]] extends [HKT<F, infer A>] ? A : never }>
export function sequenceS<F>(F: Apply<F>): (r: Record<string, HKT<F, any>>) => HKT<F, Record<string, any>> {
  return r => {
    const keys = Object.keys(r)
    const len = keys.length
    const f = getRecordConstructor(keys)
    let fr = F.map(r[keys[0]], f)
    for (let i = 1; i < len; i++) {
      fr = F.ap(fr, r[keys[i]])
    }
    return fr
  }
}