import { PipeFn } from './types'

/**
 * Left-to-right function composition.
 * @name pipe<A, B>(...fns: Array<Function>): (value: A) => B
 */
export const pipe: PipeFn = function pipe<A, B>(...fns: Array<Function>) {
  return function(a: A): B {
    switch (fns.length) {
      case 1:
        return fns[0](a)
      case 2:
        return fns[1](fns[0](a))
      case 3:
        return fns[2](fns[1](fns[0](a)))
      case 4:
        return fns[3](fns[2](fns[1](fns[0](a))))
      case 5:
        return fns[4](fns[3](fns[2](fns[1](fns[0](a)))))
      default:
        return fns.reduce((accumulator: any, value: Function) => value(accumulator), a)
    }
  }
}