import assert from 'assert'
import { isFunction } from '../../is'
import pipe from '../../fp/pipeTwo'
import pipeAll from '../../fp/pipe'

describe('pipe', () => {
  it('is in correct order', () => {
    function x(val) {
      return `${val}x`
    }
    function y(val) {
      return `${val}y`
    }
    function z(val) {
      return `${val}z`
    }

    expect(pipeAll(x, y, z)('w')).toBe('wxyz')
  })
  it('is a variadic function', () => {
    expect(isFunction(pipe)).toBe(true)
    expect(isFunction(pipeAll)).toBe(true)

    // is a smaller version just 2 args
    // expect(pipe.length).toBe(0)
  })

  it('passes context to functions', () => {
    function x(val) {
      return this.x * val
    }
    function y(val) {
      return this.y * val
    }
    function z(val) {
      return this.z * val
    }
    const context = {
      a: pipe(
        pipe(
          x,
          y
        ),
        z
      ),
      x: 4,
      y: 2,
      z: 1,
    }
    expect(context.a(5)).toBe(40)
  })

  it.skip('throws if given no arguments', () => {
    assert.throws(() => {
      pipe()
    }, err => err.constructor === Error && err.message === 'pipe requires at least one argument')
  })

  it('can be applied to one argument, (with 2 fns)', () => {
    const f = (a, b, c) => [a, b, c]
    const g = pipe(
      f,
      x => x
    )
    // expect(g.length).toEqual(3)
    expect(g(1, 2, 3)).toEqual([1, 2, 3])
  })
})