const indexMap = [
  'firstCall',
  'secondCall',
  'thirdCall',
]

export function spy() {
  return stub()
}

export function stub(returnFunc = null) {
  if (returnFunc && typeof(returnFunc) !== 'function') {
    throw new Error('stub() was called with non-function argument')
  }
  let returner = returnFunc ? returnFunc : null
  let calls = []
  let func = function(...args) {
    func.called = true
    calls.push(args)
    if (func.callCount < indexMap.length) {
      func[indexMap[func.callCount]] = args
    }
    func.callCount++
    if (returner) {
      return returner(...args)
    }
  }
  func.called = false
  func.callCount = 0
  func.onCall = function(i) {
    return calls[i]
  }
  func.returns = function(data) {
    returner = function() { return data }
  }
  func.returnWith = function(returnFunc) {
    if (typeof(returnFunc) !== 'function') {
      throw new Error('stub() was called with non-function argument')
    }
    returner = returnFunc
  }
  func.throws = function(data) {
    returner = function() { throw data }
  }
  func.resolves = function(data) {
    returner = function() { return Promise.resolve(data) }
  }
  func.rejects = function(data) {
    returner = function() { return Promise.reject(data) }
  }
  for (let i = 0; i < indexMap.length; i++) {
    func[indexMap[i]] = null
  }
  return func
}