// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Test that unbuffered channels act as pure fifos.

'use strict'

const Channel = require('../../lib')

it(`fifo`, function () {
  const N = 10

  const AsynchFifo = async () => {
    const ch = Channel(10)

    for (let i = 0; i < N; i++) {
      await ch.push(i)
    }

    for (let i = 0; i < N; i++) {
      if (await ch.shift() !== i) {
        throw new Error(`bad receive`)
      }
    }
  }

  const Chain = async (ch, val, input, output) => {
    await input.shift()

    if (await ch.shift() !== val) {
      throw new Error(val)
    }

    await output.push(1)
  }

  // thread together a daisy chain to read the elements in sequence
  const SynchFifo = async () => {
    const ch = Channel()
    let input = Channel()
    let start = input

    for (let i = 0; i < N; i++) {
      const output = Channel()
      Chain(ch, i, input, output)
      input = output
    }

    await start.push(0)

    for (let i = 0; i < N; i++) {
      await ch.push(i)
    }

    await input.shift()
  }

  AsynchFifo()
  SynchFifo()
})