var fs = require('fs')
var Q = require('q')
var fs_stat = Q.denodeify(fs.stat)
var fs_readdir = Q.denodeify(fs.readdir)

var files = [
  './fixtures/file1',
  './fixtures/file2',
  './fixtures/file3',
  './fixtures/file4'
]

var dirs = [
  '.',
  '../',
  '../../'
]

// each, eachSeries, and eachLimit are very similar to their map counterparts, only the results are ignored
// order is always preserved, regardless if done in parallel or series

function map (arr, func) {
  return Q().then(function () {
    return arr.map(function (el) { return func(el) })
  }).all()
}

function mapSeries (arr, func) {
  var currentPromise = Q()
  var promises = arr.map(function (el) {
    return currentPromise = currentPromise.then(function () {
      return func(el)
    })
  })
  return Q.all(promises)
}

function mapLimit (arr, limit, func) {
  var batches = arr.reduce(function (last, next, index) {
    if (index % limit == 0) last.push([next])
    else last[last.length-1].push(next)
    return last
  }, [])

  var currentPromise = Q()
  var promises = batches.map(function (batch) {
    return currentPromise = currentPromise.then(function () {
      var batchPromises = batch.map(function (el) { return func(el) })
      return Q.all(batchPromises)
    })
  })

  return Q.all(promises)
    .then(function (results) {
      return Array.prototype.concat.apply([], results) // flatten array
    })
}

// map(files, fs_stat).then(console.log, console.error)
// function word (file) { throw 'oh no dawg'; return 'word to this file: ' + file }
// map(files, word).then(console.log, function (er) { console.error('oh no', er) })
// mapSeries(files, fs_stat).then(console.log, console.error)
// mapLimit(files, 2, fs_stat).then(console.log, console.error)

function filter (arr, func) {
  var promises = arr.map(function (el) { return func(el) })
  return Q.all(promises).then(function (results) {
    return arr.filter(function (el,i) { return results[i] })
  })
}

function filterSeries (arr, func) {
  var currentPromise = Q()
  var promises = arr.map(function (el) {
    return currentPromise = currentPromise.then(function () {
      return func(el)
    })
  })
  return Q.all(promises).then(function (results) {
    return arr.filter(function (el,i) { return results[i] })
  })
}

// filter(files, fs_stat).then(console.log, console.error)
// filterSeries(files, fs_stat).then(console.log, console.error)

function reject (arr, func) {
  var promises = arr.map(function (el) { return func(el) })
  return Q.all(promises).then(function (results) {
    return arr.filter(function (el,i) { return !results[i] })
  })
}

function rejectSeries (arr, func) {
  var currentPromise = Q()
  var promises = arr.map(function (el) {
    return currentPromise = currentPromise.then(function () {
      return func(el)
    })
  })
  return Q.all(promises).then(function (results) {
    return arr.filter(function (el,i) { return !results[i] })
  })
}

// reject(files, fs_stat).then(console.log, console.error)
// rejectSeries(files, fs_stat).then(console.log, console.error)

function reduce (arr, initialVal, func) {
  var currentPromise = Q(initialVal)
  arr.map(function (el) {
    return currentPromise = currentPromise.then(function (memo) {
      return func(memo, el)
    })
  })
  return currentPromise
}

function reduceRight (arr, initialVal, func) {
  var currentPromise = Q(initialVal)
  arr.reverse().map(function (el) {
    return currentPromise = currentPromise.then(function (memo) {
      return func(memo, el)
    })
  })
  return currentPromise
}

// reduce([1,2,3], 0, function (memo, item) { return Q.delay(100).thenResolve(memo + item) }).then(console.log, console.error)
// reduceRight([1,2,3], 0, function (memo, item) { return Q.delay(100).thenResolve(memo + item) }).then(console.log, console.error)

function detect (arr, func) {
  var promises = arr.map(function (el) { return func(el) })
  return Q.all(promises).then(function (results) {
    return arr.filter(function (el,i) { return results[i] }).shift()
  })
}

function detectSeries (arr, func) {
  var currentPromise = Q()
  var promises = arr.map(function (el) {
    return currentPromise = currentPromise.then(function () {
      return func(el)
    })
  })
  return Q.all(promises).then(function (results) {
    return arr.filter(function (el,i) { return results[i] }).shift() // could be optimized to return first
  })
}

// detect(files, fs_stat).then(console.log, console.error)
// detectSeries(files, fs_stat).then(console.log, console.error)

function sortBy (arr, func) {
  var promises = arr.map(function (el) { return func(el) })
  return Q.all(promises).then(function (results) {
    return arr.sort(function (a, b) {
      return results[arr.indexOf(a)] < results[arr.indexOf(b)] ? -1 : 1
    })
  })
}

// sortBy([2,1,3], function (item) { return Q.delay(100).thenResolve(item) }).then(console.log, console.error)

function some (arr, func) {
  var promises = arr.map(function (el) { return func(el) })
  return Q.all(promises).then(function (results) {
    return results.some(function (el) { return el })
  })
}

// some([2,1,3], function (item) { return Q.delay(100).thenResolve(item == 1) }).then(console.log, console.error)

function every (arr, func) {
  var promises = arr.map(function (el) { return func(el) })
  return Q.all(promises).then(function (results) {
    return results.every(function (el) { return el })
  })
}

// every([1,1,1], function (item) { return Q.delay(100).thenResolve(item == 1) }).then(console.log, console.error)

function concat (arr, func) {
  var promises = arr.map(function (el) { return func(el) })
  return Q.all(promises).then(function (results) {
    return Array.prototype.concat.apply([], results) // flatten results
  })
}

function concatSeries (arr, func) {
  var currentPromise = Q()
  var promises = arr.map(function (el) {
    return currentPromise = currentPromise.then(function () {
      return func(el)
    })
  })
  return Q.all(promises).then(function (results) {
    return Array.prototype.concat.apply([], results) // flatten results
  })
}

// concat(dirs, fs_readdir).then(console.log, console.error)
// concatSeries(dirs, fs_readdir).then(console.log, console.error)

function parallel (funcs) {
  var promises = funcs.map(function (func) { return func() })
  return Q.all(promises)
}

function series (funcs) {
  var currentPromise = Q()
  var promises = funcs.map(function (func) {
    return currentPromise = currentPromise.then(func)
  })
  return Q.all(promises)
}

function parallelLimit (funcs) {
  var batches = funcs.reduce(function (last, next, index) {
    if (index % limit == 0) last.push([next])
    else last[last.length-1].push(next)
    return last
  }, [])

  var currentPromise = Q()
  var promises = batches.map(function (batch) {
    return currentPromise = currentPromise.then(function () {
      return Q.all(batch)
    })
  })

  return Q.all(promises)
    .then(function (results) {
      return Array.prototype.concat.apply([], results) // flatten array
    })
}

function wilst (test, func) {
  if (!test()) return Q('wilst')
  return func().then(function () {
    return wilst(test, func)
  })
}

function doWilst (func, test) {
  return func().then(function () {
    if (!test()) return Q('dowilst')
    return doWilst(func, test)
  })
}

// var count = 0
// wilst(function () { return count < 5 }, function () { count++; return Q.delay(100) }).then(console.log, console.error)
// var doCount = 0
// doWilst(function () { doCount++; return Q.delay(100) }, function () { return doCount < 5 }).then(console.log, console.error)

function until (test, func) {
  if (test()) return Q('until')
  return func().then(function () {
    return wilst(test, func)
  })
}

function doUntil (func, test) {
  return func().then(function () {
    if (test()) return Q('dountil')
    return doUntil(func, test)
  })
}

// var acount = 0
// until(function () { return count > 5 }, function () { acount++; return Q.delay(100) }).then(console.log, console.error)
// var adoCount = 0
// doUntil(function () { adoCount++; return Q.delay(100) }, function () { return adoCount < 5 }).then(console.log, console.error)

function forever (func) {
  return func().then(function () { return forever(func) })
}

// var trigger = 0
// forever(function () {
//   if (trigger > 10000) throw "oh no"
//   return Q.delay(1)
// }).then(console.log, console.error)

function waterfall (funcs) {
  return funcs.reduce(Q.when, Q())
}

// waterfall([ function () { return fs_stat('./fixtures/file1') }, function (stat) { console.log(stat) } ]).then(console.log, console.error)

function compose () {
  var funcs = Array.prototype.slice.call(arguments)
  return function () {
    return funcs.reduce(Q.when, Q.apply(null, arguments))
  }
}

// function add1 (n) { return Q.delay(1000).thenResolve(n+1) }
// function mul3 (n) { return Q.delay(1000).thenResolve(n*3) }
// var add1mul3 = compose(add1, mul3)
// add1mul3(20).then(console.log, console.error)

function applyEach (funcs) {
  var args = Array.prototype.slice.call(arguments, 1)
  var promises = funcs.map(function (func) { return Q.apply(Q, args).then(func) })
  return Q.all(promises)
}

function applyEachSeries (funcs) {
  var args = Array.prototype.slice.call(arguments, 1)
  var currentPromise = Q()
  var promises = funcs.map(function (func) {
    return currentPromise = currentPromise.then(function () {
      return Q.apply(Q, args).then(func)
    })
  })
  return Q.all(promises)
}

// function add2 (n) { return Q.delay(1000).thenResolve(n+2) }
// function mul4 (n) { return Q.delay(1000).thenResolve(n*4) }
// applyEach([ add2, mul4 ], 34).then(console.log, console.error)
// applyEachSeries([ add2, mul4 ], 34).then(console.log, console.error)