DependencyControl = require "l0.DependencyControl"
version = DependencyControl{
    name: "(Almost) Functional Suite",
    version: "0.6.0",
    description: "Collection of commonly used functions",
    author: "line0",
    moduleName: "l0.Functional",
    url: "https://github.com/TypesettingTools/Functional",
    feed: "https://raw.githubusercontent.com/TypesettingTools/Functional/master/DependencyControl.json",
    {"aegisub.util", "aegisub.unicode", "aegisub.re"},
}
util, unicode, re = version\requireModules!
logger = version\getLogger!

local list, _table, _math, _string, _function, _unicode, _util, _re, rngSeed

-- define some generic functions to be used as default parameters for callbacks
_function = {
  identity: (...) -> ...
  identical: (a, b) -> a == b
  true: -> true
}
-- provide a convenient way to check if these generic functions were passed as an argument
-- so special optimized code paths can be easily provided
getArgType = (arg) ->
  valType = type arg
  if valType != "function"
    return valType

  for k, v in pairs _function
    return v if arg == v

  return "function"


-- list functions are designed to work on numerically keyed tables
-- calling list will create a new table that provides all of the list functions as methods
listMeta = {
  __index: (tbl, key) -> list[key] or nil
}

list = setmetatable {
  makeSet: (source, target = {}, overwrite = true, value = true) ->
    target[v] = value for v in *source when overwrite or not target[v]
    return target

  chunk: (tbl, size = 1) ->
    chunks, c, nextStart = {}, 0, 1
    for i, v in ipairs tbl
      if i == nextStart
        c += 1
        chunks[c], nextStart = {v}, i + size
      else chunks[c][i+size+1-nextStart] = v

    return chunks, c

  compact: (tbl, includeFalse = false) ->
    if includeFalse
      [v for _, v in pairs tbl when v]
    else [v for _, v in pairs tbl when v != nil]

  compare: (a, b, target, iteratee) ->
    if not iteratee and "function" == type target
      target, iteratee = a, target

    seenIndices, s = {}, 0
    for i, v in ipairs b
      target[i] = iteratee a[i], v, i, a, b
      seenIndices[i] = true
      s += 1

    for i, v in ipairs a
      unless seenIndices[i]
        target[i] = iteratee v, b[i], i, a, b
        s += 1

    return target, s

  compareLeft: (a, b, target, iteratee) ->
    if not iteratee and "function" == type target
      target, iteratee = a, target

    s = 0
    for i, v in ipairs a
      target[i] = iteratee v, b[i], i, a, b
      s += 1

    return target, s

  copy: (tbl) -> [v for v in *tbl]

  diff: (left, ...) ->
    rightSet = {}
    list.makeSet right, rightSet for right in *{...}
    diff = [v for v in *left when not rightSet[v]]
    return diff, rightSet

  filter: (tbl, predicate) ->
    [v for i, v in ipairs tbl when predicate v, i, tbl]

  findInRange: (tbl, first = 1, last = #tbl, predicate) ->
    for i = first, last, #tbl
      return tbl[i], i if predicate tbl[i], i, tbl

  find: (tbl, predicate) ->
    for i, v in ipairs tbl
      return v, i if predicate v, i, tbl

  groupBy: (tbl, selector = _function.identity) ->
    groups = {}
    selType = getArgType selector

    for i, v in ipairs tbl
      groupKey = switch selType
        when _function.identity then v
        when "function" then selector v, i, tbl
      else v[selector]

      group = groups[groupKey]
      if group
        group.n += 1
        group[group.n] = v
      else groups[groupKey] = {v, n: 1}

    return groups

  indexBy: (tbl, key, onlyTables = true) ->
    {v[key], v for v in *tbl when not onlyTables or type(v) == "table" and v[key] != nil}

  indexOf: (tbl, item, first = 1, last = #tbl, reverse) ->
    return if #tbl == 0
    first = #tbl - first + 1 if first < 0
    last = #tbl - last + 1 if last < 0

    if reverse
      return i for i = last, first, -1 when tbl[i] == item
    else
      return i for i = first, last when tbl[i] == item

  intersect: (tbl, ...) ->
    others = {...}
    otherCnt = #others
    switch otherCnt
      when 0 then return list.copy tbl
      when 1
        set = list.makeSet tbl
        return [v for v in *others[1] when set[v]]
      else
        intersection = {v, 0 for v in *tbl}

        for i, other in ipairs others
          intersection[v] = i for v in *other when intersection[v] == i-1

        return [k for k, v in pairs intersection when v == otherCnt]

  join: (...) ->
    joined, j, tbls = {}, 0, {...}
    return if #tbls == 0

    for tbl in *tbls
      for v in *tbl
        j += 1
        joined[j] = v

    return joined, j

  joinInto: (target, ...) ->
    t, tbls = #target, {...}

    for tbl in *tbls
      for v in *tbl
        t += 1
        target[t] = v

    return target, t

  lastIndexOf: (tbl, item, first = 1, last = #tbl) ->
    list.indexOf tbl, item, first, last, true

  map: (tbl, selector = _function.identity, compact = false, remapNumKeys = false) ->
    mapped, m, n = {}, 0, 0
    for i, v in ipairs tbl
      mapVal, mapKey = selector v, i, tbl
      continue if compact and mapVal == nil
      if mapKey == nil or remapNumKeys and mapKey == type "number"
        m += 1
        mapped[m] = mapVal
      else
        mapped[mapKey] = mapVal
        n += 1

    return mapped, m + n

  mapCompact: (tbl, selector = _function.identity, remapNumKeys = false) ->
    return list.map tbl, selector, true, remapNumKeys

  pluck: (tbl, key, onlyTables = true) ->
    [v[key] for v in *tbl when not onlyTables or "table" == type v]

  reduce: (tbl, initial = nil, iteratee = _function.identity) ->
    haveInitial = initial != nil
    reduced = initial if haveInitial else tbl[1]

    reduced = iteratee(reduced, v, i, tbl) for i, v in ipairs tbl when haveInitial or i > 1
    return reduced

  removeRange: (tbl, first, last = -1) ->
    len, removed = #tbl, {}
    first += len+1 if first < 0
    last += len+1 if last < 0
    rmCnt = last - first + 1
    for i = first, last
      tbl[i], removed[i-first+1] = tbl[i+rmCnt], tbl[i]
    for i = last + 1, len
      tbl[i] = tbl[i+rmCnt]

    return removed, rmCnt

  removeIndices: (tbl, indices = {}) ->
    removed, shift = {}, 0
    indexCnt = #indices

    switch indexCnt
      when 0 then return removed, 0
      when 1 then return {table.remove tbl, indices[1]}, 1
      else
        i, tblLen, indexSet = 1, #tbl, list.makeSet indices
        while i <= tblLen + shift
          if i <= tblLen and indexSet[i]
            shift += 1
            removed[shift] = tbl[i]
          elseif shift > 0
            tbl[i-shift] = tbl[i]
          i += 1
        return removed, shift

  removeValues: (tbl, ...) ->
    values, tblLen, i, removed, shift = {...}, #tbl, 1, {}, 0
    valCnt, valueSet = #values, list.makeSet values
    return removed, 0 if valCnt == 0

    while i <= tblLen + shift
      if i <= tblLen and valueSet[tbl[i]]
        shift += 1
        removed[shift] = tbl[i]
      elseif shift > 0
        tbl[i-shift] = tbl[i]
      i += 1
    return removed, shift

  removeWhere: (tbl, predicate = _function.true, sparse = false) ->
    removeAll = predicate == _function.true
    removed, r = {}, 0
    for i, v in ipairs tbl
      if removeAll or predicate v, i, tbl
        r += 1
        if sparse
          removed[r], tbl[i] = v
        else removed[r] = i

    if sparse
      return removed, r
    else
      return list.removeIndexes(tbl, removed), r

  reverse: (tbl) ->
    reversed, r = {}, #tbl
    for v in *tbl
      reversed[r] = v
      r -= 1
    return reversed

  slice: (tbl, first = 1, last = -1) ->
    len = #tbl
    first += len+1 if first < 0
    last += len+1 if last < 0

    return [v for v in *tbl[first, last]]

  trim: (tbl, first = 1, last = -1) ->
    len = #tbl
    first += len+1 if first < 0
    last += len+1 if last < 0
    removed = {}

    if first > 1
      removed[first + i - last - 1] = tbl[i] for i = last + 1, len
      removed[i] = tbl[i] for i = 1, first - 1

      tbl[i] = tbl[i+first-1] for i = 1, last - first + 1
      tbl[i] = nil for i = last - first + 2, len

    elseif last < len
      for i = last + 1, len
        removed[i-last], tbl[i] = tbl[i]

    return removed, len - last + first - 1

  uniq: (tbl, selector = _function.identity) -> -- TODO: optimization for sorted lists
    values, unique, u = {}, {}, 0
    identitySel = selector == _function.identity

    for i, v in ipairs tbl
      cmp = identitySel and v or not identitySel and selector v, i, tbl
      continue if cmp == nil or values[cmp]
      u += 1
      unique[u], values[cmp] = v, true

    return unique, u

}, { __call: (_, tbl = {}) -> setmetatable tbl, listMeta }

_math = {
  degrees: (rad) ->
    return rad * 180/math.pi

  isInt: (num) ->
    type_ = type num
    return type_ == "number" and num == math.floor(num), type_

  assertInt: (num, varName = "Number") ->
      isInt, type_ = _math.isInt num
      logger\assert isInt, "%s must be an integer, got a %s.", varName, type_

  inRange: (num, min, max, checkInt) ->
    type(num) == "number" and num >= min and num <= max and (not checkInt or math.floor(num) == num)

  assertInRange: (num, min, max, checkInt, varName = "Number") ->
    logger\assert _math.inRange(num, min, max, checkInt), "%s must be %sin range %d-%d, got %s.", varName,
                   checkInt and "an integer " or "", min, max, tostring(num)

  nan: 0/0

  randomFloat: (min = 0, max = 1) ->
    return min + math.random! * (max - min)

  round: (num, idp = 0) ->
    return num if idp == math.huge
    fac = 10^idp
    return math.floor(num * fac + 0.5) / fac

  roundMany: (idp = 0, ...) ->
    fac = 10^idp
    return unpack for i = 1, select '#', ...
      math.floor(select(i, ...) * fac + 0.5) / fac

  seedRNG: (seed = false) ->
    if "boolean" == type seed
      return rngSeed if seed == false and rngSeed
      rngSeed = os.time!
    else rngSeed = seed

    math.randomseed rngSeed
    return rngSeed

  sign: (num, signedZero) ->
    return _math.nan if num != num
    return 1 if num > 0
    return -1 if num < 0

    if signedZero
      return #tostring(num/math.abs num) > 1 and -1 or 1
    return 0

  sum: (num, ...) ->
    num += n for n in *{...}
    return num

  toStrings: (...) -> unpack [tostring n for n in *table.pack ...]

  vector2: {
    distance: (x1, y1, x2, y2) ->
      return math.sqrt (x2-x1)^2 + (y2-y1)^2

    normalize: (x, y, length = 1) ->
      return _math.nan, _math.nan if x == 0 and y == 0

      fac = length / _math.vector2.distance 0, 0, x, y
      return x*fac, y*fac
  }
}

formatError = (args, a, opts, type_, msg) ->
  "failed to format arg #{a} (#{tostring args[a]}) to #{opts}#{type_}: #{msg}"

_string = {
  escLuaExp: (str) -> str\gsub "([%%%(%)%[%]%.%*%-%+%?%$%^])", "%%%1"

  escRegExp: (str) -> str\gsub "([\\/%^%$%.|%?%*%+%(%)%[%]%{%}])", "\\%1"

  split: (str, sep = " ", init = 1, plain = true, limit = -1) ->
    first, last = str\find sep, init, plain
    -- fast return if there's nothing to split - saves one str.sub()
    return {str}, 1 if not first or limit == 0

    splits, s = {}, 1
    while first and s != limit + 1
      splits[s] = str\sub init, first - 1
      s += 1
      init = last + 1
      first, last = str\find sep, init, plain

    splits[s] = str\sub init
    return splits, s

  formatEx: (fmtStr, ...) ->
    args, a = table.pack(...), 1
    local errors
    str = fmtStr\gsub "(%%[%+%- 0]*%d*.?%d*[hlLzjtI]*)([aABcedEfFgGcnNopiuAsuxX])", (opts, type_) ->
      repl = switch type_
        when "N" -- nicely formatted float (no trailing zeroes)
          success, result = pcall string.format, "#{opts}f", args[a]
          if success
            tonumber result
          else
            errors or= {}
            errors[#errors+1] = formatError args, a, opts, type_, result

        when "B" -- trueish/falsish as 1 and 0
          args[a] and 1 or 0
        else
          success, result = pcall string.format, opts..type_, args[a]
          if success
            result
          else
            errors or= {}
            errors[#errors+1] = formatError args, a, opts, type_, result
      a += 1
      return repl

    if errors
      return nil, table.concat errors, '; '
    return str

  pad: (str, charCnt, padStr = "0", right = false) ->
    repCnt = charCnt - #str
    return str if repCnt < 1
    padding = padStr\rep(math.ceil repCnt / #padStr)\sub 1, repCnt
    return right and str .. padding or padding .. str

  trim: (str) -> str\gsub "^%s*(.-)%s*$", "%1"

  trimLeft: (str) -> str\gsub "^%s*(.+)$", "%1"

  trimRight: (str) -> str\gsub "^(.-)%s*$", "%1"

  toNumbers: (base, ...) ->
    numbers, n = {}, 1
    if type(base) != "number"
      numbers[1], n = base, 2
      base = 10

    for str in table.pack ...
      numbers[n] = tonumber str, base
      n += 1

    return numbers, n-1

}

_table = {
  addDefaults: (tbl, defaults, predicate) ->
    addedCnt = 0

    for k, v in pairs defaults
      if not predicate and tbl[k] == nil or predicate and predicate tbl[k], k, tbl
        addedCnt += 1
        tbl[k] = v

    return addedCnt


  compare: (a, b, target, iteratee) ->
    if not iteratee and "function" == type target
      target, iteratee = a, target

    seenKeys, s = {}, 0
    for k, v in pairs b
      target[k] = iteratee a[k], v, k, a, b
      seenKeys[k] = true
      s += 1

    for k, v in pairs a
      unless seenKeys[k]
        target[k] = iteratee v, b[k], k, a, b
        s += 1

    return target, s

  compareLeft: (a, b, target, iteratee) ->
    if not iteratee and "function" == type target
      target, iteratee = a, target

    s = 0
    for k, v in pairs a
      target[k] = iteratee v, b[k], k, a, b
      s += 1

    return target, s

  copy: (tbl) -> {k, v for k, v in pairs tbl}

  copy_deep: util.deep_copy

  deepCopy: util.deep_copy

  -- selects key/value pairs from left which are different from the values found at the same key in right
  diff: (left, right, sparse = false, comparator = _function.identical) ->
    diff, d = {}, 0
    identicalComp = comparator == _function.identical

    for k, vLeft in pairs left
      vRight = right[k]
      continue if sparse and vRight == nil
      if identicalComp and vRight != vLeft or not identicalComp and not comparator vLeft, vRight, k
        diff[k] = vLeft
        d += 1

    return diff, d

  equals: (a, b) ->
    return _util.equals a, b, "table", "table"

  filter: (tbl, predicate) ->
    filtered, f = {}, 0
    for k, v in pairs tbl
      if predicate v, k, tbl
        filtered[k] = v
        f += 1

    return filtered, f

  find: (tbl, predicate) ->
    for k, v in pairs tbl
      return v, k if predicate v, k, tbl

  findKey: (tbl, value) ->
    for k, v in pairs tbl
      return k if v == value

  intersect: (...) ->
    tbls = table.pack ...
    return _table.intersectEqual tbls, _function.identical, tbls.n

  intersectEqual: (tbls, comparator = _table.equals, tblCnt = #tbls) ->
    first = tbls[1]
    intersection, i = {}, 0
    return nil if tblCnt == 0
    identicalComp = comparator == nil or comparator == _function.identical

    for k, v in pairs first
      allEqual = true
      for j = 2, tblCnt
        if identicalComp and tbls[j][k] != v or not identicalComp and comparator v, tbls[j][k], k
          allEqual = false
          break

      if allEqual
        intersection[k] = v
        i += 1

    return intersection, i

  invert: (tbl, multiValue) ->
    unless multiValue
      return {v, k for k, v in pairs tbl}

    inverted = {}
    for k, v in pairs tbl
      if inverted[v]
        inverted[v].n += 1
        inverted[v][inverted[v].n] = k
      else inverted[v] = {k, n: 1}

    return inverted

  isList: (tbl) ->
    len = _table.length tbl
    return #tbl == len, len

  keys: (tbl, except) ->
    keys, k = {}, 0

    exceptSet = switch type except
      when "table" then list.makeSet except
      when "nil" then nil
      else {[except]: true}

    for key, _ in pairs tbl
      if except == nil or not exceptSet[key]
        k += 1
        keys[k] = key

    return keys, k

  length: (tbl) ->
    n = 0
    n += 1 for _, _ in pairs tbl
    return n

  continuous: (tbl) ->
    continuous, c = {}, 1
    for k, v in pairs tbl
        if "number" == type k
          continuous[c], c = v, c + 1
        else continuous[k] = v

    return continuous

  map: (tbl, selector = _function.identity, compact = true, remapNumKeys = false) ->
    mapped, m, n = {}, 0, 0
    for k, v in pairs tbl
      mapVal, mapKey = selector v, k, tbl
      continue if compact and mapVal == nil
      if mapKey == nil or remapNumKeys and mapKey == type "number"
        m += 1
        mapped[m] = mapVal
      else
        mapped[mapKey] = mapVal
        n += 1

    return mapped, m + n

  merge: (target, source, overwrite = true) ->
    mergeCnt = 0
    for k, v in pairs source
      if overwrite or target[k] == nil
        target[k] = v
        mergeCnt += 1
    return target, mergeCnt

  pick: (tbl, selector) ->
    picked, p = {}, 0

    switch type selector
      when "table"
        keySet = list.makeSet selector
        for k, v in pairs tbl
          if keySet[k]
            picked[k] = v
            p += 1

      when "function"
        for k, v in pairs tbl
          if selector v, k tbl
            picked[k] = v
            p += 1

    return picked, p

  pluck: (tbl, key, onlyTables = true) ->
    [v[key] for _,v in pairs tbl when not onlyTables or "table" == type v]

  -- fast in-place intersect
  purgeDiff: (target, ...) ->
    tbls = table.pack ...
    tblCnt, intCnt = tbls.n, 0

    for k, v in pairs target
      allEqual = true
      for i = 1, tblCnt
        if tbls[i][k] != v
          allEqual = false
          break

      if allEqual
        intCnt += 1
      else target[k] = nil

    return intCnt

  reduce: (tbl, iteratee = _function.identity, initial) ->
    reduced = initial
    reduced = iteratee(reduced, v, i, tbl) for i, v in pairs tbl
    return reduced

  removeAll: (tbl) ->
    return _table.removeWhere tbl, _function.true

  removeKeys: (tbl, keys, exceptMode) ->
    keySet = list.makeSet keys
    removed, r = {}, 0

    for k, v in pairs tbl
      if not exceptMode and keySet[k] or exceptMode and not keySet[k]
        r += 1
        removed, tbl[k] = tbl[k]

    return removed, r

  removeKeysExcept: (tbl, keys) ->
    return _table.removeKeys tbl, keys, true

  removeWhere: (tbl, predicate) ->
    removeAll = predicate == _function.true
    removed, r = {}, 0
    for k, v in pairs tbl
      if removeAll or predicate v, k, tbl
        r += 1
        removed[k], tbl[k] = v

    return removed, r

  transform: (tbl, iteratee = _function.identity) ->
    return _table.reduce tbl, iteratee, {}

  union: (...) ->
    tbls = table.pack ...
    union, u = {}, 0

    for i = 1, tbls.n
      for k, v in pairs tbls[i]
        if union[k] == nil
          union[k] = v
          u += 1

    return union, u

  uniq: (tbl, selector = _function.identity) -> -- TODO: optimization for sorted lists
    values, unique, u = {}, {}, 0
    identitySel = selector == _function.identity

    for k, v in pairs tbl
      cmp = identitySel and v or not identitySel and selector v, k, tbl
      continue if cmp == nil or values[cmp]
      u += 1
      unique[k], values[cmp] = v, true

    return unique, u

  values: (tbl, sortComp) ->
    values, i = {}, 0
    for _, v in pairs tbl
      i += 1
      values[i] = v

    if sortComp == true
      table.sort values
    elseif sortComp
      table.sort values, sortComp

    return values, i
}

_util = {
  equals: DependencyControl.UnitTestSuite.UnitTest.equals
  itemsEqual: DependencyControl.UnitTestSuite.UnitTest.itemsEqual

  formatTimecode: (time, format) ->
    splits = _util.splitTimestamp time

    return _re.replace format, "(h+|m+|s+|f+)", (flag) ->
      _string.pad tostring(splits[flag\sub 1, 1]), #flag

  splitTimestamp: (time) ->
    splitTime = (time, div) ->
      split = time % div
      return split, (time - split) / div

    splits = {}
    splits.f, time = splitTime time, 1000
    splits.s, time = splitTime time, 60
    splits.m, time = splitTime time, 60
    splits.h = time
    return splits

  getScriptInfo: (sub) ->
    infoBlockSeen, scriptInfo = false, {}
    for line in *sub
      if line.class == "info"
        infoBlockSeen = true
        scriptInfo[line.key] = line.value
      elseif infoBlockSeen
        break
    return scriptInfo

  RGB_to_HSV: (r, g, b) ->
    r, g, b = util.clamp(r, 0, 255), util.clamp(g, 0, 255), util.clamp(b, 0, 255)
    v = math.max r, g, b
    delta = v - math.min r, g, b
    if delta == 0
        return 0, 0, v/255
    else
        s = delta/v
        h = 60*(r == v and (g-b)/delta or g == v and (b-r)/delta + 2 or (r-g)/delta + 4)
        return h > 0 and h or h+360, s, v/255

  assTimecode2ms: (tc) ->
    num = tonumber
    split = {tc\match "^(%d):(%d%d):(%d%d)%.(%d%d)$"}
    if #split != 4
      return nil, "invalid ASS timecode"
    return ((num(split[1])*60 + num(split[2]))*60 + num(split[3]))*1000 + num(split[4])*10

  ms2AssTimecode: (time) ->
    {:h, :m, :s, :f} = _util.splitTimestamp time
    if h > 9
      return nil, "value too large to create an ASS timecode"
    return string.format("%01d:%02d:%02d.%02d", h, m, s, f/10)

  uuid: ->
    -- https://gist.github.com/jrus/3197011
    "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx"\gsub "[xy]", (c) ->
      v = c == "x" and math.random(0, 0xf) or math.random 8, 0xb
      return "%x"\format v
}

_unicode = {
  toCharTable: (s) ->
    charNum, charStart, uniChars = 1, 1, {}
    while charStart <= #s
        charEnd = charStart - 1 + unicode.charwidth s\sub charStart, charStart
        uniChars[charNum] = s\sub charStart, charEnd
        charStart, charNum = charEnd+1, charNum+1

    return uniChars

  reverse: (s) -> table.concat list.reverse _unicode.toCharTable s

  sub: (s, i = 1, j) ->
    uniChars = _unicode.toCharTable s
    charCnt = #uniChars
    j or= charCnt

    i = i < 0 and math.max(charCnt+i+1,1) or util.clamp i, 1, charCnt
    j = j < 0 and math.max(charCnt+j+1,1) or util.clamp j, 1, charCnt
    return table.concat uniChars, "", i, j
}

_re = {
  matches: (str, pattern, ...) ->
    regex = re.compile pattern, ...
    chars = _unicode.toCharTable str
    charCnt, last = #chars, 0
    ->
        return if last >= charCnt
        matches = regex\match table.concat chars, "", last+1, charCnt
        matchCnt = #matches
        return unless matches
        last += matches[1].last
        start = matchCnt == 1 and 1 or 2
        unpack [matches[i].str for i = start, matchCnt]

  replace: (str, pattern, callback, ...) ->
    regex = if type(pattern) == "table" and type(pattern._regex) == "cdata"
      pattern
    else re.compile pattern, ...

    chars = _unicode.toCharTable str
    charCnt, last, replacements, r = #chars, 0, {}, 1
    -- since we can only ever get one match at a time out of re.match
    -- we need to run recursively over the not-yet-matched substring
    -- until we either hit the end of string or no more matches are found
    while last < charCnt
        matches = regex\match table.concat chars, "", last+1, charCnt
        -- stop if no further matches can be found
        break unless matches
        matchCnt = #matches

        -- discard the overall match table when there are subgroups
        start = matchCnt == 1 and 1 or 2
        -- pass the matches to the callback, and insert a replacement table
        -- to the global list of replacements for every return value that is a string
        rep = {callback unpack [matches[i].str for i = start, matchCnt]}

        for i = start, matchCnt
            continue if "string" != type rep[i+1-start]
            -- add offset to make first/last index into the source string
            -- rather than the current substring
            replacements[r] = first: matches[i].first+last, last: matches[i].last+last, str: rep[i+1-start]
            r += 1

        last += matches[1].last

    -- splice together the result using the replacement strings
    -- as well as the original unicode characters for the gaps inbetween their indexes
    fragments, f, last = {}, 0, 0

    for rep in *replacements
        fragments[f+c] = chars[c+last] for c = 1, rep.first-last-1
        f += rep.first - last
        fragments[f], last = rep.str, rep.last

    -- don't forget the tail after the last replacement
    fragments[f+c] = chars[c+last] for c = 1, #chars-last

    return table.concat fragments
}

return version\register {
  function: _function
  :list
  List: list
  string: _table.union string, _string
  math: _table.union math, _math
  table: _table.union table, _table
  util: _table.union util, _util
  :version
  re: _table.union re, _re
  unicode: _table.union unicode, _unicode
}