local utils = {}

utils.sizeof = function(t)
  if not t then
    return 0
  end

  local size = 0
  for k,v in pairs(t) do
    size = size + 1
  end
  return size
end

utils.shallowDiff = function(a, b)
  local counters = {}

  for k,v in pairs(a) do
    local currentCounter = counters[v] or 0
    counters[v] = currentCounter + 1
  end

  for k,v in pairs(b) do
    if counters[v] then
      counters[v] = counters[v] - 1
    end
  end

  local ret = {}
  local n = 0

  for k,v in pairs(a) do
    if counters[v] and counters[v] > 0 then
      counters[v] = counters[v] - 1
      n = n + 1
      ret[n] = v
    end
  end

  return ret
end

utils.shallowClone = function(t)
  if not t then
    return t
  end

  local res = {}
  for k,v in pairs(t) do
    res[k] = v
  end

  return res
end

utils.merge = function(a, b)
  local res = {}

  for k, v in pairs(a) do
    res[k] = v
  end

  for k, v in pairs(b) do
    res[k] = v
  end

  return res
end

utils.concat = function(a, b)
  local res = {}
  local i = 0

  for _, v in pairs(a) do
    res[i] = v
    i = i + 1
  end

  for _, v in pairs(b) do
    res[i] = v
    i = i + 1
  end

  return res
end

utils.find = function(t, predicate)
  for k,v in pairs(t) do
    if predicate(v, k) then
      return v, k
    end
  end
end

-- repeat n times the given element x in a new table
utils.rep = function(x, n)
  if n < 1 then
    return {}
  end

  local result = {}
  for i=1, n, 1 do
    result[i] = x
  end

  return result
end

return utils