vkapi.lua

local requests = require 'requests'
local json     = require 'cjson'

local url = 'https://api.vk.com/method/%s'
local mt  = {}

-- http://lua-users.org/wiki/CopyTable
local function shallowcopy(orig)
  local orig_type = type(orig)
  local copy
  if orig_type == 'table' then
      copy = {}
      for orig_key, orig_value in pairs(orig) do
          copy[orig_key] = orig_value
      end
  else -- number, string, boolean, etc
      copy = orig
  end
  return copy
end

local function send(self, method, data, full_info)
  local params = shallowcopy(data)
  params.access_token = self.token
  params.v = self.v

  local res = requests.get{url:format(method), params = params}
  return full_info and res or json.decode(res.text)
end

function mt.__index(self, index)
  local v = rawget(self, index)
  if v ~= nil then return v end
  
  local t = shallowcopy(self)
  if not t.method then t.method = {} end
  table.insert(t.method, tostring(index))
  
  return setmetatable(t, getmetatable(self))
end

function mt.__call(self, data, full_info)
  return send(self, table.concat(self.method, '.'), data, full_info)
end

local function new(token, version)
  return setmetatable({ token = token, v = version, send = send }, mt)
end

return { new = new }

Example:

local vkapi = require 'vkapi'
local me = vkapi.new(require('config'), '5.126')

local info = me.friends.areFriends{ user_ids = { 93787870, 103509140 } }
-- equivalent: local info = me:send('friends.areFriends', { user_ids = { 93787870, 103509140 } })

assert(info and info.response)
for i, k in pairs(info.response) do
  print(k.user_id, k.friend_status)
end

-- 93787870        3
-- 103509140       3