json4lua's rpc.lua translation to minetest

function rpc.call(url, method, ...)
  local JSONRequestArray = {
    id=tostring(math.random()),
    ["method"]=method,
    params = ...
  }
  local httpResponse, result , code
  local jsonRequest = minetest.write_json(JSONRequestArray)
  -- We use the sophisticated http.request form (with ltn12 sources and sinks) so that
  -- we can set the content-type to text/plain. While this shouldn't strictly-speaking be true,
  -- it seems a good idea (Xavante won't work w/out a content-type header, although a patch
  -- is needed to Xavante to make it work with text/plain)
  local ltn12 = require('ltn12')
  local resultChunks = {}
  httpResponse, code = http.request(
    { ['url'] = url,
      sink = ltn12.sink.table(resultChunks),
      method = 'POST',
      headers = { ['content-type']='text/plain', ['content-length']=string.len(jsonRequest) },
      source = ltn12.source.string(jsonRequest)
    }
  )
  httpResponse = table.concat(resultChunks)
  -- Check the http response code
  if (code~=200) then
    return nil, "HTTP ERROR: " .. code
  end
  -- And decode the httpResponse and check the JSON RPC result code
  result = minetest.parse_json( httpResponse )
  if result.result then
    return result.result, nil
  else
    return nil, result.error
  end
end