export function rateLimitFetchLua()

in packages/sqrl-redis-functions/src/lua/rateLimitFetchLua.ts [8:62]

• 43 lines of code
• 6 McCabe index (conditional complexity)

export function rateLimitFetchLua() {
  // It is likely inefficient to update the expiry time on every ratelimit,
  // change, that could be optimized a lot.
  return (
    `
local maxAmount = tonumber(ARGV[1])
local take = tonumber(ARGV[2])
local at = tonumber(ARGV[3])
local refillTime = tonumber(ARGV[4])
local refillAmount = tonumber(ARGV[5])
local strict = tonumber(ARGV[6]) > 0


local current = redis.call("get", KEYS[1]);
local tokens
local lastRefill

if not current then
  tokens = maxAmount
  lastRefill = at
else
  tokens, lastRefill = struct.unpack("i8i8", current)
end

if take == 0 then
  return tokens
end

if tokens < take then
  local refills = math.floor((at - lastRefill) / refillTime);
  lastRefill = lastRefill + refills * refillTime
  tokens = math.min(maxAmount, tokens + refills * refillAmount)
end

local beforeTake = tokens

if tokens == 0 then
  if strict then
    lastRefill = at
  else
    return 0
  end
else
  tokens = math.max(0, tokens - take)
end

local expiry = math.ceil((maxAmount - tokens) / refillAmount) * refillTime

local value = struct.pack("i8i8", tokens, lastRefill)
redis.call("set", KEYS[1], value, "px", expiry)

return beforeTake
  `.trim() + "\n"
  );
}