local storedPermits = 'storedPermits'

local maxPermits = 'maxPermits'

local stableIntervalMicros = 'stableIntervalMicros'

local nextFreeTicketMicros = 'nextFreeTicketMicros'

local function reserveAndGetWaitLength(key, permits, nowMicros)

local limiterInfo = redis.call('HMGET', key, storedPermits, maxPermits, stableIntervalMicros, nextFreeTicketMicros)

local stored = tonumber(limiterInfo[1])

local max = tonumber(limiterInfo[2])

local interval = tonumber(limiterInfo[3])

local nextMicros = tonumber(limiterInfo[4])

if (nowMicros >= nextMicros)

then

local newPermits = (nowMicros - nextMicros) / interval

local newStored = math.min(max, stored + newPermits)

redis.call('HMSET', key, storedPermits, newStored, nextFreeTicketMicros, nowMicros)

end

nextMicros = tonumber(redis.call('HGET', key, nextFreeTicketMicros))

stored = tonumber(redis.call('HGET', key, storedPermits))

local storedToSpend = math.min(stored, permits)

local freshPermits = permits - storedToSpend

local waitMicros = freshPermits * interval

local newNextMicros = nextMicros + waitMicros

stored = stored - storedToSpend

redis.call('HMSET', key, storedPermits, stored, nextFreeTicketMicros, newNextMicros)

return newNextMicros

end

local function acquire(key, permits, nowMicros)

local wait = reserveAndGetWaitLength(key, permits, nowMicros)

return math.max(wait - nowMicros, 0)

end

local function tryAcquire(key, permits, nowMicros, timeoutMicros)

local next = tonumber(redis.call('HGET', key, nextFreeTicketMicros))

if (nowMicros + timeoutMicros <= next)

then

-- tryAcquire false

return -1

else

local wait = reserveAndGetWaitLength(key, permits, nowMicros)

return math.max(wait - nowMicros, 0)

end

end

local key = KEYS[1]

local method = ARGV[1]

if method == 'acquire' then

return acquire(key, tonumber(ARGV[2]), tonumber(ARGV[3]))

elseif method == 'tryAcquire' then

return tryAcquire(key, tonumber(ARGV[2]), tonumber(ARGV[3]), tonumber(ARGV[4]))

end