feat: migrate lua script to lua file (#4069)

core/limit/tokenscript.lua

@@ -0,0 +1,31 @@
+-- to be compatible with aliyun redis, we cannot use `local key = KEYS[1]` to reuse the key
+-- KEYS[1] as tokens_key
+-- KEYS[2] as timestamp_key
+local rate = tonumber(ARGV[1])
+local capacity = tonumber(ARGV[2])
+local now = tonumber(ARGV[3])
+local requested = tonumber(ARGV[4])
+local fill_time = capacity/rate
+local ttl = math.floor(fill_time*2)
+local last_tokens = tonumber(redis.call("get", KEYS[1]))
+if last_tokens == nil then
+    last_tokens = capacity
+end
+
+local last_refreshed = tonumber(redis.call("get", KEYS[2]))
+if last_refreshed == nil then
+    last_refreshed = 0
+end
+
+local delta = math.max(0, now-last_refreshed)
+local filled_tokens = math.min(capacity, last_tokens+(delta*rate))
+local allowed = filled_tokens >= requested
+local new_tokens = filled_tokens
+if allowed then
+    new_tokens = filled_tokens - requested
+end
+
+redis.call("setex", KEYS[1], ttl, new_tokens)
+redis.call("setex", KEYS[2], ttl, now)
+
+return allowed