-- obtain.lua: arguments => [value, tokenLen, ttl]
-- Obtain.lua try to set provided keys's with value and ttl if they do not exists.
-- Keys can be overriden if they already exists and the correct value+tokenLen is provided. 

-- 设置过期时间
local function pexpire(ttl) 
	-- Update keys ttls.
	for _, key in ipairs(KEYS) do
		redis.call("pexpire", key, ttl)
	end
end

-- canOverrideLock check either or not the provided token match
-- previously set lock's tokens.
-- 判断某个Key是否已经被占用了, 如果是自己占用的, 那么则可以尝试覆盖
local function canOverrideKeys() 
	local offset = tonumber(ARGV[2])

	for _, key in ipairs(KEYS) do
		if redis.call("getrange", key, 0, offset-1) ~= string.sub(ARGV[1], 1, offset) then
			return false
		end
	end
	return true
end

-- Prepare mset arguments.
local setArgs = {}
for _, key in ipairs(KEYS) do
	table.insert(setArgs, key)
	table.insert(setArgs, ARGV[1])
end

-- 尝试范围性的使用setnx , 如果有值已经存在, 则尝试覆盖, 如果没法覆盖, 则失败.
if redis.call("msetnx", unpack(setArgs)) ~= 1 then
	if canOverrideKeys() == false then
		return false
	end
	redis.call("mset", unpack(setArgs))
end

pexpire(ARGV[3])
return redis.status_reply("OK")

-- refresh.lua: => Arguments: [value, ttl]
-- refresh.lua refreshes provided keys's ttls if all their values match the input. 

-- Check all keys values matches provided input.
-- 检查是否拥有以上锁的权限
local values = redis.call("mget", unpack(KEYS))
for i, _ in ipairs(KEYS) do
	if values[i] ~= ARGV[1] then
		return false
	end
end

-- 如果有, 则刷新keys的ttl
for _, key in ipairs(KEYS) do
	redis.call("pexpire", key, ARGV[2]) 
end

return redis.status_reply("OK")

-- release.lua: => Arguments: [value]
-- Release.lua deletes provided keys if all their values match the input. 

-- Check all keys values matches provided input.
-- 检查是否拥有以上锁的权限, 如果没有所有的权限, 则取消
local values = redis.call("mget", unpack(KEYS))
for i, _ in ipairs(KEYS) do
	if values[i] ~= ARGV[1] then
		return false
	end
end
-- 删除所有的可以
-- Delete keys.
redis.call("del", unpack(KEYS))

return redis.status_reply("OK")

-- pttl.lua: => Arguments: [value]
-- pttl.lua returns provided keys's ttls if all their values match the input. 

-- Check all keys values matches provided input.
-- 检查是否拥有以上锁的权限, 如果没有所有的权限, 则取消
local values = redis.call("mget", unpack(KEYS))
for i, _ in ipairs(KEYS) do
	if values[i] ~= ARGV[1] then
		return false
	end
end

-- 返回所有key的最短ttl
local minTTL = 0
for _, key in ipairs(KEYS) do
	local ttl = redis.call("pttl", key)
	-- Note: ttl < 0 probably means the key no longer exists.
	if ttl > 0 and (minTTL == 0 or ttl < minTTL) then
		minTTL = ttl
	end
end
return minTTL

type Client struct {
	client RedisClient
	tmp    []byte
	tmpMu  sync.Mutex
}

type Lock struct {
	*Client
	keys     []string
	value    string
	tokenLen int
}