<?php

namespace app\common\library;

class RedpacketLua
{
    /**
     * 抢红包Lua脚本
     * 保证原子性操作，防止超抢
     */
    public static function grabRedpacketScript()
    {
        return <<<LUA
-- KEYS[1]: 红包key, KEYS[2]: 用户集合key, KEYS[3]: 用户ID
-- ARGV[1]: 当前时间

local redpacketKey = KEYS[1]
local userSetKey = KEYS[2]
local userId = KEYS[3]
local currentTime = tonumber(ARGV[1])

-- 检查红包是否存在
local redpacketData = redis.call('HGETALL', redpacketKey)
if not redpacketData or #redpacketData == 0 then
    return {0, "红包不存在", 0}
end

-- 将哈希数据转为table
local redpacket = {}
for i = 1, #redpacketData, 2 do
    redpacket[redpacketData[i]] = redpacketData[i + 1]
end

-- 检查红包状态
local status = tonumber(redpacket['status'])
local startTime = tonumber(redpacket['start_time'])
local endTime = tonumber(redpacket['end_time'])

if status == 0 then
    if currentTime < startTime then
        return {0, "红包还未开始", 0}
    else
        -- 更新状态为进行中(1)
        redis.call('HSET', redpacketKey, 'status', 1)
        status = 1
    end
end

if status ~= 1 then
    return {0, "红包已结束", 0}
end

if currentTime > endTime then
    redis.call('HSET', redpacketKey, 'status', 2)
    return {0, "红包已结束", 0}
end

-- 检查是否已经抢过
local hasGrabbed = redis.call('SISMEMBER', userSetKey, userId)
if hasGrabbed == 1 then
    return {0, "已经抢过该红包", 0}
end

-- 检查是否还有剩余
local leftAmount = tonumber(redpacket['left_amount'])
local leftCount = tonumber(redpacket['left_count'])

if leftCount <= 0 or leftAmount <= 0 then
    return {0, "红包已抢完", 0}
end

-- 计算红包金额
local amount = 0
local isFinished = 0

if leftCount == 1 then
    -- 最后一个红包，获得剩余所有金额
    amount = leftAmount
    isFinished = 1
else
    -- 随机算法：二倍均值法，保证公平性
    local maxAmount = leftAmount / leftCount * 2
    amount = math.random(1, math.floor(maxAmount))
    -- 确保金额不会超过剩余金额
    if amount > leftAmount then
        amount = leftAmount
    end
    -- 检查是否是最后一个（由于浮点数计算可能有误差）
    if leftCount == 1 or (leftAmount - amount) < 0.01 then
        isFinished = 1
    end
end

-- 更新红包数据
local newLeftAmount = leftAmount - amount
local newLeftCount = leftCount - 1

redis.call('HSET', redpacketKey, 'left_amount', newLeftAmount)
redis.call('HSET', redpacketKey, 'left_count', newLeftCount)

-- 标记用户已抢
redis.call('SADD', userSetKey, userId)

-- 如果抢完了，更新状态为已结束(2)
if isFinished == 1 then
    redis.call('HSET', redpacketKey, 'status', 2)
end

return {1, tostring(amount), isFinished}
LUA;
    }


}