刮刮乐活动：每日限刮的权重中奖

; scratch.txt 奖励权重表
ID=1 奖励=1001 数量=1  权重=6000
ID=2 奖励=1002 数量=2  权重=3000
ID=3 奖励=1003 数量=5  权重=900
ID=4 奖励=1004 数量=10 权重=100

local W = {{1001,1,6000},{1002,2,3000},
           {1003,5,900},{1004,10,100}}
local function scratch(actor)
    local n = getplayvar(actor, "scratchN") or 0
    if n >= 5 then
        sendmsg(actor, 1, "今日 5 张已刮完")
        return
    end
    setplayvar(actor, "scratchN", n + 1)
    local roll, acc = math.random(1, 10000), 0
    for _, r in ipairs(W) do
        acc = acc + r[3]
        if roll <= acc then
            giveitem(actor, r[1], r[2])
            sendmsg(actor, 1, "刮中 " .. r[2] .. " 份奖励")
            return
        end
    end
end