【性能调优】批量邮件：活动奖励的分批投递

---批量邮件：分批的投递队列
local MailBatch = { list = {}, cursor = 1, batch = 300 }

function MailBatch.enqueue(recipients, title, reward)
    MailBatch.list = recipients
    MailBatch.cursor = 1
    MailBatch.meta = { title = title, reward = reward }
end

setontimerex(113, 5)
function MailBatch.tick()
    local from = MailBatch.cursor
    local to = math.min(from + MailBatch.batch - 1,
        #MailBatch.list)
    for i = from, to do
        sendmail(MailBatch.list[i], 8014,
            MailBatch.meta.title,
            MailBatch.meta.text or "",
            MailBatch.meta.reward)
    end
    MailBatch.cursor = to + 1
    if MailBatch.cursor > #MailBatch.list then
        Ops.log("批量邮件投递完成，共 " .. #MailBatch.list .. " 封")
        MailBatch.list = {}
    end
end

---紧急补偿的插队：优先于常规批量
function MailBatch.urgent(recipients, title, reward)
    -- 紧急的投递插到队列头部，翻倍速率
    local urgent = { recipients = recipients,
        title = title, reward = reward }
    table.insert(MailBatch.queue, 1, urgent)
end

---投递的进度可视化
function MailBatch.progress()
    if #MailBatch.list == 0 then return "空闲" end
    return string.format("投递中 %d/%d",
        MailBatch.cursor - 1, #MailBatch.list)
end