【网络通信】面对面交易：握手、锁定与确认的协议

---交易的发起：3 格内建立会话
function Trade.request(actor, targetName)
    local player = class(actor)
    if not player then return false end
    local target = getplayerbyname(targetName)
    if not target then return false end
    if not Trade.inRange(actor, target, 3) then
        sendmsg(actor, 1, "走近些再发起交易")
        return false
    end
    -- 双方都不能已在交易中
    if Trade.busy(actor) or Trade.busy(targetName) then
        sendmsg(actor, 1, "对方或自己正在交易中")
        return false
    end
    Trade.open(actor, targetName)
    sendmsg(target, 1, actor .. " 发来了交易请求")
    return true
end

---两段式确认：锁定后不能改，确认后成交
function Trade.lock(actor)
    local player = class(actor)
    if not player then return false end
    local sess = Trade.sessionOf(actor)
    sess.locked[actor] = true
    -- 双方都锁定后通知对方
    if sess.locked[actor] and sess.locked[sess.other(actor)] then
        sendmsg(actor, 1, "双方已锁定，点击确认完成交易")
        sendmsg(sess.other(actor), 1,
            "双方已锁定，点击确认完成交易")
    end
end

---确认成交：以锁定时的快照结算
function Trade.confirm(actor)
    local player = class(actor)
    if not player then return false end
    local sess = Trade.sessionOf(actor)
    if not sess.allLocked() then
        sendmsg(actor, 1, "对方尚未锁定")
        return false
    end
    -- 以锁定快照结算，防中途换物
    Trade.settle(sess, sess.snapshot)
    Trade.close(sess)
    return true
end