装备结晶：碎片熔铸的结晶兑换

local function melt(actor, shardId)
    local n = getplayvar(actor, "shard_" .. shardId) or 0
    local canMelt = math.floor(n / 10)
    if canMelt == 0 then
        sendmsg(actor, 1, "碎片不足 10 个")
        return
    end
    setplayvar(actor, "shard_" .. shardId, n - canMelt * 10)
    setplayvar(actor, "crystal_" .. shardId,
        (getplayvar(actor, "crystal_" .. shardId) or 0)
        + canMelt)
    sendmsg(actor, 1, "熔得结晶 " .. canMelt .. " 颗")
end

local function exchange(actor, shardId, goodsId, need)
    local have = getplayvar(actor, "crystal_" .. shardId) or 0
    if have < need then
        sendmsg(actor, 1, "结晶不足，需 " .. need)
        return
    end
    setplayvar(actor, "crystal_" .. shardId, have - need)
    giveitem(actor, goodsId, 1)
end