【玩法设计】交易行搜索：筛选器与收藏订阅

---交易行的多维筛选
function TradeSearch.filter(filters)
    local out = {}
    for _, listing in ipairs(listings) do
        local match = true
        if filters.category and listing.category ~= filters.category then match = false end
        if filters.minPrice and listing.price < filters.minPrice then match = false end
        if filters.maxPrice and listing.price > filters.maxPrice then match = false end
        if filters.strengthen and listing.strengthen < filters.strengthen then match = false end
        if match then out[#out + 1] = listing end
    end
    return out
end

function TradeSearch.subscribe(actor, filters)
    actor.subscriptions[#actor.subscriptions + 1] = {
        filters = filters, at = os.time(), notified = false,
    }
    sendmsg(actor, 1, "订阅成功，有匹配的物品会通知")
end

function TradeSearch.checkNew(actor)
    for _, sub in ipairs(actor.subscriptions) do
        local matches = TradeSearch.filter(sub.filters)
        if #matches > 0 and not sub.notified then
            sub.notified = true
            sendmsg(actor, 1, "有 " .. #matches .. " 件匹配的物品上架")
        end
    end
end