【进阶实战】交易撮合引擎：买卖单的自动匹配实现

local engine = { buys = {}, sells = {} }
local function addBuy(buyer, item, price)
    engine.buys[#engine.buys + 1] =
        { buyer = buyer, item = item, price = price }
end
local function addSell(seller, item, price)
    engine.sells[#engine.sells + 1] =
        { seller = seller, item = item, price = price }
end
local function matchAndTrade()
    for i = #engine.buys, 1, -1 do
        local b = engine.buys[i]
        for j = #engine.sells, 1, -1 do
            local s = engine.sells[j]
            if s.item == b.item and s.price <= b.price then
                executeTrade(b.buyer, s.seller, s.item, s.price)
                table.remove(engine.buys, i)
                table.remove(engine.sells, j)
                break
            end
        end
    end
end

local function executeTrade(buyer, seller, item, price)
    print("成交：" .. item .. " " .. price .. "金币 " ..
        seller .. "->" .. buyer)
end