Concert Ticket Packets

A ticket exchange receives a stream of packets and must process them strictly in arrival order. Each packet is a list of four values:

• ["OFFER", ticket_id, price, quantity]: the seller now offers quantity tickets for ticket_id at price each. This replaces any earlier offer for the same ticket_id entirely (both price and remaining quantity); leftover tickets from the old offer are gone.
• ["BUY", ticket_id, max_price, quantity]: a buyer wants exactly quantity tickets for ticket_id and will pay at most max_price per ticket.

A buy succeeds only if, at the moment it arrives, there is an offer for that ticket_id whose price is <= max_price and whose remaining quantity is >= quantity. Partial fills are not allowed. A successful buy reduces the offer's remaining quantity and produces the allocation [ticket_id, quantity, total_cost], where total_cost is the offer price times quantity. A failed buy changes nothing and is not retried later.

Return all allocations in the order the successful buys arrived.