better course material

buyorder.sol

uint buyBookOffersCount;
uint pairsAmountBuyPrices;

// Contains a buy book order offers
// dict[pairIndex, price, offerIndex]
mapping (uint => mapping(uint => mapping(uint => Offer))) buyBookOffers;

// TokenPairInfo eg ETH/PAX, ETH/PAX
mapping (uint => TokenPairInfo) pairs;

// Contains a buy book order prices
mapping (uint => mapping(unint => OrderBookOfferPrice) buyBookPrices;

// TODO... same for sell


addBuyOrder(pairIndex, priceInWei, amount, user) {
buyBookOffersCount++;
buyBookOffers[pairIndex][priceInWei][buyBookOffersCount] = Offer(amount, token, priceInWei, user)

if (buyBookOffersCount == 1) {

buyBookPrices[pairIndex][priceInWei].offersKey = 1;

pairsAmountBuyPrices++;

currentBuyPrice = pairs[pairIndex].currentBuyPrice;
lowestBuyPrice  =  pairs[pairIndex].lowestBuyPrice;

if (lowestBuyPrice == 0 || lowestBuyPrice > priceInWei) {

if (currentBuyPrice == 0) {
   pairs[pairIndex].currentBuyPrice = priceInWei;
   buyBookPrices[pairIndex][priceInWei].higherPrice = priceInWei;
   buyBookPrices[pairIndex][priceInWei].lowerPrice = 0;
} else {
   pairs[pairIndex].currentBuyPrice = priceInWei;
   buyBookPrices[pairIndex][priceInWei].higherPrice = lowestBuyPrice;
   buyBookPrices[pairIndex][priceInWei].lowerPrice = 0;
}

pairs[pairIndex].lowestBuyPrice = priceInWei;

} else if (currentBuyPrice < priceInWei) {
 ...
} else {

   uint buyPrice = pairs[pairIndex].currentBuyPrice;
   book found = false;
   while (buyPrice > 0 && !found) {
    
     if (buyPrice < priceInWei && buyBookPrices[pairIndex][priceInWei].higherPrice > priceInWei) {
       buyBookPrices[pairIndex][priceInWei].lowerPrice = buyPrice;
       buyBookPrices[pairIndex][priceInWei].higherPrice =        buyBookPrices[pairIndex][buyPrice].higherPrice;
       
       uint temp =        buyBookPrices[pairIndex][buyPrice].higherPrice
       buyBookPrices[pairIndex][temp].lowerPrice = priceInWei;
       buyBookPrices[pairIndex][temp].higherPrice = priceInWei;

       found = true;
      }

      buyPrice =        buyBookPrices[pairIndex][buyPrice].lowerPrice;
  }
}