exchangemarket-usd/src/coupling.js

'use strict';

const group = require("./group");
const price = require("./price");

var DB; //container for database

function initiate() {
    price.getRates().then(cur_rate => {
        group.getBestPairs(cur_rate)
            .then(bestPairQueue => processCoupling(bestPairQueue))
            .catch(error => console.error("initiateCoupling", error))
    }).catch(error => console.error(error));
}

function processCoupling(bestPairQueue) {
    bestPairQueue.get().then(pair_result => {
        let buyer_best = pair_result.buyOrder,
            seller_best = pair_result.sellOrder;
        console.debug("Sell:", seller_best);
        console.debug("Buy:", buyer_best);
        spendFLO(buyer_best, seller_best, pair_result.null_base).then(spend_result => {
            let tx_quantity = spend_result.quantity,
                txQueries = spend_result.txQueries,
                clear_sell = spend_result.incomplete && !spend_result.flag_baseNull; //clear_sell can be true only if an order is placed without enough FLO
            processOrders(seller_best, buyer_best, txQueries, tx_quantity, clear_sell);
            updateBalance(seller_best, buyer_best, txQueries, bestPairQueue.cur_rate, tx_quantity);
            //process txn query in SQL
            DB.transaction(txQueries).then(_ => {
                bestPairQueue.next(tx_quantity, spend_result.incomplete, spend_result.flag_baseNull);
                console.log(`Transaction was successful! BuyOrder:${buyer_best.id}| SellOrder:${seller_best.id}`);
                price.updateLastTime();
                //Since a tx was successful, match again
                processCoupling(bestPairQueue);
            }).catch(error => console.error(error));
        }).catch(error => console.error(error));
    }).catch(error => {
        let noBuy, noSell;
        if (error.buy === undefined)
            noBuy = false;
        else if (error.buy !== false) {
            console.error(error.buy);
            noBuy = null;
        } else {
            console.log("No valid buyOrders.");
            noBuy = true;
        }
        if (error.sell === undefined)
            noSell = false;
        else if (error.sell !== false) {
            console.error(error.sell);
            noSell = null;
        } else {
            console.log("No valid sellOrders.");
            noSell = true;
        }
        price.noOrder(noBuy, noSell);
    });
}

function spendFLO(buyOrder, sellOrder, null_base) {
    return new Promise((resolve, reject) => {
        DB.query("SELECT id, quantity, base FROM Vault WHERE floID=? ORDER BY base", [sellOrder.floID]).then(result => {
            let rem = Math.min(buyOrder.quantity, sellOrder.quantity),
                txQueries = [],
                flag_baseNull = false;
            for (let i = 0; i < result.length && rem > 0; i++)
                if (result[i].base || null_base) {
                    if (rem < result[i].quantity) {
                        txQueries.push(["UPDATE Vault SET quantity=quantity-? WHERE id=?", [rem, result[i].id]]);
                        rem = 0;
                    } else {
                        txQueries.push(["DELETE FROM Vault WHERE id=?", [result[i].id]]);
                        rem -= result[i].quantity;
                    }
                } else
                    flag_baseNull = true;
            resolve({
                quantity: Math.min(buyOrder.quantity, sellOrder.quantity) - rem,
                txQueries,
                incomplete: rem > 0,
                flag_baseNull
            });
        }).catch(error => reject(error));
    })
}

function processOrders(seller_best, buyer_best, txQueries, quantity, clear_sell) {
    if (quantity > buyer_best.quantity || quantity > seller_best.quantity)
        throw Error("Tx quantity cannot be more than order quantity");
    //Process Buy Order
    if (quantity == buyer_best.quantity)
        txQueries.push(["DELETE FROM BuyOrder WHERE id=?", [buyer_best.id]]);
    else
        txQueries.push(["UPDATE BuyOrder SET quantity=quantity-? WHERE id=?", [quantity, buyer_best.id]]);
    //Process Sell Order
    if (quantity == seller_best.quantity || clear_sell)
        txQueries.push(["DELETE FROM SellOrder WHERE id=?", [seller_best.id]]);
    else
        txQueries.push(["UPDATE SellOrder SET quantity=quantity-? WHERE id=?", [quantity, seller_best.id]]);
}

function updateBalance(seller_best, buyer_best, txQueries, cur_price, quantity) {
    //Update rupee balance for seller and buyer
    let totalAmount = cur_price * quantity;
    txQueries.push(["UPDATE Cash SET rupeeBalance=rupeeBalance+? WHERE floID=?", [totalAmount, seller_best.floID]]);
    txQueries.push(["UPDATE Cash SET rupeeBalance=rupeeBalance-? WHERE floID=?", [totalAmount, buyer_best.floID]]);
    //Add coins to Buyer
    txQueries.push(["INSERT INTO Vault(floID, base, quantity) VALUES (?, ?, ?)", [buyer_best.floID, cur_price, quantity]])
    //Record transaction
    txQueries.push(["INSERT INTO Transactions (seller, buyer, quantity, unitValue) VALUES (?, ?, ?, ?)", [seller_best.floID, buyer_best.floID, quantity, cur_price]]);
}

module.exports = {
    initiate,
    group,
    price,
    set DB(db) {
        DB = db;
        group.DB = db;
        price.DB = db;
    }
}