@gnosis.pm/dex-contracts/build/esm/src/fee_token_liquidity.js

Contracts for dFusion multi-token batch auction exchange

import BN from "bn.js";
const MAXU32 = new BN(2).pow(new BN(32)).sub(new BN(1));
/**
 * Used to recover relevant {@link TokenInfo | TokenInfo} by ID from the exchange such as number of decimals or name.
 * @param exchange - An instance of deployed Batch Exchange Contract
 * @param tokenIds - An array of token ids as listed on the Batch Exchange.
 * @param artifacts - A context-like object providing a gateway to Truffle contract ABIs.
 * @returns A mapping of TokenInfo objects fetched from the exchange.
 *   Note that nullish TokenInfo objects are returned in places where the requested token ID failed to fetch.
 */
export async function fetchTokenInfoFromExchange(exchange, tokenIds, artifacts) {
    const ERC20 = artifacts.require("ERC20Detailed");
    // Fetching token data from EVM
    const tokenObjects = new Map();
    await Promise.all(tokenIds.map(async (id) => {
        const tokenAddress = await exchange.tokenIdToAddressMap(id);
        let tokenInfo;
        try {
            const tokenInstance = await ERC20.at(tokenAddress);
            const [symbol, decimals] = await Promise.all([
                tokenInstance.symbol(),
                tokenInstance.decimals(),
            ]);
            tokenInfo = {
                id: id,
                symbol: symbol,
                decimals: decimals.toNumber(),
                address: tokenAddress,
            };
        }
        catch (err) {
            // This generic try-catch is essentially a TokenNotFoundError
            // Could occur when the given ID slot is not occupied by a registered token on the exhchange
            // or if the code registered at address occupied by a token slot is not that of and ERC20 token
            tokenInfo = {
                id: id,
                address: tokenAddress,
            };
        }
        tokenObjects.set(id, tokenInfo);
    }));
    return tokenObjects;
}
/**
 * A handy function providing fee token liquidity by placing orders selling the fee token
 * at the specified provision price for each specified token.
 * @param exchange - BatchExchange Smart Contract
 * @param tokenIds - An array of token indices as represented on the exchange
 * @param provisionPrice - Price at which liquidity is to be provided
 * @param sellAmountOwl - Amount of feeToken to be sold
 * @param artifacts - A context-like object providing a gateway to Truffle contract ABIs.
 * @returns Void Promise
 */
export async function placeFeeTokenLiquidityOrders(exchange, tokenIds, provisionPrice, sellAmountOwl, artifacts) {
    const minBuyAmounts = [];
    const validTokenIds = [];
    const feeToken = await fetchTokenInfoFromExchange(exchange, [0], artifacts);
    // This is expected to always be OWL which has 18 digits.
    const feeDigits = feeToken.get(0)?.decimals || 18;
    const tokenInfo = await fetchTokenInfoFromExchange(exchange, tokenIds, artifacts);
    for (const tokenId of tokenIds) {
        const numDigits = tokenInfo.get(tokenId)?.decimals;
        if (numDigits) {
            validTokenIds.push(tokenId);
            if (numDigits < feeDigits) {
                minBuyAmounts.push(sellAmountOwl
                    .mul(provisionPrice)
                    .div(new BN(10).pow(new BN(feeDigits - numDigits))));
            }
            else {
                minBuyAmounts.push(sellAmountOwl
                    .mul(provisionPrice)
                    .mul(new BN(10).pow(new BN(numDigits - feeDigits))));
            }
        }
    }
    const numOrders = validTokenIds.length;
    const batchId = (await exchange.getCurrentBatchId()).toNumber();
    if (numOrders == 0) {
        return [];
    }
    await exchange.placeValidFromOrders(validTokenIds, // buyTokens
    Array(numOrders).fill(0), // sellTokens
    Array(numOrders).fill(batchId + 2), // validFroms (all to begin 2 batches from now)
    Array(numOrders).fill(MAXU32), // validTos
    minBuyAmounts, // buyAmounts
    Array(numOrders).fill(sellAmountOwl));
    return validTokenIds;
}