soroswap-utils/src/pools.ts

Utilities for interacting with Soroswap, the decentralized exchange (DEX) on Soroban, which is the smart contracts platform of the Stellar network.

import {
    Address,
    BASE_FEE,
    Contract,
    nativeToScVal,
    Networks,
    scValToNative,
    SorobanRpc,
    TransactionBuilder,
    xdr,
} from "@stellar/stellar-sdk";

import { getAssetData as readAssetData } from "./assets";
import { getConfig } from "./config";
import type { Asset, PoolData } from "./types";
import { validateString } from "./utils";

const transactionTimeout = 30;

type SorobanFunctions = "all_pairs" | "get_reserves" | "k_last" | "token_0" | "token_1";

const callSorobanFunction = async (
    contractAddress: string,
    sorobanFunctionName: SorobanFunctions,
    sorobanFunctionArguments?: Readonly<xdr.ScVal>,
): Promise<SorobanRpc.Api.RawSimulateTransactionResponse> => {
    const {
        rpc: { url, wallet },
    } = getConfig();

    const server = new SorobanRpc.Server(url);

    // We always need to fetch the source account, to make sure we have the
    // latest sequence number.
    const sourceAccount = await server.getAccount(wallet);
    const contract = new Contract(contractAddress);

    const call = sorobanFunctionArguments
        ? contract.call(sorobanFunctionName, sorobanFunctionArguments)
        : contract.call(sorobanFunctionName);

    const transaction = new TransactionBuilder(sourceAccount, {
        fee: BASE_FEE,
        networkPassphrase: Networks.TESTNET,
    })
        .addOperation(call)
        .setTimeout(transactionTimeout)
        .build();

    // Rule disabled because it refers to a dependency we cannot change.
    // eslint-disable-next-line no-underscore-dangle
    return await server._simulateTransaction(transaction);
};

const callPoolContract = async <SomePoolData>(
    poolAddress: string,
    sorobanFunctionName: "get_reserves" | "k_last" | "token_0" | "token_1",
): Promise<SomePoolData> => {
    const result = await callSorobanFunction(poolAddress, sorobanFunctionName);
    const firstResult = result.results?.[0];

    if (firstResult === undefined) {
        throw new Error("Calling the contract failed");
    }

    return scValToNative(xdr.ScVal.fromXDR(firstResult.xdr, "base64")) as SomePoolData;
};

const getAssetData = async (
    poolAddress: string,
    functionName: "token_0" | "token_1",
): Promise<Asset> => {
    const assetAddress = await callPoolContract<string>(poolAddress, functionName);

    return await readAssetData(assetAddress);
};

/**
 * Retrieves the total number of liquidity pools from the Soroswap Factory
 * contract's storage, returning the total number of pairs.
 *
 * @returns A promise that resolves to the total number of liquidity pools.
 * @throws If the contract data cannot be read.
 */
const getLiquidityPoolCount = async (): Promise<number> => {
    const config = getConfig();
    const server = new SorobanRpc.Server(config.rpc.url);

    const { val: value } = await server.getContractData(
        config.contracts.factory,
        xdr.ScVal.scvLedgerKeyContractInstance(),
    );

    const storage = value.contractData().val().instance().storage();

    if (storage === null) {
        throw new Error("Could not read the contract data");
    }

    // Rule disabled because this property is not camelCased in
    // the smart contract
    // eslint-disable-next-line @typescript-eslint/naming-convention
    return (scValToNative(xdr.ScVal.scvMap(storage)) as { TotalPairs: number }).TotalPairs;
};

const getLiquidityPoolAddress = async (index: number) => {
    const config = getConfig();

    const liquidityPoolAddress = await callSorobanFunction(
        config.contracts.factory,
        "all_pairs",
        nativeToScVal(index, { type: "u32" }),
    );

    if (!liquidityPoolAddress.results) {
        return undefined;
    }

    const address = xdr.ScVal.fromXDR(
        validateString(
            liquidityPoolAddress.results[0]?.xdr,
            "Invalid response: missing pool address",
        ),
        "base64",
    );

    return Address.fromScVal(address).toString();
};

/**
 * Retrieves all liquidity pool addresses from the Soroswap Factory contract.
 * Since there is no function to do that directly, this function fetches the
 * addresses by iterating through all pairs using their index.
 *
 * @returns A promise that resolves to an array of liquidity pool addresses.
 */
const getLiquidityPoolAddresses = async (): Promise<string[]> =>
    await Promise.all(
        Array.from(
            { length: await getLiquidityPoolCount() },
            // eslint-disable-next-line no-underscore-dangle, @typescript-eslint/naming-convention
            async (_unused, index) => await getLiquidityPoolAddress(index),
        ),
    ).then((results) => results.filter((address): address is string => address !== undefined));

/**
 * Retrieves data about a liquidity pool.
 *
 * @param poolAddress The address of the liquidity pool.
 * @returns A promise that resolves to the data about the liquidity pool.
 * @throws If any contract call fails or if asset data cannot be retrieved.
 */
const getLiquidityPoolData = async (poolAddress: string): Promise<PoolData> => ({
    // We call Soroban functions on the contract to populate the pool data.
    // Then we try to get more detailed data about the tokens.
    constantProductOfReserves: await callPoolContract<number>(poolAddress, "k_last"),
    firstToken: await getAssetData(poolAddress, "token_0"),
    poolContract: poolAddress,
    reserves: await callPoolContract<[number, number]>(poolAddress, "get_reserves"),
    secondToken: await getAssetData(poolAddress, "token_1"),
});

export { getLiquidityPoolAddresses, getLiquidityPoolCount, getLiquidityPoolData };