query_osmosis_spot_price.ts

import { Tendermint34Client } from "@cosmjs/tendermint-rpc";
import { createProtobufRpcClient, QueryClient } from "@cosmjs/stargate";
import { osmosis } from "osmojs";
import { Long } from "@osmonauts/helpers";

const rpcEndpoint = "https://rpc.osmosis.zone:443";

async function querySpotPrice(
  poolId: number,
  token1Denom: string,
  token2Denom: string,
) {
  // 4 steps just to create a query service!
  const tmClient = await Tendermint34Client.connect(rpcEndpoint);
  const queryClient = new QueryClient(tmClient);
  const protobufRpcClient = createProtobufRpcClient(queryClient);
  const queryService = new osmosis.gamm.v1beta1.QueryClientImpl(protobufRpcClient);
  
  // do the actual query
  const queryRes = await queryService.pool({
    // poolId needs to be in `Long` type
    poolId: Long.fromInt(poolId),
  });
  
  // `pool` has protobuf `Any` type, so neesd to be decoded
  const pool = osmosis.gamm.v1beta1.Pool.decode(queryRes.pool.value);
  
  const token1InPool = pool
    .poolAssets
    .find((asset) => asset.token.denom === token1Denom)!
    .token
    .amount;
  const token2InPool = pool
    .poolAssets
    .find((asset) => asset.token.denom === token2Denom)!
    .token
    .amount;
  
  return {
    token1PerToken2: token1InPool / token2InPool,
    token2PerToken1: token2InPool / token1InPool,
  };
}