Finding the COMP APY

Get_COMP_APY.md

From Blockchain With JSON RPC and JavaScript

const Compound = require('@compound-finance/compound-js');

const provider = 'https://mainnet.infura.io/v3/' + process.env.infuraApiKey;

const cTokenToGetCompApy = Compound.cUSDC; // Pick an asset

const underlying = cTokenToGetCompApy.slice(1, 10);
const underlyingDecimals = Compound.decimals[underlying];
const cTokenDecimals = 8; // always 8
const comptroller = Compound.util.getAddress(Compound.Comptroller);
const pf = Compound.util.getAddress(Compound.PriceFeed);
const cTokenAddr = Compound.util.getAddress(cTokenToGetCompApy);
const apxBlockSpeedInSeconds = 12;

(async function() {

  // let compSpeed = await Compound.eth.read(
  //   comptroller,
  //   'function compSpeeds(address cToken) public returns (uint)',
  //   [ cTokenAddr ],
  //   { provider }
  // );

  let compBorrowSpeed = await Compound.eth.read(
    comptroller,
    'function compBorrowSpeeds(address cToken) public returns (uint)',
    [ cTokenAddr ],
    { provider }
  );

  let compSupplySpeed = await Compound.eth.read(
    comptroller,
    'function compSupplySpeeds(address cToken) public returns (uint)',
    [ cTokenAddr ],
    { provider }
  );

  let compPrice = await Compound.eth.read(
    pf,
    'function price(string memory symbol) external view returns (uint)',
    [ Compound.COMP ],
    { provider }
  );

  let assetPrice = await Compound.eth.read(
    pf,
    'function price(string memory symbol) external view returns (uint)',
    [ underlying ],
    { provider }
  );

  let totalBorrows = await Compound.eth.read(
    cTokenAddr,
    'function totalBorrowsCurrent() returns (uint)',
    [],
    { provider }
  );

  let totalSupply = await Compound.eth.read(
    cTokenAddr,
    'function totalSupply() returns (uint)',
    [],
    { provider }
  );

  let exchangeRate = await Compound.eth.read(
    cTokenAddr,
    'function exchangeRateCurrent() returns (uint)',
    [],
    { provider }
  );

  // Total supply needs to be converted from cTokens
  const mantissa = 18 + parseInt(underlyingDecimals) - cTokenDecimals;
  exchangeRate = +exchangeRate.toString() / Math.pow(10, 18);

  // compSpeed = compSpeed / 1e18; // COMP has 18 decimal places
  compBorrowSpeed = compBorrowSpeed / 1e18;
  compSupplySpeed = compSupplySpeed / 1e18;
  compPrice = compPrice / 1e6;  // price feed is USD price with 6 decimal places
  assetPrice = assetPrice / 1e6;
  totalBorrows = +totalBorrows.toString() / (Math.pow(10, underlyingDecimals));
  totalSupply = (+totalSupply.toString() * exchangeRate) / (Math.pow(10, underlyingDecimals));

  // console.log('compSpeed:', compSpeed);
  // console.log('compBorrowSpeed:', compBorrowSpeed);
  // console.log('compSupplySpeed:', compSupplySpeed);
  // console.log('compPrice:', compPrice);
  // console.log('assetPrice:', assetPrice);
  // console.log('totalBorrows:', totalBorrows);
  // console.log('totalSupply:', totalSupply);
  // console.log('exchangeRate:', exchangeRate);

  // const compPerDay = compSpeed * parseInt((60 * 60 * 24) / apxBlockSpeedInSeconds);
  const compToBorrowersPerDay = compBorrowSpeed * parseInt((60 * 60 * 24) / apxBlockSpeedInSeconds);
  const compToSuppliersPerDay = compSupplySpeed * parseInt((60 * 60 * 24) / apxBlockSpeedInSeconds);

  const compBorrowApy = 100 * (Math.pow((1 + (compPrice * compToBorrowersPerDay / (totalBorrows * assetPrice))), 365) - 1);
  const compSupplyApy = 100 * (Math.pow((1 + (compPrice * compToSuppliersPerDay / (totalSupply * assetPrice))), 365) - 1);

  console.log('COMP Borrow APY %:', compBorrowApy);
  console.log('COMP Supply APY %:', compSupplyApy);

})().catch(console.error);

Thanks! now that the v2 API is being deprecated, this should be in the compound docs.

One thing to note: the price feed does not seem to be returning the correct COMP price. when plugging in the COMP price from another source the numbers line up with the compound v2 frontend.