How to query prices on Fantom blockchain

Question

I'm trying to write some Javascript code to query Fantom DEXes to find out the price wFTM in various wFTM / USDC liquidity pools and I'm a bit lost as to what contract method to call.

I'm starting with Spookyswap and I'm thinking what I need to do is first get a reference to the Factory Contract, and then call getPair() on it with the contract addresses for wFTM (0x21be370D5312f44cB42ce377BC9b8a0cEF1A4C83) and USDC (0x04068DA6C83AFCFA0e13ba15A6696662335D5B75)

https://ftmscan.com/address/0x152ee697f2e276fa89e96742e9bb9ab1f2e61be3#readContract

When I call that method, I get a reference to this contract

https://ftmscan.com/address/0x2b4C76d0dc16BE1C31D4C1DC53bF9B45987Fc75c#readContract

which has two variables

price0CumulativeLast

price1CumulativeLast

which logically seem like the variables I want, but I'm not really sure that's correct and I have no idea how to translate them into USDC.

There's probably something very obvious I'm not grokking, so any help will be much appreciated. This is my first attempt to learn web3 by creating something on my own.

Thanks!

Answer 1

Since spookyswap is pretty much uniswapv2 its probably best to reference the uniswapv2 docs for pricing https://docs.uniswap.org/protocol/V2/reference/smart-contracts/pair#getreserves

For any ERC20/stable pair you should be able to do something along these lines. Get the reserves and calculate the spot price

    uReserves = await uPair0.methods.getReserves().call()
    uReserve0 = uReserves[0] //dai
    uReserve1 = uReserves[1] //eth
    priceEth = (uReserve0/uReserve1) //dai per eth