[Ethereum] How to calculate the number of tokens owned by the liquidity pool via bonding curve on Uniswap

bonding-curvestokensuniswap

I know a little bit about the Uniswap, providing liquidity, bonding curves…

But I'm still struggling to perform the actual math – what is the actual formula?

Real-life example (easier to operate on real numbers)

Uniswap pool: https://uniswap.info/pair/0x2680a95fc9de215f1034f073185cc1f2a28b4107
Bonding curve contract: https://etherscan.io/address/0x2680a95fc9de215f1034f073185cc1f2a28b4107

Situation

Round numbers:

300 ETH
300k GET

Say I'm a whale and I add 60 ETH and 60k GET to the bonding curve.

The bonding curve now:

360 ETH
360k GET

I have 20% of the liquidity pool.

Calculation

What will happen in cases 1 and 2?

Someone sends 10 ETH into the bonding curve?
Someone sends 10k GET into the bonding curve?

My understanding is that I will still own 20% of the liquidity pool but what about the actual numbers of ETH and GET?

Best Answer

As a liquidity provider, you cannot send money on either side of the pool, they need to be added in the same proportions.

However, someone is free to buy ETH/GET or buy GET/ETH from the pool. In this case the number of tokens left in the pool changes and the price moves using the following formula:

ETH/GET price before = 360/360k = 1000

For the case (1): bought 1000 GET with 10 ETH

ETH/GET new price = 350k/370 = 945

For the sake of simplification, I left of liquidity provider fees from the calculations.

Related Solutions

Uniswap API – How to Query for Pair ID of a Chosen Token

You can write a query to filter all the liquidity pairs on Uniswap and get the pair address

    {  pairs (where :{token0 : "0x0f7f961648ae6db43c75663ac7e5414eb79b5704", token1 :"0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2"}) { // token1 is the ethereum address
    id
    createdAtTimestamp
    volumeUSD
    //any other field you want
  }
}

[Ethereum] Trying to make sense of Uniswap v3 fees (feeGrowthInside0LastX128, feeGrowthGlobal0X128)

There is a bunch of functions on the smart contract that explains how to use the liquidity field: In Uniswap V3 core repository, in Position.sol line 60:

// calculate accumulated fees
  uint128 tokensOwed0 =
     uint128(
        FullMath.mulDiv(
           feeGrowthInside0X128 - _self.feeGrowthInside0LastX128,
           _self.liquidity,
           FixedPoint128.Q128
        )
     );

This would translate to this in javascript, using bignumber.js

const tokensOwed0 = feeGrowthInside0LastX128
    .times(liquidity)
    .div(new bn(2).pow(128));
const tokensOwed1 = feeGrowthInside1LastX128
    .times(liquidity)
    .div(new bn(2).pow(128));

You may need to divide further by the decimals of the underlying ERC20