adding dynamic swap fee to fx pools

[gmbronco]

closes #802

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[franzns]

We should think about how a negative fee and APR affects our UI and if this is what we want to show

[franzns]

How can we hardcode this? Isnt this different for each chain?

[franzns]

Do we only compare against USDC? No other FOREX such as EURC?

[gmbronco]

It looks like all the markets are against USDC, but true that it needs to be done for other chains as well.

[schystz]

Hi @franzns, @gmbronco, would it be possible to add a quoteToken property on the Pool model? This new prop will hold the quote token address, whether USDC, USDC.e, or any token.

This is how we assign the quoteToken value in our balancer-subgraph fork:

function handleNewFXPool(event: ethereum.Event, permissionless: boolean): void {
...
  pool.quoteToken = getFXPoolQuoteToken(poolAddress);
...
}

function getFXPoolQuoteToken(poolAddress: Address): Bytes {
  let poolContract = FXPool.bind(poolAddress);
  // FXPool **always** holds the quote token in the second position
  let call = poolContract.try_derivatives(BigInt.fromI32(1));
  if (call.reverted) {
    log.error('Failed to get quote token for FXPool: {}', [poolAddress.toHexString()]);
    return stringToBytes('0x');
  }
  return call.value;
}

We then refer to quoteToken instead of hardcoded USDC addresses to determine base and quote:

let isTokenInBase = tokenOutAddress === pool.quoteToken;

[franzns]

Hi @franzns, @gmbronco, would it be possible to add a quoteToken property on the Pool model? This new prop will hold the quote token address, whether USDC, USDC.e, or any token.

This is how we assign the quoteToken value in our balancer-subgraph fork:

function handleNewFXPool(event: ethereum.Event, permissionless: boolean): void {
...
  pool.quoteToken = getFXPoolQuoteToken(poolAddress);
...
}

function getFXPoolQuoteToken(poolAddress: Address): Bytes {
  let poolContract = FXPool.bind(poolAddress);
  // FXPool **always** holds the quote token in the second position
  let call = poolContract.try_derivatives(BigInt.fromI32(1));
  if (call.reverted) {
    log.error('Failed to get quote token for FXPool: {}', [poolAddress.toHexString()]);
    return stringToBytes('0x');
  }
  return call.value;
}

We then refer to quoteToken instead of hardcoded USDC addresses to determine base and quote:

let isTokenInBase = tokenOutAddress === pool.quoteToken;

Yes, we should definitely do that. We already have pool type specific data where we can add the quote token. Is the quote token immutable?

[schystz]

Yes, the quote token is immutable for FX pools

[franzns]

Think we talked about the option of a possible negative APR. Would that mean that his fee might be negative? What are the downstream effects if so?

[gmbronco]

is there upside / downside? i assume it's just a property of FX pools. unless you mean if some other parts of the app will need to be updated. that i'm not sure. Is there anything that depends on the apr?

[schystz]

Hi @gmbronco, don't we also need to update how the fees24h is computed in pool.snapshot-service.ts? (note: this file seems to exist in two places)

The code assumes a static pool swap fee, but FX pools have a dynamic swap fee

fees24h: volume24h * parseFloat(poolAtBlock.swapFee)

I'm thinking something like this might work:

fees24h: parseFloat(pool.totalSwapFee) - parseFloat(pool24hAgo.totalSwapFee)

[franzns]

Hi @gmbronco, don't we also need to update how the fees24h is computed in pool.snapshot-service.ts? (note: this file seems to exist in two places)

The code assumes a static pool swap fee, but FX pools have a dynamic swap fee

fees24h: volume24h * parseFloat(poolAtBlock.swapFee)

I'm thinking something like this might work:

fees24h: parseFloat(pool.totalSwapFee) - parseFloat(pool24hAgo.totalSwapFee)

Good catch. We'll need to think about that as we'll change the snapshot generation not to rely on subgraph pricing anymore. We can calculate fees24h based on the swap events for example which would be more accurate.

[schystz]

Hi @gmbronco, don't we also need to update how the fees24h is computed in pool.snapshot-service.ts? (note: this file seems to exist in two places)
The code assumes a static pool swap fee, but FX pools have a dynamic swap fee

fees24h: volume24h * parseFloat(poolAtBlock.swapFee)

I'm thinking something like this might work:

fees24h: parseFloat(pool.totalSwapFee) - parseFloat(pool24hAgo.totalSwapFee)

Good catch. We'll need to think about that as we'll change the snapshot generation not to rely on subgraph pricing anymore. We can calculate fees24h based on the swap events for example which would be more accurate.

Great, that makes sense to me!