v4-constant-sum

Constant-sum swap on Uniswap v4 🦄

This repo is not production ready, and only serves as an example for custom curves on v4

With recent changes to v4, Hooks can swap on custom curves!

v4-constant-sum implements constant-sum swaps (x + y = k), allowing for an exact 1:1 swap everytime

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Methodology

1. To faciliate a custom curve, we need to skip the concentrated liquidity swap. We'll use the NoOp pattern, allowing us to implement the constant-sum swap.

2. The hook will hold its own token balances (as liquidity for the constant-sum curve)

3. The beforeSwap hook will handle the constant-sum curve:

   1. inbound tokens are taken from the PoolManager
      • this creates a debt, that is paid for by the swapper via the swap router
      • the inbound token is added to the hook's reserves
   2. an equivalent number of outbound tokens is sent from the hook to the PoolManager
      • the outbound token is removed from the hook's reserves
      • this creates a credit -- the swap router claims it and sends it to the swapper

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NOTE: The tests are dependent on v4-core#430

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Additional resources:

v4-template provides a minimal template and environment for developing v4 hooks

v4-periphery contains advanced hook implementations that serve as a great reference

v4-core