Uniswap V2 on Uniswap V4

[marktoda]

Proof of concept for a purist approach of Uniswap V2 style liquidity on Uniswap V4:

• Every pair has its own fungible ERC20 token
• reserves are stored as ERC6909 claims on Uniswap V4 for efficient routing across pools
• Full interface parity with Uniswap V2
• Possible to build uniswap v2 style routers directly integrating with the pair contract

[marktoda]

swap with tokens could look something like this:

+    function _swap(uint256 amount0Out, uint256 amount1Out, address to, bytes calldata data) internal {
+        // settle any raw token balances that we've received
+        uint256 amount0In = _settle(token0);
+        uint256 amount1In = _settle(token1);
+
+        // mint into new claims
+        if (amount0In > 0) poolManager.mint(address(this), token0.toId(), amount0In);
+        if (amount1In > 0) poolManager.mint(address(this), token0.toId(), amount1In);
+
+        // swap input claims for output claims
+        swapClaims(amount0Out, amount1Out, address(this), data);
+
+        // take outputs and send to the recipient
+        if (amount0Out > 0) {
+            poolManager.burn(address(this), token0.toId(), amount0Out);
+            poolManager.take(token0, to, amount0Out);
+        }
+        if (amount1Out > 0) {
+            poolManager.burn(address(this), token1.toId(), amount1Out);
+            poolManager.take(token1, to, amount1Out);
+        }
+    }