feat: (WIP) Support selection of transfer into router

- For protocols like Balancer and Curve, which expect funds to be in the router at the time of swap, we must support also transferring funds from the user into the router. Doing this in the router would mean we are dealing with transfers in two different places: in the router main methods and in the executors. To avoid this, we are now performing transfers just in the executors, and two transfer types have been added to support transfers into the router.

TODO:
- Add this for Balancer and Curve (only added for USV4 atm).
- TODO consider renaming TRANSFER_FROM and TRANSFER_PERMIT2 to include "pool" in the name

src/encoding/evm/strategy_encoder/strategy_encoders.rs

@@ -39,6 +39,7 @@ pub struct SingleSwapStrategyEncoder {
     swap_encoder_registry: SwapEncoderRegistry,
     permit2: Option<Permit2>,
     selector: String,
+    native_address: Bytes,
     router_address: Bytes,
 }
 
@@ -57,7 +58,13 @@ impl SingleSwapStrategyEncoder {
                 "singleSwap(uint256,address,address,uint256,bool,bool,address,bytes)".to_string(),
             )
         };
-        Ok(Self { permit2, selector, swap_encoder_registry, router_address })
+        Ok(Self {
+            permit2,
+            selector,
+            swap_encoder_registry,
+            native_address: chain.native_token()?,
+            router_address,
+        })
     }
 
     /// Encodes information necessary for performing a single hop against a given executor for
@@ -117,6 +124,7 @@ impl StrategyEncoder for SingleSwapStrategyEncoder {
             let transfer_type = self.get_transfer_method(
                 swap.clone(),
                 solution.given_token.clone(),
+                self.native_address.clone(),
                 self.permit2.clone().is_some(),
             );
 
@@ -289,6 +297,7 @@ impl StrategyEncoder for SequentialSwapStrategyEncoder {
                 let transfer_type = self.get_transfer_method(
                     swap.clone(),
                     solution.given_token.clone(),
+                    self.native_address.clone(),
                     self.permit2.clone().is_some(),
                 );
 
@@ -515,6 +524,7 @@ impl StrategyEncoder for SplitSwapStrategyEncoder {
                 let transfer_type = self.get_transfer_method(
                     swap.clone(),
                     solution.given_token.clone(),
+                    self.native_address.clone(),
                     self.permit2.clone().is_some(),
                 );
 
@@ -857,6 +867,7 @@ mod tests {
             "0000000000000000000000000000",             // padding
         ));
         let hex_calldata = encode(&calldata);
+        println!("{}", hex_calldata);
 
         assert_eq!(hex_calldata[..456], expected_input);
         assert_eq!(hex_calldata[1224..], expected_swap);
@@ -1354,9 +1365,9 @@ mod tests {
 
         let expected_swaps = String::from(concat!(
             // length of ple encoded swaps without padding
-            "0000000000000000000000000000000000000000000000000000000000000078",
+            "0000000000000000000000000000000000000000000000000000000000000079",
             // ple encoded swaps
-            "0076",   // Swap length
+            "0077",   // Swap length
             "00",     // token in index
             "01",     // token out index
             "000000", // split
@@ -1366,6 +1377,7 @@ mod tests {
             "a0b86991c6218b36c1d19d4a2e9eb0ce3606eb48", // group token in
             "6982508145454ce325ddbe47a25d4ec3d2311933", // group token in
             "00",                                       // zero2one
+            "04",                                       // transfer type (transfer to router)
             // First pool params
             "0000000000000000000000000000000000000000", // intermediary token (ETH)
             "000bb8",                                   // fee
@@ -1374,7 +1386,7 @@ mod tests {
             "6982508145454ce325ddbe47a25d4ec3d2311933", // intermediary token (PEPE)
             "0061a8",                                   // fee
             "0001f4",                                   // tick spacing
-            "0000000000000000"                          // padding
+            "00000000000000"                          // padding
         ));
 
         let hex_calldata = encode(&calldata);