feat: enforce checked amount when encoding to router

- If using the tycho router, you must either set the slippage with the expected amount in the solution, or you must set the checked amount
- Decided to put this in the split swap strategy validator, since this is not relevant when it comes to direct execution (no checks are performed inside the executors)

src/encoding/evm/strategy_encoder/strategy_validators.rs

@@ -4,7 +4,7 @@ use tycho_core::Bytes;
 
 use crate::encoding::{
     errors::EncodingError,
-    models::{NativeAction, Swap},
+    models::{NativeAction, Solution, Swap},
 };
 
 /// Validates whether a sequence of split swaps represents a valid solution.
@@ -90,6 +90,19 @@ impl SplitSwapValidator {
         Ok(())
     }
 
+    /// Raises an error if the solution does not have checked amount set or slippage with checked
+    /// amount set.
+    pub fn validate_solution_min_amounts(&self, solution: &Solution) -> Result<(), EncodingError> {
+        if solution.checked_amount.is_none() &&
+            (solution.slippage.is_none() || solution.expected_amount.is_none())
+        {
+            return Err(EncodingError::InvalidInput(
+                "Checked amount or slippage with expected amount must be provided".to_string(),
+            ))
+        }
+        Ok(())
+    }
+
     /// Raises an error if swaps do not represent a valid path from the given token to the checked
     /// token.
     ///
@@ -178,6 +191,8 @@ impl SplitSwapValidator {
 mod tests {
     use std::str::FromStr;
 
+    use num_bigint::BigUint;
+    use rstest::rstest;
     use tycho_core::{models::protocol::ProtocolComponent, Bytes};
 
     use super::*;
@@ -549,4 +564,80 @@ mod tests {
         );
         assert_eq!(result, Ok(()));
     }
+
+    #[rstest]
+    #[case::slippage_with_expected_amount_set(
+        Some(0.01),
+        Some(BigUint::from(1000u32)),
+        None,
+        Ok(())
+    )]
+    #[case::min_amount_set(
+        None,
+        None,
+        Some(BigUint::from(1000u32)),
+        Ok(())
+    )]
+    #[case::slippage_with_min_amount_set(
+        Some(0.01),
+        Some(BigUint::from(1000u32)),
+        Some(BigUint::from(1000u32)),
+        Ok(())
+    )]
+    #[case::slippage_without_expected_amount_set(
+        Some(0.01),
+        None,
+        None,
+        Err(
+            EncodingError::InvalidInput(
+                "Checked amount or slippage with expected amount must be provided".to_string()
+            )
+        )
+    )]
+    #[case::none_set(
+        None,
+        None,
+        None,
+        Err(
+            EncodingError::InvalidInput(
+                "Checked amount or slippage with expected amount must be provided".to_string()
+            )
+        )
+    )]
+    fn test_validate_min_amount_passed(
+        #[case] slippage: Option<f64>,
+        #[case] expected_amount: Option<BigUint>,
+        #[case] min_amount: Option<BigUint>,
+        #[case] expected_result: Result<(), EncodingError>,
+    ) {
+        let weth = Bytes::from_str("0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2").unwrap();
+        let usdc = Bytes::from_str("0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48").unwrap();
+
+        let validator = SplitSwapValidator;
+        let swap = Swap {
+            component: ProtocolComponent {
+                id: "0xA478c2975Ab1Ea89e8196811F51A7B7Ade33eB11".to_string(),
+                protocol_system: "uniswap_v2".to_string(),
+                ..Default::default()
+            },
+            token_in: weth.clone(),
+            token_out: usdc.clone(),
+            split: 0f64,
+        };
+
+        let solution = Solution {
+            exact_out: false,
+            given_token: weth,
+            checked_token: usdc,
+            slippage,
+            checked_amount: min_amount,
+            expected_amount,
+            swaps: vec![swap],
+            native_action: Some(NativeAction::Wrap),
+            ..Default::default()
+        };
+
+        let result = validator.validate_solution_min_amounts(&solution);
+        assert_eq!(result, expected_result);
+    }
 }