fix(interop): use correct input order to match redeemers (#487)

pallas-traverse/src/input.rs

@@ -62,6 +62,11 @@ impl<'b> MultiEraInput<'b> {
         }
     }
 
+    /// Returns the key used for lexicographical ordering of the input
+    pub fn lexicographical_key(&self) -> String {
+        format!("{}#{}", self.hash(), self.index())
+    }
+
     pub fn hash(&self) -> &Hash<32> {
         match self {
             MultiEraInput::Byron(x) => match x.deref().deref() {

pallas-traverse/src/tx.rs

@@ -196,6 +196,19 @@ impl<'b> MultiEraTx<'b> {
         }
     }
 
+    /// Return inputs as expected for processing
+    ///
+    /// To process inputs we need a set (no duplicated) and lexicographical
+    /// order (hash#idx). This function will take the raw inputs and apply the
+    /// aforementioned cleanup changes.
+    pub fn inputs_sorted_set(&self) -> Vec<MultiEraInput> {
+        let mut raw = self.inputs();
+        raw.sort_by_key(|x| x.lexicographical_key());
+        raw.dedup_by_key(|x| x.lexicographical_key());
+
+        raw
+    }
+
     /// Return the transaction reference inputs
     ///
     /// NOTE: It is possible for this to return duplicates. See

pallas-traverse/src/witnesses.rs

@@ -155,6 +155,12 @@ impl<'b> MultiEraTx<'b> {
         }
     }
 
+    pub fn find_spend_redeemer(&self, input_order: u32) -> Option<MultiEraRedeemer> {
+        self.redeemers().into_iter().find(|r| {
+            r.tag() == pallas_primitives::conway::RedeemerTag::Spend && r.index() == input_order
+        })
+    }
+
     pub fn plutus_v2_scripts(&self) -> &[PlutusV2Script] {
         match self {
             Self::Byron(_) => &[],