Implement splits (ordinals#2530)

src/index/updater/rune_updater.rs

@@ -97,8 +97,12 @@ impl<'a, 'db, 'tx> RuneUpdater<'a, 'db, 'tx> {
 
       if !burn {
         for Edict { id, amount, output } in runestone.edicts {
+          let Ok(output) = usize::try_from(output) else {
+            continue;
+          };
+
           // Skip edicts not referring to valid outputs
-          if output >= tx.output.len() as u128 {
+          if output > tx.output.len() {
             continue;
           }
 
@@ -119,19 +123,46 @@ impl<'a, 'db, 'tx> RuneUpdater<'a, 'db, 'tx> {
             }
           };
 
-          // Get the allocatable amount
-          let amount = if amount == 0 {
-            *balance
-          } else {
-            amount.min(*balance)
+          let mut allocate = |balance: &mut u128, amount: u128, output: usize| {
+            if amount > 0 {
+              *balance -= amount;
+              *allocated[output].entry(id).or_default() += amount;
+            }
           };
 
-          // If the amount to be allocated is greater than zero,
-          // deduct it from the remaining balance, and increment
-          // the allocated entry.
-          if amount > 0 {
-            *balance -= amount;
-            *allocated[output as usize].entry(id).or_default() += amount;
+          if output == tx.output.len() {
+            // find non-OP_RETURN outputs
+            let destinations = tx
+              .output
+              .iter()
+              .enumerate()
+              .filter_map(|(output, tx_out)| {
+                (!tx_out.script_pubkey.is_op_return()).then_some(output)
+              })
+              .collect::<Vec<usize>>();
+
+            if amount == 0 {
+              // if amount is zero, divide balance between eligible outputs
+              let amount = *balance / destinations.len() as u128;
+
+              for output in destinations {
+                allocate(balance, amount, output);
+              }
+            } else {
+              // if amount is non-zero, distribute amount to eligible outputs
+              for output in destinations {
+                allocate(balance, amount.min(*balance), output);
+              }
+            }
+          } else {
+            // Get the allocatable amount
+            let amount = if amount == 0 {
+              *balance
+            } else {
+              amount.min(*balance)
+            };
+
+            allocate(balance, amount, output);
           }
         }
       }