Factor out a dissolve_spare_bucket fn

This function takes a spare bucket, specified by the given key, and
repurposes the bridges as unallocated.

crates/lox-library/src/lib.rs

@@ -94,6 +94,12 @@ pub enum OpenInvitationError {
     NoBridgesAvailable,
 }
 
+#[derive(Error, Debug)]
+pub enum BridgeTableError {
+    #[error("The bucket corresponding to key {0} was not in the bridge table")]
+    MissingBucket(u32),
+}
+
 /// Private Key of the Issuer
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct IssuerPrivKey {
@@ -510,6 +516,25 @@ impl BridgeAuth {
         res
     }
 
+    // Repurpose a bucket of spares into unallocated bridges
+    pub fn dissolve_spare_bucket(&mut self, key: u32) -> Result<(), BridgeTableError> {
+        self.bridge_table.spares.remove(&key);
+        // Get the actual bridges from the spare bucket
+        let spare_bucket = self
+            .bridge_table
+            .buckets
+            .remove(&key)
+            .ok_or(BridgeTableError::MissingBucket(key))?;
+        for bridge in spare_bucket.iter() {
+            self.bridge_table.unallocated_bridges.push(*bridge);
+            // Mark bucket as unreachable while it is unallocated
+            self.bridge_table.reachable.remove(bridge);
+        }
+        self.bridge_table.keys.remove(&key);
+        self.bridge_table.recycleable_keys.push(key);
+        Ok(())
+    }
+
     /// Attempt to remove a bridge that is failing tests and replace it with a bridge from
     /// available_bridge or from a spare bucket
     pub fn bridge_replace(
@@ -573,28 +598,10 @@ impl BridgeAuth {
             else {
                 return ReplaceSuccess::NotReplaced;
             };
-            self.bridge_table.spares.remove(&spare);
-            // Get the actual bridges from the spare bucket
-            let spare_bucket = match self.bridge_table.buckets.remove(&spare) {
-                Some(spare_bucket) => spare_bucket,
-                // This should not happen if the rest of the functions are correct, we can assume unwrap will succeed
-                None => return ReplaceSuccess::NotReplaced,
+            let Ok(_) = self.dissolve_spare_bucket(spare) else {
+                return ReplaceSuccess::NotReplaced;
             };
-            // Remove the spare bucket uid from the keys map
-            self.bridge_table.keys.remove(&spare);
-            self.bridge_table.recycleable_keys.push(spare);
-            let mut replacement: &BridgeLine = &BridgeLine::default();
-            // Make the first spare the replacement bridge, add the others to the set of
-            // unallocated_bridges
-            for spare_bridge in spare_bucket.iter() {
-                if replacement.port > 0 {
-                    self.bridge_table.unallocated_bridges.push(*spare_bridge);
-                    // Mark bucket as unreachable while it is unallocated
-                    self.bridge_table.reachable.remove(spare_bridge);
-                } else {
-                    replacement = spare_bridge;
-                }
-            }
+            let replacement = &self.bridge_table.unallocated_bridges.pop().unwrap();
             for (bucketnum, offset) in positions.iter() {
                 let mut bridgelines = match self.bridge_table.buckets.get(bucketnum) {
                     Some(bridgelines) => *bridgelines,