server: Allow to create a GolombCodedSet from block addresses

server/app/com/xsn/explorer/gcs/GolombEncoding.scala

@@ -1,6 +1,7 @@
 package com.xsn.explorer.gcs
 
 import com.google.common.hash.Hashing
+import com.xsn.explorer.models.persisted.Block
 
 import scala.collection.SortedSet
 
@@ -180,4 +181,11 @@ object GolombEncoding {
   def default(key: SipHashKey): GolombEncoding = {
     new GolombEncoding(p = DefaultP, m = DefaultM, key = key)
   }
+
+  def encode(block: Block.HasTransactions): Option[GolombCodedSet] = {
+    val key = SipHashKey.fromBtcutil(block.hash)
+    val encoder = default(key)
+    val addresses = block.collectAddresses
+    encoder.encode(addresses.map(_.string))
+  }
 }

server/app/com/xsn/explorer/models/persisted/Block.scala

@@ -37,5 +37,16 @@ object Block {
     def height: Height = block.height
     def previousBlockhash: Option[Blockhash] = block.previousBlockhash
     def asTip: HasTransactions = HasTransactions(block.copy(nextBlockhash = None), transactions)
+
+    /**
+     * Collect the addresses involved in the block.
+     */
+    def collectAddresses: Set[Address] = {
+      transactions.foldLeft(Set.empty[Address]) { case (acc, tx) =>
+        val spending = tx.inputs.map(_.address)
+        val receiving = tx.outputs.map(_.address)
+        spending.toSet ++ receiving.toSet ++ acc
+      }
+    }
   }
 }