server: Add getLatestTransactionBy method to the TransactionDataHandler

The method returns the latest transaction id for each of the given addresses.

server/app/com/xsn/explorer/data/TransactionDataHandler.scala

@@ -20,6 +20,8 @@ trait TransactionDataHandler[F[_]] {
       blockhash: Blockhash,
       paginatedQuery: PaginatedQuery,
       ordering: FieldOrdering[TransactionField]): F[PaginatedResult[TransactionWithValues]]
+
+  def getLatestTransactionBy(addresses: List[Address]): F[Map[String, String]]
 }
 
 trait TransactionBlockingDataHandler extends TransactionDataHandler[ApplicationResult]

server/app/com/xsn/explorer/data/anorm/TransactionPostgresDataHandler.scala

@@ -45,4 +45,10 @@ class TransactionPostgresDataHandler @Inject() (
 
     Good(result)
   }
+
+  def getLatestTransactionBy(addresses: List[Address]): ApplicationResult[Map[String, String]] = withConnection { implicit conn =>
+    val result = transactionPostgresDAO.getLatestTransactionBy(addresses)
+
+    Good(result)
+  }
 }

server/app/com/xsn/explorer/data/anorm/dao/TransactionPostgresDAO.scala

@@ -206,6 +206,30 @@ class TransactionPostgresDAO @Inject() (fieldOrderingSQLInterpreter: FieldOrderi
     ).as(parseTransactionOutput.*).flatten
   }
 
+  def getLatestTransactionBy(addresses: List[Address])(implicit conn: Connection): Map[String, String] = {
+
+    import SqlParser._
+
+    val result = SQL(
+      s"""
+        |SELECT address, (
+        |  SELECT txid
+        |  FROM address_transaction_details
+        |  WHERE address = a.address
+        |  ORDER BY time DESC
+        |  LIMIT 1
+        |) AS txid
+        |FROM address_transaction_details a
+        |GROUP BY address
+        |HAVING address IN ({addresses});
+      """.stripMargin
+    ).on(
+      'addresses -> addresses.map(_.string)
+    ).as((str("address") ~ str("txid")).map(flatten).*)
+
+    result.toMap
+  }
+
   private def upsertTransaction(transaction: Transaction)(implicit conn: Connection): Option[Transaction] = {
     SQL(
       """

server/app/com/xsn/explorer/data/async/TransactionFutureDataHandler.scala

@@ -35,4 +35,8 @@ class TransactionFutureDataHandler @Inject() (
 
     blockingDataHandler.getByBlockhash(blockhash, paginatedQuery, ordering)
   }
+
+  override def getLatestTransactionBy(addresses: List[Address]): FutureApplicationResult[Map[String, String]] = Future {
+    blockingDataHandler.getLatestTransactionBy(addresses)
+  }
 }

server/test/com/xsn/explorer/data/TransactionPostgresDataHandlerSpec.scala

@@ -296,6 +296,27 @@ class TransactionPostgresDataHandlerSpec extends PostgresDataHandlerSpec with Be
     }
   }
 
+  "getLatestTransactionBy" should {
+    "return the relation address -> latest txid" in {
+      clearDatabase()
+      val blocks = blockList
+      blocks.map(createBlock)
+
+      val expected = Map(
+        "XcqpUChZhNkVDgQqFF9U4DdewDGUMWwG53" -> "41e315108dc2df60caddbc7e8740a5614217f996c96898019e69b3195fd7ee10",
+        "XdJnCKYNwzCz8ATv8Eu75gonaHyfr9qXg9" -> "1e591eae200f719344fc5df0c4286e3fb191fb8a645bdf054f9b36a856fce41e"
+      )
+
+      val addresses = List(
+        createAddress("XdJnCKYNwzCz8ATv8Eu75gonaHyfr9qXg9"),
+        createAddress("XcqpUChZhNkVDgQqFF9U4DdewDGUMWwG53"),
+        createAddress("XcqpUChZhNkVDgQqFF9U4DdewDGUMWwG54"),
+      )
+      val result = dataHandler.getLatestTransactionBy(addresses).get
+      result mustEqual expected
+    }
+  }
+
   private def createBlock(block: Block) = {
     val transactions = block.transactions
         .map(_.string)

server/test/com/xsn/explorer/helpers/TransactionDummyDataHandler.scala

@@ -13,4 +13,6 @@ class TransactionDummyDataHandler extends TransactionBlockingDataHandler {
   override def getUnspentOutputs(address: Address): ApplicationResult[List[Transaction.Output]] = ???
 
   override def getByBlockhash(blockhash: Blockhash, paginatedQuery: PaginatedQuery, ordering: FieldOrdering[TransactionField]): ApplicationResult[PaginatedResult[TransactionWithValues]] = ???
+
+  override def getLatestTransactionBy(addresses: List[Address]): ApplicationResult[Map[String, String]] = ???
 }