server: Reuse the paginated query on the BlockPostgresDAO

The getFirstBlock and getLatestBlock methods use the paginated
query to get the results.

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

@@ -4,7 +4,7 @@ import java.sql.Connection
 import javax.inject.Inject
 
 import anorm._
-import com.alexitc.playsonify.models.{Count, FieldOrdering, PaginatedQuery}
+import com.alexitc.playsonify.models._
 import com.xsn.explorer.data.anorm.interpreters.FieldOrderingSQLInterpreter
 import com.xsn.explorer.data.anorm.parsers.BlockParsers._
 import com.xsn.explorer.models.fields.BlockField
@@ -138,26 +138,14 @@ class BlockPostgresDAO @Inject() (fieldOrderingSQLInterpreter: FieldOrderingSQLI
   }
 
   def getLatestBlock(implicit conn: Connection): Option[Block] = {
-    SQL(
-      """
-        |SELECT blockhash, previous_blockhash, next_blockhash, tpos_contract, merkle_root, size,
-        |       height, version, time, median_time, nonce, bits, chainwork, difficulty
-        |FROM blocks
-        |ORDER BY height DESC
-        |LIMIT 1
-      """.stripMargin
-    ).as(parseBlock.singleOpt).flatten
+    val query = PaginatedQuery(Offset(0), Limit(1))
+    val ordering = FieldOrdering(BlockField.Height, OrderingCondition.DescendingOrder)
+    getBy(query, ordering).headOption
   }
 
   def getFirstBlock(implicit conn: Connection): Option[Block] = {
-    SQL(
-      """
-        |SELECT blockhash, previous_blockhash, next_blockhash, tpos_contract, merkle_root, size,
-        |       height, version, time, median_time, nonce, bits, chainwork, difficulty
-        |FROM blocks
-        |ORDER BY height
-        |LIMIT 1
-      """.stripMargin
-    ).as(parseBlock.singleOpt).flatten
+    val query = PaginatedQuery(Offset(0), Limit(1))
+    val ordering = FieldOrdering(BlockField.Height, OrderingCondition.AscendingOrder)
+    getBy(query, ordering).headOption
   }
 }