server: Add endpoint - GET /v2/balances

Returns the highest balances allowing to paginate from highest to smallest.

server/app/com/xsn/explorer/services/BalanceService.scala

@@ -1,14 +1,16 @@
 package com.xsn.explorer.services
 
 import com.alexitc.playsonify.core.FutureOr.Implicits.{FutureOps, OrOps}
-import com.alexitc.playsonify.core.FuturePaginatedResult
+import com.alexitc.playsonify.core.{FutureApplicationResult, FuturePaginatedResult}
 import com.alexitc.playsonify.models.ordering.OrderingQuery
-import com.alexitc.playsonify.models.pagination.PaginatedQuery
+import com.alexitc.playsonify.models.pagination.{Limit, Offset, PaginatedQuery}
 import com.alexitc.playsonify.validators.PaginatedQueryValidator
 import com.xsn.explorer.data.async.BalanceFutureDataHandler
-import com.xsn.explorer.models.Balance
+import com.xsn.explorer.errors.AddressFormatError
+import com.xsn.explorer.models.{Address, Balance, WrappedResult}
 import com.xsn.explorer.parsers.BalanceOrderingParser
 import javax.inject.Inject
+import org.scalactic.{Good, One, Or}
 
 import scala.concurrent.ExecutionContext
 
@@ -27,4 +29,22 @@ class BalanceService @Inject() (
 
     result.toFuture
   }
+
+  def getHighest(limit: Limit, lastSeenAddressString: Option[String]): FutureApplicationResult[WrappedResult[List[Balance]]] = {
+    val result = for {
+      _ <- paginatedQueryValidator.validate(PaginatedQuery(Offset(0), limit), 100).toFutureOr
+
+      lastSeenAddress <- {
+        lastSeenAddressString
+            .map(Address.from)
+            .map { txid => Or.from(txid, One(AddressFormatError)).map(Option.apply) }
+            .getOrElse(Good(Option.empty))
+            .toFutureOr
+      }
+
+      data <- balanceFutureDataHandler.getHighestBalances(limit, lastSeenAddress).toFutureOr
+    } yield WrappedResult(data)
+
+    result.toFuture
+  }
 }

server/app/controllers/BalancesController.scala

@@ -19,4 +19,8 @@ class BalancesController @Inject() (
 
     balanceService.get(paginatedQuery, orderingQuery)
   }
+
+  def getHighest(limit: Int, lastSeenAddress: Option[String]) = public { _ =>
+    balanceService.getHighest(Limit(limit), lastSeenAddress)
+  }
 }

server/conf/routes

@@ -23,6 +23,7 @@ GET   /blocks/:blockhash/transactions    controllers.BlocksController.getTransac
 GET   /stats                 controllers.StatisticsController.getStatus()
 
 GET   /balances              controllers.BalancesController.get(offset: Int ?= 0, limit: Int ?= 10, orderBy: String ?= "")
+GET   /v2/balances           controllers.BalancesController.getHighest(limit: Int ?= 10, lastSeenAddress: Option[String])
 
 GET   /masternodes           controllers.MasternodesController.get(offset: Int ?= 0, limit: Int ?= 10, orderBy: String ?= "")
 GET   /masternodes/:ip       controllers.MasternodesController.getBy(ip: String)