server: allow to get block extractionMethod from the BlockService

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

@@ -101,6 +101,31 @@ class BlockService @Inject() (
     result.toFuture
   }
 
+  def extractionMethod(block: rpc.Block): FutureApplicationResult[BlockExtractionMethod] = {
+    if (block.tposContract.isDefined) {
+      Future.successful(Good(BlockExtractionMethod.TrustlessProofOfStake))
+    } else if (block.transactions.isEmpty) {
+      Future.successful(Good(BlockExtractionMethod.ProofOfWork))
+    } else {
+      isPoS(block)
+          .toFutureOr
+          .map {
+            case true => BlockExtractionMethod.ProofOfStake
+            case false => BlockExtractionMethod.ProofOfWork
+          }
+          .toFuture
+    }
+  }
+
+  private def isPoS(block: rpc.Block): FutureApplicationResult[Boolean] = {
+    val result = for {
+      coinbaseTxid <- blockLogic.getCoinbase(block).toFutureOr
+      coinbase <- xsnService.getTransaction(coinbaseTxid).toFutureOr
+    } yield blockLogic.isPoS(block, coinbase)
+
+    result.toFuture
+  }
+
   private def getBlockRewards(block: Block): FutureApplicationResult[BlockRewards] = {
     if (block.transactions.isEmpty) {
       Future.successful(Bad(BlockRewardsNotFoundError).accumulating)

server/app/com/xsn/explorer/services/logic/BlockLogic.scala

@@ -1,7 +1,7 @@
 package com.xsn.explorer.services.logic
 
 import com.alexitc.playsonify.core.ApplicationResult
-import com.xsn.explorer.errors.{BlockNotFoundError, BlockhashFormatError}
+import com.xsn.explorer.errors.{BlockNotFoundError, BlockhashFormatError, TransactionNotFoundError}
 import com.xsn.explorer.models._
 import com.xsn.explorer.models.rpc.{Block, Transaction}
 import com.xsn.explorer.models.values.{Address, Blockhash, TransactionId}
@@ -20,6 +20,12 @@ class BlockLogic {
     Or.from(maybe, One(BlockNotFoundError))
   }
 
+  def getCoinbase(block: Block): ApplicationResult[TransactionId] = {
+    val maybe = block.transactions.headOption
+
+    Or.from(maybe, One(TransactionNotFoundError))
+  }
+
   /**
    * Get the coinstake transaction id for the given block.
    *
@@ -144,4 +150,10 @@ class BlockLogic {
 
     Good(TPoSBlockRewards(ownerReward, merchantReward, masternodeRewardMaybe))
   }
+
+  def isPoS(block: rpc.Block, coinbase: rpc.Transaction): Boolean = {
+    block.nonce == 0 &&
+        coinbase.vin.isEmpty &&
+        coinbase.vout.flatMap(_.address).isEmpty
+  }
 }