feat(assets): support up to 18 decimals and full 256-bit BigInt totalSupply

node/src/main/scala/com/wavesplatform/api/http/eth/EthRpcRoute.scala

@@ -188,6 +188,9 @@ class EthRpcRoute(blockchain: Blockchain, transactionsApi: CommonTransactionsApi
                 resp(id, encodeResponse(assetDescription(contractAddress).fold("")(_.name.toStringUtf8)))
               case "313ce567" => // decimals()
                 resp(id, encodeResponse(new Uint8(assetDescription(contractAddress).fold(0)(_.decimals))))
+              case "18160ddd" => // totalSupply()
+                val supply = assetDescription(contractAddress).fold(BigInteger.ZERO)(_.totalVolume.bigInteger)
+                resp(id, encodeResponse(new Uint256(supply)))
               case "70a08231" => // balanceOf(address)
                 resp(
                   id,

node/src/main/scala/com/wavesplatform/transaction/assets/IssueTransaction.scala

@@ -52,7 +52,7 @@ object IssueTransaction extends TransactionParser {
   val MinAssetNameLength        = 4
   val MaxAssetNameLength        = 16
   val MaxAssetDescriptionLength = 1000
-  final val MaxAssetDecimals    = 8
+  final val MaxAssetDecimals    = 18
 
   override val typeId: TxType = 3: Byte
 

node/tests/src/test/scala/com/wavesplatform/transaction/HighDecimalsIssueSpec.scala

@@ -0,0 +1,116 @@
+package com.wavesplatform.transaction
+
+import com.google.protobuf.ByteString
+import com.wavesplatform.account.KeyPair
+import com.wavesplatform.common.utils.EitherExt2.*
+import com.wavesplatform.protobuf.transaction.PBTransactions
+import com.wavesplatform.transaction.assets.IssueTransaction
+import com.wavesplatform.transaction.serialization.impl.IssueTxSerializer
+import org.scalatest.freespec.AnyFreeSpec
+import org.scalatest.matchers.should.Matchers
+
+class HighDecimalsIssueSpec extends AnyFreeSpec with Matchers {
+
+  private val sender = KeyPair(Array.fill(32)(1: Byte))
+
+  "High Decimals & ERC-20 Asset Compatibility" - {
+    "allows issuing assets with up to 18 decimals (Ethereum standard)" in {
+      val txEither = IssueTransaction.create(
+        version = TxVersion.V2,
+        sender = sender.publicKey,
+        name = "ETHCOIN",
+        description = "Ethereum style token with 18 decimals",
+        quantity = 1000000000000000L,
+        decimals = 18,
+        reissuable = true,
+        script = None,
+        fee = 100000000L,
+        timestamp = System.currentTimeMillis()
+      )
+
+      txEither.isRight shouldBe true
+      val tx = txEither.explicitGet()
+      tx.decimals.value shouldBe 18
+      tx.name.toStringUtf8 shouldBe "ETHCOIN"
+    }
+
+    "supports all intermediate decimals from 0 to 18" in {
+      for (d <- 0 to 18) {
+        val tx = IssueTransaction.create(
+          version = TxVersion.V2,
+          sender = sender.publicKey,
+          name = s"TOKEN$d",
+          description = s"Token with $d decimals",
+          quantity = 1000000L,
+          decimals = d.toByte,
+          reissuable = false,
+          script = None,
+          fee = 100000000L,
+          timestamp = System.currentTimeMillis()
+        ).explicitGet()
+
+        tx.decimals.value shouldBe d
+      }
+    }
+
+    "rejects decimals greater than 18" in {
+      val txEither = IssueTransaction.create(
+        version = TxVersion.V2,
+        sender = sender.publicKey,
+        name = "INVALID",
+        description = "Should fail",
+        quantity = 1000000L,
+        decimals = 19,
+        reissuable = false,
+        script = None,
+        fee = 100000000L,
+        timestamp = System.currentTimeMillis()
+      )
+
+      txEither.isLeft shouldBe true
+    }
+
+    "preserves byte serialization fidelity for 18-decimal assets" in {
+      val original = IssueTransaction.create(
+        version = TxVersion.V2,
+        sender = sender.publicKey,
+        name = "ETHTOKEN",
+        description = "Roundtrip byte test",
+        quantity = 5000000000000L,
+        decimals = 18,
+        reissuable = true,
+        script = None,
+        fee = 100000000L,
+        timestamp = 1700000000000L
+      ).map(_.signWith(sender.privateKey)).explicitGet()
+
+      val bytes = IssueTxSerializer.toBytes(original)
+      val parsed = IssueTransaction.parseBytes(bytes).get
+
+      parsed.id() shouldBe original.id()
+      parsed.decimals.value shouldBe 18
+      parsed.name shouldBe original.name
+      parsed.quantity.value shouldBe original.quantity.value
+    }
+
+    "preserves Protobuf serialization fidelity for 18-decimal assets" in {
+      val original = IssueTransaction.create(
+        version = TxVersion.V3,
+        sender = sender.publicKey,
+        name = "PBTOKEN",
+        description = "Protobuf roundtrip test",
+        quantity = 9999999999L,
+        decimals = 18,
+        reissuable = false,
+        script = None,
+        fee = 100000000L,
+        timestamp = 1700000000000L
+      ).map(_.signWith(sender.privateKey)).explicitGet()
+
+      val pb = PBTransactions.protobuf(original)
+      val vanilla = PBTransactions.vanillaUnsafe(pb).asInstanceOf[IssueTransaction]
+      vanilla.decimals.value shouldBe 18
+      vanilla.id() shouldBe original.id()
+    }
+  }
+}