slot height matcher implementation (#353)

src/main/kotlin/io/emeraldpay/dshackle/upstream/AbstractHead.kt

@@ -151,6 +151,10 @@ abstract class AbstractHead @JvmOverloads constructor(
         return getCurrent()?.height
     }
 
+    override fun getCurrentSlotHeight(): Long? {
+        return getCurrent()?.slot
+    }
+
     override fun stop() {
         stopping = true
         future?.let {

src/main/kotlin/io/emeraldpay/dshackle/upstream/EmptyHead.kt

@@ -31,6 +31,10 @@ class EmptyHead : Head {
     override fun getCurrentHeight(): Long? {
         return null
     }
+
+    override fun getCurrentSlotHeight(): Long? {
+        return null
+    }
     override fun start() {
     }
 

src/main/kotlin/io/emeraldpay/dshackle/upstream/Head.kt

@@ -38,6 +38,8 @@ interface Head {
 
     fun getCurrentHeight(): Long?
 
+    fun getCurrentSlotHeight(): Long?
+
     fun start()
 
     fun stop()

src/main/kotlin/io/emeraldpay/dshackle/upstream/MatchesResponse.kt

@@ -17,6 +17,7 @@ sealed class MatchesResponse {
             is ExistsResponse -> "Label ${this.name} does not exist"
             GrpcResponse -> "Upstream is not grpc"
             is HeightResponse -> "Upstream height ${this.currentHeight} is less than ${this.height}"
+            is SlotHeightResponse -> "Upstream slot height ${this.currentSlotHeight} is less than ${this.slot}"
             is MethodResponse -> "Method ${this.method} is not supported"
             is MultiResponse ->
                 this.allResponses
@@ -75,6 +76,11 @@ sealed class MatchesResponse {
         val currentHeight: Long,
     ) : MatchesResponse()
 
+    data class SlotHeightResponse(
+        val slot: Long,
+        val currentSlotHeight: Long,
+    ) : MatchesResponse()
+
     data class SameNodeResponse(
         val upstreamHash: Byte,
     ) : MatchesResponse()

src/main/kotlin/io/emeraldpay/dshackle/upstream/Selector.kt

@@ -25,6 +25,7 @@ import io.emeraldpay.dshackle.upstream.MatchesResponse.GrpcResponse
 import io.emeraldpay.dshackle.upstream.MatchesResponse.HeightResponse
 import io.emeraldpay.dshackle.upstream.MatchesResponse.NotMatchedResponse
 import io.emeraldpay.dshackle.upstream.MatchesResponse.SameNodeResponse
+import io.emeraldpay.dshackle.upstream.MatchesResponse.SlotHeightResponse
 import io.emeraldpay.dshackle.upstream.MatchesResponse.Success
 import org.apache.commons.lang3.StringUtils
 import java.util.Collections
@@ -44,6 +45,9 @@ class Selector {
             return selectors
                 .map {
                     when {
+                        it.hasSlotHeightSelector() -> {
+                            SlotMatcher(it.slotHeightSelector.slotHeight)
+                        }
                         it.hasHeightSelector() -> {
                             val height = if (it.heightSelector.height == -1L) head.getCurrentHeight() else it.heightSelector.height
                             if (height == null) {
@@ -488,6 +492,39 @@ class Selector {
         }
     }
 
+    class SlotMatcher(val slotHeight: Long) : Matcher() {
+
+        override fun matchesWithCause(up: Upstream): MatchesResponse {
+            val currentHeight = up.getHead().getCurrentSlotHeight() ?: 0
+            return if (currentHeight >= slotHeight) {
+                Success
+            } else {
+                SlotHeightResponse(slotHeight, currentHeight)
+            }
+        }
+
+        override fun equals(other: Any?): Boolean {
+            if (this === other) return true
+            if (other !is SlotMatcher) return false
+
+            if (slotHeight != other.slotHeight) return false
+
+            return true
+        }
+
+        override fun hashCode(): Int {
+            return slotHeight.hashCode()
+        }
+
+        override fun describeInternal(): String {
+            return "slot height $slotHeight"
+        }
+
+        override fun toString(): String {
+            return "Matcher: ${describeInternal()}"
+        }
+    }
+
     class SameNodeMatcher(private val upstreamHash: Byte) : Matcher() {
 
         override fun matchesWithCause(up: Upstream): MatchesResponse =

src/main/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EnrichedMergedHead.kt

@@ -63,6 +63,10 @@ class EnrichedMergedHead constructor(
         return referenceHead.getCurrentHeight()
     }
 
+    override fun getCurrentSlotHeight(): Long? {
+        return referenceHead.getCurrentSlotHeight()
+    }
+
     override fun isRunning(): Boolean {
         return cacheSub != null
     }