Lower bound for block data (#453)

src/main/kotlin/io/emeraldpay/dshackle/rpc/StreamHead.kt

@@ -95,6 +95,7 @@ class StreamHead(
             LowerBoundType.SLOT -> BlockchainOuterClass.LowerBoundType.LOWER_BOUND_SLOT
             LowerBoundType.UNKNOWN -> BlockchainOuterClass.LowerBoundType.UNRECOGNIZED
             LowerBoundType.STATE -> BlockchainOuterClass.LowerBoundType.LOWER_BOUND_STATE
+            LowerBoundType.BLOCK -> BlockchainOuterClass.LowerBoundType.LOWER_BOUND_BLOCK
         }
     }
 

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

@@ -0,0 +1,44 @@
+package io.emeraldpay.dshackle.upstream.ethereum
+
+import io.emeraldpay.dshackle.upstream.ChainRequest
+import io.emeraldpay.dshackle.upstream.ChainResponse
+import io.emeraldpay.dshackle.upstream.Upstream
+import io.emeraldpay.dshackle.upstream.lowerbound.LowerBoundData
+import io.emeraldpay.dshackle.upstream.lowerbound.LowerBoundDetector
+import io.emeraldpay.dshackle.upstream.lowerbound.LowerBoundType
+import io.emeraldpay.dshackle.upstream.lowerbound.detector.RecursiveLowerBound
+import io.emeraldpay.dshackle.upstream.lowerbound.toHex
+import io.emeraldpay.dshackle.upstream.rpcclient.ListParams
+import reactor.core.publisher.Flux
+import reactor.core.publisher.Mono
+
+class EthereumLowerBoundBlockDetector(
+    private val upstream: Upstream,
+) : LowerBoundDetector() {
+    private val recursiveLowerBound = RecursiveLowerBound(upstream, LowerBoundType.BLOCK, setOf("No block data"))
+
+    override fun period(): Long {
+        return 5
+    }
+
+    override fun internalDetectLowerBound(): Flux<LowerBoundData> {
+        return recursiveLowerBound.recursiveDetectLowerBound { block ->
+            if (block == 0L) {
+                Mono.just(ChainResponse(ByteArray(0), null))
+            } else {
+                upstream.getIngressReader()
+                    .read(
+                        ChainRequest(
+                            "eth_getBlockByNumber",
+                            ListParams(block.toHex(), false),
+                        ),
+                    )
+                    .doOnNext {
+                        if (it.hasResult() && it.getResult().contentEquals("null".toByteArray())) {
+                            throw IllegalStateException("No block data")
+                        }
+                    }
+            }
+        }
+    }
+}

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

@@ -10,6 +10,9 @@ class EthereumLowerBoundService(
     private val upstream: Upstream,
 ) : LowerBoundService(chain, upstream) {
     override fun detectors(): List<LowerBoundDetector> {
-        return listOf(EthereumLowerBoundStateDetector(upstream))
+        return listOf(
+            EthereumLowerBoundStateDetector(upstream),
+            EthereumLowerBoundBlockDetector(upstream),
+        )
     }
 }

src/main/kotlin/io/emeraldpay/dshackle/upstream/lowerbound/LowerBoundData.kt

@@ -19,5 +19,5 @@ data class LowerBoundData(
 }
 
 enum class LowerBoundType {
-    UNKNOWN, STATE, SLOT
+    UNKNOWN, STATE, SLOT, BLOCK
 }