problem: doesn't parse block selector specified as object EIP-1898

rel: #81

src/main/kotlin/io/emeraldpay/dshackle/upstream/calls/EthereumCallSelector.kt

@@ -61,24 +61,37 @@ class EthereumCallSelector {
             log.debug("Tag is not specified. Ignoring")
             return null
         }
-        // integer block number, or the string "latest", "earliest" or "pending"
-        val minHeight = when (val tag = list[pos].toString()) {
-            "latest" -> head.getCurrentHeight() ?: 0
+        // integer block number, a string "latest", "earliest" or "pending", or an object with block reference
+        val minHeight: Long? = when (val tag = list[pos].toString()) {
+            "latest" -> head.getCurrentHeight()
             // for earliest it doesn't nothing, we expect to have 0 block
             "earliest" -> 0L
             else -> if (tag.startsWith("0x")) {
+                try {
+                    HexQuantity.from(tag).value.toLong()
+                } catch (t: Throwable) {
+                    log.debug("Invalid tag: $tag. ${t.javaClass}: ${t.message}")
+                    null
+                }
+            } else if (tag.startsWith("{") && list[pos] is Map<*, *>) {
+                // see https://eips.ethereum.org/EIPS/eip-1898
+                val obj = list[pos] as Map<*, *>
+                if (obj.containsKey("blockNumber")) {
                     try {
-                        HexQuantity.from(tag).value.toLong()
+                        HexQuantity.from(obj["blockNumber"].toString()).value.toLong()
                     } catch (t: Throwable) {
-                        log.debug("Invalid tag: $tag. ${t.javaClass}: ${t.message}")
-                        0L
+                        log.warn("Invalid blockNumber: $tag")
+                        null
                     }
                 } else {
-                    log.debug("Invalid tag: $tag")
-                    0L
+                    null
                 }
+            } else {
+                log.debug("Invalid tag: $tag")
+                null
+            }
         }
-        return if (minHeight > 0) {
+        return if (minHeight != null && minHeight >= 0) {
             Selector.HeightMatcher(minHeight)
         } else {
             null

src/test/groovy/io/emeraldpay/dshackle/upstream/calls/EthereumCallSelectorSpec.groovy

@@ -78,4 +78,12 @@ class EthereumCallSelectorSpec extends Specification {
         act == null
     }
 
+    def "Get height matcher with EIP-1898"() {
+        setup:
+        def head = Stub(Head)
+        when:
+        def act = callSelector.getMatcher("eth_call", '["0x0000", {"blockNumber": "0x100"}]', head)
+        then:
+        act == new Selector.HeightMatcher(0x100)
+    }
 }