add fake execution engine server (#4250)

Useful for testing beacon node without running an execution client
(results in an
optimistically synced node)

Makefile

@@ -61,6 +61,7 @@ TOOLS := \
 	ncli \
 	ncli_db \
 	ncli_split_keystore \
+	fakeee \
 	wss_sim \
 	stack_sizes \
 	nimbus_light_client \

research/fakeee.nim

@@ -0,0 +1,73 @@
+## Fake execution engine API implementation useful for testing beacon node without a running execution node
+
+# Nimbus
+# Copyright (c) 2018 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
+# at your option.
+# This file may not be copied, modified, or distributed except according to
+# those terms.
+
+import
+  std/typetraits,
+  json_rpc/[rpcserver, errors],
+  web3/[conversions, engine_api_types],
+  chronicles
+
+proc setupEngineAPI*(server: RpcServer) =
+  # https://github.com/ethereum/execution-apis/blob/main/src/engine/specification.md#engine_newpayloadv1
+  # cannot use `params` as param name. see https:#github.com/status-im/nim-json-rpc/issues/128
+  server.rpc("engine_newPayloadV1") do(payload: ExecutionPayloadV1) -> PayloadStatusV1:
+    info "engine_newPayloadV1",
+      number = $(distinctBase payload.blockNumber), hash = payload.blockHash
+
+    return PayloadStatusV1(
+      status: PayloadExecutionStatus.syncing,
+    )
+
+  # https://github.com/ethereum/execution-apis/blob/main/src/engine/specification.md#engine_getpayloadv1
+  server.rpc("engine_getPayloadV1") do(payloadId: PayloadID) -> ExecutionPayloadV1:
+    info "engine_getPayloadV1",
+      id = payloadId.toHex
+
+    raise (ref InvalidRequest)(
+      code: engineApiUnknownPayload,
+      msg: "Unkown payload"
+    )
+
+  # https://github.com/ethereum/execution-apis/blob/main/src/engine/specification.md#engine_exchangetransitionconfigurationv1
+  server.rpc("engine_exchangeTransitionConfigurationV1") do(conf: TransitionConfigurationV1) -> TransitionConfigurationV1:
+    info "engine_exchangeTransitionConfigurationV1",
+      ttd = conf.terminalTotalDifficulty,
+      number = uint64(conf.terminalBlockNumber),
+      blockHash = conf.terminalBlockHash
+
+    return conf
+
+  # https://github.com/ethereum/execution-apis/blob/main/src/engine/specification.md#engine_forkchoiceupdatedv1
+  server.rpc("engine_forkchoiceUpdatedV1") do(
+      update: ForkchoiceStateV1,
+      payloadAttributes: Option[PayloadAttributesV1]) -> ForkchoiceUpdatedResponse:
+    info "engine_forkchoiceUpdatedV1",
+      update,
+      payloadAttributes
+
+    return ForkchoiceUpdatedResponse(
+      payloadStatus: PayloadStatusV1(
+      status: PayloadExecutionStatus.syncing))
+
+when isMainModule:
+  let server = newRpcHttpServer(
+        [initTAddress("127.0.0.1", 8551)],
+        # authHooks = @[httpJwtAuthHook, httpCorsHook]
+  )
+
+  server.setupEngineAPI()
+  server.start()
+
+  when compiles(waitFor waitSignal(SIGINT)):
+    waitFor waitSignal(SIGINT)
+    waitFor server.stop()
+  else:
+    runForever()