feat(reth): add flashblocks env validation helper

reth/validate_flashblocks_env.sh

@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Sanity checks for a Base Reth + Flashblocks environment.
+#
+# This script is intended to be run before starting the reth-based node.
+# It validates a minimal set of environment variables that are commonly
+# required when running with Flashblocks support:
+#
+#   NODE_TYPE               - should be set to "base"
+#   NETWORK_ENV             - points to the env file describing the network
+#   RETH_FB_WEBSOCKET_URL   - websocket endpoint for Flashblocks
+#
+# Exit code:
+#   0 - configuration looks good
+#   1 - one or more validation errors were found
+
+errors=0
+
+log_err() {
+  echo "[flashblocks-env] $*" >&2
+}
+
+require_var() {
+  local name="$1"
+  local value="${!name:-}"
+  if [ -z "${value}" ]; then
+    log_err "required environment variable ${name} is not set"
+    errors=1
+  fi
+}
+
+# Check that the key variables are present
+require_var "NODE_TYPE"
+require_var "NETWORK_ENV"
+require_var "RETH_FB_WEBSOCKET_URL"
+
+# Validate values where we can
+if [ "${NODE_TYPE:-}" != "base" ]; then
+  log_err "NODE_TYPE should be 'base' when running a Base Reth node (current: '${NODE_TYPE:-}')"
+  errors=1
+fi
+
+fb_url="${RETH_FB_WEBSOCKET_URL:-}"
+if [ -n "${fb_url}" ]; then
+  case "${fb_url}" in
+    ws://*|wss://*)
+      # looks fine
+      ;;
+    *)
+      log_err "RETH_FB_WEBSOCKET_URL should start with ws:// or wss:// (current: '${fb_url}')"
+      errors=1
+      ;;
+  esac
+fi
+
+# NETWORK_ENV is expected to be a file name like ".env.mainnet" or ".env.sepolia".
+# We only warn if the file does not exist in the current working directory;
+# the caller may still be sourcing it from elsewhere.
+if [ -n "${NETWORK_ENV:-}" ] && [ ! -f "${NETWORK_ENV}" ]; then
+  log_err "NETWORK_ENV='${NETWORK_ENV}' does not point to a file in the current directory"
+  errors=1
+fi
+
+if [ "${errors}" -ne 0 ]; then
+  log_err "invalid Flashblocks / Base Reth environment configuration"
+  exit 1
+fi
+
+echo "[flashblocks-env] configuration looks good"
+exit 0