fix: Add transaction drop listener (#2)

README.md

@@ -33,6 +33,11 @@ The plugin jar will be available at `build/libs/`.
 ## Usage
 
 Drop the `drop-transactions-reporter-plugin-<version>.jar` in the `/plugins` folder under Besu installation.
+The plugin will expose following additional cli options:
+```shell
+--plugin-drop-transaction-reporter-endpoint=<URI>
+                                URI to report drop transactions
+```
 
 ## License
 `SPDX-License-Identifier: Apache-2.0`

src/main/java/net/consensys/linea/DropTransactionReporterPlugin.java

@@ -2,9 +2,15 @@
 // SPDX-License-Identifier: Apache-2.0
 package net.consensys.linea;
 
+import static net.consensys.linea.DropTransactionsReporterCliOptions.NAMESPACE;
+
 import com.google.auto.service.AutoService;
+import java.util.Optional;
+import org.hyperledger.besu.datatypes.Transaction;
 import org.hyperledger.besu.plugin.BesuContext;
 import org.hyperledger.besu.plugin.BesuPlugin;
+import org.hyperledger.besu.plugin.services.BesuEvents;
+import org.hyperledger.besu.plugin.services.PicoCLIOptions;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -15,19 +21,51 @@
 @AutoService(BesuPlugin.class)
 public class DropTransactionReporterPlugin implements BesuPlugin {
   private static final Logger LOG = LoggerFactory.getLogger(DropTransactionReporterPlugin.class);
+  private BesuContext besuContext;
+  private Optional<Long> subscriptionId = Optional.empty();
+  private final DropTransactionsReporterCliOptions cliParams =
+      new DropTransactionsReporterCliOptions();
 
   @Override
   public void register(final BesuContext besuContext) {
     LOG.trace("Registering plugin ...");
+    this.besuContext = besuContext;
+    registerCliOptions(besuContext);
   }
 
   @Override
   public void start() {
     LOG.trace("Starting plugin ...");
+    subscriptionId =
+        besuContext
+            .getService(BesuEvents.class)
+            .map(events -> events.addTransactionDroppedListener(this::onTransactionDropped));
+    LOG.trace("Transaction Drop Listener with ID#{} registered.", subscriptionId);
+  }
+
+  private void onTransactionDropped(Transaction transaction) {
+    LOG.trace(
+        "Transaction dropped: {}. Reporting to: {}",
+        transaction.getHash(),
+        cliParams.getEndpoint());
+    // TODO: Implement the logic to report the transaction to a configured endpoint
   }
 
   @Override
   public void stop() {
     LOG.trace("Stopping plugin ...");
+    subscriptionId.ifPresent(
+        id ->
+            besuContext
+                .getService(BesuEvents.class)
+                .ifPresent(besuEvents -> besuEvents.removeTransactionDroppedListener(id)));
+    LOG.trace("Transaction dropped listener with ID#{} removed.", subscriptionId);
+  }
+
+  private void registerCliOptions(final BesuContext besuContext) {
+    besuContext
+        .getService(PicoCLIOptions.class)
+        .orElseThrow(() -> new IllegalStateException("Expecting PicoCLIOptions to be present"))
+        .addPicoCLIOptions(NAMESPACE, cliParams);
   }
 }

src/main/java/net/consensys/linea/DropTransactionsReporterCliOptions.java

@@ -0,0 +1,27 @@
+// Copyright 2024, Consensys Software Inc.
+// SPDX-License-Identifier: Apache-2.0
+package net.consensys.linea;
+
+import java.net.URI;
+import picocli.CommandLine;
+
+public class DropTransactionsReporterCliOptions {
+  static final String NAMESPACE = "drop-transaction-reporter";
+
+  @CommandLine.Option(
+      names = "--plugin-" + NAMESPACE + "-endpoint",
+      description = "URI to report drop transactions",
+      required = true,
+      paramLabel = "<URI>")
+  private URI endpoint = URI.create("http://localhost:8080");
+
+  public URI getEndpoint() {
+    return endpoint;
+  }
+
+  public void setEndpoint(final URI endpoint) {
+    this.endpoint = endpoint;
+  }
+
+  public DropTransactionsReporterCliOptions() {}
+}