Implement help <method-name>

consensusj-jrpc-echod/src/test/java/org/consensusj/jsonrpc/daemon/ApplicationTest.java

@@ -80,38 +80,42 @@ void echoMethodWrongNumberOfArgs() throws IOException {
         assertEquals(expectedErrorCode, exception.jsonRpcCode);
     }
 
+    @Test
+    void helpForHelpMethod() throws IOException {
+        var expectedResultSubstring  = "Displays detailed help text for the specified method.";
+        try (var client = new DefaultRpcClient(endpoint, "", "")) {
+            String result = (String) client.send("help", "help");
+            assertTrue(result.contains(expectedResultSubstring));
+        }
+    }
 
     @Test
-    void helpMethod() throws IOException {
-        var expectedResult  = """
-echo message
-help
-stop
-    """;
+    void helpForEchoMethod() throws IOException {
+        var expectedResultSubstring  = "Returns the provided message exactly as it was sent.";
         try (var client = new DefaultRpcClient(endpoint, "", "")) {
-            String result = (String) client.send("help");
-            assertEquals(expectedResult, result);
+            String result = (String) client.send("help", "echo");
+            assertTrue(result.contains(expectedResultSubstring));
         }
     }
 
-    /*
-     * The help method is currently not fully implemented. It SHOULD allow
-     * for an argument, and only fail if the argument doesn't match an existing
-     * command. Once the help method is properly implemented we will need to change
-     * our tests
-     */
     @Test
-    void helpMethodOneArg() throws IOException {
-        int expectedErrorCode = JsonRpcError.Error.INVALID_PARAMS.getCode();
-        var expectedErrorMessagePrefix = "Invalid params:";
-        JsonRpcStatusException exception =
-                assertThrows(JsonRpcStatusException.class, () -> {
-                    try (var client = new DefaultRpcClient(endpoint, "", "")) {
-                        client.send("help", "echo");
-                    }
-                });
-        assertTrue(exception.getMessage().startsWith(expectedErrorMessagePrefix));
-        assertEquals(expectedErrorCode, exception.jsonRpcCode);
+    void helpForStopMethod() throws IOException {
+        var expectedResultSubstring  = "Initiates the shutdown process of the JSON-RPC server.";
+        try (var client = new DefaultRpcClient(endpoint, "", "")) {
+            String result = (String) client.send("help", "stop");
+            assertTrue(result.contains(expectedResultSubstring));
+        }
+    }
+
+    @Test
+    void helpMethodNoArg() throws IOException {
+        var expectedResult  = "echo message\n" +
+                "help (method)\n" +
+                "stop ";
+        try (var client = new DefaultRpcClient(endpoint, "", "")) {
+            String result = (String) client.send("help");
+            assertEquals(expectedResult, result);
+        }
     }
 
     @Test

consensusj-jsonrpc/src/main/java/org/consensusj/jsonrpc/help/JsonRpcHelp.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2014-2026 ConsensusJ Developers.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.consensusj.jsonrpc.help;
+
+/**
+ * Recordlike object to store help information about a given command
+ */
+public class JsonRpcHelp {
+    private final String summary;
+    private final String detail;
+
+    public JsonRpcHelp(String summary, String detail) {
+        this.summary = summary;
+        this.detail = detail;
+    }
+
+    /**
+     * @return The summary information for a command.
+     */
+    public String summary() {
+        return summary;
+    }
+
+    /**
+     * @return The detailed information for a command.
+     */
+    public String detail() {
+        return detail;
+    }
+}

consensusj-jsonrpc/src/main/java/org/consensusj/jsonrpc/services/EchoJsonRpcService.java

@@ -25,18 +25,60 @@
 import java.lang.invoke.MethodHandles;
 import java.lang.reflect.Method;
 import java.util.Map;
+import org.consensusj.jsonrpc.help.JsonRpcHelp;
 import java.util.concurrent.CompletableFuture;
+import java.util.function.Function;
+import java.util.stream.Collectors;
 
 /**
  * Simple Echo JSON-RPC Service
  */
 public class EchoJsonRpcService extends AbstractJsonRpcService implements Closeable {
     private static final Logger log = LoggerFactory.getLogger(EchoJsonRpcService.class);
     private static final Map<String, Method> methods = JsonRpcServiceWrapper.reflect(MethodHandles.lookup().lookupClass());
-    private static final String helpString =
-            "echo message\n" +
-            "help\n" +
-            "stop\n";
+    private static final Map<String, JsonRpcHelp> helpMap = Map.of(
+            "echo", new JsonRpcHelp("message",
+                    "Usage:\n"
+                            + "  echo <message>\n"
+                            + "\n"
+                            + "Description:\n"
+                            + "  Returns the provided message exactly as it was sent.\n"
+                            + "\n"
+                            + "Parameters:\n"
+                            + "  message (string, required)\n"
+                            + "    The text to be echoed back by the server.\n"
+                            + "\n"
+                            + "Example:\n"
+                            + "  echo \"hello world\"\n"),
+            "help", new JsonRpcHelp("(method)",
+                    "Usage:\n"
+                            + "  help <method>\n"
+                            + "\n"
+                            + "Description:\n"
+                            + "  Displays detailed help text for the specified method.\n"
+                            + "  If the method name is not recognized or not given, a list of available\n"
+                            + "  methods and their parameters is returned instead.\n"
+                            + "\n"
+                            + "Parameters:\n"
+                            + "  method (string, optional)\n"
+                            + "    The name of the method to display help for.\n"
+                            + "\n"
+                            + "Example:\n"
+                            + "  help echo\n"),
+            "stop", new JsonRpcHelp("",
+                    "Usage:\n"
+                            + "  stop\n"
+                            + "\n"
+                            + "Description:\n"
+                            + "  Initiates the shutdown process of the JSON-RPC server.\n"
+                            + "  The server will respond to this request before the\n"
+                            + "  shutdown completes, allowing the client to receive\n"
+                            + "  confirmation of the action.\n"
+                            + "\n"
+                            + "Parameters:\n"
+                            + "  None.\n")
+    );
+    private static final String helpString = createHelpString(EchoJsonRpcService::createHelpStringLine);
 
     private final JsonRpcShutdownService shutdownService;
 
@@ -50,14 +92,31 @@ public void close() {
         log.info("Closing");
     }
 
+    /**
+     * Echo a given message back to the client.
+     * @param message: A string containing the message to be echoed
+     * @return A string containing the echoed message
+     */
     public CompletableFuture<String> echo(String message) {
         log.debug("EchoJsonRpcService: echo {}", message);
         return result(message);
     }
 
-    public CompletableFuture<String> help() {
+    /**
+     * Get detailed help information for a given command.
+     * @param method: A string containing the method name
+     * @return A string containing help information
+     */
+    public CompletableFuture<String> help(String method) {
         log.debug("EchoJsonRpcService: help");
-        return result(helpString);
+        if (method == null) {
+            return result(helpString);
+        }
+        if (helpMap.containsKey(method)) {
+            return result(helpMap.get(method).detail());
+        } else {
+            return result("Method not found.\n" + helpString);
+        }
     }
 
     /**
@@ -70,4 +129,26 @@ public CompletableFuture<String> stop() {
         String message = shutdownService.stopServer();
         return result(message);
     }
+
+    /**
+     * Create a string containing the name of each method and it's parameters in alphabetical order.
+     * @param formatFunction A function determining how to format each line
+     * @return A string containing the name and parameters of each method
+     */
+    private static String createHelpString(Function<Map.Entry<String, JsonRpcHelp>, String> formatFunction) {
+        return helpMap.entrySet().stream()
+                .sorted(Map.Entry.comparingByKey())
+                .map(formatFunction)
+                .collect(Collectors.joining("\n"));
+    }
+
+    /**
+     * Default formatter. Appends the method's summary delimited with a space
+     * @param entry Map entry for a given method from `helpMap`
+     * @return Formatted line for `helpString`
+     */
+    private static String createHelpStringLine(Map.Entry<String, JsonRpcHelp> entry) {
+        return entry.getKey() + " " + entry.getValue().summary();
+    }
+
 }