Implement basic help command, which provides an overview over all registered commands

src/main/java/org/telegram/telegrambots/api/commands/HelpCommand.java

@@ -0,0 +1,37 @@
+package org.telegram.telegrambots.api.commands;
+
+import org.telegram.telegrambots.BotLogger;
+import org.telegram.telegrambots.TelegramApiException;
+import org.telegram.telegrambots.api.methods.send.SendMessage;
+
+/**
+ * standard help command, which gets registered by default, to supply a list of all available commands
+ *
+ * @author tschulz
+ */
+public class HelpCommand extends Command {
+
+    private static final String LOGTAG = "HELPCOMMAND";
+    private final ICommandRegistery commandRegistry;
+
+    public HelpCommand(ICommandRegistery commandRegistry, String botToken) {
+        super("help", "Gives an overview over all Commands registered for this bot", botToken);
+        this.commandRegistry = commandRegistry;
+    }
+
+    @Override
+    void execute(String[] arguments, long chatId) {
+        for (Command registeredCommand : commandRegistry.getRegisteredCommands()) {
+            SendMessage sendMessage = new SendMessage();
+            sendMessage.setChatId(chatId);
+            sendMessage.enableHtml(true);
+            sendMessage.setText("<b>" + registeredCommand.getCommandIdentifier() + "</b>\n" + registeredCommand.getDescription());
+
+            try {
+                sendMessage(sendMessage);
+            } catch (TelegramApiException e) {
+                BotLogger.error("Failed to send HelpMessage", LOGTAG, e);
+            }
+        }
+    }
+}