Add cli-completion mode in --help

gh-53

src/main/java/am/ik/rsocket/Args.java

@@ -49,6 +49,7 @@
 import io.rsocket.metadata.WellKnownMimeType;
 import io.rsocket.transport.ClientTransport;
 import io.rsocket.util.DefaultPayload;
+import joptsimple.HelpFormatter;
 import joptsimple.OptionParser;
 import joptsimple.OptionSet;
 import joptsimple.OptionSpec;
@@ -66,7 +67,7 @@ public class Args {
 
 	private final OptionSpec<Void> version = parser.acceptsAll(Arrays.asList("v", "version"), "Print version");
 
-	private final OptionSpec<Void> help = parser.acceptsAll(Arrays.asList("help"), "Print help");
+	private final OptionSpec<String> help = parser.acceptsAll(Arrays.asList("h", "help"), "Print help").withOptionalArg();
 
 	private final OptionSpec<Void> wiretap = parser.acceptsAll(Arrays.asList("w", "wiretap"), "Enable wiretap");
 
@@ -606,6 +607,10 @@ public boolean help() {
 		return this.options.has(this.help);
 	}
 
+	public String helpFormatter() {
+		return this.options.valueOf(this.help);
+	}
+
 	public boolean version() {
 		return this.options.has(this.version);
 	}
@@ -621,6 +626,16 @@ public void printHelp(PrintStream stream) {
 		}
 	}
 
+	public void printHelp(PrintStream stream, HelpFormatter helpFormatter) {
+		try {
+			this.parser.formatHelpWith(helpFormatter);
+			this.parser.printHelpOn(stream);
+		}
+		catch (IOException e) {
+			throw new UncheckedIOException(e);
+		}
+	}
+
 	public boolean showSystemProperties() {
 		return this.options.has(this.showSystemProperties);
 	}

src/main/java/am/ik/rsocket/CliCompletionHelpFormatter.java

@@ -0,0 +1,65 @@
+package am.ik.rsocket;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeSet;
+
+import io.rsocket.metadata.TracingMetadataCodec;
+import joptsimple.HelpFormatter;
+import joptsimple.OptionDescriptor;
+
+public class CliCompletionHelpFormatter implements HelpFormatter {
+	private final Map<String, Object[]> possibleValues = new HashMap<String, Object[]>() {
+		{
+			put("am.ik.rsocket.InteractionModel", InteractionModel.values());
+			put("io.rsocket.metadata.TracingMetadataCodec$Flags", TracingMetadataCodec.Flags.values());
+		}
+	};
+
+	@Override
+	public String format(Map<String, ? extends OptionDescriptor> options) {
+		Comparator<OptionDescriptor> comparator = Comparator.comparing(optionDescriptor -> optionDescriptor.options().iterator().next());
+		Set<OptionDescriptor> sorted = new TreeSet<>(comparator);
+		sorted.addAll(options.values());
+		final StringBuilder sb = new StringBuilder();
+		sb.append("name: rsc").append(System.lineSeparator());
+		sb.append("binary_name: rsc").append(System.lineSeparator());
+		sb.append("before_help: |").append(System.lineSeparator());
+		sb.append("  usage: rsc Uri [Options]").append(System.lineSeparator());
+		sb.append("  Non-option arguments: [String: Uri]").append(System.lineSeparator());
+		sb.append(System.lineSeparator());
+		sb.append("args:").append(System.lineSeparator());
+		sorted.forEach(descriptor -> {
+			final List<String> opts = new ArrayList<>(descriptor.options());
+			if (opts.contains("[arguments]")) {
+				return;
+			}
+			Collections.sort(opts, Comparator.comparingInt(String::length).reversed());
+			final String longest = opts.get(0);
+			final String shortest = opts.get(opts.size() - 1);
+			sb.append("- ").append(longest).append(":").append(System.lineSeparator());
+			if (shortest.length() == 1) {
+				sb.append("    short: ").append(shortest).append(System.lineSeparator());
+				opts.remove(shortest);
+			}
+			sb.append("    long: ").append(longest).append(System.lineSeparator());
+			if (opts.size() > 1) {
+				sb.append("    aliases: ").append(opts.subList(1, opts.size())).append(System.lineSeparator());
+			}
+			sb.append("    required: ").append(descriptor.isRequired()).append(System.lineSeparator());
+			sb.append("    about: \"").append(descriptor.description()).append("\"").append(System.lineSeparator());
+			final String indicator = descriptor.argumentTypeIndicator();
+			sb.append("    takes_value: ").append(!"".equals(indicator)).append(System.lineSeparator());
+			if (possibleValues.containsKey(indicator)) {
+				sb.append("    possible_values: ").append(Arrays.toString(possibleValues.get(indicator))).append(System.lineSeparator());
+			}
+		});
+		return sb.toString();
+	}
+}

src/main/java/am/ik/rsocket/RscCommandLineRunner.java

@@ -42,7 +42,12 @@ public void run(String... a) throws Exception {
 		final Args args = new Args(a);
 		try {
 			if (args.help()) {
-				args.printHelp(System.out);
+				if ("cli-completion".equals(args.helpFormatter())) {
+					args.printHelp(System.out, new CliCompletionHelpFormatter());
+				}
+				else {
+					args.printHelp(System.out);
+				}
 				return;
 			}
 			if (args.version()) {

src/test/java/am/ik/rsocket/RscApplicationTests.java

@@ -12,9 +12,14 @@
 class RscApplicationTests {
 
 	@Test
-	void test(CapturedOutput capture) throws Exception {
+	void help(CapturedOutput capture) throws Exception {
 		RscApplication.main(new String[] { "-h" });
 		assertThat(capture.toString()).isNotEmpty();
 	}
 
+	@Test
+	void helpYamlMode(CapturedOutput capture) throws Exception {
+		RscApplication.main(new String[] { "-h", "cli-completion" });
+		assertThat(capture.toString()).isNotEmpty();
+	}
 }