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Extensible Command Line Interface
There is a newer version: 2024.9.0
package org.nasdanika.cli;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;

import org.apache.commons.text.StringEscapeUtils;
import org.nasdanika.common.DefaultConverter;
import org.nasdanika.common.MarkdownHelper;
import org.nasdanika.common.Util;

import picocli.CommandLine;
import picocli.CommandLine.Command;
import picocli.CommandLine.Help;
import picocli.CommandLine.Model.CommandSpec;
import picocli.CommandLine.Option;

@Command(
		description = "Outputs usage for all registred commands",
		name = "help")
public class HelpCommand extends CommandBase {
	
	/**
	 * To be implemented by output format mix-ins
	 */
	public interface OutputFormatMixIn {
		
		boolean match();
		
		void write(OutputStream out) throws IOException;
		
	}
	
	private CommandLine root;
	
	public HelpCommand(CommandLine root) {
		this.root = root;
	}
	
	@Option(names = {"-o", "--output"}, description = "Output file")
	private File output;
	
	@Option(names = {"-H", "--html"}, defaultValue = "false", description = "Output to HTML")
	private boolean html;
	
	@Option(names = {"-l", "--header-level"}, defaultValue = "1", description = "Starting level for HTML header tags in HTML output, the default value is ${DEFAULT-VALUE}.")
	private int level;
	
	private static final int WIDTH = 80;
	
	public CommandLine getRoot() {
		return root;
	}
	
	private void usage(
			List cmdPath, 
			CommandLine cmd,
			PrintStream out) throws IOException {
		
		CommandSpec commandSpec = cmd.getCommandSpec();
		String[] version = commandSpec.version();
		if (html) {
			int hLevel = Math.min(cmdPath.size() + level, 6);
			out.println("" + cmd.getCommandName() + "");
			if (version.length > 0) {
				out.print("Version:  ");			
				for (String vs: version) {
					out.print(vs);
					out.print("
");
				}
				out.print("");
			}
			
			out.print(usageToHTML(cmd));

			// Description 
			Object userObject = commandSpec.userObject();
			if (userObject != null) {
				Class clazz = userObject.getClass();
				Description description = clazz.getAnnotation(Description.class);
				if (description != null) {
					String markdown = description.value();
					if (Util.isBlank(markdown)) {
						String dResource = description.resource();
						if (Util.isBlank(dResource)) {
							dResource = clazz.getName().substring(clazz.getName().lastIndexOf('.') + 1) + ".md";						
						}
						InputStream dStream = clazz.getResourceAsStream(dResource);
						if (dStream != null) {
							markdown = DefaultConverter.INSTANCE.toString(dStream);
						}
					}
					
					out.println("" + MarkdownHelper.INSTANCE.markdownToHtml(markdown) + "");
				}
			}
		} else {
			out.println();
			for (int i = 0; i < WIDTH; ++i) {
				out.print("*");
			}
			out.println();
			out.print("* ");
			StringBuilder hb = new StringBuilder();
			for (String ps: cmdPath) {
				hb.append(ps).append(" > ");
			}
			hb.append(cmd.getCommandName());
			out.print(center(hb, WIDTH - 4));
			out.println(" *");
			
			for (String vs: version) {
				out.print("* ");
				out.print(center(vs, WIDTH - 4));
				out.println(" *");			
			}
			
			for (int i = 0; i < WIDTH; ++i) {
				out.print("*");
			}
			out.println();
			cmd.usage(out);
		}		
		
		List cPath = new ArrayList<>(cmdPath);
		cPath.add(cmd.getCommandName());
		for (CommandLine subCommand: cmd.getSubcommands().values().stream().sorted((a,b) -> a.getCommandName().compareTo(b.getCommandName())).collect(Collectors.toList())) {
			usage(cPath, subCommand, out);
		}
	}
	
	private String center(CharSequence text, int width) {
		StringBuilder sb = new StringBuilder();
		int toPad = width - text.length();
		for (int i=0, padding = toPad/2; i < padding; ++i) {
			sb.append(" ");
		}
		sb.append(text);
		while (sb.length() < width) {
			sb.append(" ");
		}
		return sb.toString();
	}
	
	@Override
	public Integer call() throws Exception {
		// TODO - mix-ins such as  and validation of exclusiveness of html with mix-ins
		
		if (output == null) {
			for (CommandSpec mixIn: spec.mixins().values()) {
				Object userObject = mixIn.userObject();
				if (userObject instanceof OutputFormatMixIn) {
					OutputFormatMixIn outputFormatMixIn = (OutputFormatMixIn) userObject;
					if (outputFormatMixIn.match()) {
						outputFormatMixIn.write(System.out);
						return 0;
					}
				}
			}
			
			usage(Collections.emptyList(), root, System.out);
		} else {
			for (CommandSpec mixIn: spec.mixins().values()) {
				Object userObject = mixIn.userObject();
				if (userObject instanceof OutputFormatMixIn) {
					OutputFormatMixIn outputFormatMixIn = (OutputFormatMixIn) userObject;
					if (outputFormatMixIn.match()) {
						try (OutputStream out = new FileOutputStream(output)) {
							outputFormatMixIn.write(out);
						}
						return 0;
					}
				}
			}
			try (PrintStream out = new PrintStream(output)) {
				usage(Collections.emptyList(), root, out);
			}
		}
		return 0;
	}
	
	/**
	 * Writes HTML-escaped usage in PRE
	 * @param commandLine
	 * @return
	 * @throws IOException 
	 */
	public static String usageToHTML(CommandLine commandLine) throws IOException {
		StringBuilder builder = new StringBuilder("").append(System.lineSeparator());
		StringWriter usageWriter = new StringWriter();		
		try (PrintWriter pw = new PrintWriter(usageWriter)) {
			commandLine.usage(pw, Help.Ansi.OFF);
		}
		usageWriter.close();
		builder.append(StringEscapeUtils.escapeHtml4(usageWriter.toString()));
		builder.append("").append(System.lineSeparator());
		return builder.toString();
	}

}