mvn2jbang.java

//DEPS org.apache.maven:maven-model:3.9.9

package scripts;

import org.apache.maven.model.*;
import org.apache.maven.model.io.xpp3.MavenXpp3Reader;
import org.codehaus.plexus.util.xml.pull.XmlPullParserException;

import java.io.*;
import java.nio.file.*;
import java.util.regex.*;
import java.util.stream.*;

public class mvn2jbang {

    static Model readModel(Path pom) throws IOException, XmlPullParserException {
        try (BufferedReader br = Files.newBufferedReader(pom)) {
            Model model = readModel(br);
            model.setPomFile(pom.toFile());
            return model;
        }
    }

    static Model readModel(Reader rdr) throws IOException, XmlPullParserException {
        try (Reader reader = rdr) {
            MavenXpp3Reader mavenXpp3Reader = new MavenXpp3Reader();
            return mavenXpp3Reader.read(reader);
        }
    }

    static void writeTags(PrintWriter writer, Model model, boolean usePrefix) {
        String prefix = usePrefix ? "//" : "";

        if (model.getDependencyManagement() != null) {
            for (Dependency d : model.getDependencyManagement().getDependencies()) {
                String dep = d.getGroupId() + ":" + d.getArtifactId();
                if (d.getVersion() != null) {
                    dep += ":" + d.getVersion();
                }
                dep += "@pom";
                dep = replaceProps(dep, model);
                writer.println(prefix + "DEPS " + dep);
            }
        }

        for (Dependency d : model.getDependencies()) {
            String dep = d.getGroupId() + ":" + d.getArtifactId();
            if (d.getVersion() != null) {
                dep += ":" + d.getVersion();
            }
            dep = replaceProps(dep, model);
            writer.println(prefix + "DEPS " + dep);
        }

        if (model.getGroupId() != null && model.getArtifactId() != null && model.getVersion() != null) {
            writer.println(prefix + "GAV " + model.getGroupId() + ":" + model.getArtifactId() + ":" + model.getVersion());
        }

        int sourceVer = safeInt(model.getProperties().getProperty("maven.compiler.source"), 0);
        int targetVer = safeInt(model.getProperties().getProperty("maven.compiler.target"), 0);
        int javaVer = Math.max(sourceVer, targetVer);
        if (javaVer >= 8) {
            writer.println(prefix + "JAVA " + javaVer + "+");
        }
    }

    static String replaceProps(String text, Model model) {
        return Pattern.compile("\\$\\{([^}]+)\\}").matcher(text).replaceAll(matchResult -> {
            String key = matchResult.group(1);
            return model.getProperties().getProperty(key, matchResult.group(0));
        });
    }
    
    static int safeInt(String num, int def) {
        if (num == null) {
            return def;
        }
        try {
            return Integer.parseInt(num);
        } catch (NumberFormatException e) {
            return def;
        }
    }

    public static void main(String... args) {
        if (args.length == 1 && ("--help".equals(args[0])) || args.length > 2) {
            System.err.println("Usage: mvn2jbang [<pom_file_or_folder>] [<output_file>]");
            System.exit(1);
        }
        try {
            Path pom = Paths.get(args.length > 0 ? args[0] : "pom.xml");
            Path output = Paths.get(args.length > 1 ? args[1] : "build.jbang");
            if (!Files.exists(pom)) {
                System.err.println("Pom file not found: " + pom);
                System.exit(2);
            }
            Model model = readModel(pom);
            boolean isJavaFile = output.toString().endsWith(".java");
            boolean append = isJavaFile && Files.exists(output);
            Path output2 = append ? Paths.get(output.toString() + ".tmp") : output;
            try (PrintWriter writer = new PrintWriter(Files.newBufferedWriter(output2))) {
                writeTags(writer, model, isJavaFile);
                if (append) {
                    try (Stream<String> lines = Files.lines(output)) {
                        lines.forEach(writer::println);
                    }
                }
            } catch (IOException e) {
                System.err.println("Error writing output: " + e.getMessage());
                System.exit(4);
            }
            if (append) {
                Files.move(output, Paths.get(output.toString() + ".bak"), StandardCopyOption.REPLACE_EXISTING);
                Files.move(output2, output);
            }
        } catch (IOException | XmlPullParserException e) {
            System.err.println("Error reading pom: " + e.getMessage());
            System.exit(3);
        }
    }
}