import java.nio.file.Path;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Element;

/** Exact module-wide line gate; consumes JaCoCo XML without rounding percentages. */
public class Coverage {
    /**
     * Gates a JaCoCo XML report at 80 percent module line coverage without rounding.
     *
     * @param args the report path as the sole argument
     * @throws Exception if the report cannot be read, has no line counter, or fails the coverage gate
     */
    public static void main(final String... args) throws Exception {
        final var factory = DocumentBuilderFactory.newInstance();
        factory.setFeature("http://xml.org/sax/features/external-general-entities", false);
        factory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
        factory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
        final Element report =
                factory.newDocumentBuilder().parse(Path.of(args[0]).toFile()).getDocumentElement();
        for (var child = report.getFirstChild(); child != null; child = child.getNextSibling()) {
            if (child instanceof Element counter
                    && counter.getTagName().equals("counter")
                    && counter.getAttribute("type").equals("LINE")) {
                final long covered = Long.parseLong(counter.getAttribute("covered"));
                final long missed = Long.parseLong(counter.getAttribute("missed"));
                final long total = covered + missed;
                IO.println("Backend line coverage: " + covered + "/" + total + " (" + 100.0 * covered / total + "%)");
                if (total == 0 || 5 * covered < 4 * total)
                    throw new IllegalStateException("Backend line coverage must reach 80%: " + args[0]);
                return;
            }
        }
        throw new IllegalStateException("Missing module LINE counter: " + args[0]);
    }
}