paper-mc/paper-checkstyle/src/main/java/io/papermc/checkstyle/Util.java

package io.papermc.checkstyle;

import com.puppycrawl.tools.checkstyle.JavaParser;
import com.puppycrawl.tools.checkstyle.api.CheckstyleException;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.DetailNode;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
import com.puppycrawl.tools.checkstyle.utils.JavadocUtil;
import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.function.Predicate;
import org.jspecify.annotations.Nullable;

/**
 * Utility class containing utility methods for custom checkstyle checks.
 */
public final class Util {

    private Util() {
    }

    /**
     * Gets the previous sibling of the given node with the given type.
     *
     * @param node the node
     * @param type the type
     * @return the previous sibling with the given type, or {@code null} if not found
     */
    public static @Nullable DetailNode getPreviousSibling(final DetailNode node, final int type) {
        DetailNode sibling = JavadocUtil.getPreviousSibling(node);
        while (sibling != null && sibling.getType() != type) {
            sibling = JavadocUtil.getPreviousSibling(sibling);
        }
        return sibling;
    }

    /**
     * Gets the next sibling of the given node with the given type.
     *
     * @param node the node
     * @param type the type
     * @return the next sibling with the given type, or {@code null} if not found
     */
    public static @Nullable DetailAST getNextSibling(final DetailAST node, final int type) {
        DetailAST sibling = node.getNextSibling();
        while (sibling != null && sibling.getType() != type) {
            sibling = sibling.getNextSibling();
        }
        return sibling;
    }

    /**
     * Gets the enclosing type declaration of the given node.
     *
     * @param node the node
     * @return the enclosing type declaration, or {@code null} if not found
     */
    public static @Nullable DetailAST getEnclosingTypeDeclaration(final DetailAST node) {
        DetailAST parent = node.getParent();
        while (parent != null && !TokenUtil.isTypeDeclaration(parent.getType())) {
            parent = parent.getParent();
        }
        return parent;
    }

    /**
     * Gets an iterator over the children of the given node with the given type.
     *
     * @param ast  the node
     * @param type the type
     * @return the iterator
     */
    public static Iterable<DetailAST> childrenIterator(final DetailAST ast, final int type) {
        return () -> new Iterator<>() {
            private @Nullable DetailAST current = TokenUtil.findFirstTokenByPredicate(ast, child -> child.getType() == type).orElse(null);

            @Override
            public boolean hasNext() {
                return this.current != null;
            }

            @Override
            public DetailAST next() {
                if (this.current == null) {
                    throw new NoSuchElementException();
                }
                final DetailAST result = this.current;
                this.current = getNextSibling(this.current, type);
                return result;
            }
        };
    }

    public static @Nullable DetailAST findPackageInfoFor(final Path filePath) {
        final Path packageInfo = filePath.getParent().resolve("package-info.java");
        if (Files.notExists(packageInfo)) {
            return null;
        }
        final DetailAST packageInfoAst;
        try {
            packageInfoAst = JavaParser.parseFile(packageInfo.toFile(), JavaParser.Options.WITHOUT_COMMENTS);
        } catch (final IOException | CheckstyleException e) {
            throw new RuntimeException(e);
        }
        return packageInfoAst;
    }

    public static boolean isPackageInfoAnnotated(final Path filePath, final Predicate<DetailAST> annotationPredicate) {
        final DetailAST packageInfoAst = Util.findPackageInfoFor(filePath);
        if (packageInfoAst == null) {
            return false;
        }
        final DetailAST firstToken = packageInfoAst.findFirstToken(TokenTypes.PACKAGE_DEF);
        if (firstToken == null) {
            return false;
        }
        final DetailAST annotations = firstToken.findFirstToken(TokenTypes.ANNOTATIONS);
        for (final DetailAST annotation : Util.childrenIterator(annotations, TokenTypes.ANNOTATION)) {
            if (annotationPredicate.test(annotation)) {
                return true;
            }
        }
        return false;
    }
}