SyntaxChecker.java

package org.thewonderlemming.c4plantuml.syntaxchecker;

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.util.Optional;

import org.antlr.v4.runtime.Parser;
import org.antlr.v4.runtime.tree.ParseTree;
import org.antlr.v4.runtime.tree.ParseTreeListener;
import org.antlr.v4.runtime.tree.ParseTreeWalker;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.thewonderlemming.c4plantuml.commons.Reporter;
import org.thewonderlemming.c4plantuml.grammars.C4BaseListener;
import org.thewonderlemming.c4plantuml.grammars.SourceType;
import org.thewonderlemming.c4plantuml.grammars.generated.C4L1Parser;
import org.thewonderlemming.c4plantuml.grammars.generated.C4L2Parser;
import org.thewonderlemming.c4plantuml.grammars.generated.C4L3Parser;

/**
 * An ANTLR4 based tool to analyse C4 PlantUML source files syntax.
 *
 * @author thewonderlemming
 *
 */
public class SyntaxChecker {

    private static final Logger LOGGER = LoggerFactory.getLogger(SyntaxChecker.class);

    private static final ParseTreeListener PARSE_TREE_LISTENER = new C4BaseListener();

    private final Reporter reporter;


    /**
     * Default constructor.
     *
     * @param reporter the {@link Reporter} to report to.
     */
    public SyntaxChecker(final Reporter reporter) {
        this.reporter = reporter;
    }

    /**
     * Parses a given file and checks its syntax for errors, using {@code UTF-8} encoding.
     *
     * @param c4SourceFile the given file to parse.
     */
    public void check(final Path c4SourceFile) {
        check(c4SourceFile, StandardCharsets.UTF_8);
    }

    /**
     * Parses a given file and checks its syntax for errors.
     *
     * @param c4SourceFile the given file to parse.
     * @param charset the {@link Charset} to use while parsing the file.
     */
    public void check(final Path c4SourceFile, final Charset charset) {

        SourceType
            .getSourceTypeFromFilename(c4SourceFile)
                .ifPresent(sourceType -> {

                    final SyntaxCheckerErrorListener errorListener = new SyntaxCheckerErrorListener(
                        this.reporter,
                            c4SourceFile);

                    sourceType
                        .createParser(c4SourceFile, charset, errorListener)
                            .ifPresent(parser -> getParseTree(parser)
                                .ifPresent(tree -> new ParseTreeWalker().walk(PARSE_TREE_LISTENER, tree)));
                });
    }

    private Optional<ParseTree> getParseTree(final Parser parser) {

        final ParseTree tree;

        if (parser instanceof C4L1Parser) {
            tree = ((C4L1Parser) parser).diagram();

        } else if (parser instanceof C4L2Parser) {
            tree = ((C4L2Parser) parser).diagram();

        } else if (parser instanceof C4L3Parser) {
            tree = ((C4L3Parser) parser).diagram();

        } else {
            LOGGER.error("Unsupported parser type {} was given", parser.getClass());
            return Optional.empty();
        }

        return Optional.ofNullable(tree);
    }
}