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package org.parboiled.examples.doublequotedstring;

import org.parboiled.BaseParser;
import org.parboiled.Parboiled;
import org.parboiled.Rule;
import org.parboiled.annotations.BuildParseTree;
import org.parboiled.errors.ErrorUtils;
import org.parboiled.parserunners.TracingParseRunner;
import org.parboiled.support.ParseTreeUtils;
import org.parboiled.support.ParsingResult;

import java.util.Scanner;

/**
 * A simple, double quoted string matching grammar
 *
 * This will match inputs such as:
 *
 * 
 *     {@code "hello world"};
 *     {@code "hello \"world\""};
 *     {@code ""};
 *     {@code "\""}
 * 
 *
 * and so on.
 *
 * This parser builds the parse tree (the class is annotated using {@link
 * BuildParseTree}) and uses a {@link TracingParseRunner} so that you can see
 * the parsing process in action.
 *
 * This parser uses the {@code normal* (special normal*)*} pattern, often
 * used in regexes to "unroll the loop". In this case:
 *
 * 
 *     {@code normal} is everything but a backslash or a double quote,
 *     {@code special} is the character sequence {@code '\', '"'}.
 * 
 */
@BuildParseTree
public class DoubleQuotedString
    extends BaseParser
{
    Rule Normal()
    {
        return NoneOf("\\\"");
    }

    Rule Special()
    {
        return String("\\\"");
    }

    Rule NSN()
    {
        return Sequence(
            ZeroOrMore(Normal()),
            ZeroOrMore(Special(), ZeroOrMore(Normal()))
        );
    }

    Rule DoubleQuotedString()
    {
        return Sequence('"', NSN(), '"', EOI);
    }

    public static void main(final String... args)
    {
        final DoubleQuotedString parser
            = Parboiled.createParser(DoubleQuotedString.class);

        final Scanner scanner = new Scanner(System.in);
        ParsingResult result;
        String line;

        while (true) {
            System.out.print("Enter a value to test (empty to quit): ");
            line = scanner.nextLine();
            if (line.isEmpty())
                break;
            result = new TracingParseRunner(parser.DoubleQuotedString())
                .run(line);
            if (result.hasErrors()) {
                System.out.println("Invalid input!");
                System.out.println(ErrorUtils.printParseErrors(result));
            } else {
                System.out.println(ParseTreeUtils.printNodeTree(result));
            }
        }
    }
}