javax0.jamal.builtins.If Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of jamal-core Show documentation
Jamal macro library built-in macros
There is a newer version: 2.8.2
package javax0.jamal.builtins;

import javax0.jamal.api.BadSyntax;
import javax0.jamal.api.Input;
import javax0.jamal.api.Macro;
import javax0.jamal.api.Processor;

import java.util.regex.Pattern;

import static javax0.jamal.tools.InputHandler.skip;
import static javax0.jamal.tools.InputHandler.skipWhiteSpaces;

/**
 * Define the {@code if} conditional macro. The syntax of the macro is
 *
 *  *     {#if/test/then content/else content}
 * 
 * 
 * The result of the evaluated macro will be the {@code then content} when the {@code test} is true and the
 * {@code else} content otherwise. The {@code test} is true, if it is the literal {@code "true"} (case insensitive),
 * an integer number and the value is not zero or any other string that contains at least one non-space character,
 * except when the {@code test} is the literal {@code "false"} (case insensitive) then the test is false.
 * 
 * The syntax depicted above using the {@code /} character as separator. It is only convention. Any non-space character
 * can be used as separator. The first non-space character following the {@code if} will be used as separator
 * character.
 *
 */
public class If implements Macro {

    @Override
    public String evaluate(Input input, Processor processor) throws BadSyntax {
        skipWhiteSpaces(input);
        final var separator = input.substring(0, 1);
        skip(input, 1);
        var testEnd = input.indexOf(separator);
        if (testEnd == -1) {
            throw new BadSyntax("Test is not terminated by the separator character '" + separator + "' after {@if ...");
        }
        var test = input.substring(0, testEnd);
        skip(input, testEnd + 1);
        var positiveEnd = input.indexOf(separator);
        final String positive;
        if (positiveEnd > 0) {
            positive = input.substring(0, positiveEnd);
            skip(input, positiveEnd + 1);
        } else {
            positive = input.toString();
            skip(input, input.length());
        }
        var negative = input.toString();
        if (isTrue(test)) {
            return positive;
        } else {
            return negative;
        }
    }

    private boolean isTrue(String test) {
        if (test.trim().equalsIgnoreCase("true")) {
            return true;
        }
        if (test.trim().equalsIgnoreCase("false")) {
            return false;
        }
        if (test.trim().matches("[+-]?\\d+")) {
            return Integer.parseInt(test) != 0;
        }
        return test.trim().length() > 0;
    }

}