PlaceholderCalc.java

package me.fromgate.reactions.placeholders;

import me.fromgate.reactions.util.MathEval;
import me.fromgate.reactions.util.Variables;
import org.bukkit.entity.Player;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

@PlaceholderDefine(id = "Calculate", needPlayer = false, keys = {"CALC", "calculate", "expression"})
public class PlaceholderCalc extends Placeholder {

    @Override
    public String processPlaceholder(Player player, String key, String param) {
        String expression = replaceVariablesInExpression(param);
        MathEval math = new MathEval();
        try {
            double result = math.evaluate(expression);
            return (result == (int) result) ? Integer.toString((int) result) : Double.toString(result);
        } catch (Exception ignore) {
        }
        return null;
    }


    private String replaceVariablesInExpression(String expression) {
        String result = expression;
        Pattern pattern = Pattern.compile("\\w+");
        Matcher matcher = pattern.matcher(expression);
        while (matcher.find()) {
            String var = matcher.group();
            result = result.replace(var, Variables.getVar("", var, var));
        }
        return result;
    }
}