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/*
 * Copyright (c) 2000, 2020, Oracle and/or its affiliates.
 *
 * Licensed under the Universal Permissive License v 1.0 as shown at
 * http://oss.oracle.com/licenses/upl.
 */
package com.tangosol.coherence.config.xml.preprocessor;

import com.tangosol.coherence.config.Config;

import com.tangosol.config.ConfigurationException;
import com.tangosol.config.expression.SystemPropertyParameterResolver;
import com.tangosol.config.expression.ValueMacroExpression;
import com.tangosol.config.xml.ProcessingContext;
import com.tangosol.config.xml.DocumentElementPreprocessor.ElementPreprocessor;


import com.tangosol.run.xml.XmlElement;
import com.tangosol.run.xml.XmlValue;
import com.tangosol.run.xml.XmlHelper;

/**
 * A {@link SystemPropertyPreprocessor} is an {@link ElementPreprocessor} that will
 * replace {@link XmlElement} content annotated with "system-property" attributes with appropriate
 * {@link System#getProperties()}.
 * 
 * The element's value is processed for macro expansion. The macro syntax is ${system-property default-value}.
 * Thus, a value of near-${coherence.client direct} can be macro expanded by default to near-direct.
 * If system property coherence.client is set to remote, then the value would be expanded to near-remote.
 *
 * @author bo  2011.08.03
 * @since Coherence 12.1.2
 */
public class SystemPropertyPreprocessor
        implements ElementPreprocessor
    {
    // ----- ElementPreprocessor methods ------------------------------------

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean preprocess(ProcessingContext context, XmlElement element)
            throws ConfigurationException
        {
        boolean fUpdated = false;
        XmlValue attribute = element.getAttribute(SYSTEM_PROPERTY);
        if (attribute != null)
            {
            // remove the attribute
            element.setAttribute(SYSTEM_PROPERTY, null);

            // set the element's value from the specified system property
            try
                {
                String sName  = attribute.getString();
                String sValue = Config.getProperty(sName);

                if (sValue != null)
                    {
                    element.setString(sValue);
                    fUpdated = true;
                    }
                }
            catch (Exception e)
                {
                // ignore security exception accessing config property
                }
            }

        fUpdated |= processValueMacro(element);

        return fUpdated;
        }

    /**
     * Process macros embedded in element's value
     *
     * @param element the {@link XmlElement} to preprocess
     *
     * @return true iff the String value of element was macro expanded
     */
    static public boolean processValueMacro(XmlElement element)
        {
        if (ValueMacroExpression.containsMacro(element.getString()))
            {
            ValueMacroExpression macroExpr = new ValueMacroExpression(element.getString().trim());
            String sValue = macroExpr.evaluate(SystemPropertyParameterResolver.INSTANCE);
            element.setString(sValue);
            return true;
            }
        else
            {
            return false;
            }
        }

    // ----- constants ------------------------------------------------------

    /**
     * This singleton instance of the {@link SystemPropertyPreprocessor}.
     */
    public static final SystemPropertyPreprocessor INSTANCE = new SystemPropertyPreprocessor();

    /**
     * The constant for the "system-property" attribute.
     */
    private static final String SYSTEM_PROPERTY = "system-property";
    }