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Common utilities and classes for reflection
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/**
 * 
 */
package org.kasource.commons.util;

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

/**
 * @author rikardwigforss
 *
 */
public class StringUtils {
    
    private static final Pattern VARIABLE_PATTERN = Pattern.compile("\\$\\{\\w*\\}");
    
  
    /**
     * Returns a string where maven-style variables ${variableName} are replaced with variables from
     * the variable map, system variable or environment variables.
     * 
     * Will resolve variable values differently depending on the systemOverrideMode flag, where true = override and false = fall back. 
     * See the list below in which order variable values are resolved.
     * 

     * systemOverrideMode = true
     *

     * 1. Find variable value in system properties
 
     * 2. Find variable value in environment variables

     * 3. Find variable value in the variables map

     * 

     * systemOverrideMode = true
     * 
     * 1. Find variable value in the variables map

     * 2. Find variable value in system properties
 
     * 3. Find variable value in environment variables

     * 
     * 
     * @param input                    The text to perform variable substitution upon
     * @param variables                Map of variable values
     * @param systemOverrideMode       true system variables will override what's in the variables map
     * 
     * @return the input with the variables found replaced with it's values.
     **/
    public static String replaceVariables(String input, Map variables, boolean systemOverrideMode) {
        Matcher matcher = VARIABLE_PATTERN.matcher(input);
        String result = input;
        while(matcher.find()) {
            String variableName = matcher.group();
            variableName = variableName.substring(2, variableName.length()-1);
            Object variable = resolveVariable(variableName, variables, systemOverrideMode);
            if(variable != null) {
               result = result.replaceFirst(VARIABLE_PATTERN.pattern(), variable.toString().replace("\\", "\\\\"));
            }
        }
        return result;
    }
    
    /**
     *  Helper to {@link #replaceVariables(String, Map, boolean)} which resolves and returns a variable value
     *  depending on mode.
     *  
     * @param variableName              Name of the variable to find
     * @param variables                 Map of variable values
     * @param systemOverrideMode        Override = true, Fall back = false
     * 
     * @return The variable value for variableName.
     */
    private static Object resolveVariable (String variableName, Map variables, boolean systemOverrideMode) {
        Object variable = (variables != null) ? variables.get(variableName) : null;
        String environmentValue = System.getenv(variableName);
        String systemValue = System.getProperty(variableName);
        if(systemOverrideMode) {
            return (systemValue != null ? systemValue : (environmentValue != null) ? environmentValue : variable);
        } else {
            return (variable != null ? variable : (systemValue != null) ? systemValue : environmentValue);
        }
       
    }
}