# TemplateHelper.java

    /*
    ** Module   : TemplateHelper.java
    ** Abstract : Defines methods to fill templates with provided values.
    **
    ** Copyright (c) 2019-2019, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ---------------------------------Description----------------------------------
    ** 001 SBI 20180404 Initial version.
    ** 002 SBI 20191120 Added charset parameter for template reading.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program is distributed in the hope that it will be useful,
    ** but WITHOUT ANY WARRANTY; without even the implied warranty of
    ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ** GNU Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
    **   2. No Misrepresentation of Affiliation.
    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
    **     You may not represent yourself for publicity purposes as associated with
    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.util;

    import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.io.PrintWriter;
    import java.util.Map;
    import java.util.Set;
    import java.util.function.Supplier;

    /**
     * Defines helper static methods to fill templates with provided values.
     */
    public class TemplateHelper
    {
       /** The keys template */
       private static String KEY_TEMPLATE = "${%s}";

       /**
        * This private constructor is defined according to this class responsibility to provide helper
        * static methods to fill templates with values.
        */
       private TemplateHelper()
       {
       }

       /**
        * Process template and make any replacements of parameter values as needed. The replacement
        * placeholder follow the JEE expression language (EL) format for immediate evaluation.
        * <p>
        * Example: ${expression}
        *
        * @param   template
        *          The template as an input stream.
        * @param   keysProvider
        *          The keys provider to fill gaps with values.
        * @param   writer
        *          The print writer to output the target document with help of the given template.
        * @param   charset
        *          The charset used to read the given template
        */
       public static void fill(InputStream template,
                               Map<String, Supplier<String>> keysProvider,
                               PrintWriter writer,
                               String      charset)
       throws IOException
       {
          Set<String> keys = keysProvider.keySet();

          BufferedReader reader = new BufferedReader(new InputStreamReader(template, charset));

          String str = null;

          // read the skeleton page and translate %substitutions
          // on the fly

          while (null != (str = reader.readLine()))
          {
             for(String key : keys)
             {
                String keyTemplate = String.format(KEY_TEMPLATE, key);
                if (str.contains(keyTemplate))
                {
                   str = str.replace(keyTemplate, keysProvider.get(key).get());
                }
             }
             writer.println(str);
          }

          reader.close();
       }
    }