/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package org.apache.tools.ant.types.selectors.modifiedselector;


import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.nio.file.Files;
import java.util.Iterator;
import java.util.Properties;


Use java.util.Properties for storing the values.
The use of this Cache-implementation requires the use of the parameter
<param name="cache.cachefile" .../> for defining, where to store the
properties file.
The ModifiedSelector sets the cachefile to the default value
cache.properties.
Supported <param>s are:

Cache parameters

  
name
values
description
required


  
cache.cachefile
  
path to file
  
the name of the properties file
  
yes


Version:
2003-09-13
Since:
 Ant 1.6/**
 * Use java.util.Properties for storing the values.
 * The use of this Cache-implementation requires the use of the parameter
 * &lt;param name="cache.cachefile" .../&gt; for defining, where to store the
 * properties file.
 *
 * The ModifiedSelector sets the <i>cachefile</i> to the default value
 * <i>cache.properties</i>.
 *
 * Supported &lt;param&gt;s are:
 * <table>
 * <caption>Cache parameters</caption>
 * <tr>
 *   <th>name</th><th>values</th><th>description</th><th>required</th>
 * </tr>
 * <tr>
 *   <td>cache.cachefile</td>
 *   <td><i>path to file</i></td>
 *   <td>the name of the properties file</td>
 *   <td>yes</td>
 * </tr>
 * </table>
 *
 * @version 2003-09-13
 * @since  Ant 1.6
 */
public class PropertiesfileCache implements Cache {


    // -----  member variables - configuration  -----


    
Where to store the properties? /** Where to store the properties? */
    private File cachefile = null;

    
Object for storing the key-value-pairs. /** Object for storing the key-value-pairs. */
    private Properties cache = new Properties();


    // -----  member variables - internal use  -----


    
Is the cache already loaded? Prevents from multiple load operations. /** Is the cache already loaded? Prevents from multiple load operations. */
    private boolean cacheLoaded = false;

    
Must the cache be saved? Prevents from multiple save operations. /** Must the cache be saved? Prevents from multiple save operations. */
    private boolean cacheDirty  = true;


    // -----  Constructors  -----


    
Bean-Constructor. /** Bean-Constructor. */
    public PropertiesfileCache() {
    }

    
Constructor.
Params:
cachefile – set the cachefile/**
     * Constructor.
     * @param cachefile set the cachefile
     */
    public PropertiesfileCache(File cachefile) {
        this.cachefile = cachefile;
    }


    // -----  Cache-Configuration  -----


    
Setter.
Params:
file – new value/**
     * Setter.
     * @param file new value
     */
    public void setCachefile(File file) {
        cachefile = file;
    }


    
Getter.
Returns:
the cachefile/**
     * Getter.
     * @return the cachefile
     */
    public File getCachefile() {
        return cachefile;
    }

    
This cache is valid if the cachefile is set.
Returns:
true if all is ok false otherwise/**
     * This cache is valid if the cachefile is set.
     * @return true if all is ok false otherwise
     */
    @Override
    public boolean isValid() {
        return (cachefile != null);
    }


    // -----  Data Access


    
Load the cache from underlying properties file.
/**
     * Load the cache from underlying properties file.
     */
    @Override
    public void load() {
        if (cachefile != null && cachefile.isFile() && cachefile.canRead()) {
            try (BufferedInputStream bis = new BufferedInputStream(
                Files.newInputStream(cachefile.toPath()))) {
                cache.load(bis);
            } catch (Exception e) {
                e.printStackTrace(); //NOSONAR
            }
        }
        // after loading the cache is up to date with the file
        cacheLoaded = true;
        cacheDirty  = false;
    }

    
Saves modification of the cache.
Cache is only saved if there is one ore more entries.
Because entries can not be deleted by this API, this Cache
implementation checks the existence of entries before creating the file
for performance optimisation.
/**
     * Saves modification of the cache.
     * Cache is only saved if there is one ore more entries.
     * Because entries can not be deleted by this API, this Cache
     * implementation checks the existence of entries before creating the file
     * for performance optimisation.
     */
    @Override
    public void save() {
        if (!cacheDirty) {
            return;
        }
        if (cachefile != null && cache.propertyNames().hasMoreElements()) {
            try (BufferedOutputStream bos = new BufferedOutputStream(
                Files.newOutputStream(cachefile.toPath()))) {
                cache.store(bos, null);
                bos.flush();
            } catch (Exception e) {
                e.printStackTrace(); //NOSONAR
            }
        }
        cacheDirty = false;
    }

    
Deletes the cache and its underlying file. /** Deletes the cache and its underlying file. */
    @Override
    public void delete() {
        cache = new Properties();
        cachefile.delete();
        cacheLoaded = true;
        cacheDirty = false;
    }

    
Returns a value for a given key from the cache.
Params:
key – the key
Returns:
the stored value/**
     * Returns a value for a given key from the cache.
     * @param key the key
     * @return the stored value
     */
    @Override
    public Object get(Object key) {
        if (!cacheLoaded) {
            load();
        }
        try {
            return cache.getProperty(String.valueOf(key));
        } catch (ClassCastException e) {
            return null;
        }
    }

    
Saves a key-value-pair in the cache.
Params:
key – the key
value – the value/**
     * Saves a key-value-pair in the cache.
     * @param key the key
     * @param value the value
     */
    @Override
    public void put(Object key, Object value) {
        cache.put(String.valueOf(key), String.valueOf(value));
        cacheDirty = true;
    }

    
Returns an iterator over the keys in the cache.
Returns:
An iterator over the keys./**
     * Returns an iterator over the keys in the cache.
     * @return An iterator over the keys.
     */
    @Override
    public Iterator<String> iterator() {
        return cache.stringPropertyNames().iterator();
    }


    // -----  additional  -----


    
Override Object.toString().
Returns:
information about this cache/**
     * Override Object.toString().
     * @return information about this cache
     */
    @Override
    public String toString() {
        return String.format("<PropertiesfileCache:cachefile=%s;noOfEntries=%d>",
                cachefile, cache.size());
    }
}