/**
 * Copyright (c) 2012, 2014, Credit Suisse (Anatole Tresch), Werner Keil and others by the @author tag.
 *
 * Licensed 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
 *
 * http://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.javamoney.moneta.loader.internal;

import java.io.*;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Default implementation of {@link ResourceCache}, using the local file system.
 *
 * @author Anatole Tresch
 */
public class DefaultResourceCache implements ResourceCache{
    /**
     * The logger used.
     */
    private static final Logger LOG = Logger.getLogger(DefaultResourceCache.class.getName());
    /**
     * Suffix for files created.
     */
    private static final String SUFFIX = ".dat";
    /**
     * Local temp directory.
     */
    private File localDir = new File(System.getProperty("temp.dir", ".resourceCache"));
    /**
     * Cached resources.
     */
    private Map<String,File> cachedResources = new ConcurrentHashMap<>();

    /**
     * Constructor.
     */
    public DefaultResourceCache(){
        if(!localDir.exists()){
            if(!localDir.mkdirs()){
                LOG.severe("Error creating cache dir  " + localDir + ", resource cache disabled!");
                localDir = null;
            }else{
                LOG.finest("Created cache dir  " + localDir);
            }
        }else if(!localDir.isDirectory()){
            LOG.severe("Error initializing cache dir  " + localDir + ", not a directory, resource cache disabled!");
            localDir = null;
        }else if(!localDir.canWrite()){
            LOG.severe("Error initializing cache dir  " + localDir + ", not writable, resource cache disabled!");
            localDir = null;
        }
        if(Objects.nonNull(localDir)){
            File[] files = localDir.listFiles();
            if(files != null){
                for(File file : files){
                    if(file.isFile()){
                        String resourceId = file.getName().substring(0, file.getName().length() - 4);
                        cachedResources.put(resourceId, file);
                    }
                }
            }
        }
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * org.javamoney.moneta.loader.internal.ResourceCache#write(java.lang.String
     * , byte[])
     */
    @Override
    public void write(String resourceId, byte[] data){
        try{
            File f = this.cachedResources.get(resourceId);
            if(Objects.isNull(f)){
                f = new File(localDir, resourceId + SUFFIX);
                writeFile(f, data);
                this.cachedResources.put(resourceId, f);
            }else{
                writeFile(f, data);
            }
        }
        catch(Exception e){
            LOG.log(Level.WARNING, "Caching of resource failed: " + resourceId, e);
        }
    }

    /**
     * Writees a file with the given data,
     *
     * @param f    the file
     * @param data the data
     * @throws IOException if writing failed.
     */
    private void writeFile(File f, byte[] data) throws IOException{
        BufferedOutputStream bos = null;
        try{
            bos = new BufferedOutputStream(new FileOutputStream(f));
            bos.write(data);
            bos.flush();
        }
        finally{
            try{
                if(Objects.nonNull(bos)){
                    bos.close();
                }
            }
            catch(Exception e2){
                LOG.log(Level.SEVERE, "Error closing output stream for " + f, e2);
            }
        }

    }

    /*
     * (non-Javadoc)
     *
     * @see
     * org.javamoney.moneta.loader.internal.ResourceCache#isCached(java.lang
     * .String)
     */
    @Override
    public boolean isCached(String resourceId){
        return this.cachedResources.containsKey(resourceId);
    }

    /*
     * (non-Javadoc)
     *
     * @see
     * org.javamoney.moneta.loader.internal.ResourceCache#read(java.lang.String)
     */
    @Override
    public byte[] read(String resourceId){
        File f = this.cachedResources.get(resourceId);
        if(Objects.isNull(f)){
            return null;
        }
        return readFile(f);
    }

    @Override
    public void clear(String resourceId){
        File f = this.cachedResources.get(resourceId);
        if(f != null){
            if(f.exists()){
                if(!f.delete()){
                    LOG.warning("Failed to delete caching file: " + f.getAbsolutePath());
                }
            }
            this.cachedResources.remove(resourceId);
        }
    }

    /**
     * Read a file.
     *
     * @param f the file
     * @return the bytes read.
     */
    private byte[] readFile(File f){
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        BufferedInputStream is = null;
        try{
            is = new BufferedInputStream(new FileInputStream(f));
            byte[] input = new byte[1024];
            int read = 1;
            while(read > 0){
                read = is.read(input);
                if(read > 0){
                    bos.write(input, 0, read);
                }
            }
            return bos.toByteArray();
        }
        catch(Exception e){
            LOG.log(Level.SEVERE, "Error reading cached resource from " + f, e);
            return null;
        }
        finally{
            try{
                if(Objects.nonNull(is)){
                    is.close();
                }
            }
            catch(Exception e2){
                LOG.log(Level.SEVERE, "Error closing input stream from " + f, e2);
            }
        }
/*
URI fileUri = this.cachedResource;
        if(fileUri == null){
            String userHome = System.getProperty("user.home");
            File file = new File(userHome + "/.cache", resourceId);
            if(file.exists()){
                fileUri = file.toURI();
            }
        }
        if(fileUri != null){
            File file = new File(fileUri);
            try(
                    FileInputStream fis = new FileInputStream(file);
                    BufferedInputStream bis = new BufferedInputStream(fis);
                    ObjectInputStream ois = new ObjectInputStream(bis)
            ){
                long loadTS = ois.readLong();
                byte[] data = (byte[]) ois.readObject();
                this.lastLoaded = loadTS;
                setData(data);
                return true;
            }
            catch(Exception e){
                LOG.log(Level.WARNING, "Failed to read data from cache: " + fileUri, e);
            }
        }
        return false;
 */
    }

    @Override
    public String toString(){
        return "DefaultResourceCache [localDir=" + localDir + ", cachedResources=" + cachedResources + "]";
    }

}