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/*
 * Copyright (c) 2013, Francis Galiegue 
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the Lesser GNU 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
 * Lesser GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */

package com.github.fge.msgsimple.source;

import com.github.fge.msgsimple.InternalBundle;

import java.io.Closeable;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URL;
import java.nio.charset.Charset;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import java.util.ResourceBundle;

/**
 * A message source built from a properties files
 *
 * This can be viewed as a "single locale equivalent" of a {@link
 * ResourceBundle}, with the key difference that the property file is read
 * using UTF-8 instead of ISO-8859-1.
 *
 * @see Properties#load(Reader)
 */
public final class PropertiesMessageSource
    implements MessageSource
{
    private static final InternalBundle BUNDLE
        = InternalBundle.getInstance();

    private static final Charset UTF8 = Charset.forName("UTF-8");

    private final Map messages = new HashMap();

    /**
     * Create a message source from a classpath resource
     *
     * @param resourcePath the path to the properties file
     * @return a newly created source
     * @throws NullPointerException resource path is null
     * @throws IOException no such resource, or an I/O error occurred while
     * reading the file
     */
    public static MessageSource fromResource(final String resourcePath)
        throws IOException
    {
        BUNDLE.checkNotNull(resourcePath, "cfg.nullResourcePath");

        final URL url = PropertiesMessageSource.class.getResource(resourcePath);

        if (url == null)
            throw new IOException("resource \"" + resourcePath
                + "\" not found");

        final InputStream in = url.openStream();
        try {
            return fromInputStream(in);
        } finally {
            closeQuietly(in);
        }
    }

    /**
     * Create a message source from a file object
     *
     * @param file the file to read from
     * @return a newly created message source
     * @throws NullPointerException file is null
     * @throws FileNotFoundException file does not exist, or cannot access file
     * @throws IOException failed to read from file
     */
    public static MessageSource fromFile(final File file)
        throws IOException
    {
        BUNDLE.checkNotNull(file, "cfg.nullFile");

        final FileInputStream in = new FileInputStream(file);

        try {
            return fromInputStream(in);
        } finally {
            closeQuietly(in);
        }
    }

    /**
     * Create a message source from a file path
     *
     * This essentially calls {@link #fromFile(File)}.
     *
     * @param path the file path
     * @return a newly created message source
     * @throws NullPointerException path is null
     * @throws IOException see {@link #fromFile(File)}
     */
    public static MessageSource fromPath(final String path)
        throws IOException
    {
        BUNDLE.checkNotNull(path, "cfg.nullPath");
        return fromFile(new File(path));
    }

    private static MessageSource fromInputStream(final InputStream in)
        throws IOException
    {
        BUNDLE.checkNotNull(in, "cfg.nullInputStream");

        final Reader reader = new InputStreamReader(in, UTF8);
        try {
            final Properties properties = new Properties();
            // This method is available only since 1.6+
            properties.load(reader);
            return new PropertiesMessageSource(properties);
        } finally {
            closeQuietly(reader);
        }
    }

    private PropertiesMessageSource(final Properties properties)
    {
        for (final String key: properties.stringPropertyNames())
            messages.put(key, properties.getProperty(key));
    }

    @Override
    public String getKey(final String key)
    {
        return messages.get(key);
    }

    private static void closeQuietly(final Closeable closeable)
    {
        try {
            closeable.close();
        } catch (IOException ignored) {
        }
    }
}