/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * particular file as subject to the "Classpath" exception as provided

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 */

package sun.nio.cs;

import java.lang.ref.SoftReference;

import java.nio.charset.Charset;

import java.nio.charset.spi.CharsetProvider;

import java.util.ArrayList;

import java.util.TreeMap;

import java.util.Iterator;

import java.util.Locale;

import java.util.Map;

import sun.misc.ASCIICaseInsensitiveComparator;

/**

 * Abstract base class for charset providers.

 *

 * @author Mark Reinhold

 */

public class AbstractCharsetProvider

    extends CharsetProvider

{

    /* Maps canonical names to class names

     */

    private Map<String,String> classMap

        = new TreeMap<>(ASCIICaseInsensitiveComparator.CASE_INSENSITIVE_ORDER);

    /* Maps alias names to canonical names

     */

    private Map<String,String> aliasMap

        = new TreeMap<>(ASCIICaseInsensitiveComparator.CASE_INSENSITIVE_ORDER);

    /* Maps canonical names to alias-name arrays

     */

    private Map<String,String[]> aliasNameMap

        = new TreeMap<>(ASCIICaseInsensitiveComparator.CASE_INSENSITIVE_ORDER);

    /* Maps canonical names to soft references that hold cached instances

     */

    private Map<String,SoftReference<Charset>> cache

        = new TreeMap<>(ASCIICaseInsensitiveComparator.CASE_INSENSITIVE_ORDER);

    private String packagePrefix;

    protected AbstractCharsetProvider() {

        packagePrefix = "sun.nio.cs";

    }

    protected AbstractCharsetProvider(String pkgPrefixName) {

        packagePrefix = pkgPrefixName;

    }

    /* Add an entry to the given map, but only if no mapping yet exists

     * for the given name.

     */

    private static <K,V> void put(Map<K,V> m, K name, V value) {

        if (!m.containsKey(name))

            m.put(name, value);

    }

    private static <K,V> void remove(Map<K,V> m, K name) {

        V x  = m.remove(name);

        assert (x != null);

    }

    /* Declare support for the given charset

     */

    protected void charset(String name, String className, String[] aliases) {

        synchronized (this) {

            put(classMap, name, className);

            for (int i = 0; i < aliases.length; i++)

                put(aliasMap, aliases[i], name);

            put(aliasNameMap, name, aliases);

            cache.clear();

        }

    }

    protected void deleteCharset(String name, String[] aliases) {

        synchronized (this) {

            remove(classMap, name);

            for (int i = 0; i < aliases.length; i++)

                remove(aliasMap, aliases[i]);

            remove(aliasNameMap, name);

            cache.clear();

        }

    }

    /* Late initialization hook, needed by some providers

     */

    protected void init() { }

    private String canonicalize(String charsetName) {

        String acn = aliasMap.get(charsetName);

        return (acn != null) ? acn : charsetName;

    }

    private Charset lookup(String csn) {

        // Check cache first

        SoftReference<Charset> sr = cache.get(csn);

        if (sr != null) {

            Charset cs = sr.get();

            if (cs != null)

                return cs;

        }

        // Do we even support this charset?

        String cln = classMap.get(csn);

        if (cln == null)

            return null;

        // Instantiate the charset and cache it

        try {

            Class<?> c = Class.forName(packagePrefix + "." + cln,

                                       true,

                                       this.getClass().getClassLoader());

            Charset cs = (Charset)c.newInstance();

            cache.put(csn, new SoftReference<Charset>(cs));

            return cs;

        } catch (ClassNotFoundException x) {

            return null;

        } catch (IllegalAccessException x) {

            return null;

        } catch (InstantiationException x) {

            return null;

        }

    }

    public final Charset charsetForName(String charsetName) {

        synchronized (this) {

            init();

            return lookup(canonicalize(charsetName));

        }

    }

    public final Iterator<Charset> charsets() {

        final ArrayList<String> ks;

        synchronized (this) {

            init();

            ks = new ArrayList<>(classMap.keySet());

        }

        return new Iterator<Charset>() {

                Iterator<String> i = ks.iterator();

                public boolean hasNext() {

                    return i.hasNext();

                }

                public Charset next() {

                    String csn = i.next();

                    return lookup(csn);

                }

                public void remove() {

                    throw new UnsupportedOperationException();

                }

            };

    }

    public final String[] aliases(String charsetName) {

        synchronized (this) {

            init();

            return aliasNameMap.get(charsetName);

        }

    }

}