/*

 * Copyright (c) 2004, 2011, Oracle and/or its affiliates. All rights reserved.

 * 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

 * published by the Free Software Foundation.  Oracle designates this

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

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.nio.cs;

import java.nio.charset.Charset;

import java.nio.charset.spi.CharsetProvider;

import java.util.Iterator;

import java.util.Map;

/**

 * Abstract base class for fast charset providers.

 *

 * @author Mark Reinhold

 */

public class FastCharsetProvider

    extends CharsetProvider

{

    // Maps canonical names to class names

    private Map<String,String> classMap;

    // Maps alias names to canonical names

    private Map<String,String> aliasMap;

    // Maps canonical names to cached instances

    private Map<String,Charset> cache;

    private String packagePrefix;

    protected FastCharsetProvider(String pp,

                                  Map<String,String> am,

                                  Map<String,String> cm,

                                  Map<String,Charset> c)

    {

        packagePrefix = pp;

        aliasMap = am;

        classMap = cm;

        cache = c;

    }

    private String canonicalize(String csn) {

        String acn = aliasMap.get(csn);

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

    }

    // Private ASCII-only version, optimized for interpretation during startup

    //

    private static String toLower(String s) {

        int n = s.length();

        boolean allLower = true;

        for (int i = 0; i < n; i++) {

            int c = s.charAt(i);

            if (((c - 'A') | ('Z' - c)) >= 0) {

                allLower = false;

                break;

            }

        }

        if (allLower)

            return s;

        char[] ca = new char[n];

        for (int i = 0; i < n; i++) {

            int c = s.charAt(i);

            if (((c - 'A') | ('Z' - c)) >= 0)

                ca[i] = (char)(c + 0x20);

            else

                ca[i] = (char)c;

        }

        return new String(ca);

    }

    private Charset lookup(String charsetName) {

        String csn = canonicalize(toLower(charsetName));

        // Check cache first

        Charset cs = cache.get(csn);

        if (cs != null)

            return cs;

        // Do we even support this charset?

        String cln = classMap.get(csn);

        if (cln == null)

            return null;

        if (cln.equals("US_ASCII")) {

            cs = new US_ASCII();

            cache.put(csn, cs);

            return cs;

        }

        // Instantiate the charset and cache it

        try {

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

                                    true,

                                    this.getClass().getClassLoader());

            cs = (Charset)c.newInstance();

            cache.put(csn, cs);

            return cs;

        } catch (ClassNotFoundException |

                 IllegalAccessException |

                 InstantiationException x) {

            return null;

        }

    }

    public final Charset charsetForName(String charsetName) {

        synchronized (this) {

            return lookup(canonicalize(charsetName));

        }

    }

    public final Iterator<Charset> charsets() {

        return new Iterator<Charset>() {

                Iterator<String> i = classMap.keySet().iterator();

                public boolean hasNext() {

                    return i.hasNext();

                }

                public Charset next() {

                    String csn = i.next();

                    return lookup(csn);

                }

                public void remove() {

                    throw new UnsupportedOperationException();

                }

            };

    }

}