/*

 * Copyright (c) 2016, 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

 */

package java.net.http;

import java.nio.ByteBuffer;

import java.nio.CharBuffer;

import java.nio.charset.CharacterCodingException;

import java.nio.charset.CharsetDecoder;

import java.nio.charset.CharsetEncoder;

import java.nio.charset.CoderResult;

import java.nio.charset.CodingErrorAction;

import java.nio.charset.StandardCharsets;

import static java.lang.System.Logger.Level.WARNING;

import static java.net.http.WSUtils.EMPTY_BYTE_BUFFER;

import static java.net.http.WSUtils.logger;

import static java.nio.charset.StandardCharsets.UTF_8;

/*

 * A collection of tools for UTF-8 coding.

 */

final class WSCharsetToolkit {

    private WSCharsetToolkit() { }

    static final class Encoder {

        private final CharsetEncoder encoder = UTF_8.newEncoder();

        ByteBuffer encode(CharBuffer in) throws CharacterCodingException {

            return encoder.encode(in);

        }

        // TODO:

        // ByteBuffer[] encode(CharBuffer in) throws CharacterCodingException {

        //     return encoder.encode(in);

        // }

    }

    static CharBuffer decode(ByteBuffer in) throws CharacterCodingException {

        return UTF_8.newDecoder().decode(in);

    }

    static final class Decoder {

        private final CharsetDecoder decoder = StandardCharsets.UTF_8.newDecoder();

        {

            decoder.onMalformedInput(CodingErrorAction.REPORT);

            decoder.onUnmappableCharacter(CodingErrorAction.REPORT);

        }

        private ByteBuffer leftovers = EMPTY_BYTE_BUFFER;

        WSShared<CharBuffer> decode(WSShared<ByteBuffer> in, boolean endOfInput)

                throws CharacterCodingException {

            ByteBuffer b;

            int rem = leftovers.remaining();

            if (rem != 0) {

                // TODO: We won't need this wasteful allocation & copying when

                // JDK-8155222 has been resolved

                b = ByteBuffer.allocate(rem + in.remaining());

                b.put(leftovers).put(in.buffer()).flip();

            } else {

                b = in.buffer();

            }

            CharBuffer out = CharBuffer.allocate(b.remaining());

            CoderResult r = decoder.decode(b, out, endOfInput);

            if (r.isError()) {

                r.throwException();

            }

            if (b.hasRemaining()) {

                leftovers = ByteBuffer.allocate(b.remaining()).put(b).flip();

            } else {

                leftovers = EMPTY_BYTE_BUFFER;

            }

            // Since it's UTF-8, the assumption is leftovers.remaining() < 4

            // (i.e. small). Otherwise a shared buffer should be used

            if (!(leftovers.remaining() < 4)) {

                logger.log(WARNING,

                        "The size of decoding leftovers is greater than expected: {0}",

                        leftovers.remaining());

            }

            b.position(b.limit()); // As if we always read to the end

            in.dispose();

            // Decoder promises that in the case of endOfInput == true:

            // "...any remaining undecoded input will be treated as being

            // malformed"

            assert !(endOfInput && leftovers.hasRemaining()) : endOfInput + ", " + leftovers;

            if (endOfInput) {

                r = decoder.flush(out);

                decoder.reset();

                if (r.isOverflow()) {

                    // FIXME: for now I know flush() does nothing. But the

                    // implementation of UTF8 decoder might change. And if now

                    // flush() is a no-op, it is not guaranteed to remain so in

                    // the future

                    throw new InternalError("Not yet implemented");

                }

            }

            out.flip();

            return WSShared.wrap(out);

        }

    }

}