/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

/* $Id$ */

package org.apache.fop.afp.fonts;

import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CodingErrorAction;

An abstraction that wraps the encoding mechanism for encoding a Unicode character sequence into a
specified format.
/**
 * An abstraction that wraps the encoding mechanism for encoding a Unicode character sequence into a
 * specified format.
 */
public abstract class CharactersetEncoder {

    private final CharsetEncoder encoder;

    private CharactersetEncoder(String encoding) {
        this.encoder = Charset.forName(encoding).newEncoder();
        this.encoder.onUnmappableCharacter(CodingErrorAction.REPLACE);
    }

    
Tells whether or not this encoder can encode the given character.
Params:
c – the character
Throws:
IllegalStateException – - If an encoding operation is already in progress
Returns:
true if, and only if, this encoder can encode the given character/**
     * Tells whether or not this encoder can encode the given character.
     *
     * @param c the character
     * @return true if, and only if, this encoder can encode the given character
     * @throws IllegalStateException - If an encoding operation is already in progress
     */
    final boolean canEncode(char c) {
        return encoder.canEncode(c);
    }

    
Encodes a character sequence to a byte array.
Params:
chars – the character sequence
Throws:
CharacterCodingException – if the encoding operation fails
Returns:
the encoded character sequence/**
     * Encodes a character sequence to a byte array.
     *
     * @param chars the character sequence
     * @return the encoded character sequence
     * @throws CharacterCodingException if the encoding operation fails
     */
    final EncodedChars encode(CharSequence chars) throws CharacterCodingException {
        ByteBuffer bb;
        // encode method is not thread safe
        synchronized (encoder) {
            bb = encoder.encode(CharBuffer.wrap(chars));
        }
        if (bb.hasArray()) {
            return getEncodedChars(bb.array(), bb.limit());
        } else {
            bb.rewind();
            byte[] bytes = new byte[bb.remaining()];
            bb.get(bytes);
            return getEncodedChars(bytes, bytes.length);
        }
    }

    abstract EncodedChars getEncodedChars(byte[] byteArray, int length);

    
Encodes chars into a format specified by encoding.
Params:
chars – the character sequence
encoding – the encoding type
Throws:
CharacterCodingException – if encoding fails
Returns:
encoded data/**
     * Encodes <code>chars</code> into a format specified by <code>encoding</code>.
     *
     * @param chars the character sequence
     * @param encoding the encoding type
     * @return encoded data
     * @throws CharacterCodingException if encoding fails
     */
    public static EncodedChars encodeSBCS(CharSequence chars, String encoding)
            throws CharacterCodingException {
        CharactersetEncoder encoder = CharacterSetType.SINGLE_BYTE.getEncoder(encoding);
        return encoder.encode(chars);
    }

    
The EBCDIC double byte encoder is used for encoding IBM format DBCS (double byte character
sets) with an EBCDIC code-page. Given a double byte EBCDIC code page and a Unicode character
sequence it will return its EBCDIC code-point, however, the "Shift In - Shift Out" operators
are removed from the sequence of bytes. These are only used in Line Data.
/**
     * The EBCDIC double byte encoder is used for encoding IBM format DBCS (double byte character
     * sets) with an EBCDIC code-page. Given a double byte EBCDIC code page and a Unicode character
     * sequence it will return its EBCDIC code-point, however, the "Shift In - Shift Out" operators
     * are removed from the sequence of bytes. These are only used in Line Data.
     */
    static final class EbcdicDoubleByteLineDataEncoder extends CharactersetEncoder {
        EbcdicDoubleByteLineDataEncoder(String encoding) {
            super(encoding);
        }
        @Override
        EncodedChars getEncodedChars(byte[] byteArray, int length) {
            if (byteArray[0] == 0x0E && byteArray[length - 1] == 0x0F) {
                return new EncodedChars(byteArray, 1, length - 2, true);
            }
            return new EncodedChars(byteArray, true);
        }
    }

    
The default encoder is used for encoding IBM format SBCS (single byte character sets), this
the primary format for most Latin character sets. This can also be used for Unicode double-
byte character sets (DBCS).
/**
     * The default encoder is used for encoding IBM format SBCS (single byte character sets), this
     * the primary format for most Latin character sets. This can also be used for Unicode double-
     * byte character sets (DBCS).
     */
    static final class DefaultEncoder extends CharactersetEncoder {
        private final boolean isDBCS;

        DefaultEncoder(String encoding, boolean isDBCS) {
            super(encoding);
            this.isDBCS = isDBCS;
        }

        @Override
        EncodedChars getEncodedChars(byte[] byteArray, int length) {
            return new EncodedChars(byteArray, isDBCS);
        }
    }

    
A container for encoded character bytes
/**
     * A container for encoded character bytes
     */
    // CSOFF: FinalClass - disabling "final" modifier so that this class can be mocked
    public static class EncodedChars {

        private final byte[] bytes;
        private final int offset;
        private final int length;
        private final boolean isDBCS;

        private EncodedChars(byte[] bytes, int offset, int length, boolean isDBCS) {
            if (offset < 0 || length < 0 || offset + length > bytes.length) {
                throw new IllegalArgumentException();
            }
            this.bytes = bytes;
            this.offset = offset;
            this.length = length;
            this.isDBCS = isDBCS;
        }

        private EncodedChars(byte[] bytes, boolean isDBCS) {
            this(bytes, 0, bytes.length, isDBCS);
        }

        
write length bytes from offset to the output stream
Params:
out – output to write the bytes to
offset – the offset where to write
length – the length to write
Throws:
IOException – if an I/O error occurs/**
         * write <code>length</code> bytes from <code>offset</code> to the output stream
         *
         * @param out output to write the bytes to
         * @param offset the offset where to write
         * @param length the length to write
         * @throws IOException if an I/O error occurs
         */
        public void writeTo(OutputStream out, int offset, int length) throws IOException {
            if (offset < 0 || length < 0 || offset + length > bytes.length) {
                throw new IllegalArgumentException();
            }
            out.write(bytes, this.offset + offset, length);
        }

        
The number of containing bytes.
Returns:
the length/**
         * The number of containing bytes.
         *
         * @return the length
         */
        public int getLength() {
            return length;
        }

        
Indicates whether or not the EncodedChars object wraps double byte characters.
Returns:
true if the wrapped characters are double byte (DBCSs)/**
         * Indicates whether or not the EncodedChars object wraps double byte characters.
         *
         * @return true if the wrapped characters are double byte (DBCSs)
         */
        public boolean isDBCS() {
            return isDBCS;
        }

        
The bytes
Returns:
the bytes/**
         * The bytes
         *
         * @return the bytes
         */
        public byte[] getBytes() {
            // return copy just in case
            byte[] copy = new byte[bytes.length];
            System.arraycopy(bytes, 0, copy, 0, bytes.length);
            return copy;
        }
    }
}