/*

  * 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.

  */

 package org.apache.commons.io.input;

 import java.io.IOException;

 import java.io.InputStream;

 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.CoderResult;

 import java.nio.charset.CodingErrorAction;

 /**

  * {@link InputStream} implementation that can read from String, StringBuffer,

  * StringBuilder or CharBuffer.

  * <p>

  * <strong>Note:</strong> Supports {@link #mark(int)} and {@link #reset()}.

  *

  * @since 2.2

  */

 public class CharSequenceInputStream extends InputStream {

     private static final int BUFFER_SIZE = 2048;

     private static final int EOS = -1;

     private static final int NO_MARK = -1;

     private final CharsetEncoder encoder;

     private final CharBuffer cbuf;

     private final ByteBuffer bbuf;

     private int mark_cbuf; // position in cbuf

     private int mark_bbuf; // position in bbuf

     /**

      * Constructor.

      *

      * @param cs the input character sequence

      * @param charset the character set name to use

      * @param bufferSize the buffer size to use.

      * @throws IllegalArgumentException if the buffer is not large enough to hold a complete character

      */

     public CharSequenceInputStream(final CharSequence cs, final Charset charset, final int bufferSize) {

         super();

         this.encoder = charset.newEncoder()

             .onMalformedInput(CodingErrorAction.REPLACE)

             .onUnmappableCharacter(CodingErrorAction.REPLACE);

         // Ensure that buffer is long enough to hold a complete character

         final float maxBytesPerChar = encoder.maxBytesPerChar();

         if (bufferSize < maxBytesPerChar) {

             throw new IllegalArgumentException("Buffer size " + bufferSize + " is less than maxBytesPerChar " + maxBytesPerChar);

         }

         this.bbuf = ByteBuffer.allocate(bufferSize);

         this.bbuf.flip();

         this.cbuf = CharBuffer.wrap(cs);

         this.mark_cbuf = NO_MARK;

         this.mark_bbuf = NO_MARK;

     }

     /**

      * Constructor, calls {@link #CharSequenceInputStream(CharSequence, Charset, int)}.

      *

      * @param cs the input character sequence

      * @param charset the character set name to use

      * @param bufferSize the buffer size to use.

      * @throws IllegalArgumentException if the buffer is not large enough to hold a complete character

      */

     public CharSequenceInputStream(final CharSequence cs, final String charset, final int bufferSize) {

         this(cs, Charset.forName(charset), bufferSize);

     }

     /**

      * Constructor, calls {@link #CharSequenceInputStream(CharSequence, Charset, int)}

      * with a buffer size of 2048.

      *

      * @param cs the input character sequence

      * @param charset the character set name to use

      * @throws IllegalArgumentException if the buffer is not large enough to hold a complete character

      */

     public CharSequenceInputStream(final CharSequence cs, final Charset charset) {

         this(cs, charset, BUFFER_SIZE);

     }

     /**

      * Constructor, calls {@link #CharSequenceInputStream(CharSequence, String, int)}

      * with a buffer size of 2048.

      *

      * @param cs the input character sequence

      * @param charset the character set name to use

      * @throws IllegalArgumentException if the buffer is not large enough to hold a complete character

      */

     public CharSequenceInputStream(final CharSequence cs, final String charset) {

         this(cs, charset, BUFFER_SIZE);

     }

     /**

      * Fills the byte output buffer from the input char buffer.

      *

      * @throws CharacterCodingException

      *             an error encoding data

      */

     private void fillBuffer() throws CharacterCodingException {

         this.bbuf.compact();

         final CoderResult result = this.encoder.encode(this.cbuf, this.bbuf, true);

         if (result.isError()) {

             result.throwException();

         }

         this.bbuf.flip();

     }

     @Override

     public int read(final byte[] b, int off, int len) throws IOException {

         if (b == null) {

             throw new NullPointerException("Byte array is null");

         }

         if (len < 0 || (off + len) > b.length) {

             throw new IndexOutOfBoundsException("Array Size=" + b.length +

                     ", offset=" + off + ", length=" + len);

         }

         if (len == 0) {

             return 0; // must return 0 for zero length read

         }

         if (!this.bbuf.hasRemaining() && !this.cbuf.hasRemaining()) {

             return EOS;

         }

         int bytesRead = 0;

         while (len > 0) {

             if (this.bbuf.hasRemaining()) {

                 final int chunk = Math.min(this.bbuf.remaining(), len);

                 this.bbuf.get(b, off, chunk);

                 off += chunk;

                 len -= chunk;

                 bytesRead += chunk;

             } else {

                 fillBuffer();

                 if (!this.bbuf.hasRemaining() && !this.cbuf.hasRemaining()) {

                     break;

                 }

             }

         }

         return bytesRead == 0 && !this.cbuf.hasRemaining() ? EOS : bytesRead;

     }

     @Override

     public int read() throws IOException {

         for (;;) {

             if (this.bbuf.hasRemaining()) {

                 return this.bbuf.get() & 0xFF;

             } else {

                 fillBuffer();

                 if (!this.bbuf.hasRemaining() && !this.cbuf.hasRemaining()) {

                     return EOS;

                 }

             }

         }

     }

     @Override

     public int read(final byte[] b) throws IOException {

         return read(b, 0, b.length);

     }

     @Override

     public long skip(long n) throws IOException {

         /*

          * This could be made more efficient by using position to skip within the current buffer.

          */

         long skipped = 0;

         while (n > 0 && available() > 0) {

             this.read();

             n--;

             skipped++;

         }

         return skipped;

     }

     /**

      * Return an estimate of the number of bytes remaining in the byte stream.

      * @return the count of bytes that can be read without blocking (or returning EOF).

      *

      * @throws IOException if an error occurs (probably not possible)

      */

     @Override

     public int available() throws IOException {

         // The cached entries are in bbuf; since encoding always creates at least one byte

         // per character, we can add the two to get a better estimate (e.g. if bbuf is empty)

         // Note that the previous implementation (2.4) could return zero even though there were

         // encoded bytes still available.

         return this.bbuf.remaining() + this.cbuf.remaining();

     }

     @Override

     public void close() throws IOException {

     }

     /**

      * {@inheritDoc}

      * @param readlimit max read limit (ignored)

      */

     @Override

     public synchronized void mark(final int readlimit) {

         this.mark_cbuf = this.cbuf.position();

         this.mark_bbuf = this.bbuf.position();

         this.cbuf.mark();

         this.bbuf.mark();

         // It would be nice to be able to use mark & reset on the cbuf and bbuf;

         // however the bbuf is re-used so that won't work

     }

     @Override

     public synchronized void reset() throws IOException {

         /*

          * This is not the most efficient implementation, as it re-encodes from the beginning.

          *

          * Since the bbuf is re-used, in general it's necessary to re-encode the data.

          *

          * It should be possible to apply some optimisations however:

          * + use mark/reset on the cbuf and bbuf. This would only work if the buffer had not been (re)filled since the mark.

          * The code would have to catch InvalidMarkException - does not seem possible to check if mark is valid otherwise.

          * + Try saving the state of the cbuf before each fillBuffer; it might be possible to restart from there.

          */

         if (this.mark_cbuf != NO_MARK) {

             // if cbuf is at 0, we have not started reading anything, so skip re-encoding

             if (this.cbuf.position() != 0) {

                 this.encoder.reset();

                 this.cbuf.rewind();

                 this.bbuf.rewind();

                 this.bbuf.limit(0); // rewind does not clear the buffer

                 while(this.cbuf.position() < this.mark_cbuf) {

                     this.bbuf.rewind(); // empty the buffer (we only refill when empty during normal processing)

                     this.bbuf.limit(0);

                     fillBuffer();

                 }

             }

             if (this.cbuf.position() != this.mark_cbuf) {

                 throw new IllegalStateException("Unexpected CharBuffer postion: actual="+cbuf.position() + " expected=" + this.mark_cbuf);

             }

             this.bbuf.position(this.mark_bbuf);

             this.mark_cbuf = NO_MARK;

             this.mark_bbuf = NO_MARK;

         }

     }

     @Override

     public boolean markSupported() {

         return true;

     }

 }