/*  
 * Copyright 2012 Sebastian Annies, Hamburg
 *
 * Licensed 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 com.googlecode.mp4parser;

import com.coremedia.iso.BoxParser;
import com.coremedia.iso.ChannelHelper;
import com.coremedia.iso.Hex;
import com.coremedia.iso.IsoFile;
import com.coremedia.iso.IsoTypeWriter;
import com.coremedia.iso.boxes.Box;
import com.coremedia.iso.boxes.ContainerBox;
import com.coremedia.iso.boxes.UserBox;
import com.googlecode.mp4parser.annotations.DoNotParseDetail;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.util.logging.Logger;

import static com.googlecode.mp4parser.util.CastUtils.l2i;

/**
 * A basic on-demand parsing box. Requires the implementation of three methods to become a fully working box:
 * <ol>
 * <li>{@link #_parseDetails(java.nio.ByteBuffer)}</li>
 * <li>{@link #getContent(java.nio.ByteBuffer)}</li>
 * <li>{@link #getContentSize()}</li>
 * </ol>
 * additionally this new box has to be put into the <code>isoparser-default.properties</code> file so that
 * it is accessible by the <code>PropertyBoxParserImpl</code>
 */
public abstract class AbstractBox implements Box {
    public static int MEM_MAP_THRESHOLD = 100 * 1024;
    private static Logger LOG = Logger.getLogger(AbstractBox.class.getName());

    protected String type;
    private byte[] userType;
    private ContainerBox parent;

    private ByteBuffer content;
    private ByteBuffer deadBytes = null;


    protected AbstractBox(String type) {
        this.type = type;
    }

    protected AbstractBox(String type, byte[] userType) {
        this.type = type;
        this.userType = userType;
    }

    /**
     * Get the box's content size without its header. This must be the exact number of bytes
     * that <code>getContent(ByteBuffer)</code> writes.
     *
     * @return Gets the box's content size in bytes
     * @see #getContent(java.nio.ByteBuffer)
     */
    protected abstract long getContentSize();

    /**
     * Write the box's content into the given <code>ByteBuffer</code>. This must include flags
     * and version in case of a full box. <code>byteBuffer</code> has been initialized with
     * <code>getSize()</code> bytes.
     *
     * @param byteBuffer the sink for the box's content
     */
    protected abstract void getContent(ByteBuffer byteBuffer);

    /**
     * Parse the box's fields and child boxes if any.
     *
     * @param content the box's raw content beginning after the 4-cc field.
     */
    protected abstract void _parseDetails(ByteBuffer content);

    /**
     * Read the box's content from a byte channel without parsing it. Parsing is done on-demand.
     *
     * @param readableByteChannel the (part of the) iso file to parse
     * @param contentSize         expected contentSize of the box
     * @param boxParser           creates inner boxes
     * @throws IOException in case of an I/O error.
     */
    @DoNotParseDetail
    public void parse(ReadableByteChannel readableByteChannel, ByteBuffer header, long contentSize, BoxParser boxParser) throws IOException {
        if (readableByteChannel instanceof FileChannel && contentSize > MEM_MAP_THRESHOLD) {
            // todo: if I map this here delayed I could use transferFrom/transferTo in the getBox method
            // todo: potentially this could speed up writing.
            //
            // It's quite expensive to map a file into the memory. Just do it when the box is larger than a MB.
            content = ((FileChannel) readableByteChannel).map(FileChannel.MapMode.READ_ONLY, ((FileChannel) readableByteChannel).position(), contentSize);
            ((FileChannel) readableByteChannel).position(((FileChannel) readableByteChannel).position() + contentSize);
        } else {
            assert contentSize < Integer.MAX_VALUE;
            content = ChannelHelper.readFully(readableByteChannel, contentSize);
        }
        if (isParsed() == false) {
            parseDetails();
        }

    }

    public void getBox(WritableByteChannel os) throws IOException {
        ByteBuffer bb = ByteBuffer.allocate(l2i(getSize()));
        getHeader(bb);
        if (content == null) {
            getContent(bb);
            if (deadBytes != null) {
                deadBytes.rewind();
                while (deadBytes.remaining() > 0) {
                    bb.put(deadBytes);
                }
            }
        } else {
            content.rewind();
            bb.put(content);
        }
        bb.rewind();
        os.write(bb);
    }


    /**
     * Parses the raw content of the box. It surrounds the actual parsing
     * which is done
     */
    synchronized final void parseDetails() {
        if (content != null) {
            ByteBuffer content = this.content;
            this.content = null;
            content.rewind();
            _parseDetails(content);
            if (content.remaining() > 0) {
                deadBytes = content.slice();
            }
            assert verify(content);
        }
    }

    /**
     * Sets the 'dead' bytes. These bytes are left if the content of the box
     * has been parsed but not all bytes have been used up.
     *
     * @param newDeadBytes the unused bytes with no meaning but required for bytewise reconstruction
     */
    protected void setDeadBytes(ByteBuffer newDeadBytes) {
        deadBytes = newDeadBytes;
    }


    /**
     * Gets the full size of the box including header and content.
     *
     * @return the box's size
     */
    public long getSize() {
        long size = (content == null ? getContentSize() : content.limit());
        size += (8 + // size|type
                (size >= ((1L << 32) - 8) ? 8 : 0) + // 32bit - 8 byte size and type
                (UserBox.TYPE.equals(getType()) ? 16 : 0));
        size += (deadBytes == null ? 0 : deadBytes.limit());
        return size;
    }

    @DoNotParseDetail
    public String getType() {
        return type;
    }

    @DoNotParseDetail
    public byte[] getUserType() {
        return userType;
    }

    @DoNotParseDetail
    public ContainerBox getParent() {
        return parent;
    }

    @DoNotParseDetail
    public void setParent(ContainerBox parent) {
        this.parent = parent;
    }

    @DoNotParseDetail
    public IsoFile getIsoFile() {
        return parent.getIsoFile();
    }

    /**
     * Check if details are parsed.
     *
     * @return <code>true</code> whenever the content <code>ByteBuffer</code> is not <code>null</code>
     */
    public boolean isParsed() {
        return content == null;
    }


    /**
     * Verifies that a box can be reconstructed byte-exact after parsing.
     *
     * @param content the raw content of the box
     * @return <code>true</code> if raw content exactly matches the reconstructed content
     */
    private boolean verify(ByteBuffer content) {
        ByteBuffer bb = ByteBuffer.allocate(l2i(getContentSize() + (deadBytes != null ? deadBytes.limit() : 0)));
        getContent(bb);
        if (deadBytes != null) {
            deadBytes.rewind();
            while (deadBytes.remaining() > 0) {
                bb.put(deadBytes);
            }
        }
        content.rewind();
        bb.rewind();


        if (content.remaining() != bb.remaining()) {
            LOG.severe(this.getType() + ": remaining differs " + content.remaining() + " vs. " + bb.remaining());
            return false;
        }
        int p = content.position();
        for (int i = content.limit() - 1, j = bb.limit() - 1; i >= p; i--, j--) {
            byte v1 = content.get(i);
            byte v2 = bb.get(j);
            if (v1 != v2) {
                LOG.severe(String.format("%s: buffers differ at %d: %2X/%2X", this.getType(), i, v1, v2));
                byte[] b1 = new byte[content.remaining()];
                byte[] b2 = new byte[bb.remaining()];
                content.get(b1);
                bb.get(b2);
                System.err.println("original      : " + Hex.encodeHex(b1, 4));
                System.err.println("reconstructed : " + Hex.encodeHex(b2, 4));
                return false;
            }
        }
        return true;

    }

    private boolean isSmallBox() {
        return (content == null ? (getContentSize() + (deadBytes != null ? deadBytes.limit() : 0) + 8) : content.limit()) < 1L << 32;
    }

    private void getHeader(ByteBuffer byteBuffer) {
        if (isSmallBox()) {
            IsoTypeWriter.writeUInt32(byteBuffer, this.getSize());
            byteBuffer.put(IsoFile.fourCCtoBytes(getType()));
        } else {
            IsoTypeWriter.writeUInt32(byteBuffer, 1);
            byteBuffer.put(IsoFile.fourCCtoBytes(getType()));
            IsoTypeWriter.writeUInt64(byteBuffer, getSize());
        }
        if (UserBox.TYPE.equals(getType())) {
            byteBuffer.put(getUserType());
        }


    }
}
