/*

   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.batik.ext.awt.image.codec.tiff;

import java.io.IOException;
import java.io.Serializable;
import java.util.Iterator;
import java.util.HashMap;
import java.util.Map;
import java.util.List;
import java.util.ArrayList;

import org.apache.batik.ext.awt.image.codec.util.SeekableStream;

/**
 * A class representing an Image File Directory (IFD) from a TIFF 6.0
 * stream.  The TIFF file format is described in more detail in the
 * comments for the TIFFDescriptor class.
 *
 * <p> A TIFF IFD consists of a set of TIFFField tags.  Methods are
 * provided to query the set of tags and to obtain the raw field
 * array.  In addition, convenience methods are provided for acquiring
 * the values of tags that contain a single value that fits into a
 * byte, int, long, float, or double.
 *
 * <p> Every TIFF file is made up of one or more public IFDs that are
 * joined in a linked list, rooted in the file header.  A file may
 * also contain so-called private IFDs that are referenced from
 * tag data and do not appear in the main list.
 *
 * <p><b> This class is not a committed part of the JAI API.  It may
 * be removed or changed in future releases of JAI.</b>
 *
 * @see TIFFField
 * @version $Id$
 */
public class TIFFDirectory implements Serializable {

    /** A boolean storing the endianness of the stream. */
    boolean isBigEndian;

    /** The number of entries in the IFD. */
    int numEntries;

    /** An array of TIFFFields. */
    TIFFField[] fields;

    /** A Hashtable indexing the fields by tag number. */
    Map fieldIndex = new HashMap();

    /** The offset of this IFD. */
    long IFDOffset = 8;

    /** The offset of the next IFD. */
    long nextIFDOffset = 0;

    /** The default constructor. */
    TIFFDirectory() {}

    private static boolean isValidEndianTag(int endian) {
        return ((endian == 0x4949) || (endian == 0x4d4d));
    }

    /**
     * Constructs a TIFFDirectory from a SeekableStream.
     * The directory parameter specifies which directory to read from
     * the linked list present in the stream; directory 0 is normally
     * read but it is possible to store multiple images in a single
     * TIFF file by maintaing multiple directories.
     *
     * @param stream a SeekableStream to read from.
     * @param directory the index of the directory to read.
     */
    public TIFFDirectory(SeekableStream stream, int directory)
        throws IOException {

        long global_save_offset = stream.getFilePointer();
        long ifd_offset;

        // Read the TIFF header
        stream.seek(0L);
        int endian = stream.readUnsignedShort();
        if (!isValidEndianTag(endian)) {
            throw new
                IllegalArgumentException("TIFFDirectory1");
        }
        isBigEndian = (endian == 0x4d4d);

        int magic = readUnsignedShort(stream);
        if (magic != 42) {
            throw new
                IllegalArgumentException("TIFFDirectory2");
        }

        // Get the initial ifd offset as an unsigned int (using a long)
        ifd_offset = readUnsignedInt(stream);

        for (int i = 0; i < directory; i++) {
            if (ifd_offset == 0L) {
                throw new
                   IllegalArgumentException("TIFFDirectory3");
            }

            stream.seek(ifd_offset);
            long entries = readUnsignedShort(stream);
            stream.skip(12*entries);

            ifd_offset = readUnsignedInt(stream);
        }

        stream.seek(ifd_offset);
        initialize(stream);
        stream.seek(global_save_offset);
    }

    /**
     * Constructs a TIFFDirectory by reading a SeekableStream.
     * The ifd_offset parameter specifies the stream offset from which
     * to begin reading; this mechanism is sometimes used to store
     * private IFDs within a TIFF file that are not part of the normal
     * sequence of IFDs.
     *
     * @param stream a SeekableStream to read from.
     * @param ifd_offset the long byte offset of the directory.
     * @param directory the index of the directory to read beyond the
     *        one at the current stream offset; zero indicates the IFD
     *        at the current offset.
     */
    public TIFFDirectory(SeekableStream stream, long ifd_offset, int directory)
        throws IOException {

        long global_save_offset = stream.getFilePointer();
        stream.seek(0L);
        int endian = stream.readUnsignedShort();
        if (!isValidEndianTag(endian)) {
            throw new
                IllegalArgumentException("TIFFDirectory1");
        }
        isBigEndian = (endian == 0x4d4d);

        // Seek to the first IFD.
        stream.seek(ifd_offset);

        // Seek to desired IFD if necessary.
        int dirNum = 0;
        while(dirNum < directory) {
            // Get the number of fields in the current IFD.
            long numEntries = readUnsignedShort(stream);

            // Skip to the next IFD offset value field.
            stream.seek(ifd_offset + 12*numEntries);

            // Read the offset to the next IFD beyond this one.
            ifd_offset = readUnsignedInt(stream);

            // Seek to the next IFD.
            stream.seek(ifd_offset);

            // Increment the directory.
            dirNum++;
        }

        initialize(stream);
        stream.seek(global_save_offset);
    }

    private static final int[] sizeOfType = {
        0, //  0 = n/a
        1, //  1 = byte
        1, //  2 = ascii
        2, //  3 = short
        4, //  4 = long
        8, //  5 = rational
        1, //  6 = sbyte
        1, //  7 = undefined
        2, //  8 = sshort
        4, //  9 = slong
        8, // 10 = srational
        4, // 11 = float
        8  // 12 = double
    };

    private void initialize(SeekableStream stream) throws IOException {
        long nextTagOffset;
        int i, j;

        IFDOffset = stream.getFilePointer();

        numEntries = readUnsignedShort(stream);
        fields = new TIFFField[numEntries];

        for (i = 0; i < numEntries; i++) {
            int tag = readUnsignedShort(stream);
            int type = readUnsignedShort(stream);
            int count = (int)(readUnsignedInt(stream));
            int value = 0;

            // The place to return to to read the next tag
            nextTagOffset = stream.getFilePointer() + 4;

            try {
                // If the tag data can't fit in 4 bytes, the next 4 bytes
                // contain the starting offset of the data
                if (count*sizeOfType[type] > 4) {
                    value = (int)(readUnsignedInt(stream));
                    stream.seek(value);
                }
            } catch (ArrayIndexOutOfBoundsException ae) {

                System.err.println(tag + " " + "TIFFDirectory4");
                // if the data type is unknown we should skip this TIFF Field
                stream.seek(nextTagOffset);
                continue;
            }

            fieldIndex.put(new Integer(tag), new Integer(i));
            Object obj = null;

            switch (type) {
            case TIFFField.TIFF_BYTE:
            case TIFFField.TIFF_SBYTE:
            case TIFFField.TIFF_UNDEFINED:
            case TIFFField.TIFF_ASCII:
                byte[] bvalues = new byte[count];
                stream.readFully(bvalues, 0, count);

                if (type == TIFFField.TIFF_ASCII) {

                    // Can be multiple strings
                    int index = 0, prevIndex = 0;
                    List v = new ArrayList();

                    while (index < count) {

                        while ((index < count) && (bvalues[index++] != 0));

                        // When we encountered zero, means one string has ended
                        v.add(new String(bvalues, prevIndex,
                                         (index - prevIndex)) );
                        prevIndex = index;
                    }

                    count = v.size();
                    String[] strings = new String[count];
                    v.toArray( strings );
                    obj = strings;
                } else {
                    obj = bvalues;
                }

                break;

            case TIFFField.TIFF_SHORT:
                char[] cvalues = new char[count];
                for (j = 0; j < count; j++) {
                    cvalues[j] = (char)(readUnsignedShort(stream));
                }
                obj = cvalues;
                break;

            case TIFFField.TIFF_LONG:
                long[] lvalues = new long[count];
                for (j = 0; j < count; j++) {
                    lvalues[j] = readUnsignedInt(stream);
                }
                obj = lvalues;
                break;

            case TIFFField.TIFF_RATIONAL:
                long[][] llvalues = new long[count][2];
                for (j = 0; j < count; j++) {
                    llvalues[j][0] = readUnsignedInt(stream);
                    llvalues[j][1] = readUnsignedInt(stream);
                }
                obj = llvalues;
                break;

            case TIFFField.TIFF_SSHORT:
                short[] svalues = new short[count];
                for (j = 0; j < count; j++) {
                    svalues[j] = readShort(stream);
                }
                obj = svalues;
                break;

            case TIFFField.TIFF_SLONG:
                int[] ivalues = new int[count];
                for (j = 0; j < count; j++) {
                    ivalues[j] = readInt(stream);
                }
                obj = ivalues;
                break;

            case TIFFField.TIFF_SRATIONAL:
                int[][] iivalues = new int[count][2];
                for (j = 0; j < count; j++) {
                    iivalues[j][0] = readInt(stream);
                    iivalues[j][1] = readInt(stream);
                }
                obj = iivalues;
                break;

            case TIFFField.TIFF_FLOAT:
                float[] fvalues = new float[count];
                for (j = 0; j < count; j++) {
                    fvalues[j] = readFloat(stream);
                }
                obj = fvalues;
                break;

            case TIFFField.TIFF_DOUBLE:
                double[] dvalues = new double[count];
                for (j = 0; j < count; j++) {
                    dvalues[j] = readDouble(stream);
                }
                obj = dvalues;
                break;

            default:
                System.err.println("TIFFDirectory0");
                break;
            }

            fields[i] = new TIFFField(tag, type, count, obj);
            stream.seek(nextTagOffset);
        }

        // Read the offset of the next IFD.
        nextIFDOffset = readUnsignedInt(stream);
    }

    /** Returns the number of directory entries. */
    public int getNumEntries() {
        return numEntries;
    }

    /**
     * Returns the value of a given tag as a TIFFField,
     * or null if the tag is not present.
     */
    public TIFFField getField(int tag) {
        Integer i = (Integer)fieldIndex.get(new Integer(tag));
        if (i == null) {
            return null;
        } else {
            return fields[i.intValue()];
        }
    }

    /**
     * Returns true if a tag appears in the directory.
     */
    public boolean isTagPresent(int tag) {
        return fieldIndex.containsKey(new Integer(tag));
    }

    /**
     * Returns an ordered array of ints indicating the tag
     * values.
     */
    public int[] getTags() {
        int[] tags = new int[fieldIndex.size()];
        Iterator iter = fieldIndex.keySet().iterator();
        int i = 0;

        while (iter.hasNext()) {
            tags[i++] = ((Integer)iter.next()).intValue();
        }

        return tags;
    }

    /**
     * Returns an array of TIFFFields containing all the fields
     * in this directory.
     */
    public TIFFField[] getFields() {
        return fields;
    }

    /**
     * Returns the value of a particular index of a given tag as a
     * byte.  The caller is responsible for ensuring that the tag is
     * present and has type TIFFField.TIFF_SBYTE, TIFF_BYTE, or
     * TIFF_UNDEFINED.
     */
    public byte getFieldAsByte(int tag, int index) {
        Integer i = (Integer)fieldIndex.get(new Integer(tag));
        byte [] b = (fields[i.intValue()]).getAsBytes();
        return b[index];
    }

    /**
     * Returns the value of index 0 of a given tag as a
     * byte.  The caller is responsible for ensuring that the tag is
     * present and has  type TIFFField.TIFF_SBYTE, TIFF_BYTE, or
     * TIFF_UNDEFINED.
     */
    public byte getFieldAsByte(int tag) {
        return getFieldAsByte(tag, 0);
    }

    /**
     * Returns the value of a particular index of a given tag as a
     * long.  The caller is responsible for ensuring that the tag is
     * present and has type TIFF_BYTE, TIFF_SBYTE, TIFF_UNDEFINED,
     * TIFF_SHORT, TIFF_SSHORT, TIFF_SLONG or TIFF_LONG.
     */
    public long getFieldAsLong(int tag, int index) {
        Integer i = (Integer)fieldIndex.get(new Integer(tag));
        return (fields[i.intValue()]).getAsLong(index);
    }

    /**
     * Returns the value of index 0 of a given tag as a
     * long.  The caller is responsible for ensuring that the tag is
     * present and has type TIFF_BYTE, TIFF_SBYTE, TIFF_UNDEFINED,
     * TIFF_SHORT, TIFF_SSHORT, TIFF_SLONG or TIFF_LONG.
     */
    public long getFieldAsLong(int tag) {
        return getFieldAsLong(tag, 0);
    }

    /**
     * Returns the value of a particular index of a given tag as a
     * float.  The caller is responsible for ensuring that the tag is
     * present and has numeric type (all but TIFF_UNDEFINED and
     * TIFF_ASCII).
     */
    public float getFieldAsFloat(int tag, int index) {
        Integer i = (Integer)fieldIndex.get(new Integer(tag));
        return fields[i.intValue()].getAsFloat(index);
    }

    /**
     * Returns the value of index 0 of a given tag as a float.  The
     * caller is responsible for ensuring that the tag is present and
     * has numeric type (all but TIFF_UNDEFINED and TIFF_ASCII).
     */
    public float getFieldAsFloat(int tag) {
        return getFieldAsFloat(tag, 0);
    }

    /**
     * Returns the value of a particular index of a given tag as a
     * double.  The caller is responsible for ensuring that the tag is
     * present and has numeric type (all but TIFF_UNDEFINED and
     * TIFF_ASCII).
     */
    public double getFieldAsDouble(int tag, int index) {
        Integer i = (Integer)fieldIndex.get(new Integer(tag));
        return fields[i.intValue()].getAsDouble(index);
    }

    /**
     * Returns the value of index 0 of a given tag as a double.  The
     * caller is responsible for ensuring that the tag is present and
     * has numeric type (all but TIFF_UNDEFINED and TIFF_ASCII).
     */
    public double getFieldAsDouble(int tag) {
        return getFieldAsDouble(tag, 0);
    }

    // Methods to read primitive data types from the stream

    private short readShort(SeekableStream stream)
        throws IOException {
        if (isBigEndian) {
            return stream.readShort();
        } else {
            return stream.readShortLE();
        }
    }

    private int readUnsignedShort(SeekableStream stream)
        throws IOException {
        if (isBigEndian) {
            return stream.readUnsignedShort();
        } else {
            return stream.readUnsignedShortLE();
        }
    }

    private int readInt(SeekableStream stream)
        throws IOException {
        if (isBigEndian) {
            return stream.readInt();
        } else {
            return stream.readIntLE();
        }
    }

    private long readUnsignedInt(SeekableStream stream)
        throws IOException {
        if (isBigEndian) {
            return stream.readUnsignedInt();
        } else {
            return stream.readUnsignedIntLE();
        }
    }

    private long readLong(SeekableStream stream)
        throws IOException {
        if (isBigEndian) {
            return stream.readLong();
        } else {
            return stream.readLongLE();
        }
    }

    private float readFloat(SeekableStream stream)
        throws IOException {
        if (isBigEndian) {
            return stream.readFloat();
        } else {
            return stream.readFloatLE();
        }
    }

    private double readDouble(SeekableStream stream)
        throws IOException {
        if (isBigEndian) {
            return stream.readDouble();
        } else {
            return stream.readDoubleLE();
        }
    }

    private static int readUnsignedShort(SeekableStream stream,
                                         boolean isBigEndian)
        throws IOException {
        if (isBigEndian) {
            return stream.readUnsignedShort();
        } else {
            return stream.readUnsignedShortLE();
        }
    }

    private static long readUnsignedInt(SeekableStream stream,
                                        boolean isBigEndian)
        throws IOException {
        if (isBigEndian) {
            return stream.readUnsignedInt();
        } else {
            return stream.readUnsignedIntLE();
        }
    }

    // Utilities

    /**
     * Returns the number of image directories (subimages) stored in a
     * given TIFF file, represented by a <code>SeekableStream</code>.
     */
    public static int getNumDirectories(SeekableStream stream)
        throws IOException{
        long pointer = stream.getFilePointer(); // Save stream pointer

        stream.seek(0L);
        int endian = stream.readUnsignedShort();
        if (!isValidEndianTag(endian)) {
            throw new
                IllegalArgumentException("TIFFDirectory1");
        }
        boolean isBigEndian = (endian == 0x4d4d);
        int magic = readUnsignedShort(stream, isBigEndian);
        if (magic != 42) {
            throw new
                IllegalArgumentException("TIFFDirectory2");
        }

        stream.seek(4L);
        long offset = readUnsignedInt(stream, isBigEndian);

        int numDirectories = 0;
        while (offset != 0L) {
            ++numDirectories;

            stream.seek(offset);
            long entries = readUnsignedShort(stream, isBigEndian);
            stream.skip(12*entries);
            offset = readUnsignedInt(stream, isBigEndian);
        }

        stream.seek(pointer); // Reset stream pointer
        return numDirectories;
    }

    /**
     * Returns a boolean indicating whether the byte order used in the
     * the TIFF file is big-endian.  That is, whether the byte order is from
     * the most significant to the least significant.
     */
    public boolean isBigEndian() {
        return isBigEndian;
    }

    /**
     * Returns the offset of the IFD corresponding to this
     * <code>TIFFDirectory</code>.
     */
    public long getIFDOffset() {
        return IFDOffset;
    }

    /**
     * Returns the offset of the next IFD after the IFD corresponding to this
     * <code>TIFFDirectory</code>.
     */
    public long getNextIFDOffset() {
        return nextIFDOffset;
    }
}