/*
 * 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.xmlgraphics.image.codec.tiff;

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

import org.apache.xmlgraphics.image.codec.util.PropertyUtil;
import org.apache.xmlgraphics.image.codec.util.SeekableStream;

// CSOFF: ConstantName
// CSOFF: EmptyStatement
// CSOFF: InnerAssignment
// CSOFF: LocalVariableName
// CSOFF: MemberName
// CSOFF: MultipleVariableDeclarations
// CSOFF: NeedBraces
// CSOFF: ParameterName
// CSOFF: WhitespaceAround

/**
 * 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 {

    private static final long serialVersionUID = 2007844835460959003L;
    /** 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;

    /** 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 globalSaveOffset = stream.getFilePointer();
        long ifdOffset;

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

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

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

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

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

            ifdOffset = readUnsignedInt(stream);
        }
        if (ifdOffset == 0L) {
            throw new IllegalArgumentException(PropertyUtil.getString("TIFFDirectory3"));
        }

        stream.seek(ifdOffset);
        initialize(stream);
        stream.seek(globalSaveOffset);
    }

    /**
     * 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 ifdOffset 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 ifdOffset, int directory)
        throws IOException {

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

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

        // 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(ifdOffset + 12 * numEntries);

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

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

            // Increment the directory.
            dirNum++;
        }

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

    private static final int[] SIZE_OF_TYPE = {
        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;
        int 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 * SIZE_OF_TYPE[type] > 4) {
                    value = (int)(readUnsignedInt(stream));
                    stream.seek(value);
                }
            } catch (ArrayIndexOutOfBoundsException ae) {
                // System.err.println(tag + " " + "TIFFDirectory4"); TODO - log this message
                // if the data type is unknown we should skip this TIFF Field
                stream.seek(nextTagOffset);
                continue;
            }

            fieldIndex.put(tag, 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;
                    int prevIndex = 0;
                    List v = new ArrayList();

                    while (index < count) {

                        while ((index < count) && (bvalues[index++] != 0)) {
                            // NOP
                        }

                        // When we encountered zero, means one string has ended
                        v.add(new String(bvalues, prevIndex,
                                         (index - prevIndex), StandardCharsets.UTF_8));
                        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:
                throw new RuntimeException(PropertyUtil.getString("TIFFDirectory0"));
            }

            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(tag);
        if (i == null) {
            return null;
        } else {
            return fields[i];
        }
    }

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

        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(tag);
        byte [] b = (fields[i]).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(tag);
        return (fields[i]).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(tag);
        return fields[i].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(tag);
        return fields[i].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(PropertyUtil.getString("TIFFDirectory1"));
        }
        boolean isBigEndian = (endian == 0x4d4d);
        int magic = readUnsignedShort(stream, isBigEndian);
        if (magic != 42) {
            throw new IllegalArgumentException(PropertyUtil.getString("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;
    }
}
