/*
 * Copyright 2003 by Paulo Soares.
 *
 * The contents of this file are subject to the Mozilla Public License Version 1.1
 * (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the License.
 *
 * The Original Code is 'iText, a free JAVA-PDF library'.
 *
 * The Initial Developer of the Original Code is Bruno Lowagie. Portions created by
 * the Initial Developer are Copyright (C) 1999, 2000, 2001, 2002 by Bruno Lowagie.
 * All Rights Reserved.
 * Co-Developer of the code is Paulo Soares. Portions created by the Co-Developer
 * are Copyright (C) 2000, 2001, 2002 by Paulo Soares. All Rights Reserved.
 *
 * Contributor(s): all the names of the contributors are added in the source code
 * where applicable.
 *
 * Alternatively, the contents of this file may be used under the terms of the
 * LGPL license (the "GNU LIBRARY GENERAL PUBLIC LICENSE"), in which case the
 * provisions of LGPL are applicable instead of those above.  If you wish to
 * allow use of your version of this file only under the terms of the LGPL
 * License and not to allow others to use your version of this file under
 * the MPL, indicate your decision by deleting the provisions above and
 * replace them with the notice and other provisions required by the LGPL.
 * If you do not delete the provisions above, a recipient may use your version
 * of this file under either the MPL or the GNU LIBRARY GENERAL PUBLIC LICENSE.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the MPL as stated above or under the terms of the GNU
 * Library General Public License as published by the Free Software Foundation;
 * either version 2 of the License, or any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Library general Public License for more
 * details.
 *
 * If you didn't download this code from the following link, you should check if
 * you aren't using an obsolete version:
 * http://www.lowagie.com/iText/
 */
package com.lowagie.text.pdf.codec;

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;

import com.lowagie.text.ExceptionConverter;
import com.lowagie.text.Image;
import com.lowagie.text.ImgRaw;
import com.lowagie.text.Utilities;
import com.lowagie.text.pdf.PdfArray;
import com.lowagie.text.pdf.PdfDictionary;
import com.lowagie.text.pdf.PdfName;
import com.lowagie.text.pdf.PdfNumber;
import com.lowagie.text.pdf.PdfString;

/** Reads gif images of all types. All the images in a gif are read in the constructors
 * and can be retrieved with other methods.
 * @author Paulo Soares (psoares@consiste.pt)
 */
public class GifImage {
    
    protected DataInputStream in;
    protected int width;            // full image width
    protected int height;           // full image height
    protected boolean gctFlag;      // global color table used

    protected int bgIndex;          // background color index
    protected int bgColor;          // background color
    protected int pixelAspect;      // pixel aspect ratio

    protected boolean lctFlag;      // local color table flag
    protected boolean interlace;    // interlace flag
    protected int lctSize;          // local color table size

    protected int ix, iy, iw, ih;   // current image rectangle

    protected byte[] block = new byte[256];  // current data block
    protected int blockSize = 0;    // block size

    // last graphic control extension info
    protected int dispose = 0;   // 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev
    protected boolean transparency = false;   // use transparent color
    protected int delay = 0;        // delay in milliseconds
    protected int transIndex;       // transparent color index

    protected static final int MaxStackSize = 4096;   // max decoder pixel stack size

    // LZW decoder working arrays
    protected short[] prefix;
    protected byte[] suffix;
    protected byte[] pixelStack;
    protected byte[] pixels;

    protected byte m_out[];
    protected int m_bpc;
    protected int m_gbpc;
    protected byte m_global_table[];
    protected byte m_local_table[];
    protected byte m_curr_table[];
    protected int m_line_stride;
    protected byte fromData[];
    protected URL fromUrl;


    protected ArrayList frames = new ArrayList();     // frames read from current file

    /** Reads gif images from an URL.
     * @param url the URL
     * @throws IOException on error
     */    
    public GifImage(URL url) throws IOException {
        fromUrl = url;
        InputStream is = null;
        try {
            is = url.openStream();
            process(is);
        }
        finally {
            if (is != null) {
                is.close();
            }
        }
    }
    
    /** Reads gif images from a file.
     * @param file the file
     * @throws IOException on error
     */    
    public GifImage(String file) throws IOException {
        this(Utilities.toURL(file));
    }
    
    /** Reads gif images from a byte array.
     * @param data the byte array
     * @throws IOException on error
     */    
    public GifImage(byte data[]) throws IOException {
        fromData = data;
        InputStream is = null;
        try {
            is = new ByteArrayInputStream(data);
            process(is);
        }
        finally {
            if (is != null) {
                is.close();
            }
        }
    }
    
    /** Reads gif images from a stream. The stream is not closed.
     * @param is the stream
     * @throws IOException on error
     */    
    public GifImage(InputStream is) throws IOException {
        process(is);
    }
    
    /** Gets the number of frames the gif has.
     * @return the number of frames the gif has
     */    
    public int getFrameCount() {
        return frames.size();
    }
    
    /** Gets the image from a frame. The first frame is 1.
     * @param frame the frame to get the image from
     * @return the image
     */    
    public Image getImage(int frame) {
        GifFrame gf = (GifFrame)frames.get(frame - 1);
        return gf.image;
    }
    
    /** Gets the [x,y] position of the frame in reference to the
     * logical screen.
     * @param frame the frame
     * @return the [x,y] position of the frame
     */    
    public int[] getFramePosition(int frame) {
        GifFrame gf = (GifFrame)frames.get(frame - 1);
        return new int[]{gf.ix, gf.iy};
        
    }
    
    /** Gets the logical screen. The images may be smaller and placed
     * in some position in this screen to playback some animation.
     * No image will be be bigger that this.
     * @return the logical screen dimensions as [x,y]
     */    
    public int[] getLogicalScreen() {
        return new int[]{width, height};
    }
    
    void process(InputStream is) throws IOException {
        in = new DataInputStream(new BufferedInputStream(is));
        readHeader();
        readContents();
        if (frames.isEmpty())
            throw new IOException("The file does not contain any valid image.");
    }
    
    /**
     * Reads GIF file header information.
     */
    protected void readHeader() throws IOException {
        String id = "";
        for (int i = 0; i < 6; i++)
            id += (char)in.read();
        if (!id.startsWith("GIF8")) {
            throw new IOException("Gif signature nor found.");
        }
        
        readLSD();
        if (gctFlag) {
            m_global_table = readColorTable(m_gbpc);
        }
    }

    /**
     * Reads Logical Screen Descriptor
     */
    protected void readLSD() throws IOException {
        
        // logical screen size
        width = readShort();
        height = readShort();
        
        // packed fields
        int packed = in.read();
        gctFlag = (packed & 0x80) != 0;      // 1   : global color table flag
        m_gbpc = (packed & 7) + 1;
        bgIndex = in.read();        // background color index
        pixelAspect = in.read();    // pixel aspect ratio
    }

    /**
     * Reads next 16-bit value, LSB first
     */
    protected int readShort() throws IOException {
        // read 16-bit value, LSB first
        return in.read() | (in.read() << 8);
    }

    /**
     * Reads next variable length block from input.
     *
     * @return number of bytes stored in "buffer"
     */
    protected int readBlock() throws IOException {
        blockSize = in.read();
        if (blockSize <= 0)
            return blockSize = 0;
        for (int k = 0; k < blockSize; ++k) {
            int v = in.read();
            if (v < 0) {
                return blockSize = k;
            }
            block[k] = (byte)v;
        }
        return blockSize;
    }

    protected byte[] readColorTable(int bpc) throws IOException {
        int ncolors = 1 << bpc;
        int nbytes = 3*ncolors;
        bpc = newBpc(bpc);
        byte table[] = new byte[(1 << bpc) * 3];
        in.readFully(table, 0, nbytes);
        return table;
    }
 
    
    static protected int newBpc(int bpc) {
        switch (bpc) {
            case 1:
            case 2:
            case 4:
                break;
            case 3:
                return 4;
            default:
                return 8;
        }
        return bpc;
    }
    
    protected void readContents() throws IOException {
        // read GIF file content blocks
        boolean done = false;
        while (!done) {
            int code = in.read();
            switch (code) {
                
                case 0x2C:    // image separator
                    readImage();
                    break;
                    
                case 0x21:    // extension
                    code = in.read();
                    switch (code) {
                        
                        case 0xf9:    // graphics control extension
                            readGraphicControlExt();
                            break;
                            
                        case 0xff:    // application extension
                            readBlock();
                            skip();        // don't care
                            break;
                            
                        default:    // uninteresting extension
                            skip();
                    }
                    break;
                    
                default:
                    done = true;
                    break;
            }
        }
    }

    /**
     * Reads next frame image
     */
    protected void readImage() throws IOException {
        ix = readShort();    // (sub)image position & size
        iy = readShort();
        iw = readShort();
        ih = readShort();
        
        int packed = in.read();
        lctFlag = (packed & 0x80) != 0;     // 1 - local color table flag
        interlace = (packed & 0x40) != 0;   // 2 - interlace flag
        // 3 - sort flag
        // 4-5 - reserved
        lctSize = 2 << (packed & 7);        // 6-8 - local color table size
        m_bpc = newBpc(m_gbpc);
        if (lctFlag) {
            m_curr_table = readColorTable((packed & 7) + 1);   // read table
            m_bpc = newBpc((packed & 7) + 1);
        }
        else {
            m_curr_table = m_global_table;
        }
        if (transparency && transIndex >= m_curr_table.length / 3)
            transparency = false;
        if (transparency && m_bpc == 1) { // Acrobat 5.05 doesn't like this combination
            byte tp[] = new byte[12];
            System.arraycopy(m_curr_table, 0, tp, 0, 6);
            m_curr_table = tp;
            m_bpc = 2;
        }
        boolean skipZero = decodeImageData();   // decode pixel data
        if (!skipZero)
            skip();
        
        Image img = null;
        try {
            img = new ImgRaw(iw, ih, 1, m_bpc, m_out);
            PdfArray colorspace = new PdfArray();
            colorspace.add(PdfName.INDEXED);
            colorspace.add(PdfName.DEVICERGB);
            int len = m_curr_table.length;
            colorspace.add(new PdfNumber(len / 3 - 1));
            colorspace.add(new PdfString(m_curr_table));
            PdfDictionary ad = new PdfDictionary();
            ad.put(PdfName.COLORSPACE, colorspace);
            img.setAdditional(ad);
            if (transparency) {
                img.setTransparency(new int[]{transIndex, transIndex});
            }
        }
        catch (Exception e) {
            throw new ExceptionConverter(e);
        }
        img.setOriginalType(Image.ORIGINAL_GIF);
        img.setOriginalData(fromData);
        img.setUrl(fromUrl);
        GifFrame gf = new GifFrame();
        gf.image = img;
        gf.ix = ix;
        gf.iy = iy;
        frames.add(gf);   // add image to frame list
        
        //resetFrame();
        
    }
    
    protected boolean decodeImageData() throws IOException {
        int NullCode = -1;
        int npix = iw * ih;
        int available, clear, code_mask, code_size, end_of_information, in_code, old_code,
        bits, code, count, i, datum, data_size, first, top, bi;
        boolean skipZero = false;
        
        if (prefix == null)
            prefix = new short[MaxStackSize];
        if (suffix == null)
            suffix = new byte[MaxStackSize];
        if (pixelStack == null)
            pixelStack = new byte[MaxStackSize+1];
        
        m_line_stride = (iw * m_bpc + 7) / 8;
        m_out = new byte[m_line_stride * ih];
        int pass = 1;
        int inc = interlace ? 8 : 1;
        int line = 0;
        int xpos = 0;
        
        //  Initialize GIF data stream decoder.
        
        data_size = in.read();
        clear = 1 << data_size;
        end_of_information = clear + 1;
        available = clear + 2;
        old_code = NullCode;
        code_size = data_size + 1;
        code_mask = (1 << code_size) - 1;
        for (code = 0; code < clear; code++) {
            prefix[code] = 0;
            suffix[code] = (byte) code;
        }
        
        //  Decode GIF pixel stream.
        
        datum = bits = count = first = top = bi = 0;
        
        for (i = 0; i < npix; ) {
            if (top == 0) {
                if (bits < code_size) {
                    //  Load bytes until there are enough bits for a code.
                    if (count == 0) {
                        // Read a new data block.
                        count = readBlock();
                        if (count <= 0) {
                            skipZero = true;
                            break;
                        }
                        bi = 0;
                    }
                    datum += (((int) block[bi]) & 0xff) << bits;
                    bits += 8;
                    bi++;
                    count--;
                    continue;
                }
                
                //  Get the next code.
                
                code = datum & code_mask;
                datum >>= code_size;
                bits -= code_size;
                
                //  Interpret the code
                
                if ((code > available) || (code == end_of_information))
                    break;
                if (code == clear) {
                    //  Reset decoder.
                    code_size = data_size + 1;
                    code_mask = (1 << code_size) - 1;
                    available = clear + 2;
                    old_code = NullCode;
                    continue;
                }
                if (old_code == NullCode) {
                    pixelStack[top++] = suffix[code];
                    old_code = code;
                    first = code;
                    continue;
                }
                in_code = code;
                if (code == available) {
                    pixelStack[top++] = (byte) first;
                    code = old_code;
                }
                while (code > clear) {
                    pixelStack[top++] = suffix[code];
                    code = prefix[code];
                }
                first = ((int) suffix[code]) & 0xff;
                
                //  Add a new string to the string table,
                
                if (available >= MaxStackSize)
                    break;
                pixelStack[top++] = (byte) first;
                prefix[available] = (short) old_code;
                suffix[available] = (byte) first;
                available++;
                if (((available & code_mask) == 0) && (available < MaxStackSize)) {
                    code_size++;
                    code_mask += available;
                }
                old_code = in_code;
            }
            
            //  Pop a pixel off the pixel stack.
            
            top--;
            i++;
            
            setPixel(xpos, line, pixelStack[top]);
            ++xpos;
            if (xpos >= iw) {
                xpos = 0;
                line += inc;
                if (line >= ih) {
                    if (interlace) {
                        do {
                            pass++;
                            switch (pass) {
                                case 2:
                                    line = 4;
                                    break;
                                case 3:
                                    line = 2;
                                    inc = 4;
                                    break;
                                case 4:
                                    line = 1;
                                    inc = 2;
                                    break;
                                default: // this shouldn't happen
                                    line = ih - 1;
                                    inc = 0;
                            }
                        } while (line >= ih);
                    }
                    else {
                        line = ih - 1; // this shouldn't happen
                        inc = 0;
                    }
                }
            }
        }
        return skipZero;
    }
    
    
    protected void setPixel(int x, int y, int v) {
        if (m_bpc == 8) {
            int pos = x + iw * y;
            m_out[pos] = (byte)v;
        }
        else {
            int pos = m_line_stride * y + x / (8 / m_bpc);
            int vout = v << (8 - m_bpc * (x % (8 / m_bpc))- m_bpc);
            m_out[pos] |= vout;
        }
    }
    
    /**
     * Resets frame state for reading next image.
     */
    protected void resetFrame() {
        // it does nothing in the pdf context
        //boolean transparency = false;
        //int delay = 0;
    }

    /**
     * Reads Graphics Control Extension values
     */
    protected void readGraphicControlExt() throws IOException {
        in.read();    // block size
        int packed = in.read();   // packed fields
        dispose = (packed & 0x1c) >> 2;   // disposal method
        if (dispose == 0)
            dispose = 1;   // elect to keep old image if discretionary
        transparency = (packed & 1) != 0;
        delay = readShort() * 10;   // delay in milliseconds
        transIndex = in.read();        // transparent color index
        in.read();                     // block terminator
    }
    
    /**
     * Skips variable length blocks up to and including
     * next zero length block.
     */
    protected void skip() throws IOException {
        do {
            readBlock();
        } while (blockSize > 0);
    }

    static class GifFrame {
        Image image;
        int ix;
        int iy;
    }
}
