/*******************************************************************************
 * Copyright (c) 2000, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 * Port to the D programming language:
 *     Frank Benoit <benoit@tionex.de>
 *******************************************************************************/
module org.eclipse.swt.internal.image.GIFFileFormat;

public import org.eclipse.swt.internal.image.FileFormat;
public import org.eclipse.swt.graphics.PaletteData;
import org.eclipse.swt.internal.image.LEDataInputStream;
import org.eclipse.swt.internal.image.LZWCodec;
import org.eclipse.swt.graphics.RGB;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.ImageData;
import org.eclipse.swt.graphics.ImageLoaderEvent;
import org.eclipse.swt.graphics.ImageLoader;
import java.lang.all;


final class GIFFileFormat : FileFormat {
    String signature;
    int screenWidth, screenHeight, backgroundPixel, bitsPerPixel, defaultDepth;
    int disposalMethod = 0;
    int delayTime = 0;
    int transparentPixel = -1;
    int repeatCount = 1;

    static const int GIF_APPLICATION_EXTENSION_BLOCK_ID = 0xFF;
    static const int GIF_GRAPHICS_CONTROL_BLOCK_ID = 0xF9;
    static const int GIF_PLAIN_TEXT_BLOCK_ID = 0x01;
    static const int GIF_COMMENT_BLOCK_ID = 0xFE;
    static const int GIF_EXTENSION_BLOCK_ID = 0x21;
    static const int GIF_IMAGE_BLOCK_ID = 0x2C;
    static const int GIF_TRAILER_ID = 0x3B;
    static const byte[] GIF89a = cast(byte[])"GIF89a";
    static const byte[] NETSCAPE2_0 = cast(byte[])"NETSCAPE2.0";

    /**
     * Answer a palette containing numGrays
     * shades of gray, ranging from black to white.
     */
    static PaletteData grayRamp(int numGrays) {
        int n = numGrays - 1;
        RGB[] colors = new RGB[numGrays];
        for (int i = 0; i < numGrays; i++) {
            int intensity = cast(byte)((i * 3) * 256 / n);
            colors[i] = new RGB(intensity, intensity, intensity);
        }
        return new PaletteData(colors);
    }

    override bool isFileFormat(LEDataInputStream stream) {
        try {
            byte[3] signature;
            stream.read(signature);
            stream.unread(signature);
            return signature[0] is 'G' && signature[1] is 'I' && signature[2] is 'F';
        } catch (Exception e) {
            return false;
        }
    }

    /**
     * Load the GIF image(s) stored in the input stream.
     * Return an array of ImageData representing the image(s).
     */
    override ImageData[] loadFromByteStream() {
        byte[3] signature;
        byte[3] versionBytes;
        byte[7] block;
        try {
            inputStream.read(signature);
            if (!(signature[0] is 'G' && signature[1] is 'I' && signature[2] is 'F'))
                SWT.error(SWT.ERROR_INVALID_IMAGE);

            inputStream.read(versionBytes);

            inputStream.read(block);
        } catch (IOException e) {
            SWT.error(SWT.ERROR_IO, e);
        }
        screenWidth = (block[0] & 0xFF) | ((block[1] & 0xFF) << 8);
        loader.logicalScreenWidth = screenWidth;
        screenHeight = (block[2] & 0xFF) | ((block[3] & 0xFF) << 8);
        loader.logicalScreenHeight = screenHeight;
        byte bitField = block[4];
        backgroundPixel = block[5] & 0xFF;
        //aspect = block[6] & 0xFF;
        bitsPerPixel = ((bitField >> 4) & 0x07) + 1;
        defaultDepth = (bitField & 0x7) + 1;
        PaletteData palette = null;
        if ((bitField & 0x80) !is 0) {
            // Global palette.
            //sorted = (bitField & 0x8) !is 0;
            palette = readPalette(1 << defaultDepth);
        } else {
            // No global palette.
            //sorted = false;
            backgroundPixel = -1;
            defaultDepth = bitsPerPixel;
        }
        loader.backgroundPixel = backgroundPixel;

        getExtensions();
        int id = readID();
        ImageData[] images = new ImageData[0];
        while (id is GIF_IMAGE_BLOCK_ID) {
            ImageData image = readImageBlock(palette);
            if (loader.hasListeners()) {
                loader.notifyListeners(new ImageLoaderEvent(loader, image, 3, true));
            }
            ImageData[] oldImages = images;
            images = new ImageData[oldImages.length + 1];
            System.arraycopy(oldImages, 0, images, 0, oldImages.length);
            images[images.length - 1] = image;
            //images ~= image;
            try {
                /* Read the 0-byte terminator at the end of the image. */
                id = inputStream.read();
                if (id > 0) {
                    /* We read the terminator earlier. */
                    byte[1] arr;
                    arr[0] = cast(byte) id;
                    inputStream.unread( arr );
                }
            } catch (IOException e) {
                SWT.error(SWT.ERROR_IO, e);
            }
            getExtensions();
            id = readID();
        }
        return images;
    }

    /**
     * Read and return the next block or extension identifier from the file.
     */
    int readID() {
        try {
            return inputStream.read();
        } catch (IOException e) {
            SWT.error(SWT.ERROR_IO, e);
        }
        return -1;
    }

    /**
     * Read extensions until an image descriptor appears.
     * In the future, if we care about the extensions, they
     * should be properly grouped with the image data before
     * which they appeared. Right now, the interesting parts
     * of some extensions are kept, but the rest is discarded.
     * Throw an error if an error occurs.
     */
    void getExtensions() {
        int id = readID();
        while (id !is GIF_IMAGE_BLOCK_ID && id !is GIF_TRAILER_ID && id > 0) {
            if (id is GIF_EXTENSION_BLOCK_ID) {
                readExtension();
            } else {
                SWT.error(SWT.ERROR_INVALID_IMAGE);
            }
            id = readID();
        }
        if (id is GIF_IMAGE_BLOCK_ID || id is GIF_TRAILER_ID) {
            try {
                byte[1] arr;
                arr[0] = cast(byte) id;
                inputStream.unread(arr);
            } catch (IOException e) {
                SWT.error(SWT.ERROR_IO, e);
            }
        }
    }

    /**
     * Read a control extension.
     * Return the extension block data.
     */
    byte[] readExtension() {
        int extensionID = readID();
        if (extensionID is GIF_COMMENT_BLOCK_ID)
            return readCommentExtension();
        if (extensionID is GIF_PLAIN_TEXT_BLOCK_ID)
            return readPlainTextExtension();
        if (extensionID is GIF_GRAPHICS_CONTROL_BLOCK_ID)
            return readGraphicsControlExtension();
        if (extensionID is GIF_APPLICATION_EXTENSION_BLOCK_ID)
            return readApplicationExtension();
        // Otherwise, we don't recognize the block. If the
        // field size is correct, we can just skip over
        // the block contents.
        try {
            int extSize = inputStream.read();
            if (extSize < 0) {
                SWT.error(SWT.ERROR_INVALID_IMAGE);
            }
            byte[] ext = new byte[extSize];
            inputStream.read(ext, 0, extSize);
            return ext;
        } catch (IOException e) {
            SWT.error(SWT.ERROR_IO, e);
            return null;
        }
    }

    /**
     * We have just read the Comment extension identifier
     * from the input stream. Read in the rest of the comment
     * and return it. GIF comment blocks are variable size.
     */
    byte[] readCommentExtension() {
        try {
            byte[] comment = new byte[0];
            byte[] block = new byte[255];
            int size = inputStream.read();
            while ((size > 0) && (inputStream.read(block, 0, size) !is -1)) {
                byte[] oldComment = comment;
                comment = new byte[oldComment.length + size];
                System.arraycopy(oldComment, 0, comment, 0, oldComment.length);
                System.arraycopy(block, 0, comment, oldComment.length, size);
                //comment ~= block[ 0 .. size ];
                size = inputStream.read();
            }
            return comment;
        } catch (Exception e) {
            SWT.error(SWT.ERROR_IO, e);
            return null;
        }
    }

    /**
     * We have just read the PlainText extension identifier
     * from the input stream. Read in the plain text info and text,
     * and return the text. GIF plain text blocks are variable size.
     */
    byte[] readPlainTextExtension() {
        try {
            // Read size of block = 0x0C.
            inputStream.read();
            // Read the text information (x, y, width, height, colors).
            byte[] info = new byte[12];
            inputStream.read(info);
            // Read the text.
            byte[] text = new byte[0];
            byte[] block = new byte[255];
            int size = inputStream.read();
            while ((size > 0) && (inputStream.read(block, 0, size) !is -1)) {
                byte[] oldText = text;
                text = new byte[oldText.length + size];
                System.arraycopy(oldText, 0, text, 0, oldText.length);
                System.arraycopy(block, 0, text, oldText.length, size);
                //text ~= block[ 0 .. size ];
                size = inputStream.read();
            }
            return text;
        } catch (Exception e) {
            SWT.error(SWT.ERROR_IO, e);
            return null;
        }
    }

    /**
     * We have just read the GraphicsControl extension identifier
     * from the input stream. Read in the control information, store
     * it, and return it.
     */
    byte[] readGraphicsControlExtension() {
        try {
            // Read size of block = 0x04.
            inputStream.read();
            // Read the control block.
            byte[] controlBlock = new byte[4];
            inputStream.read(controlBlock);
            byte bitField = controlBlock[0];
            // Store the user input field.
            //userInput = (bitField & 0x02) !is 0;
            // Store the disposal method.
            disposalMethod = (bitField >> 2) & 0x07;
            // Store the delay time.
            delayTime = (controlBlock[1] & 0xFF) | ((controlBlock[2] & 0xFF) << 8);
            // Store the transparent color.
            if ((bitField & 0x01) !is 0) {
                transparentPixel = controlBlock[3] & 0xFF;
            } else {
                transparentPixel = -1;
            }
            // Read block terminator.
            inputStream.read();
            return controlBlock;
        } catch (Exception e) {
            SWT.error(SWT.ERROR_IO, e);
            return null;
        }
    }

    /**
     * We have just read the Application extension identifier
     * from the input stream.  Read in the rest of the extension,
     * look for and store 'number of repeats', and return the data.
     */
    byte[] readApplicationExtension() {
        try {
            // Read size of block = 0x0B.
            inputStream.read();
            // Read application identifier.
            byte[] application = new byte[8];
            inputStream.read(application);
            // Read authentication code.
            byte[] authentication = new byte[3];
            inputStream.read(authentication);
            // Read application data.
            byte[] data = new byte[0];
            byte[] block = new byte[255];
            int size = inputStream.read();
            while ((size > 0) && (inputStream.read(block, 0, size) !is -1)) {
                byte[] oldData = data;
                data = new byte[oldData.length + size];
                System.arraycopy(oldData, 0, data, 0, oldData.length);
                System.arraycopy(block, 0, data, oldData.length, size);
                //data ~= block[ 0 .. size ];
                size = inputStream.read();
            }
            // Look for the NETSCAPE 'repeat count' field for an animated GIF.
            bool netscape =
                application[0] is 'N' &&
                application[1] is 'E' &&
                application[2] is 'T' &&
                application[3] is 'S' &&
                application[4] is 'C' &&
                application[5] is 'A' &&
                application[6] is 'P' &&
                application[7] is 'E';
            bool authentic =
                authentication[0] is '2' &&
                authentication[1] is '.' &&
                authentication[2] is '0';
            if (netscape && authentic && data[0] is 01) { //$NON-NLS-1$ //$NON-NLS-2$
                repeatCount = (data[1] & 0xFF) | ((data[2] & 0xFF) << 8);
                loader.repeatCount = repeatCount;
            }
            return data;
        } catch (Exception e) {
            SWT.error(SWT.ERROR_IO, e);
            return null;
        }
    }

    /**
     * Return a DeviceIndependentImage representing the
     * image block at the current position in the input stream.
     * Throw an error if an error occurs.
     */
    ImageData readImageBlock(PaletteData defaultPalette) {
        int depth;
        PaletteData palette;
        byte[] block = new byte[9];
        try {
            inputStream.read(block);
        } catch (IOException e) {
            SWT.error(SWT.ERROR_IO, e);
        }
        int left = (block[0] & 0xFF) | ((block[1] & 0xFF) << 8);
        int top = (block[2] & 0xFF) | ((block[3] & 0xFF) << 8);
        int width = (block[4] & 0xFF) | ((block[5] & 0xFF) << 8);
        int height = (block[6] & 0xFF) | ((block[7] & 0xFF) << 8);
        byte bitField = block[8];
        bool interlaced = (bitField & 0x40) !is 0;
        //bool sorted = (bitField & 0x20) !is 0;
        if ((bitField & 0x80) !is 0) {
            // Local palette.
            depth = (bitField & 0x7) + 1;
            palette = readPalette(1 << depth);
        } else {
            // No local palette.
            depth = defaultDepth;
            palette = defaultPalette;
        }
        /* Work around: Ignore the case where a GIF specifies an
         * invalid index for the transparent pixel that is larger
         * than the number of entries in the palette. */
        if (transparentPixel > 1 << depth) {
            transparentPixel = -1;
        }
        // Promote depth to next highest supported value.
        if (!(depth is 1 || depth is 4 || depth is 8)) {
            if (depth < 4)
                depth = 4;
            else
                depth = 8;
        }
        if (palette is null) {
            palette = grayRamp(1 << depth);
        }
        int initialCodeSize = -1;
        try {
            initialCodeSize = inputStream.read();
        } catch (IOException e) {
            SWT.error(SWT.ERROR_IO, e);
        }
        if (initialCodeSize < 0) {
            SWT.error(SWT.ERROR_INVALID_IMAGE);
        }
        ImageData image = ImageData.internal_new(
            width,
            height,
            depth,
            palette,
            4,
            null,
            0,
            null,
            null,
            -1,
            transparentPixel,
            SWT.IMAGE_GIF,
            left,
            top,
            disposalMethod,
            delayTime);
        LZWCodec codec = new LZWCodec();
        codec.decode(inputStream, loader, image, interlaced, initialCodeSize);
        return image;
    }

    /**
     * Read a palette from the input stream.
     */
    PaletteData readPalette(int numColors) {
        byte[] bytes = new byte[numColors * 3];
        try {
            if (inputStream.read(bytes) !is bytes.length)
                SWT.error(SWT.ERROR_INVALID_IMAGE);
        } catch (IOException e) {
            SWT.error(SWT.ERROR_IO, e);
        }
        RGB[] colors = new RGB[numColors];
        for (int i = 0; i < numColors; i++)
            colors[i] = new RGB(bytes[i*3] & 0xFF,
                bytes[i*3+1] & 0xFF, bytes[i*3+2] & 0xFF);
        return new PaletteData(colors);
    }

    override void unloadIntoByteStream(ImageLoader loader) {

        /* Step 1: Acquire GIF parameters. */
        ImageData[] data = loader.data;
        int frameCount = data.length;
        bool multi = frameCount > 1;
        ImageData firstImage = data[0];
        int logicalScreenWidth = multi ? loader.logicalScreenWidth : firstImage.width;
        int logicalScreenHeight = multi ? loader.logicalScreenHeight : firstImage.height;
        int backgroundPixel = loader.backgroundPixel;
        int depth = firstImage.depth;
        PaletteData palette = firstImage.palette;
        RGB[] colors = palette.getRGBs();
        short globalTable = 1;

        /* Step 2: Check for validity and global/local color map. */
        if (!(depth is 1 || depth is 4 || depth is 8)) {
            SWT.error(SWT.ERROR_UNSUPPORTED_DEPTH);
        }
        for (int i=0; i<frameCount; i++) {
            if (data[i].palette.isDirect) {
                SWT.error(SWT.ERROR_INVALID_IMAGE);
            }
            if (multi) {
                if (!(data[i].height <= logicalScreenHeight && data[i].width <= logicalScreenWidth && data[i].depth is depth)) {
                    SWT.error(SWT.ERROR_INVALID_IMAGE);
                }
                if (globalTable is 1) {
                    RGB rgbs[] = data[i].palette.getRGBs();
                    if (rgbs.length !is colors.length) {
                        globalTable = 0;
                    } else {
                        for (int j=0; j<colors.length; j++) {
                            if (!(rgbs[j].red is colors[j].red &&
                                rgbs[j].green is colors[j].green &&
                                rgbs[j].blue is colors[j].blue))
                                    globalTable = 0;
                        }
                    }
                }
            }
        }

        try {
            /* Step 3: Write the GIF89a Header and Logical Screen Descriptor. */
            outputStream.write(cast(byte[])GIF89a);
            int bitField = globalTable*128 + (depth-1)*16 + depth-1;
            outputStream.writeShort(cast(short)logicalScreenWidth);
            outputStream.writeShort(cast(short)logicalScreenHeight);
            outputStream.write(bitField);
            outputStream.write(backgroundPixel);
            outputStream.write(0); // Aspect ratio is 1:1
        } catch (IOException e) {
            SWT.error(SWT.ERROR_IO, e);
        }

        /* Step 4: Write Global Color Table if applicable. */
        if (globalTable is 1) {
            writePalette(palette, depth);
        }

        /* Step 5: Write Application Extension if applicable. */
        if (multi) {
            int repeatCount = loader.repeatCount;
            try {
                outputStream.write(GIF_EXTENSION_BLOCK_ID);
                outputStream.write(GIF_APPLICATION_EXTENSION_BLOCK_ID);
                outputStream.write(NETSCAPE2_0.length);
                outputStream.write(cast(byte[])NETSCAPE2_0);
                outputStream.write(3); // Three bytes follow
                outputStream.write(1); // Extension type
                outputStream.writeShort(cast(short) repeatCount);
                outputStream.write(0); // Block terminator
            } catch (IOException e) {
                SWT.error(SWT.ERROR_IO, e);
            }
        }

        for (int frame=0; frame<frameCount; frame++) {

            /* Step 6: Write Graphics Control Block for each frame if applicable. */
            if (multi || data[frame].transparentPixel !is -1) {
                writeGraphicsControlBlock(data[frame]);
            }

            /* Step 7: Write Image Header for each frame. */
            int x = data[frame].x;
            int y = data[frame].y;
            int width = data[frame].width;
            int height = data[frame].height;
            try {
                outputStream.write(GIF_IMAGE_BLOCK_ID);
                byte[] block = new byte[9];
                block[0] = cast(byte)(x & 0xFF);
                block[1] = cast(byte)((x >> 8) & 0xFF);
                block[2] = cast(byte)(y & 0xFF);
                block[3] = cast(byte)((y >> 8) & 0xFF);
                block[4] = cast(byte)(width & 0xFF);
                block[5] = cast(byte)((width >> 8) & 0xFF);
                block[6] = cast(byte)(height & 0xFF);
                block[7] = cast(byte)((height >> 8) & 0xFF);
                block[8] = cast(byte)(globalTable is 0 ? (depth-1) | 0x80 : 0x00);
                outputStream.write(block);
            } catch (IOException e) {
                SWT.error(SWT.ERROR_IO, e);
            }

            /* Step 8: Write Local Color Table for each frame if applicable. */
            if (globalTable is 0) {
                writePalette(data[frame].palette, depth);
            }

            /* Step 9: Write the actual data for each frame. */
            try {
                outputStream.write(depth); // Minimum LZW Code size
            } catch (IOException e) {
                SWT.error(SWT.ERROR_IO, e);
            }
            (new LZWCodec()).encode(outputStream, data[frame]);
        }

        /* Step 10: Write GIF terminator. */
        try {
            outputStream.write(0x3B);
        } catch (IOException e) {
            SWT.error(SWT.ERROR_IO, e);
        }
    }

    /**
     * Write out a GraphicsControlBlock to describe
     * the specified device independent image.
     */
    void writeGraphicsControlBlock(ImageData image) {
        try {
            outputStream.write(GIF_EXTENSION_BLOCK_ID);
            outputStream.write(GIF_GRAPHICS_CONTROL_BLOCK_ID);
            byte[] gcBlock = new byte[4];
            gcBlock[0] = 0;
            gcBlock[1] = 0;
            gcBlock[2] = 0;
            gcBlock[3] = 0;
            if (image.transparentPixel !is -1) {
                gcBlock[0] = cast(byte)0x01;
                gcBlock[3] = cast(byte)image.transparentPixel;
            }
            if (image.disposalMethod !is 0) {
                gcBlock[0] |= cast(byte)((image.disposalMethod & 0x07) << 2);
            }
            if (image.delayTime !is 0) {
                gcBlock[1] = cast(byte)(image.delayTime & 0xFF);
                gcBlock[2] = cast(byte)((image.delayTime >> 8) & 0xFF);
            }
            outputStream.write(cast(byte)gcBlock.length);
            outputStream.write(gcBlock);
            outputStream.write(0); // Block terminator
        } catch (IOException e) {
            SWT.error(SWT.ERROR_IO, e);
        }
    }

    /**
     * Write the specified palette to the output stream.
     */
    void writePalette(PaletteData palette, int depth) {
        byte[] bytes = new byte[(1 << depth) * 3];
        int offset = 0;
        for (int i = 0; i < palette.colors.length; i++) {
            RGB color = palette.colors[i];
            bytes[offset] = cast(byte)color.red;
            bytes[offset + 1] = cast(byte)color.green;
            bytes[offset + 2] = cast(byte)color.blue;
            offset += 3;
        }
        try {
            outputStream.write(bytes);
        } catch (IOException e) {
            SWT.error(SWT.ERROR_IO, e);
        }
    }
}