/*******************************************************************************

 * Copyright (c) 2008 Nokia Corporation and/or its subsidiary(-ies).

 * 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:

 *     Nokia Corporation - initial implementation

 *******************************************************************************/

package org.eclipse.swt.internal.qt.graphics;

import java.io.*;

import org.eclipse.swt.graphics.Point;

/**

 * ImageLoader is class for image loading from various data formats.

 *

 *

 */

final public class ImageLoader {

    /**

     * Size of block, in bytes, used for transferring read data to native side in iterative way.

     * Value given for this field affects on the memory consumption peak when loading

     * data trough java to native buffer. If value is very small, i.e. 100 the transfer

     * takes place many times and may result in performance loss, however memory usage will

     * be steadier. With bigger value transfer is faster but, it creates steeper peak in

     * memory consumption.

     *

     * If value is negative or zero, then block size is set based on InputStream.available(), otherwise

     * given positive integer value is used as block size (e.g. 4096).

     * Negative values are not allowed.

     */

    private static final int BLOCKSIZE = 0;

    /**

     * Native imageloader handle

     */

    private int handle = 0;

    /**

     * Status of native peer

     */

    private boolean disposed;

    /**

     * Creates an instance of this class and initializes native

     * image loader.

     */

    public ImageLoader() {

    	Utils.validateUiThread();

        handle = OS.imageLoader_init();

        if (handle == 0) {

            throw new OutOfMemoryError();

        }

        disposed = false;

    }

    /**

     * Disposes native image, i.e. frees resources.

     */

    public void dispose() {

    	Utils.validateUiThread();

        if (disposed) {

            return;

        } else {

            OS.imageLoader_dispose(handle);

            handle = 0;

            disposed = true;

        }

    }

    /**

     * Gets the status of this image loader.

     *

     * @return True if this instance has been already disposed otherwise false

     */

    public boolean isDisposed() {

        return disposed;

    }

    /**

     * Loads image from path specified.

     * Throws an error of image loading fails or it is unsupported format.

     *

     * @param path The path for image to be loaded

     * @return Instance of loaded image

     * @throws NullPointerException if path is null

     * @throws OutOfMemoryError if memory allocation for new image fails

     * @throws IOException if image cannot be loaded

     * @throws IllegalStateException if image data is invalid

     * @throws IllegalArgumentException if image format is not supported

     */

    public Image loadImage(String path) throws IOException {

        checkState();

        if (path == null) {

            throw new NullPointerException("path is null");

        }

        InputStream is = getClass().getResourceAsStream(path);

        if (is == null) {

            throw new IOException("Cannot obtain inputstream for given path: " +path);

        }

        return loadImage(is);

    }

    /**

     * Loads image from given byte array.

     *

     * @param data The array containing image data

     * @param offset The offset from beginnig of data where image data starts

     * @param length The length of data beginning form offset

     * @return Instance of loaded image

     * @throws NullPointerException if data is null

     * @throws IllegalArgumentException if offset is less than 0

     * @throws IllegalArgumentException if length is equal or less than 0

     * @throws ArrayIndexOutOfBoundsException if offset and length define an invalid range

     * @throws IOException if image cannot be loaded or it is unsupported format

     * @throws OutOfMemoryError if native buffer allocation fails

     */

    public Image loadImage(byte[] data, int offset, int length) throws IOException {

        checkState();

        if (data == null) {

            throw new NullPointerException("data is null");

        }

        if (offset < 0) {

            throw new IllegalArgumentException("offset is negative");

        }

        if (length <= 0) {

            throw new IllegalArgumentException("length is negative or zero");

        }

        if ((offset + length) > data.length) {

            throw new ArrayIndexOutOfBoundsException("offset and lenght define invalid range");

        }

        // All checks ok, so upload data to loader, with one go

        OS.imageLoader_beginStream(handle, length + 1);

        OS.imageLoader_append(handle, length, offset, data);

        return new Image(OS.imageLoader_endStream(handle));

    }

	/**

	 * Loads image from file directly using the native APIs. Note that Java

	 * security checks are not done.

	 *

	 * @param filename The filename to pass to the native APIs.

	 * @return Image The loaded image.

	 * @throws IOException

	 */

    public Image nativelyLoadImageFromFileNoSecurity(String filename) throws IOException {

        checkState();

        if (filename == null) {

            throw new NullPointerException("data is null");

        }

        return new Image(OS.imageLoader_load(handle, filename));

    }

    /**

     * Contructs an instance of Image by reading image data from given InputStream.

     *

     * @param is The InputStream from where to read the image data from

     * @return Instance of loaded image

     * @throws NullPointerException if InputStream is is null

     * @throws IOException if image cannot be loaded

     * @throws OutOfMemoryError if allocation of native buffer of image creation fails

     * @throws IllegalStateException if image data is invalid

     * @throws IllegalArgumentException if image format is not supported

     */

    public Image loadImage(InputStream is) throws IOException {

        checkState();

        if (is == null) {

            throw new NullPointerException("InputStream is null");

        }

        int bytesRead = 0;

        int bytesAvailable = 0;

        byte[] data;

        // Determine transfer buffer size

        if (BLOCKSIZE <= 0) {

            bytesAvailable = is.available(); // may throw IOException

            if (bytesAvailable == 0) {

                throw new IllegalArgumentException("Empty file");

            }

            data = new byte[bytesAvailable];

        } else {

            data = new byte[BLOCKSIZE];

        }

        // Start streaming to native buffer, with initial buffer size

        OS.imageLoader_beginStream(handle, bytesAvailable);

        // Read input stream and pass blocks to native buffer

        try {

            while ((bytesRead = is.read(data, 0, data.length)) != -1) {

                OS.imageLoader_append(handle, bytesRead, 0, data);

            }

        } catch (IOException e) {

            // Throw exception forward, native loader automatically resets state

            // when problems occur so there's no need to do any extra native calls here

            throw e;

        }

        catch (IllegalStateException e) {

            throw e;

        }

        catch (IllegalArgumentException e) {

            throw e;

        }

        return new Image(OS.imageLoader_endStream(handle));

    }

    /**

     * Sets the size that the Image will be scaled to when loaded. Useful for

     * SVG images.

     * @param width The width to scale to

     * @param height The height to scale to

     */

    public void setLoadSize(int width, int height) {

    	OS.imageLoader_setLoadSize(handle, width, height);

    }

    /**

     * Private helper to check the state of the current instance.

     */

    private void checkState() {

    	Utils.validateUiThread();

        if (disposed) {

            throw new IllegalStateException("Image loader already disposed");

        }

    }

}