/**
     * Issues a bitmap request with the given URL if that image is not available
     * in the cache, and returns a bitmap container that contains all of the data
     * relating to the request (as well as the default image if the requested
     * image is not available).
     * @param requestUrl The url of the remote image
     * @param imageListener The listener to call when the remote image is loaded
     * @param maxWidth The maximum width of the returned image.
     * @param maxHeight The maximum height of the returned image.
     * @return A container object that contains all of the properties of the request, as well as
     *     the currently available image (default if remote is not loaded).
     */
    public ImageContainer get(String requestUrl, ImageListener imageListener,
            int maxWidth, int maxHeight) {
        // only fulfill requests that were initiated from the main thread.
        throwIfNotOnMainThread();

        final String cacheKey = getCacheKey(requestUrl, maxWidth, maxHeight);

        // Try to look up the request in the cache of remote images.
        Bitmap cachedBitmap = mCache.getBitmap(cacheKey);
        if (cachedBitmap != null) {
            // Return the cached bitmap.
            ImageContainer container = new ImageContainer(cachedBitmap, requestUrl, null, null);
            imageListener.onResponse(container, true);
            return container;
        }

        // The bitmap did not exist in the cache, fetch it!
        ImageContainer imageContainer =
                new ImageContainer(null, requestUrl, cacheKey, imageListener);

        // Update the caller to let them know that they should use the default bitmap.
        imageListener.onResponse(imageContainer, true);

        // Check to see if a request is already in-flight.
        BatchedImageRequest request = mInFlightRequests.get(cacheKey);
        if (request != null) {
            // If it is, add this request to the list of listeners.
            request.addContainer(imageContainer);
            return imageContainer;
        }

        // The request is not already in flight. Send the new request to the network and
        // track it.
        Request<?> newRequest =
            new ImageRequest(requestUrl, new Listener<Bitmap>() {
                @Override
                public void onResponse(Bitmap response) {
                    onGetImageSuccess(cacheKey, response);
                }
            }, maxWidth, maxHeight,
            Config.RGB_565, new ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    onGetImageError(cacheKey, error);
                }
            });

        mRequestQueue.add(newRequest);
        mInFlightRequests.put(cacheKey,
                new BatchedImageRequest(newRequest, imageContainer));
        return imageContainer;
    }

/**
 * A canned request for getting an image at a given URL and calling
 * back with a decoded Bitmap.
 */
public class ImageRequest extends Request<Bitmap> {
    /** Socket timeout in milliseconds for image requests */
    private static final int IMAGE_TIMEOUT_MS = 1000;

    /** Default number of retries for image requests */
    private static final int IMAGE_MAX_RETRIES = 2;

    /** Default backoff multiplier for image requests */
    private static final float IMAGE_BACKOFF_MULT = 2f;

    private final Response.Listener<Bitmap> mListener;
    private final Config mDecodeConfig;
    private final int mMaxWidth;
    private final int mMaxHeight;

    /** Decoding lock so that we don‘t decode more than one image at a time (to avoid OOM‘s) */
    private static final Object sDecodeLock = new Object();

    /**
     * Creates a new image request, decoding to a maximum specified width and
     * height. If both width and height are zero, the image will be decoded to
     * its natural size. If one of the two is nonzero, that dimension will be
     * clamped and the other one will be set to preserve the image‘s aspect
     * ratio. If both width and height are nonzero, the image will be decoded to
     * be fit in the rectangle of dimensions width x height while keeping its
     * aspect ratio.
     *
     * @param url URL of the image
     * @param listener Listener to receive the decoded bitmap
     * @param maxWidth Maximum width to decode this bitmap to, or zero for none
     * @param maxHeight Maximum height to decode this bitmap to, or zero for
     *            none
     * @param decodeConfig Format to decode the bitmap to
     * @param errorListener Error listener, or null to ignore errors
     */
    public ImageRequest(String url, Response.Listener<Bitmap> listener, int maxWidth, int maxHeight,
            Config decodeConfig, Response.ErrorListener errorListener) {
        super(Method.GET, url, errorListener);
        setRetryPolicy(
                new DefaultRetryPolicy(IMAGE_TIMEOUT_MS, IMAGE_MAX_RETRIES, IMAGE_BACKOFF_MULT));
        mListener = listener;
        mDecodeConfig = decodeConfig;
        mMaxWidth = maxWidth;
        mMaxHeight = maxHeight;
    }

    @Override
    public Priority getPriority() {
        return Priority.LOW;
    }

    /**
     * Scales one side of a rectangle to fit aspect ratio.
     *
     * @param maxPrimary Maximum size of the primary dimension (i.e. width for
     *        max width), or zero to maintain aspect ratio with secondary
     *        dimension
     * @param maxSecondary Maximum size of the secondary dimension, or zero to
     *        maintain aspect ratio with primary dimension
     * @param actualPrimary Actual size of the primary dimension
     * @param actualSecondary Actual size of the secondary dimension
     */
    private static int getResizedDimension(int maxPrimary, int maxSecondary, int actualPrimary,
            int actualSecondary) {
        // If no dominant value at all, just return the actual.
        if (maxPrimary == 0 && maxSecondary == 0) {
            return actualPrimary;
        }

        // If primary is unspecified, scale primary to match secondary‘s scaling ratio.
        if (maxPrimary == 0) {
            double ratio = (double) maxSecondary / (double) actualSecondary;
            return (int) (actualPrimary * ratio);
        }

        if (maxSecondary == 0) {
            return maxPrimary;
        }

        double ratio = (double) actualSecondary / (double) actualPrimary;
        int resized = maxPrimary;
        if (resized * ratio > maxSecondary) {
            resized = (int) (maxSecondary / ratio);
        }
        return resized;
    }

    @Override
    protected Response<Bitmap> parseNetworkResponse(NetworkResponse response) {
        // Serialize all decode on a global lock to reduce concurrent heap usage.
        synchronized (sDecodeLock) {
            try {
                return doParse(response);
            } catch (OutOfMemoryError e) {
                VolleyLog.e("Caught OOM for %d byte image, url=%s", response.data.length, getUrl());
                return Response.error(new ParseError(e));
            }
        }
    }

    /**
     * The real guts of parseNetworkResponse. Broken out for readability.
     */
    private Response<Bitmap> doParse(NetworkResponse response) {
        byte[] data = response.data;
        BitmapFactory.Options decodeOptions = new BitmapFactory.Options();
        Bitmap bitmap = null;
        if (mMaxWidth == 0 && mMaxHeight == 0) {
            decodeOptions.inPreferredConfig = mDecodeConfig;
            bitmap = BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);
        } else {
            // If we have to resize this image, first get the natural bounds.
            decodeOptions.inJustDecodeBounds = true;
            BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);
            int actualWidth = decodeOptions.outWidth;
            int actualHeight = decodeOptions.outHeight;

            // Then compute the dimensions we would ideally like to decode to.
            int desiredWidth = getResizedDimension(mMaxWidth, mMaxHeight,
                    actualWidth, actualHeight);
            int desiredHeight = getResizedDimension(mMaxHeight, mMaxWidth,
                    actualHeight, actualWidth);

            // Decode to the nearest power of two scaling factor.
            decodeOptions.inJustDecodeBounds = false;
            // TODO(ficus): Do we need this or is it okay since API 8 doesn‘t support it?
            // decodeOptions.inPreferQualityOverSpeed = PREFER_QUALITY_OVER_SPEED;
            decodeOptions.inSampleSize =
                findBestSampleSize(actualWidth, actualHeight, desiredWidth, desiredHeight);
            Bitmap tempBitmap =
                BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);

            // If necessary, scale down to the maximal acceptable size.
            if (tempBitmap != null && (tempBitmap.getWidth() > desiredWidth ||
                    tempBitmap.getHeight() > desiredHeight)) {
                bitmap = Bitmap.createScaledBitmap(tempBitmap,
                        desiredWidth, desiredHeight, true);
                tempBitmap.recycle();
            } else {
                bitmap = tempBitmap;
            }
        }

        if (bitmap == null) {
            return Response.error(new ParseError(response));
        } else {
            return Response.success(bitmap, HttpHeaderParser.parseCacheHeaders(response));
        }
    }

    @Override
    protected void deliverResponse(Bitmap response) {
        mListener.onResponse(response);
    }

    /**
     * Returns the largest power-of-two divisor for use in downscaling a bitmap
     * that will not result in the scaling past the desired dimensions.
     *
     * @param actualWidth Actual width of the bitmap
     * @param actualHeight Actual height of the bitmap
     * @param desiredWidth Desired width of the bitmap
     * @param desiredHeight Desired height of the bitmap
     */
    // Visible for testing.
    static int findBestSampleSize(
            int actualWidth, int actualHeight, int desiredWidth, int desiredHeight) {
        double wr = (double) actualWidth / desiredWidth;
        double hr = (double) actualHeight / desiredHeight;
        double ratio = Math.min(wr, hr);
        float n = 1.0f;
        while ((n * 2) <= ratio) {
            n *= 2;
        }

        return (int) n;
    }
}