package ar.com.hjg.pngj;

/**
 * Lightweight wrapper for an image scanline, used for read and write.
 * <p>
 * This object can be (usually it is) reused while iterating over the image
 * lines.
 * <p>
 * See <code>scanline</code> field, to understand the format.
 *
 * Format: byte (one bytes per sample) (for 16bpp the extra byte is placed in an
 * extra array)
 */
public class ImageLineByte implements IImageLine, IImageLineArray {
	public final ImageInfo imgInfo;

	final byte[] scanline;
	final byte[] scanline2; // only used for 16 bpp (less significant byte) Normally you'd prefer
							// ImageLineInt in this case

	protected FilterType filterType; // informational ; only filled by the reader. not significant for
										// interlaced
	final int size; // = imgInfo.samplePerRowPacked, if packed:imgInfo.samplePerRow elswhere

	public ImageLineByte(final ImageInfo imgInfo) {
		this(imgInfo, null);
	}

	public ImageLineByte(final ImageInfo imgInfo, final byte[] sci) {
		this.imgInfo = imgInfo;
		filterType = FilterType.FILTER_UNKNOWN;
		size = imgInfo.samplesPerRow;
		scanline = sci != null && sci.length >= size ? sci : new byte[size];
		scanline2 = imgInfo.bitDepth == 16 ? new byte[size] : null;
	}

	/**
	 * Returns a factory for this object
	 */
	public static IImageLineFactory<ImageLineByte> getFactory() {
		return iminfo -> new ImageLineByte(iminfo);
	}

	public FilterType getFilterUsed() {
		return filterType;
	}

	/**
	 * One byte per sample. This can be used also for 16bpp images, but in this
	 * case this loses the less significant
	 * 8-bits ; see also getScanlineByte2 and getElem.
	 */
	public byte[] getScanlineByte() {
		return scanline;
	}

	/**
	 * only for 16bpp (less significant byte)
	 * 
	 * @return null for less than 16bpp
	 */
	public byte[] getScanlineByte2() {
		return scanline2;
	}

	/**
	 * Basic info
	 */
	@Override
	public String toString() {
		return " cols=" + imgInfo.cols + " bpc=" + imgInfo.bitDepth + " size=" + scanline.length;
	}

	@Override
	public void readFromPngRaw(final byte[] raw, final int len, final int offset, final int step) {
		filterType = FilterType.getByVal(raw[0]); // only for non interlaced line the filter is significative
		final int len1 = len - 1;
		final int step1 = (step - 1) * imgInfo.channels;
		if (imgInfo.bitDepth == 8) {
			if (step == 1)
				System.arraycopy(raw, 1, scanline, 0, len1);
			else
				for (int s = 1, c = 0, i = offset * imgInfo.channels; s <= len1; s++, i++) {
					scanline[i] = raw[s];
					c++;
					if (c == imgInfo.channels) {
						c = 0;
						i += step1;
					}
				}
		} else if (imgInfo.bitDepth == 16) {
			if (step == 1)
				for (int i = 0, s = 1; i < imgInfo.samplesPerRow; i++) {
					scanline[i] = raw[s++]; // get the first byte
					scanline2[i] = raw[s++]; // get the first byte
				}
			else
				for (int s = 1, c = 0, i = offset != 0 ? offset * imgInfo.channels : 0; s <= len1; i++) {
					scanline[i] = raw[s++];
					scanline2[i] = raw[s++];
					c++;
					if (c == imgInfo.channels) {
						c = 0;
						i += step1;
					}
				}
		} else { // packed formats
			int mask0, mask, shi, bd;
			bd = imgInfo.bitDepth;
			mask0 = ImageLineHelper.getMaskForPackedFormats(bd);
			for (int i = offset * imgInfo.channels, r = 1, c = 0; r < len; r++) {
				mask = mask0;
				shi = 8 - bd;
				do {
					scanline[i] = (byte) ((raw[r] & mask) >> shi);
					mask >>= bd;
					shi -= bd;
					i++;
					c++;
					if (c == imgInfo.channels) {
						c = 0;
						i += step1;
					}
				} while (mask != 0 && i < size);
			}
		}
	}

	@Override
	public void writeToPngRaw(final byte[] raw) {
		raw[0] = (byte) filterType.val;
		if (imgInfo.bitDepth == 8)
			System.arraycopy(scanline, 0, raw, 1, size);
		else if (imgInfo.bitDepth == 16)
			for (int i = 0, s = 1; i < size; i++) {
				raw[s++] = scanline[i];
				raw[s++] = scanline2[i];
			}
		else { // packed formats
			int shi, bd, v;
			bd = imgInfo.bitDepth;
			shi = 8 - bd;
			v = 0;
			for (int i = 0, r = 1; i < size; i++) {
				v |= scanline[i] << shi;
				shi -= bd;
				if (shi < 0 || i == size - 1) {
					raw[r++] = (byte) v;
					shi = 8 - bd;
					v = 0;
				}
			}
		}
	}

	@Override
	public void endReadFromPngRaw() {}

	@Override
	public int getSize() {
		return size;
	}

	@Override
	public int getElem(final int i) {
		return scanline2 == null ? scanline[i] & 0xFF : (scanline[i] & 0xFF) << 8 | scanline2[i] & 0xFF;
	}

	public byte[] getScanline() {
		return scanline;
	}

	@Override
	public ImageInfo getImageInfo() {
		return imgInfo;
	}

	@Override
	public FilterType getFilterType() {
		return filterType;
	}

	/**
	 * This should rarely be used by client code. Only relevant if
	 * FilterPreserve==true
	 */
	public void setFilterType(final FilterType ft) {
		filterType = ft;
	}

}