package ar.com.hjg.pngj;

import ar.com.hjg.pngj.chunks.PngChunkFDAT;

/**
 *
 * Specialization of ChunkReader, for IDAT-like chunks. These chunks are part of
 * a set of similar chunks (contiguos
 * normally, not necessariyl) which conforms a zlib stream
 */
public class DeflatedChunkReader extends ChunkReader {

	protected final DeflatedChunksSet deflatedChunksSet;
	protected boolean alsoBuffer = false;

	protected boolean skipBytes = false; // fDAT (APNG) skips 4 bytes)
	protected byte[] skippedBytes; // only for fDAT
	protected int seqNumExpected = -1; // only for fDAT

	public DeflatedChunkReader(final int clen, final String chunkid, final boolean checkCrc, final long offsetInPng, final DeflatedChunksSet iDatSet) {
		super(clen, chunkid, offsetInPng, ChunkReaderMode.PROCESS);
		deflatedChunksSet = iDatSet;
		if (chunkid.equals(PngChunkFDAT.ID)) {
			skipBytes = true;
			skippedBytes = new byte[4];
		}
		iDatSet.appendNewChunk(this);
	}

	/**
	 * Delegates to ChunkReaderDeflatedSet.processData()
	 */
	@Override
	protected void processData(final int offsetInchunk, final byte[] buf, int off, int len) {
		if (skipBytes && offsetInchunk < 4)
			for (int oc = offsetInchunk; oc < 4 && len > 0; oc++, off++, len--)
				skippedBytes[oc] = buf[off];
		if (len > 0) { // delegate to idatSet
			deflatedChunksSet.processBytes(buf, off, len);
			if (alsoBuffer)
				System.arraycopy(buf, off, getChunkRaw().data, read, len);
		}
	}

	/**
	 * only a stupid check for fDAT (I wonder how many APGN readers do this)
	 */
	@Override
	protected void chunkDone() {
		if (skipBytes && getChunkRaw().id.equals(PngChunkFDAT.ID))
			if (seqNumExpected >= 0) {
				final int seqNum = PngHelperInternal.readInt4fromBytes(skippedBytes, 0);
				if (seqNum != seqNumExpected)
					throw new PngjInputException("bad chunk sequence for fDAT chunk " + seqNum + " expected " + seqNumExpected);
			}
	}

	@Override
	public boolean isFromDeflatedSet() {
		return true;
	}

	/**
	 * In some rare cases you might want to also buffer the data?
	 */
	public void setAlsoBuffer() {
		if (read > 0)
			throw new RuntimeException("too late");
		alsoBuffer = true;
		getChunkRaw().allocData();
	}

	/** only relevant for fDAT */
	public void setSeqNumExpected(final int seqNumExpected) {
		this.seqNumExpected = seqNumExpected;
	}

}