package ar.com.hjg.pngj.chunks;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

import ar.com.hjg.pngj.ImageInfo;
import ar.com.hjg.pngj.PngjException;

/**
 * zTXt chunk.
 * <p>
 * see http://www.w3.org/TR/PNG/#11zTXt
 */
public class PngChunkZTXT extends PngChunkTextVar {
	public final static String ID = ChunkHelper.zTXt;

	// http://www.w3.org/TR/PNG/#11zTXt
	public PngChunkZTXT(ImageInfo info) {
		super(ID, info);
	}

	@Override
	public ChunkRaw createRawChunk() {
		if (key == null || key.trim().length() == 0)
			throw new PngjException("Text chunk key must be non empty");
		try {
			ByteArrayOutputStream ba = new ByteArrayOutputStream();
			ba.write(ChunkHelper.toBytes(key));
			ba.write(0); // separator
			ba.write(0); // compression method: 0
			byte[] textbytes = ChunkHelper.compressBytes(ChunkHelper.toBytes(val), true);
			ba.write(textbytes);
			byte[] b = ba.toByteArray();
			ChunkRaw chunk = createEmptyChunk(b.length, false);
			chunk.data = b;
			return chunk;
		} catch (IOException e) {
			throw new PngjException(e);
		}
	}

	@Override
	public void parseFromRaw(ChunkRaw c) {
		int nullsep = -1;
		for (int i = 0; i < c.data.length; i++) { // look for first zero
			if (c.data[i] != 0)
				continue;
			nullsep = i;
			break;
		}
		if (nullsep < 0 || nullsep > c.data.length - 2)
			throw new PngjException("bad zTXt chunk: no separator found");
		key = ChunkHelper.toString(c.data, 0, nullsep);
		int compmet = (int) c.data[nullsep + 1];
		if (compmet != 0)
			throw new PngjException("bad zTXt chunk: unknown compression method");
		byte[] uncomp = ChunkHelper.compressBytes(c.data, nullsep + 2, c.data.length - nullsep - 2, false); // uncompress
		val = ChunkHelper.toString(uncomp);
	}

}