package org.openslx.filetransfer.util;

import java.nio.ByteBuffer;
import java.util.Collection;
import java.util.List;

import org.openslx.filetransfer.FileRange;

public class FileChunk {

	public static final int CHUNK_SIZE_MIB = 16;
	public static final int CHUNK_SIZE = CHUNK_SIZE_MIB * (1024 * 1024);

	public final FileRange range;
	public final byte[] sha1sum;
	private int failCount = 0;

	public FileChunk(long startOffset, long endOffset, byte[] sha1sum) {
		this.range = new FileRange(startOffset, endOffset);
		this.sha1sum = sha1sum;
	}

	/**
	 * Signal that transferring this chunk seems to have failed (checksum
	 * mismatch).
	 * 
	 * @return Number of times the transfer failed now
	 */
	public synchronized int incFailed() {
		return ++failCount;
	}
	
	public int getChunkIndex() {
		return (int)(range.startOffset / CHUNK_SIZE);
	}
	
	@Override
	public String toString() {
		return "[Chunk " + getChunkIndex() + " (" + range.startOffset + "-" + range.endOffset + "), fails: " + failCount + "]";
	}

	//

	public static int fileSizeToChunkCount(long fileSize) {
		return (int) ((fileSize + CHUNK_SIZE - 1) / CHUNK_SIZE);
	}

	public static void createChunkList(Collection<FileChunk> list, long fileSize, List<ByteBuffer> sha1Sums) {
		if (fileSize < 0)
			throw new IllegalArgumentException("fileSize cannot be negative");
		if (!list.isEmpty())
			throw new IllegalArgumentException("Passed list is not empty");
		long chunkCount = fileSizeToChunkCount(fileSize);
		if (sha1Sums != null) {
			if (sha1Sums.size() != chunkCount)
				throw new IllegalArgumentException(
						"Passed a sha1sum list, but hash count in list doesn't match expected chunk count");
			long offset = 0;
			for (ByteBuffer sha1sum : sha1Sums) { // Do this as we don't know how efficient List.get(index) is...
				long end = offset + CHUNK_SIZE;
				if (end > fileSize)
					end = fileSize;
				list.add(new FileChunk(offset, end, sha1sum.array()));
				offset = end;
			}
			return;
		}
		long offset = 0;
		while (offset < fileSize) { // ...otherwise we could share this code
			long end = offset + CHUNK_SIZE;
			if (end > fileSize)
				end = fileSize;
			list.add(new FileChunk(offset, end, null));
			offset = end;
		}
	}
}