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package com.firefly.codec.http2.hpack;

import java.nio.ByteBuffer;

import com.firefly.codec.http2.encode.HttpFieldPreEncoder;
import com.firefly.codec.http2.model.HttpHeader;
import com.firefly.codec.http2.model.HttpVersion;
import com.firefly.utils.io.BufferUtils;

public class HpackFieldPreEncoder implements HttpFieldPreEncoder {

	@Override
	public HttpVersion getHttpVersion() {
		return HttpVersion.HTTP_2;
	}

	@Override
	public byte[] getEncodedField(HttpHeader header, String name, String value) {
		boolean not_indexed = HpackEncoder.DO_NOT_INDEX.contains(header);

		ByteBuffer buffer = BufferUtils.allocate(name.length() + value.length() + 10);
		BufferUtils.clearToFill(buffer);
		boolean huffman;
		int bits;

		if (not_indexed) {
			// Non indexed field
			boolean never_index = HpackEncoder.NEVER_INDEX.contains(header);
			huffman = !HpackEncoder.DO_NOT_HUFFMAN.contains(header);
			buffer.put(never_index ? (byte) 0x10 : (byte) 0x00);
			bits = 4;
		} else if (header == HttpHeader.CONTENT_LENGTH && value.length() > 1) {
			// Non indexed content length for 2 digits or more
			buffer.put((byte) 0x00);
			huffman = true;
			bits = 4;
		} else {
			// indexed
			buffer.put((byte) 0x40);
			huffman = !HpackEncoder.DO_NOT_HUFFMAN.contains(header);
			bits = 6;
		}

		int name_idx = HpackContext.staticIndex(header);
		if (name_idx > 0)
			NBitInteger.encode(buffer, bits, name_idx);
		else {
			buffer.put((byte) 0x80);
			NBitInteger.encode(buffer, 7, Huffman.octetsNeededLC(name));
			Huffman.encodeLC(buffer, name);
		}

		HpackEncoder.encodeValue(buffer, huffman, value);

		BufferUtils.flipToFlush(buffer, 0);
		return BufferUtils.toArray(buffer);
	}
}