/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package io.netty.handler.codec.http;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.util.AsciiString;
import io.netty.util.CharsetUtil;

import static io.netty.handler.codec.http.HttpConstants.*;
import static io.netty.handler.codec.http.HttpObjectEncoder.CRLF_SHORT;

final class HttpHeadersEncoder {
    private static final int COLON_AND_SPACE_SHORT = (COLON << 8) | SP;

    private HttpHeadersEncoder() {
    }

    static void encoderHeader(CharSequence name, CharSequence value, ByteBuf buf) {
        final int nameLen = name.length();
        final int valueLen = value.length();
        final int entryLen = nameLen + valueLen + 4;
        buf.ensureWritable(entryLen);
        int offset = buf.writerIndex();
        writeAscii(buf, offset, name);
        offset += nameLen;
        ByteBufUtil.setShortBE(buf, offset, COLON_AND_SPACE_SHORT);
        offset += 2;
        writeAscii(buf, offset, value);
        offset += valueLen;
        ByteBufUtil.setShortBE(buf, offset, CRLF_SHORT);
        offset += 2;
        buf.writerIndex(offset);
    }

    private static void writeAscii(ByteBuf buf, int offset, CharSequence value) {
        if (value instanceof AsciiString) {
            ByteBufUtil.copy((AsciiString) value, 0, buf, offset, value.length());
        } else {
            buf.setCharSequence(offset, value, CharsetUtil.US_ASCII);
        }
    }
}