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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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package org.apache.juneau.http.header;

import java.util.function.*;

import org.apache.juneau.http.annotation.*;

/**
 * Represents a parsed <l>Trailer</l> HTTP response header.
 *
 * <p>
 * The Trailer general field value indicates that the given set of header fields is present in the trailer of a message
 * encoded with chunked transfer coding.
 *
 * <h5 class='figure'>Example</h5>
 * <p class='bcode'>
 * 	Trailer: Max-Forwards
 * </p>
 *
 * <h5 class='topic'>RFC2616 Specification</h5>
 *
 * The Trailer general field value indicates that the given set of header fields is present in the trailer of a message
 * encoded with chunked transfer-coding.
 *
 * <p class='bcode'>
 * 	Trailer  = "Trailer" ":" 1#field-name
 * </p>
 *
 * <p>
 * An HTTP/1.1 message SHOULD include a Trailer header field in a message using chunked transfer-coding with a non-empty
 * trailer.
 * Doing so allows the recipient to know which header fields to expect in the trailer.
 *
 * <p>
 * If no Trailer header field is present, the trailer SHOULD NOT include any header fields.
 * See section 3.6.1 for restrictions on the use of trailer fields in a "chunked" transfer-coding.
 *
 * <p>
 * Message header fields listed in the Trailer header field MUST NOT include the following header fields:
 * <ul>
 * 	<li>Transfer-Encoding
 * 	<li>Content-Length
 * 	<li>Trailer
 * </ul>
 *
 * <ul class='seealso'>
 * 	<li class='link'>{@doc jm.HttpParts}
 * 	<li class='extlink'>{@doc ext.RFC2616}
 * 	<li class='extlink'>{@source}
 * </ul>
 *
 * @serial exclude
 */
@Header("Trailer")
public class Trailer extends BasicStringHeader {

	//-----------------------------------------------------------------------------------------------------------------
	// Static
	//-----------------------------------------------------------------------------------------------------------------

	private static final long serialVersionUID = 1L;
	private static final String NAME = "Trailer";

	/**
	 * Static creator.
	 *
	 * @param value
	 * 	The header value.
	 * 	<br>Can be <jk>null</jk>.
	 * @return A new header bean, or <jk>null</jk> if the value is <jk>null</jk>.
	 */
	public static Trailer of(String value) {
		return value == null ? null : new Trailer(value);
	}

	/**
	 * Static creator with delayed value.
	 *
	 * <p>
	 * Header value is re-evaluated on each call to {@link #getValue()}.
	 *
	 * @param value
	 * 	The supplier of the header value.
	 * 	<br>Can be <jk>null</jk>.
	 * @return A new header bean, or <jk>null</jk> if the value is <jk>null</jk>.
	 */
	public static Trailer of(Supplier<String> value) {
		return value == null ? null : new Trailer(value);
	}

	//-----------------------------------------------------------------------------------------------------------------
	// Instance
	//-----------------------------------------------------------------------------------------------------------------

	/**
	 * Constructor.
	 *
	 * @param value
	 * 	The header value.
	 * 	<br>Can be <jk>null</jk>.
	 */
	public Trailer(String value) {
		super(NAME, value);
	}

	/**
	 * Constructor with delayed value.
	 *
	 * <p>
	 * Header value is re-evaluated on each call to {@link #getValue()}.
	 *
	 * @param value
	 * 	The supplier of the header value.
	 * 	<br>Can be <jk>null</jk>.
	 */
	public Trailer(Supplier<String> value) {
		super(NAME, value);
	}
}
