juneau-core/juneau-marshall/src/main/java/org/apache/juneau/http/header/BasicEntityTagArrayHeader.java

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package org.apache.juneau.http.header;

import static org.apache.juneau.internal.StringUtils.*;
import static java.util.stream.Collectors.*;
import static java.util.Optional.*;
import static java.util.Collections.*;

import java.util.*;
import java.util.function.*;

/**
 * Category of headers that consist of a comma-delimited list of entity validator values.
 *
 * <p>
 * <h5 class='figure'>Example</h5>
 * <p class='bcode w800'>
 * 	If-Match: "xyzzy"
 * 	If-Match: "xyzzy", "r2d2xxxx", "c3piozzzz"
 * 	If-Match: *
 * </p>
 *
 * <ul class='seealso'>
 * 	<li class='extlink'>{@doc ExtRFC2616}
 * </ul>
 */
public class BasicEntityTagArrayHeader extends BasicHeader {

	private static final long serialVersionUID = 1L;

	/**
	 * Convenience creator.
	 *
	 * @param name The header name.
	 * @param value
	 * 	The header value.
	 * 	<br>Must be a comma-delimited list of entity validator values (e.g. <js>"\"xyzzy\", \"r2d2xxxx\", \"c3piozzzz\""</js>).
	 * 	<br>Can be <jk>null</jk>.
	 * @return A new header bean, or <jk>null</jk> if the name is <jk>null</jk> or empty or the value is <jk>null</jk>.
	 */
	public static BasicEntityTagArrayHeader of(String name, String value) {
		if (isEmpty(name) || value == null)
			return null;
		return new BasicEntityTagArrayHeader(name, value);
	}

	/**
	 * Convenience creator.
	 *
	 * @param name The header name.
	 * @param value
	 * 	The header value.
	 * 	<br>Can be <jk>null</jk>.
	 * @return A new header bean, or <jk>null</jk> if the name is <jk>null</jk> or empty or the value is <jk>null</jk>.
	 */
	public static BasicEntityTagArrayHeader of(String name, List<EntityTag> value) {
		if (isEmpty(name) || value == null)
			return null;
		return new BasicEntityTagArrayHeader(name, value);
	}

	/**
	 * Convenience creator with delayed value.
	 *
	 * <p>
	 * Header value is re-evaluated on each call to {@link #getValue()}.
	 *
	 * @param name The header name.
	 * @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 name is <jk>null</jk> or empty or the value is <jk>null</jk>.
	 */
	public static BasicEntityTagArrayHeader of(String name, Supplier<List<EntityTag>> value) {
		if (isEmpty(name) || value == null)
			return null;
		return new BasicEntityTagArrayHeader(name, value);
	}

	private final List<EntityTag> value;
	private final Supplier<List<EntityTag>> supplier;

	/**
	 * Constructor.
	 *
	 * @param name The header name.
	 * @param value
	 * 	The header value.
	 * 	<br>Must be a comma-delimited list of entity validator values (e.g. <js>"\"xyzzy\", \"r2d2xxxx\", \"c3piozzzz\""</js>).
	 * 	<br>Can be <jk>null</jk>.
	 */
	public BasicEntityTagArrayHeader(String name, String value) {
		super(name, value);
		this.value = parse(value);
		this.supplier = null;
	}

	/**
	 * Constructor.
	 *
	 * @param name The header name.
	 * @param value
	 * 	The header value.
	 * 	<br>Can be <jk>null</jk>.
	 */
	public BasicEntityTagArrayHeader(String name, List<EntityTag> value) {
		super(name, serialize(value));
		this.value = value == null ? null : unmodifiableList(value);
		this.supplier = null;
	}

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

	@Override /* Header */
	public String getValue() {
		if (supplier != null)
			return serialize(supplier.get());
		return super.getValue();
	}

	/**
	 * Returns this header value as an array of {@link EntityTag} objects.
	 *
	 * @return this header value as an array of {@link EntityTag} objects, or {@link Optional#empty()} if the value was <jk>null</jk>..
	 */
	public Optional<List<EntityTag>> asEntityTags() {
		if (supplier != null)
			return ofNullable(supplier.get());
		return ofNullable(value);
	}

	private static String serialize(List<EntityTag> value) {
		return join(value, ", ");
	}

	private List<EntityTag> parse(String value) {
		return value == null ? null : Arrays.asList(split(value, ',')).stream().map(x -> EntityTag.of(x)).collect(toList());
	}
}