envoy/common/src/main/java/envoy/data/MessageBuilder.java

package envoy.data;

import java.time.Instant;
import java.util.*;

import envoy.data.Message.MessageStatus;

/**
 * Provides a method of constructing the {@link Message} class.<br>
 *
 * @author Kai S. K. Engelbart
 * @since Envoy Common v0.2-alpha
 */
public final class MessageBuilder {

	// Mandatory properties without default values
	private final long senderID, recipientID;

	// Properties with default values
	private final long				id;
	private Instant					creationDate, receivedDate, readDate;
	private String					text;
	private Attachment				attachment;
	private Message.MessageStatus	status;
	private boolean					forwarded;

	/**
	 * Creates an instance of {@link MessageBuilder} with all mandatory values without defaults for
	 * the {@link Message} class.
	 *
	 * @param senderID    the ID of the user who sends the {@link Message}
	 * @param recipientID the ID of the user who receives the {@link Message}
	 * @param idGenerator the ID generator used to generate a unique {@link Message} id
	 * @since Envoy Common v0.2-alpha
	 */
	public MessageBuilder(long senderID, long recipientID, IDGenerator idGenerator) {
		this(senderID, recipientID, idGenerator.next());
	}

	/**
	 * Creates an instance of {@link MessageBuilder} with all mandatory values without defaults for
	 * the {@link Message} class.
	 *
	 * @param senderID    the ID of the user who sends the {@link Message}
	 * @param recipientID the ID of the user who receives the {@link Message}
	 * @param messageId   the ID of the {@link Message}
	 * @since Envoy Common v0.2-alpha
	 */
	public MessageBuilder(long senderID, long recipientID, long messageId) {
		this.senderID		= senderID;
		this.recipientID	= recipientID;
		id					= messageId;
	}

	/**
	 * This constructor transforms a given {@link Message} into a new message for a new receiver.
	 * This makes it especially useful in the case of forwarding messages.
	 *
	 * @param msg         the message to copy
	 * @param recipientID the ID of the user who receives the {@link Message}
	 * @param iDGenerator the ID generator used to generate a unique {@link Message} id
	 * @since Envoy v0.1-beta
	 */
	public MessageBuilder(Message msg, long recipientID, IDGenerator iDGenerator) {
		this(msg.getRecipientID(), recipientID, iDGenerator.next());
		attachment		= msg.getAttachment();
		creationDate	= Instant.now();
		forwarded		= true;
		text			= msg.getText();
		status			= MessageStatus.WAITING;
	}

	/**
	 * Creates an instance of {@link Message} with the previously supplied values. If a mandatory
	 * value is not set, a default value will be used instead:<br>
	 * <br>
	 * {@code date} {@code Instant.now()} and {@code null} for {@code receivedDate} and
	 * {@code readDate} <br>
	 * {@code text} {@code ""} <br>
	 * {@code status} {@code MessageStatus.WAITING}
	 *
	 * @return a new instance of {@link Message}
	 * @since Envoy Common v0.2-alpha
	 */
	public Message build() {
		supplyDefaults();
		return new Message(id, senderID, recipientID, creationDate, receivedDate, readDate, text,
			attachment, status, forwarded);
	}

	/**
	 * Creates an instance of {@link GroupMessage} with the previously supplied values. <br>
	 * <b> Sets all member statuses to {@link MessageStatus#WAITING}.</b><br>
	 * If a mandatory value is not set, a default value will be used instead:<br>
	 * <br>
	 * {@code time stamp} {@code Instant.now()} <br>
	 * {@code text} {@code ""} <br>
	 *
	 * @param group the {@link Group} that is used to fill the map of member statuses
	 * @return a new instance of {@link GroupMessage}
	 * @since Envoy Common v0.2-alpha
	 */
	public GroupMessage buildGroupMessage(Group group) {
		final var memberStatuses = new HashMap<Long, Message.MessageStatus>();
		group.getContacts()
			.forEach(user -> memberStatuses.put(user.getID(), MessageStatus.WAITING));
		return buildGroupMessage(group, memberStatuses);
	}

	/**
	 * Creates an instance of {@link GroupMessage} with the previously supplied values. If a
	 * mandatory value is not set, a default value will be used instead:<br>
	 * <br>
	 * {@code time stamp} {@code Instant.now()} <br>
	 * {@code text} {@code ""}
	 *
	 * @param group          the {@link Group} that is used to fill the map of member statuses
	 * @param memberStatuses the map of all current statuses
	 * @return a new instance of {@link GroupMessage}
	 * @since Envoy Common v0.1-beta
	 */
	public GroupMessage buildGroupMessage(Group group, Map<Long, MessageStatus> memberStatuses) {
		if (group == null || memberStatuses == null)
			throw new NullPointerException();
		supplyDefaults();
		return new GroupMessage(id, senderID, recipientID, creationDate, receivedDate, readDate,
			text, attachment, status, forwarded, memberStatuses);
	}

	private void supplyDefaults() {
		if (creationDate == null)
			creationDate = Instant.now();
		if (text == null)
			text = "";
		if (status == null)
			status = MessageStatus.WAITING;
	}

	/**
	 * @param creationDate the creation date of the {@link Message} to create
	 * @return this {@link MessageBuilder}
	 * @since Envoy Common v0.2-beta
	 */
	public MessageBuilder setCreationDate(Instant creationDate) {
		this.creationDate = creationDate;
		return this;
	}

	/**
	 * @param receivedDate the received date of the {@link Message} to create
	 * @return this {@link MessageBuilder}
	 * @since Envoy Common v0.2-beta
	 */
	public MessageBuilder setReceivedDate(Instant receivedDate) {
		this.receivedDate = receivedDate;
		return this;
	}

	/**
	 * @param readDate the read date of the {@link Message} to create
	 * @return this {@link MessageBuilder}
	 * @since Envoy Common v0.2-beta
	 */
	public MessageBuilder setReadDate(Instant readDate) {
		this.readDate = readDate;
		return this;
	}

	/**
	 * @param text the text of the {@link Message} to create
	 * @return this {@link MessageBuilder}
	 * @since Envoy Common v0.2-alpha
	 */
	public MessageBuilder setText(String text) {
		this.text = text;
		return this;
	}

	/**
	 * @param attachment the {@link Attachment} of the {@link Message} to create
	 * @return this {@link MessageBuilder}
	 * @since Envoy Common v0.2-alpha
	 */
	public MessageBuilder setAttachment(Attachment attachment) {
		this.attachment = attachment;
		return this;
	}

	/**
	 * @param status the {@link MessageStatus} of the {@link Message} to create
	 * @return this {@link MessageBuilder}
	 * @since Envoy Common v0.2-alpha
	 */
	public MessageBuilder setStatus(Message.MessageStatus status) {
		this.status = status;
		return this;
	}

	/**
	 * @param forwarded sets whether this message is a forwarded message or not
	 * @return this {@link MessageBuilder}
	 * @since Envoy Common v0.1-beta
	 */
	public MessageBuilder setForwarded(boolean forwarded) {
		this.forwarded = forwarded;
		return this;
	}
}