package envoy.data;

import java.io.Serializable;
import java.time.Instant;
import java.util.Objects;

/**
 * Represents a unique message with a unique, numeric ID. Further metadata includes the sender and
 * recipient {@link User}s, as well as the creation date and the current {@link MessageStatus}.<br>
 *
 * @author Kai S. K. Engelbart
 * @author Leon Hofmeister
 * @since Envoy Common v0.2-alpha
 */
public class Message implements Serializable {

	/**
	 * This enumeration defines all possible statuses a {link Message} can have.
	 *
	 * @since Envoy Common v0.2-alpha
	 */
	public enum MessageStatus {

		/**
		 * The message has not yet been sent to the server
		 */
		WAITING,

		/**
		 * The message has been sent to the server.
		 */
		SENT,

		/**
		 * The message has been received by its recipient.
		 */
		RECEIVED,

		/**
		 * The message has been read by its recipient.
		 */
		READ
	}

	private final long			id, senderID, recipientID;
	private final boolean		forwarded;
	private final Instant		creationDate;
	private final String		text;
	private final Attachment	attachment;

	private Instant			receivedDate, readDate;
	private MessageStatus	status;

	private static final long serialVersionUID = 2L;

	/**
	 * Initializes a {@link Message} with values for all of its properties. The use of this
	 * constructor is only intended for the {@link MessageBuilder} class, as this class provides
	 * {@code null} checks and default values for all properties.
	 *
	 * @param id           unique ID
	 * @param senderID     the ID of the user who sends the message
	 * @param recipientID  the ID of the user who receives the message
	 * @param creationDate the creation date of the message
	 * @param receivedDate the received date of the message
	 * @param readDate     the read date of the message
	 * @param text         the text content of the message
	 * @param attachment   the attachment of the message, if present
	 * @param status       the current {@link MessageStatus} of the message
	 * @param forwarded    whether this message was forwarded
	 * @since Envoy Common v0.2-beta
	 */
	Message(long id, long senderID, long recipientID, Instant creationDate, Instant receivedDate,
		Instant readDate, String text,
		Attachment attachment, MessageStatus status, boolean forwarded) {
		this.id				= id;
		this.senderID		= senderID;
		this.recipientID	= recipientID;
		this.creationDate	= creationDate;
		this.receivedDate	= receivedDate;
		this.readDate		= readDate;
		this.text			= text == null ? "" : text;
		this.attachment		= attachment;
		this.status			= Objects.requireNonNull(status);
		this.forwarded		= forwarded;
	}

	/**
	 * Changes the current {@link MessageStatus} to the next logical status.<br>
	 * <br>
	 * The underlying order is as follows:
	 * <ol>
	 * <li>{@link MessageStatus#WAITING}
	 * <li>{@link MessageStatus#SENT}
	 * <li>{@link MessageStatus#RECEIVED}
	 * <li>{@link MessageStatus#READ}
	 * </ol>
	 *
	 * @since Envoy Common v0.2-alpha
	 */
	public void nextStatus() {
		if (status == MessageStatus.READ)
			throw new IllegalStateException("Message status READ is already reached");
		status = MessageStatus.values()[status.ordinal() + 1];
	}

	@Override
	public String toString() {
		return String.format(
			"Message[id=%d,sender=%s,recipient=%s,date=%s,status=%s,text=%s,forwarded=%b,hasAttachment=%b]",
			id,
			senderID,
			recipientID,
			creationDate,
			status,
			text,
			forwarded,
			attachment != null);
	}

	/**
	 * @return the ID of this message
	 * @since Envoy Common v0.2-alpha
	 */
	public long getID() { return id; }

	/**
	 * @return the sender ID of this message
	 * @since Envoy Common v0.2-alpha
	 */
	public long getSenderID() { return senderID; }

	/**
	 * @return the recipient ID of this message
	 * @since Envoy Common v0.2-alpha
	 */
	public long getRecipientID() { return recipientID; }

	/**
	 * @return the date at which this message was created
	 * @since Envoy Common v0.2-beta
	 */
	public Instant getCreationDate() { return creationDate; }

	/**
	 * @return the date at which the message has been received by the sender
	 * @since Envoy Common v0.2-beta
	 */
	public Instant getReceivedDate() { return receivedDate; }

	/**
	 * @param receivedDate the date at which the message has been received by the sender
	 * @since Envoy Common v0.2-beta
	 */
	public void setReceivedDate(Instant receivedDate) { this.receivedDate = receivedDate; }

	/**
	 * @return the date at which the message has been read by the sender
	 * @since Envoy Common v0.2-beta
	 */
	public Instant getReadDate() { return readDate; }

	/**
	 * @param readDate at which the message has been read by the sender
	 * @since Envoy Common v0.2-beta
	 */
	public void setReadDate(Instant readDate) { this.readDate = readDate; }

	/**
	 * @return the text content of this message
	 * @since Envoy Common v0.2-alpha
	 */
	public String getText() { return text; }

	/**
	 * @return the messageAttachment
	 * @since Envoy Common v0.2-alpha
	 */
	public Attachment getAttachment() { return attachment; }

	/**
	 * @return {@code true} if an attachment is present
	 * @since Envoy Common v0.1-beta
	 */
	public boolean hasAttachment() {
		return attachment != null;
	}

	/**
	 * @return the current status of this message
	 * @since Envoy Common v0.2-alpha
	 */
	public MessageStatus getStatus() { return status; }

	/**
	 * @param status the new {@link MessageStatus}, if permitted
	 * @since Envoy Common v0.2-alpha
	 */
	public void setStatus(MessageStatus status) {
		if (status.ordinal() < this.status.ordinal())
			throw new IllegalStateException("This message is moving backwards in time");
		this.status = status;
	}

	/**
	 * @return whether this message was forwarded
	 * @since Envoy common v0.1-beta
	 */
	public boolean isForwarded() { return forwarded; }
}