/*
	SPDX-FileCopyrightText: © 2025 Hornwitser <code@hornwitser.no>
	SPDX-License-Identifier: AGPL-3.0-or-later
*/
import type { ApiEntity, ApiTombstone } from "~/shared/types/api";
import type { Id } from "~/shared/types/common";
import { DateTime, Zone } from "~/shared/utils/luxon";

export abstract class ClientEntity<Api extends ApiEntity> {
	/**
		Millisecond offset used to indicate this is a new entitity.
	*/
	static newEntityMillis = -1;
	/**
		Timestamp of the entity received from server. If this is
		a new entity this will have a millisecond offset equal to
		{@link ClientEntity.newEntityMillis}.
	*/
	serverUpdatedAt: DateTime;
	/**
		True if the server has deleted this entity, but the client
		is holding on to it in order to resolve an edit conflcit
	*/
	serverDeleted: boolean;

	constructor(
		/**
			Server supplied id of this entity. Each kind of entity has its own namespace of ids.
		*/
		public readonly id: Id,
		/**
			Server's timestamp of this entity at the time it was modified.  If the entity
			is unmodified this will track {@link serverUpdatedAt}.  If this is a new entity
			it'll have a millesecond offset equal to {@link ClientEntity.newEntityMillis}.
		*/
		public updatedAt: DateTime,
		/**
			Flag indicating the client intends to delete this entity.
		*/
		public deleted: boolean,
	) {
		this.serverUpdatedAt = updatedAt;
		this.serverDeleted = deleted;
	}

	/**
		True if this entity does not yet exist on the server.
	*/
	isNew() {
		return this.serverUpdatedAt.toMillis() === ClientEntity.newEntityMillis;
	}

	/**
		True if both the server and the client have modified this entity
		independently of each other.
	*/
	isConflict() {
		return this.serverUpdatedAt.toMillis() !== this.updatedAt.toMillis();
	}

	/**
		True if this entity has been modified on the client.
	*/
	isModified() {
		return (
			this.isNew()
			|| this.deleted
			|| this.serverDeleted
		);
	}

	/**
		Discard any client side modifications to this entity. Not allowed if
		{@link serverDeleted} is true or this is a new entity.
	*/
	abstract discard(): void

	/**
		Apply an update delivered from the API to this entity.
	*/
	abstract apiUpdate(api: Api, opts: { zone: Zone, locale: string }): void

	/**
		Serialise this entity to the API format. Not allowed if {@link deleted} is true.
	*/
	abstract toApi(): Api | ApiTombstone
}