Implement ClientUser based on a new concept

Create a new mutable ClientEntity type and implement ClientUser on top
of it. The mutable concept is intended to replace the immutable concept
used by the ClientSchedule entities as updating immutable types in a
deep interconnected structure is a lot of hassle for little benefit.

utils/client-user.ts

@@ -0,0 +1,168 @@
+import type { ApiUser, ApiUserType } from "~/shared/types/api";
+import type { Entity, EntityLiving, Id, Living } from "~/shared/types/common";
+import { DateTime, Zone } from "~/shared/utils/luxon";
+
+export abstract class ClientEntityNew {
+	/**
+		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 ClientEntityNew.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 ClientEntityNew.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() === ClientEntityNew.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: EntityLiving, opts: { zone: Zone, locale: string }): void
+
+	/**
+		Serialise this entity to the API format. Not allowed if {@link deleted} is true.
+	*/
+	abstract toApi(): Entity
+}
+
+export class ClientUser extends ClientEntityNew {
+	static type = "user";
+	serverName: string | undefined;
+	serverType: ApiUserType
+
+	constructor(
+		id: Id,
+		updatedAt: DateTime,
+		deleted: boolean,
+		public name: string | undefined,
+		public type: ApiUserType,
+	) {
+		super(id, updatedAt, deleted);
+		this.serverName = name;
+		this.serverType = type;
+	}
+
+	override isModified() {
+		return (
+			super.isModified()
+			|| this.name !== this.serverName
+			|| this.type !== this.serverType
+		);
+	}
+
+	override discard() {
+		if (this.isNew()) {
+			throw new Error("ClientUser.discard: Cannot discard new entity.")
+		}
+		this.updatedAt = this.serverUpdatedAt;
+		this.name = this.serverName;
+		this.type = this.serverType;
+	}
+
+	static create(
+		id: Id,
+		name: string | undefined,
+		type: ApiUserType,
+		opts: { zone: Zone, locale: string },
+	) {
+		return new this(
+			id,
+			DateTime.fromMillis(ClientEntityNew.newEntityMillis, opts),
+			false,
+			name,
+			type,
+		)
+	}
+
+	static fromApi(api: Living<ApiUser>, opts: { zone: Zone, locale: string }) {
+		try {
+		return new this(
+			api.id,
+			DateTime.fromISO(api.updatedAt, opts),
+			false,
+			api.name,
+			api.type,
+		);
+		} catch (err) {
+		console.error(api);
+		throw err;
+		}
+	}
+
+	override apiUpdate(api: Living<ApiUser>, opts: { zone: Zone, locale: string }) {
+		const wasModified = this.isModified();
+		this.serverUpdatedAt = DateTime.fromISO(api.updatedAt, opts);
+		this.serverDeleted = false;
+		this.serverName = api.name;
+		this.serverType = api.type;
+		if (!wasModified || !this.isModified()) {
+			this.discard();
+		}
+	}
+
+	toApi(): ApiUser {
+		return {
+			id: this.id,
+			updatedAt: toIso(this.updatedAt),
+			name: this.name,
+			type: this.type,
+		};
+	}
+}