import { type Entity, type EntityLiving, type Id, type Living } from "~/shared/types/common";
import { DateTime, Zone } from "~/shared/utils/luxon";
import { ClientEntityNew } from "~/utils/client-user";

export interface ApiMap<T extends Entity> {
	type: string,
	entities: T[]
}

interface EntityClass<T extends ClientEntityNew> {
	name: string,
	type: string,
	fromApi(api: EntityLiving, opts: { zone: Zone, locale: string }): T,
}


export class ClientMap<T extends ClientEntityNew> {
	static typeMap: Record<string, EntityClass<ClientEntityNew>> = {
		user: ClientUser,
	};

	constructor(
		public EntityClass: EntityClass<T>,
		public map: Map<Id, T>,
		public tombstones: Map<Id, number>,
	) {
	}

	get(id: Id) {
		return this.map.get(id);
	}

	values() {
		return this.map.values();
	}

	isModified() {
		return [...this.map.values()].some(entity => entity.isModified());
	}

	add(entity: T) {
		if (this.map.has(entity.id)) {
			throw new Error("ClientMap.add: Entity already exists");
		}
		this.map.set(entity.id, entity);
	}

	discard(id: Id) {
		const entity = this.map.get(id);
		if (!entity) {
			throw new Error("ClientMap.discard: entity does not exist.");
		}
		if (
			this.tombstones.has(id)
			|| entity.isNew()
		) {
			this.map.delete(id);
		} else {
			entity.discard();
		}
	}

	static fromApi<T extends Entity>(
		api: ApiMap<T>,
		opts: { zone: Zone, locale: string },
	) {
		const EntityClass = this.typeMap[api.type];
		const entities = api.entities.filter(entity => !entity.deleted) as Living<T>[];
		const tombstones = api.entities.filter(entity => entity.deleted === true);
		return new this(
			EntityClass,
			idMap(entities.map(apiEntity => EntityClass.fromApi(apiEntity, opts))),
			new Map(tombstones.map(tombstone => [tombstone.id, Date.parse(tombstone.updatedAt)])),
		);
	}

	apiUpdate(api: ApiMap<Entity>, opts: { zone: Zone, locale: string }) {
		if (api.type !== this.EntityClass.type) {
			throw new Error(`ClientMap: Map of ${this.EntityClass.name} received update for ${api.type}.`);
		}
		const entities = api.entities.filter(entity => !entity.deleted);
		const tombstones = api.entities.filter(entity => entity.deleted === true);
		for (const entity of entities) {
			const tombstoneMs = this.tombstones.get(entity.id);
			const updatedMs = Date.parse(entity.updatedAt);
			if (tombstoneMs !== undefined) {
				if (tombstoneMs > updatedMs) {
					continue;
				}
				this.tombstones.delete(entity.id);
			}

			const stored = this.map.get(entity.id);
			if (stored) {
				if (stored.updatedAt.toMillis() > updatedMs) {
					continue;
				}
				stored.apiUpdate(entity, opts);
			} else {
				this.map.set(entity.id, this.EntityClass.fromApi(entity, opts))
			}
		}
		for (const tombstone of tombstones) {
			const updatedMs = Date.parse(tombstone.updatedAt);
			const tombstoneMs = this.tombstones.get(tombstone.id);
			const stored = this.map.get(tombstone.id);
			if (
				stored && stored.serverUpdatedAt.toMillis() > updatedMs
				|| tombstoneMs && tombstoneMs > updatedMs
			) {
				continue;
			}
			this.tombstones.set(tombstone.id, updatedMs);
			if (stored && stored.isModified() && !stored.deleted) {
				stored.serverUpdatedAt = DateTime.fromISO(tombstone.updatedAt, opts);
				stored.serverDeleted = true;
			} else if (stored) {
				this.map.delete(tombstone.id);
			}
		}
	}

	toApi(diff: boolean): ApiMap<Entity> {
		if (!diff) {
			return {
				type: this.EntityClass.type,
				entities: [
					...[...this.map.values()].map(entity => entity.toApi()),
					...[...this.tombstones].map(([id, updatedMs]) => ({
						id,
						updatedAt: new Date(updatedMs).toISOString(),
						deleted: true as const,
					}))
				],
			};
		}

		return {
			type: this.EntityClass.type,
			entities: [
				...[...this.map.values()]
					.filter(entity => entity.isModified() && !entity.deleted)
					.map(entity => entity.toApi())
				,
				...[...this.map.values()]
					.filter(entity => entity.deleted)
					.map(entity => ({
						id: entity.id,
						updatedAt: toIso(entity.updatedAt),
						deleted: true as const,
					}))
				,
			],
		};
	}
}