/*
	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";
import { ClientEntity } from "~/utils/client-entity";

export interface EntityClass<Api extends ApiEntity, Ent extends ClientEntity<Api>> {
	fromApi(api: Api, opts: { zone: Zone, locale: string }): Ent,
}

export class ClientMap<
	Ent extends ClientEntity<Api>,
	Api extends ApiEntity = Ent extends ClientEntity<infer Api> ? Api : never
> {
	constructor(
		public EntityClass: EntityClass<Api, Ent>,
		public map: Map<Id, Ent>,
		public tombstones: Map<Id, number>,
	) {
	}

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

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

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

	get size() {
		return this.map.size;
	}

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

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

	discard() {
		for (const id of this.keys()) {
			this.discardId(id);
		}
	}

	discardId(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<Api extends ApiEntity, Ent extends ClientEntity<Api>>(
		EntityClass: EntityClass<Api, Ent>,
		entities: (Api | ApiTombstone)[],
		opts: { zone: Zone, locale: string },
	) {
		const living = entities.filter(entity => !entity.deleted);
		const tombstones = entities.filter(entity => entity.deleted === true);
		return new this(
			EntityClass,
			idMap(living.map(apiEntity => EntityClass.fromApi(apiEntity, opts))),
			new Map(tombstones.map(tombstone => [tombstone.id, Date.parse(tombstone.updatedAt)])),
		);
	}

	apiUpdate(entities: (Api | ApiTombstone)[], opts: { zone: Zone, locale: string }) {
		const living = entities.filter(entity => !entity.deleted);
		const tombstones = entities.filter(entity => entity.deleted === true);
		for (const entity of living) {
			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): (Api | ApiTombstone)[] {
		if (!diff) {
			return [
				...[...this.map.values()].map(entity => entity.toApi()),
				...[...this.tombstones].map(([id, updatedMs]) => ({
					id,
					updatedAt: new Date(updatedMs).toISOString(),
					deleted: true as const,
				})),
			];
		}

		return [
			...[...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,
				}))
			,
		];
	}
}