import type { ExpressionBuilder, ExpressionWrapper, SqlBool } from "kysely";
import type { Version, LixDatabaseSchema } from "../database/schema.js";

/**
 * Returns the difference between two versions for the version_change table.
 *
 * The difference is the set of changes that exist in version `a` but not in version `b`.
 * Modeled after https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/difference
 *
 * @example
 *   ```ts
 *   await lix.db.selectFrom("version_change")
 *     .where(versionChangeInDifference(a: versionA, b: versionB))
 *     .selectAll()
 *     .execute();
 *   ```
 */
export function versionChangeInDifference(
	a: Pick<Version, "id">,
	b: Pick<Version, "id">
) {
	return (
		eb: ExpressionBuilder<LixDatabaseSchema, "version_change">
	): ExpressionWrapper<LixDatabaseSchema, "version_change", SqlBool> =>
		eb("version_change.change_id", "in", (subquery) =>
			subquery
				.selectFrom("version_change as A")
				.leftJoin("version_change as B", (join) =>
					join
						.onRef("A.change_id", "=", "B.change_id")
						.on("B.version_id", "=", b.id)
				)
				.where("A.version_id", "=", a.id)
				.where("B.change_id", "is", null)
				.select("A.change_id")
		);
}