import {
  ok,
  type ReadonlyDB,
  type PaginationInput,
  buildPaginatedResult,
  DEFAULT_PAGE_SIZE,
} from "@tailor-platform/erp-kit/core";
import type { DB } from "../generated/kysely-tailordb";

export interface ListPositionsByDepartmentInput extends PaginationInput {
  departmentId: string;
}

/**
 * Function: listPositionsByDepartment
 * Returns the paginated list of Positions belonging to a given organization
 * Department, including both filled and vacant/TBH Positions. Only current
 * (today-effective) Position generations are returned.
 */
export async function run(db: ReadonlyDB<DB>, input: ListPositionsByDepartmentInput) {
  const limit = input.limit ?? DEFAULT_PAGE_SIZE;
  const offset = input.offset ?? 0;
  const orderBy = input.orderBy ?? "id";
  const orderDirection = input.orderDirection ?? "asc";

  const now = new Date();
  const positions = await db
    .selectFrom("Position")
    .selectAll()
    .where("departmentId", "=", input.departmentId)
    // Today-effective = the generation whose window contains now. A scheduled future change closes
    // the current generation (effectiveEnd set) and opens a future one (effectiveStart > now), so an
    // "effectiveEnd IS NULL" test would surface the future generation and drop today's (M02).
    .where("effectiveStart", "<=", now)
    .where((eb) => eb.or([eb("effectiveEnd", "is", null), eb("effectiveEnd", ">=", now)]))
    .orderBy(orderBy, orderDirection)
    .limit(limit + 1)
    .offset(offset)
    .execute();

  return ok(buildPaginatedResult(positions, limit));
}