import { err, ok, type ReadonlyDB } from "@tailor-platform/erp-kit/core";
import type { DB } from "../generated/kysely-tailordb";
import { ValidationErrorError } from "../lib/errors.generated";

export interface GetCompanyHolidayByDateInput {
  calendarId: string;
  holidayDate: Date;
}

/**
 * Function: getCompanyHolidayByDate
 * Description: Resolves the holiday fact for a specific calendar date within a
 * given HolidayCalendar, by the stable business key (calendarId, holidayDate).
 * Returns null (not an error) when the date is not registered as a holiday in
 * that calendar — an ordinary working day. This is the lookup calculation uses
 * to determine holiday classification/premium, and scheduling uses to determine
 * scheduled working-day status.
 */
export async function run(db: ReadonlyDB<DB>, input: GetCompanyHolidayByDateInput) {
  if (!input.holidayDate || Number.isNaN(input.holidayDate.getTime())) {
    return err(new ValidationErrorError("holidayDate"));
  }

  const companyHoliday = await db
    .selectFrom("CompanyHoliday")
    .selectAll()
    .where("calendarId", "=", input.calendarId)
    .where("holidayDate", "=", input.holidayDate)
    .executeTakeFirst();

  return ok({ companyHoliday: companyHoliday ?? null });
}