import { err, ok, type CommandContext } from "@tailor-platform/erp-kit/core";
import type { Transaction } from "../generated/kysely-tailordb";
import { ShiftPatternInUseError, ShiftPatternNotFoundError } from "../lib/errors.generated";

export interface DeleteShiftPatternInput {
  shiftPatternId: string;
}

/**
 * Function: deleteShiftPattern
 * Description: Removes a ShiftPattern that is no longer offered by planners.
 * Deletion is rejected while any Shift still references the pattern via
 * shiftPatternId, preserving the historical link between a Shift and its
 * originating template. The pattern's segments are embedded on the pattern
 * row (ADR-022), so they are removed together with it.
 */
export async function run(db: Transaction, input: DeleteShiftPatternInput, _ctx: CommandContext) {
  const shiftPattern = await db
    .selectFrom("ShiftPattern")
    .selectAll()
    .where("id", "=", input.shiftPatternId)
    .forUpdate()
    .executeTakeFirst();

  if (!shiftPattern) {
    return err(new ShiftPatternNotFoundError(input.shiftPatternId));
  }

  const referencingShift = await db
    .selectFrom("Shift")
    .select("id")
    .where("shiftPatternId", "=", input.shiftPatternId)
    .executeTakeFirst();

  if (referencingShift) {
    return err(new ShiftPatternInUseError(input.shiftPatternId));
  }

  await db.deleteFrom("ShiftPattern").where("id", "=", input.shiftPatternId).execute();

  return ok({});
}