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

export interface DeleteWorkRuleInput {
  id: string;
}

/**
 * Function: deleteWorkRule
 * Description: Removes a WorkRule generation, but only when no current
 * assignment references it, so an assigned worker can never lose their rule
 * unexpectedly.
 *
 * A WorkRule is "in use" — and so undeletable — when a current WorkRuleAssignment binds it to a
 * target (assignWorkRule persists these), or when an in-force EligibilityRule grants it (grantType
 * WORK_RULE). Either reference means removing the rule would strand live configuration.
 */
export async function run(db: Transaction, input: DeleteWorkRuleInput, _ctx: CommandContext) {
  const workRule = await db
    .selectFrom("WorkRule")
    .selectAll()
    .where("id", "=", input.id)
    .forUpdate()
    .executeTakeFirst();
  if (!workRule) {
    return err(new WorkRuleNotFoundError(input.id));
  }

  const referencingAssignment = await db
    .selectFrom("WorkRuleAssignment")
    .select("id")
    .where("workRuleId", "=", input.id)
    .where("effectiveEnd", "is", null)
    .executeTakeFirst();
  if (referencingAssignment) {
    return err(new WorkRuleInUseError(input.id));
  }

  const referencingGrant = await db
    .selectFrom("EligibilityRule")
    .selectAll()
    .where("grantType", "=", "WORK_RULE")
    .where("workRuleId", "=", input.id)
    .where("effectiveEnd", "is", null)
    .executeTakeFirst();
  if (referencingGrant) {
    return err(new WorkRuleInUseError(input.id));
  }

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

  return ok({});
}