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

export interface DeleteEligibilityRuleInput {
  id: string;
}

export async function run(
  db: Transaction,
  input: DeleteEligibilityRuleInput,
  _ctx: CommandContext,
) {
  const eligibilityRule = await db
    .selectFrom("EligibilityRule")
    .selectAll()
    .where("id", "=", input.id)
    .forUpdate()
    .executeTakeFirst();
  if (!eligibilityRule) {
    return err(new EligibilityRuleNotFoundError(input.id));
  }

  // A WORK_RULE grant may be the eligibility basis a current WorkRuleAssignment relies on
  // (assignWorkRule requires an in-force grant for the target). If a current assignment binds this
  // rule's (targetType, targetId, workRuleId) and no OTHER in-force grant covers the same
  // combination, deleting this generation would strand that assignment — reject it (SOLE_GRANT_IN_USE).
  if (eligibilityRule.grantType === "WORK_RULE" && eligibilityRule.workRuleId != null) {
    const dependentAssignment = await db
      .selectFrom("WorkRuleAssignment")
      .select("id")
      .where("targetType", "=", eligibilityRule.targetType)
      .where("targetId", "=", eligibilityRule.targetId)
      .where("workRuleId", "=", eligibilityRule.workRuleId)
      .where("effectiveEnd", "is", null)
      .executeTakeFirst();
    if (dependentAssignment) {
      const otherGrant = await db
        .selectFrom("EligibilityRule")
        .select("id")
        .where("id", "!=", input.id)
        .where("grantType", "=", "WORK_RULE")
        .where("targetType", "=", eligibilityRule.targetType)
        .where("targetId", "=", eligibilityRule.targetId)
        .where("workRuleId", "=", eligibilityRule.workRuleId)
        .where("effectiveEnd", "is", null)
        .executeTakeFirst();
      if (!otherGrant) {
        return err(new SoleGrantInUseError(input.id));
      }
    }
  }

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

  return ok({ eligibilityRule });
}