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

function todayUtcMidnight(): Date {
  const now = new Date();
  return new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate()));
}

export interface ExpireLeaveGrantsInput {
  /** Calendar date the sweep runs as-of; defaults to today (UTC) when omitted. Exposed for testability. */
  asOf?: Date;
}

export async function run(db: Transaction, input: ExpireLeaveGrantsInput, _ctx: CommandContext) {
  const asOf = input.asOf ?? todayUtcMidnight();
  const now = new Date();

  const candidates = await db
    .selectFrom("LeaveGrant")
    .selectAll()
    .where("expirationDate", "<", asOf)
    .where("remainingDays", ">", "0")
    .where("expiredAt", "is", null)
    .forUpdate()
    .execute();

  let expired = 0;
  let failed = 0;

  for (const grant of candidates) {
    try {
      await db
        .updateTable("LeaveGrant")
        .set({ remainingDays: "0", expiredAt: now })
        .where("id", "=", grant.id)
        .execute();
      expired++;
    } catch {
      // Individual failures are retried on the next run without blocking other grants
      // (EXPIRATION_SWEEP_PARTIAL_FAILURE — batch job; no user-facing error scenario).
      failed++;
    }
  }

  return ok({ expired, failed });
}