function buildActiveDelegationWhere(now, delegateEmployeeId, allowedScopes) {
  return {
    delegate_employee_id: delegateEmployeeId,
    scope: { in: allowedScopes },
    revoked_at: null,
    valid_from: { lte: now },
    OR: [{ valid_to: null }, { valid_to: { gt: now } }],
  };
}

async function findActiveDelegationForDelegate(
  tx,
  { principalEmployeeId, delegateEmployeeId, allowedScopes = ["all"], now = new Date() },
) {
  return tx.delegationGrant.findFirst({
    where: {
      principal_employee_id: principalEmployeeId,
      ...buildActiveDelegationWhere(now, delegateEmployeeId, allowedScopes),
    },
    orderBy: { valid_from: "desc" },
    select: {
      id: true,
      principal_employee_id: true,
      delegate_employee_id: true,
      scope: true,
      valid_from: true,
      valid_to: true,
    },
  });
}

async function listActiveDelegationPrincipals(
  tx,
  { delegateEmployeeId, allowedScopes = ["all"], now = new Date() },
) {
  const delegations = await tx.delegationGrant.findMany({
    where: buildActiveDelegationWhere(now, delegateEmployeeId, allowedScopes),
    select: {
      principal_employee_id: true,
    },
  });

  return Array.from(new Set(delegations.map((item) => item.principal_employee_id)));
}

function computeDelegationStatus(delegation, now = new Date()) {
  if (delegation.revoked_at) {
    return "revoked";
  }

  if (delegation.valid_to && delegation.valid_to <= now) {
    return "expired";
  }

  if (delegation.valid_from > now) {
    return "scheduled";
  }

  return "active";
}

module.exports = {
  findActiveDelegationForDelegate,
  listActiveDelegationPrincipals,
  computeDelegationStatus,
};