function envFlag(value, fallback = false) {
  const raw = String(value ?? '').trim().toLowerCase();
  if (!raw) return fallback;
  return ['1', 'true', 'yes', 'on'].includes(raw);
}

export function isSessionBrokerMetricsEnabled(env = process.env) {
  return envFlag(env.MEMIND_SESSION_BROKER_METRICS, false);
}

export function formatSessionBrokerMetric(metric, fields = {}) {
  return `[session_broker.${metric}] ${JSON.stringify({
    metric: `session_broker.${metric}`,
    ...fields,
  })}`;
}

export function createSessionBrokerMetrics({
  logger = console,
  enabled = isSessionBrokerMetricsEnabled(),
} = {}) {
  function emit(metric, fields = {}) {
    if (!enabled) return;
    const line = formatSessionBrokerMetric(metric, fields);
    if (typeof logger.info === 'function') logger.info(line);
    else logger.log(line);
  }

  return {
    enabled,
    ownershipDenied(fields) {
      emit('ownership.denied', fields);
    },
    registerDuplicate(fields) {
      emit('register.duplicate', fields);
    },
    resolveTargetMiss(fields) {
      emit('resolve_target.miss', fields);
    },
  };
}