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

function parseUserIdSet(raw) {
  return new Set(
    String(raw ?? '')
      .split(/[,;\s]+/)
      .map((item) => item.trim())
      .filter(Boolean),
  );
}

function boundedNumber(value, fallback, { min = 0, max = Number.MAX_SAFE_INTEGER } = {}) {
  const parsed = Number(value);
  if (!Number.isFinite(parsed)) return fallback;
  return Math.min(max, Math.max(min, parsed));
}

export function resolveDirectEscalationContextPolicy(env = process.env) {
  return {
    enabled: envFlag(env?.MEMIND_DIRECT_ESCALATION_CONTEXT_ENABLED, false),
    canaryUserIds: parseUserIdSet(env?.MEMIND_DIRECT_ESCALATION_CONTEXT_CANARY_USER_IDS),
  };
}

export function isDirectEscalationContextEnabledForUser(userId, policy) {
  if (!policy?.enabled) return false;
  if (!policy.canaryUserIds?.size) return true;
  return policy.canaryUserIds.has(String(userId ?? '').trim());
}

export function resolveChatSessionDeferPolicy(env = process.env) {
  return {
    enabled: envFlag(env?.MEMIND_CHAT_ROUTER_CHAT_SESSION_DEFER_ENABLED, false),
    canaryUserIds: parseUserIdSet(env?.MEMIND_CHAT_ROUTER_CHAT_SESSION_DEFER_CANARY_USER_IDS),
    minTextLength: Math.round(boundedNumber(
      env?.MEMIND_CHAT_ROUTER_CHAT_SESSION_DEFER_MIN_TEXT_LENGTH,
      12,
      { min: 4, max: 200 },
    )),
  };
}

export function isChatSessionDeferEnabledForUser(userId, policy) {
  if (!policy?.enabled) return false;
  if (!policy.canaryUserIds?.size) return true;
  return policy.canaryUserIds.has(String(userId ?? '').trim());
}

export function shouldDeferChatSessionRoutingToLlm({
  enabled = false,
  text = '',
  minTextLength = 12,
  isExplicitDirectChatOnlyText = () => false,
} = {}) {
  if (!enabled) return false;
  const normalized = String(text ?? '').trim();
  if (!normalized || isExplicitDirectChatOnlyText(normalized)) return false;
  return normalized.length >= Math.max(1, Number(minTextLength) || 12);
}