sclass GazelleContextCache_v2 extends F0<GazelleEvalContext> {
  transient Lock lock = lock();
  transient GazelleEvalContext cachedCtx;
  DynModule module;
  bool debug = true;
  F0<L<T3<S>>> grabRules = func -> L<T3<S>> {
    //dm_gazelle_allRulesWithComment(gazelle_requiredComment())
    gazelle_allRuleTriples()
  };
  S mechListPrefix;
  bool alwaysFullRefresh; // safer
  // TODO: add or remove if condition changes on rule

  *() {}  
  *(DynModule *module) {}
  
  GazelleContextCache_v2 fill() {
    loadRules(callF(grabRules));
    this;
  }
  
  void loadRules(L<T3S> rules) {
    lock lock;
    cachedCtx = dm_gazelle_stdEvalContext(rules);
    cachedCtx.mechListPrefix = unnull(mechListPrefix);
    gazelle_addHelpers(cachedCtx);
  }
  
  GazelleEvalContext get() {
    lock lock;
    ret gazelle_cloneCtx(cachedCtx);
  }
  
  void ruleChanged(S ruleID) {
    if (ruleID == null) ret;
    dm_q(module, r {
      lock lock;
      if (alwaysFullRefresh) ret with fill();
      if (cachedCtx == null) ret;
      print("GazelleContextCache_v2: processing rule update " + ruleID);
      RuleEngine2 engine = cachedCtx.engine;
      RuleEngine2.Rule rule = engine.getRule(ruleID);
      if (rule == null) print("GazelleContextCache_v2: rule not found, assuming it's new");
      else engine.rules.remove(rule);
      PairS p = dm_textAndCommentForRule(ruleID);
      if (p == null) ret with print("GazelleContextCache_v2: no text found for rule");
      engine.addRules2(ll(t3(p.a, p.b, ruleID)));
      rule = cachedCtx.engine.getRule(ruleID);
      if (rule == null) ret with print("GazelleContextCache_v2: rule not properly added");
      gazelle_addHelpers(nu(GazelleEvalContext, engine := gazelle_dummyEngineWithRule(rule)));
      gazelle_updateStatsForRule(cachedCtx, ruleID);
      print("GazelleContextCache_v2: rule update complete");
    });
  }

  // works only when module != null
  AutoCloseable listenToMessages() {
    ret combineAutoCloseables(
      vmBus_onMessage('gazellePleaseClearRuleCaches, r {
        dm_q(module, r fill)
      }),
      vmBus_onMessage('gazelleRuleFeedbackChanged, vf<S> ruleChanged),
      vmBus_onMessage('gazelleRuleChanged, voidfunc(O ruleObj) {
        ruleChanged(getString globalID(ruleObj))
      }),
      vmBus_onMessage('gazelleRuleDeleted, voidfunc(O rule) {
        S ruleID = getString globalID(rule);
        dm_q(module, r {
          lock lock;
          if (cachedCtx == null) ret;
          cachedCtx.engine.deleteRule(ruleID);
          print("GazelleContextCache_v2: rule " + ruleID + " deleted");
        })
      }));
  }
  
  void alwaysFullRefresh() {
    set alwaysFullRefresh;
    fill();
  }
}

Began life as a copy of #1021911