// the map is: invalidated id -> invalidators

static DependentCache<MultiMap<GlobalID>> ai_invalidatedWebs_cache = new DependentCache(f ai_invalidatedWebs_calc, f cachedNodeIndex /*_changeCount*/);

static Set<GlobalID> ai_invalidatedWebs() {

  ret keys(ai_invalidatedWebs_cache!);

}

static MultiMap<GlobalID> ai_invalidatedWebs_calc() {

  //print("ai_invalidatedWebs_calc");

  ai_onNewOrRemovedWeb(f ai_invalidatedWebs_onNewWeb, f ai_invalidatedWebs_onRemovedWeb);

  ai_invalidatedWebs_cache.set(new MultiMap);

  // old method

  //Collection<Web> webs = allWebsFromCachedNodeIndex_uncached();

  //print("Have " + nWebs(webs));

  //for (Web web : webs)

  //  ai_invalidatedWebs_onNewWeb(web);

  // new method

  new Matches m;

  for (WebNode n : indexedNodes_withInvalids("invalid"))

    for (WebRelation r : web_backwardRelations(n))

      if (web_hasLabelIC(r, "is")

        && web_match("Web *", r.a, m) && isGlobalID($1))

        ai_invalidatedWebs_cache->put(asGlobalID($1), r.web.globalIDObj());

  print("ai_invalidatedWebs calc done with " + n2(ai_invalidatedWebs_cache->keysSize(), "invalidated web", "invalidated webs"));

  ret ai_invalidatedWebs_cache!;

}

svoid ai_invalidatedWebs_onNewWeb(Web web) {

  if (web.unverified) ret;

  lock ai_invalidatedWebs_cache.lock;

  new Matches m;

  for (WebNode n : web_search_dollarX(webFromTriple("$X", "is", "invalid"), web))

    if (web_match("Web *", n, m) && isGlobalID($1))

      ai_invalidatedWebs_cache->put(asGlobalID($1), web.globalIDObj());

}

svoid ai_invalidatedWebs_onRemovedWeb(Web web) {

  if (web.unverified) ret;

  lock ai_invalidatedWebs_cache.lock;

  new Matches m;

  for (WebNode n : web_search_dollarX(webFromTriple("$X", "is", "invalid"), web))

    if (web_match("Web *", n, m) && isGlobalID($1))

      ai_invalidatedWebs_cache->remove(asGlobalID($1), web.globalIDObj());

}

svoid ai_invalidatedWebs_cache_put(GlobalID a, GlobalID b) {

  ai_invalidatedWebs_cache->put(a, b);

}