support multiple concurrent negentropy trees

src/NegentropyFilterCache.h

@@ -0,0 +1,59 @@
+#pragma once
+
+#include <string>
+
+#include <negentropy/storage/BTreeLMDB.h>
+
+#include "golpe.h"
+
+#include "filters.h"
+#include "PackedEvent.h"
+
+
+struct NegentropyFilterCache {
+    struct FilterInfo {
+        NostrFilter f;
+        uint64_t treeId;
+    };
+
+    std::vector<FilterInfo> filters;
+    uint64_t modificationCounter = 0;
+
+    void ctx(lmdb::txn &txn, const std::function<void(const std::function<void(const PackedEventView &, bool)> &)> &cb) {
+        freshenCache(txn);
+
+        std::vector<std::unique_ptr<negentropy::storage::BTreeLMDB>> storages(filters.size());
+
+        cb([&](const PackedEventView &ev, bool insert){
+            for (size_t i = 0; i < filters.size(); i++) {
+                const auto &filter = filters[i];
+
+                if (!filter.f.doesMatch(ev)) continue;
+
+                if (!storages[i]) storages[i] = std::make_unique<negentropy::storage::BTreeLMDB>(txn, negentropyDbi, filter.treeId);
+
+                if (insert) storages[i]->insert(ev.created_at(), ev.id());
+                else storages[i]->erase(ev.created_at(), ev.id());
+            }
+        });
+    }
+
+  private:
+    void freshenCache(lmdb::txn &txn) {
+        uint64_t curr = env.lookup_Meta(txn, 1)->negentropyModificationCounter();
+
+        if (curr != modificationCounter) {
+            filters.clear();
+
+            env.foreach_NegentropyFilter(txn, [&](auto &f){
+                filters.emplace_back(
+                    NostrFilter(tao::json::from_string(f.filter()), MAX_U64),
+                    f.primaryKeyId
+                );
+                return true;
+            });
+
+            modificationCounter = curr;
+        }
+    }
+};