Closes #24

core/decode_database.cpp

@@ -2,6 +2,7 @@
 // Copyright (c) 2026 Dim Himro
 
 #include "decode_database.h"
+#include "j1939.h"
 #include "signal_layout.h"
 #include <bitset>
 #include <cmath>
@@ -55,6 +56,9 @@ namespace {
         if (frame.canId > maximumId)
             throw std::invalid_argument("Invalid normalized CAN ID: " + std::to_string(frame.canId));
 
+        if (frame.hasPgn && (!frame.isExtended || frame.pgn != ExtractJ1939Pgn(frame.canId)))
+            throw std::invalid_argument("Invalid J1939 PGN metadata: " + frame.name);
+
         std::unordered_set<std::string> names;
         const DecodeSignal *selector = nullptr;
         for (const DecodeSignal &signal: frame.signals) {
@@ -99,6 +103,8 @@ DecodeDatabase::Storage::Storage(const std::vector<DecodeFrame> &definitions)
     frameIndexByKey.reserve(frames.size());
     for (std::size_t index = 0U; index < frames.size(); ++index) {
         frameIndexByKey.emplace(frames[index].GetKey(), index);
+        if (frames[index].hasPgn)
+            frameIndicesByPgn[frames[index].pgn].push_back(index);
     }
 }
 
@@ -121,6 +127,22 @@ std::shared_ptr<const DecodeFrame> DecodeDatabase::FindFrame(const FrameKey &key
     return std::shared_ptr<const DecodeFrame>(storage, &storage->frames[it->second]);
 }
 
+PgnLookupResult DecodeDatabase::FindFrameByPgn(std::uint32_t pgn) const {
+    PgnLookupResult result;
+    if (!storage)
+        return result;
+    const std::unordered_map<std::uint32_t, std::vector<std::size_t>>::const_iterator it =
+            storage->frameIndicesByPgn.find(pgn);
+    if (it == storage->frameIndicesByPgn.end())
+        return result;
+    if (it->second.size() != 1U) {
+        result.ambiguous = true;
+        return result;
+    }
+    result.definition = std::shared_ptr<const DecodeFrame>(storage, &storage->frames[it->second[0]]);
+    return result;
+}
+
 std::shared_ptr<const DecodeSignal> DecodeDatabase::FindSignal(const SignalKey &key) const {
     const std::shared_ptr<const DecodeFrame> frame = FindFrame(key.frame);
     if (!frame)