Implemented Subsonic command getNowPlaying, fixes #792

src/libs/services/scrobbling/impl/ScrobblingService.cpp

@@ -77,6 +77,8 @@ namespace lms::scrobbling
 
     void ScrobblingService::listenStarted(const Listen& listen)
     {
+        insertNowPlayingEntry(listen);
+
         if (std::optional<ScrobblingBackend> backend{ getUserBackend(listen.userId) })
             _scrobblingBackends[*backend]->listenStarted(listen);
     }
@@ -93,6 +95,24 @@ namespace lms::scrobbling
             _scrobblingBackends[*backend]->addTimedListen(listen);
     }
 
+    void ScrobblingService::visitNowPlayingListens(const std::function<void(Clock::time_point startedAt, const Listen&)>& visitor, db::UserId userId)
+    {
+        const Clock::time_point now{ Clock::now() };
+
+        std::shared_lock lock{ _nowPlayingEntriesMutex };
+
+        for (const auto& [entryUserId, entry] : _nowPlayingEntries)
+        {
+            if (userId.isValid() && entryUserId != userId)
+                continue;
+
+            if (entry.expiryAt <= now)
+                continue;
+
+            visitor(entry.startedAt, Listen{ .userId = entryUserId, .trackId = entry.trackId });
+        }
+    }
+
     std::optional<ScrobblingBackend> ScrobblingService::getUserBackend(UserId userId)
     {
         std::optional<ScrobblingBackend> backend;
@@ -253,4 +273,20 @@ namespace lms::scrobbling
         res = db::Listen::getTopTracks(session, listenFindParams);
         return res;
     }
+
+    void ScrobblingService::insertNowPlayingEntry(const Listen& listen)
+    {
+        Session& session{ _db.getTLSSession() };
+        auto transaction{ session.createReadTransaction() };
+
+        if (const db::Track::pointer track{ db::Track::find(session, listen.trackId) })
+        {
+            const Clock::time_point now{ Clock::now() };
+
+            std::unique_lock lock{ _nowPlayingEntriesMutex };
+
+            // Add an extra delay to ensure the listen is not purged too early
+            _nowPlayingEntries.insert_or_assign(listen.userId, NowPlayingEntry{ .startedAt = now, .expiryAt = now + track->getDuration() + std::chrono::seconds{ 5 }, .trackId = listen.trackId });
+        }
+    }
 } // namespace lms::scrobbling

src/libs/services/scrobbling/impl/ScrobblingService.hpp

@@ -21,6 +21,7 @@
 
 #include <memory>
 #include <optional>
+#include <shared_mutex>
 #include <unordered_map>
 
 #include "services/scrobbling/IScrobblingService.hpp"
@@ -33,12 +34,16 @@ namespace lms::scrobbling
     {
     public:
         ScrobblingService(boost::asio::io_context& ioContext, db::IDb& db);
-        ~ScrobblingService();
+        ~ScrobblingService() override;
+
+        ScrobblingService(const ScrobblingService&) = delete;
+        ScrobblingService& operator=(const ScrobblingService&) = delete;
 
     private:
         void listenStarted(const Listen& listen) override;
         void listenFinished(const Listen& listen, std::optional<std::chrono::seconds> duration) override;
         void addTimedListen(const TimedListen& listen) override;
+        void visitNowPlayingListens(const std::function<void(Clock::time_point startedAt, const Listen&)>& visitor, db::UserId userId) override;
 
         ArtistContainer getRecentArtists(const ArtistFindParameters& params) override;
         ReleaseContainer getRecentReleases(const FindParameters& params) override;
@@ -56,8 +61,18 @@ namespace lms::scrobbling
 
         std::optional<db::ScrobblingBackend> getUserBackend(db::UserId userId);
 
+        void insertNowPlayingEntry(const Listen& listen);
+
         db::IDb& _db;
         std::unordered_map<db::ScrobblingBackend, std::unique_ptr<IScrobblingBackend>> _scrobblingBackends;
-    };
 
+        std::shared_mutex _nowPlayingEntriesMutex;
+        struct NowPlayingEntry
+        {
+            Clock::time_point startedAt;
+            Clock::time_point expiryAt;
+            db::TrackId trackId;
+        };
+        std::unordered_map<db::UserId, NowPlayingEntry> _nowPlayingEntries;
+    };
 } // namespace lms::scrobbling

src/libs/services/scrobbling/include/services/scrobbling/IScrobblingService.hpp

@@ -32,6 +32,7 @@
 #include "database/objects/ReleaseId.hpp"
 #include "database/objects/TrackId.hpp"
 #include "database/objects/Types.hpp"
+#include "database/objects/UserId.hpp"
 #include "services/scrobbling/Listen.hpp"
 
 namespace lms::db
@@ -46,12 +47,22 @@ namespace lms::scrobbling
     public:
         virtual ~IScrobblingService() = default;
 
+        using Clock = std::chrono::steady_clock;
+
         // Scrobbling
+
+        // Notify that a listen has started (for now-playing purposes)
         virtual void listenStarted(const Listen& listen) = 0;
+
+        // Notify that a listen has finished (for scrobbling purposes)
         virtual void listenFinished(const Listen& listen, std::optional<std::chrono::seconds> playedDuration = std::nullopt) = 0;
 
+        // Used to add listens afterwards (after some offline listening for example)
         virtual void addTimedListen(const TimedListen& listen) = 0;
 
+        // Visit all now-playing listens
+        virtual void visitNowPlayingListens(const std::function<void(Clock::time_point startedAt, const Listen&)>& visitor, db::UserId userId = {}) = 0;
+
         // Stats
         using ArtistContainer = db::RangeResults<db::ArtistId>;
         using ReleaseContainer = db::RangeResults<db::ReleaseId>;