Implements seeking to saved position for tracks

lua/browser.lua

@@ -105,8 +105,10 @@ return screen:new{
                         local track = database.track_by_id(contents)
                         if (track) then
                             print("Track saved position: ", track.saved_position)
+                            queue.play_from(track.filepath, track.saved_position)
+                        else 
+                            queue.add(contents)
                         end
-                        queue.add(contents)
                         playback.playing:set(true)
                         backstack.push(playing:new())
                     end

src/tangara/audio/audio_events.hpp

@@ -106,6 +106,8 @@ struct QueueUpdate : tinyfsm::Event {
     kBulkLoadingUpdate,
   };
   Reason reason;
+
+  std::optional<uint32_t> seek_to_second;
 };
 
 struct StepUpVolume : tinyfsm::Event {};

src/tangara/audio/audio_fsm.cpp

@@ -113,7 +113,7 @@ auto AudioState::emitPlaybackUpdate(bool paused) -> void {
 void AudioState::react(const QueueUpdate& ev) {
   SetTrack cmd{
       .new_track = std::monostate{},
-      .seek_to_second = {},
+      .seek_to_second = ev.seek_to_second,
   };
 
   auto current = sServices->track_queue().current();

src/tangara/audio/track_queue.cpp

@@ -85,6 +85,16 @@ auto notifyChanged(bool current_changed, Reason reason) -> void {
   events::Audio().Dispatch(ev);
 }
 
+auto notifyPlayFrom(uint32_t start_from_position) -> void {
+  QueueUpdate ev{
+      .current_changed = true,
+      .reason = Reason::kExplicitUpdate,
+      .seek_to_second = start_from_position,
+  };
+  events::Ui().Dispatch(ev);
+  events::Audio().Dispatch(ev);
+}
+
 TrackQueue::TrackQueue(tasks::WorkerPool& bg_worker, database::Handle db)
     : mutex_(),
       bg_worker_(bg_worker),
@@ -109,6 +119,17 @@ auto TrackQueue::current() const -> TrackItem {
   return val;
 }
 
+auto TrackQueue::playFromPosition(const std::string& filepath,
+                                  uint32_t position) -> void {
+  clear();
+  {
+    const std::unique_lock<std::shared_mutex> lock(mutex_);
+    playlist_.append(filepath);
+    updateShuffler(true);
+  }
+  notifyPlayFrom(position);
+}
+
 auto TrackQueue::currentPosition() const -> size_t {
   const std::shared_lock<std::shared_mutex> lock(mutex_);
   return position_;
@@ -245,7 +266,7 @@ auto TrackQueue::currentPosition(size_t position) -> bool {
     goTo(position);
   }
 
-  // If we're explicitly setting the position, we want to treat it as though 
+  // If we're explicitly setting the position, we want to treat it as though
   // the current track has changed, even if the position was the same
   notifyChanged(true, Reason::kExplicitUpdate);
   return true;

src/tangara/audio/track_queue.hpp

@@ -78,6 +78,7 @@ class TrackQueue {
   auto open() -> bool;
   auto openPlaylist(const std::string& playlist_file, bool notify = true)
       -> bool;
+  auto playFromPosition(const std::string& filepath, uint32_t position) -> void;
 
   using Item =
       std::variant<database::TrackId, database::TrackIterator, std::string>;

src/tangara/lua/lua_queue.cpp

@@ -79,10 +79,24 @@ static auto queue_open_playlist(lua_State* state) -> int {
   return 0;
 }
 
+static auto queue_play_from(lua_State* state) -> int {
+  Bridge* instance = Bridge::Get(state);
+  audio::TrackQueue& queue = instance->services().track_queue();
+  size_t len = 0;
+  const char* str = luaL_checklstring(state, 1, &len);
+  if (!str) {
+    return 0;
+  }
+  auto pos = luaL_checkinteger(state, 2);
+  queue.playFromPosition(str, pos);
+  return 0;
+}
+
 static const struct luaL_Reg kQueueFuncs[] = {
     {"add", queue_add},
     {"clear", queue_clear},
     {"open_playlist", queue_open_playlist},
+    {"play_from", queue_play_from},
     {NULL, NULL}};
 
 static auto lua_queue(lua_State* state) -> int {