Use a service locator instead of passing around subsets of drivers between FSMs

39 files changed, 471 insertions, 382 deletions

diff --git a/src/app_console/app_console.cpp b/src/app_console/app_console.cpp
index 9aff20dc..2d287e5d 100644
--- a/src/app_console/app_console.cpp
+++ b/src/app_console/app_console.cpp
@@ -31,18 +31,16 @@
 #include "freertos/FreeRTOSConfig_arch.h"
 #include "freertos/projdefs.h"
 #include "index.hpp"
+#include "service_locator.hpp"
 #include "track.hpp"
 
 namespace console {
 
-std::weak_ptr<database::Database> AppConsole::sDatabase;
-audio::TrackQueue* AppConsole::sTrackQueue;
-drivers::Bluetooth* AppConsole::sBluetooth;
-drivers::Samd* AppConsole::sSamd;
+std::shared_ptr<system_fsm::ServiceLocator> AppConsole::sServices;
 
 int CmdListDir(int argc, char** argv) {
-  auto lock = AppConsole::sDatabase.lock();
-  if (lock == nullptr) {
+  auto db = AppConsole::sServices->database().lock();
+  if (!db) {
     std::cout << "storage is not available" << std::endl;
     return 1;
   }
@@ -117,7 +115,7 @@ int CmdPlayFile(int argc, char** argv) {
 
   if (is_id) {
     database::TrackId id = std::atoi(argv[1]);
-    AppConsole::sTrackQueue->AddLast(id);
+    AppConsole::sServices->track_queue().AddLast(id);
   } else {
     std::ostringstream path;
     path << '/' << argv[1];
@@ -147,7 +145,7 @@ int CmdDbInit(int argc, char** argv) {
     return 1;
   }
 
-  auto db = AppConsole::sDatabase.lock();
+  auto db = AppConsole::sServices->database().lock();
   if (!db) {
     std::cout << "no database open" << std::endl;
     return 1;
@@ -174,7 +172,7 @@ int CmdDbTracks(int argc, char** argv) {
     return 1;
   }
 
-  auto db = AppConsole::sDatabase.lock();
+  auto db = AppConsole::sServices->database().lock();
   if (!db) {
     std::cout << "no database open" << std::endl;
     return 1;
@@ -211,7 +209,7 @@ int CmdDbIndex(int argc, char** argv) {
   vTaskDelay(1);
   static const std::string usage = "usage: db_index [id] [choices ...]";
 
-  auto db = AppConsole::sDatabase.lock();
+  auto db = AppConsole::sServices->database().lock();
   if (!db) {
     std::cout << "no database open" << std::endl;
     return 1;
@@ -252,9 +250,9 @@ int CmdDbIndex(int argc, char** argv) {
       return -1;
     }
     if (res->values().at(choice).track()) {
-      AppConsole::sTrackQueue->IncludeLast(
-          std::make_shared<playlist::IndexRecordSource>(AppConsole::sDatabase,
-                                                        res, 0, res, choice));
+      AppConsole::sServices->track_queue().IncludeLast(
+          std::make_shared<playlist::IndexRecordSource>(
+              AppConsole::sServices->database(), res, 0, res, choice));
     }
     auto cont = res->values().at(choice).Expand(20);
     if (!cont) {
@@ -296,7 +294,7 @@ int CmdDbDump(int argc, char** argv) {
     return 1;
   }
 
-  auto db = AppConsole::sDatabase.lock();
+  auto db = AppConsole::sServices->database().lock();
   if (!db) {
     std::cout << "no database open" << std::endl;
     return 1;
@@ -448,14 +446,15 @@ int CmdBtList(int argc, char** argv) {
     return 1;
   }
 
-  auto devices = AppConsole::sBluetooth->KnownDevices();
+  auto devices = AppConsole::sServices->bluetooth().KnownDevices();
   if (argc == 2) {
     int index = std::atoi(argv[1]);
     if (index < 0 || index >= devices.size()) {
       std::cout << "index out of range" << std::endl;
       return -1;
     }
-    AppConsole::sBluetooth->SetPreferredDevice(devices[index].address);
+    AppConsole::sServices->bluetooth().SetPreferredDevice(
+        devices[index].address);
   } else {
     std::cout << "mac\t\trssi\tname" << std::endl;
     for (const auto& device : devices) {
@@ -493,9 +492,9 @@ int CmdSamd(int argc, char** argv) {
   if (cmd == "flash") {
     std::cout << "resetting samd..." << std::endl;
     vTaskDelay(pdMS_TO_TICKS(5));
-    AppConsole::sSamd->ResetToFlashSamd();
+    AppConsole::sServices->samd().ResetToFlashSamd();
   } else if (cmd == "charge") {
-    auto res = AppConsole::sSamd->GetChargeStatus();
+    auto res = AppConsole::sServices->samd().GetChargeStatus();
     if (res) {
       switch (res.value()) {
         case drivers::Samd::ChargeStatus::kNoBattery:
@@ -523,7 +522,7 @@ int CmdSamd(int argc, char** argv) {
   } else if (cmd == "off") {
     std::cout << "bye !!!" << std::endl;
     vTaskDelay(pdMS_TO_TICKS(5));
-    AppConsole::sSamd->PowerDown();
+    AppConsole::sServices->samd().PowerDown();
   } else {
     std::cout << usage << std::endl;
     return 1;
diff --git a/src/app_console/include/app_console.hpp b/src/app_console/include/app_console.hpp
index 6c23552e..5981cc04 100644
--- a/src/app_console/include/app_console.hpp
+++ b/src/app_console/include/app_console.hpp
@@ -12,16 +12,14 @@
 #include "console.hpp"
 #include "database.hpp"
 #include "samd.hpp"
+#include "service_locator.hpp"
 #include "track_queue.hpp"
 
 namespace console {
 
 class AppConsole : public Console {
  public:
-  static std::weak_ptr<database::Database> sDatabase;
-  static audio::TrackQueue* sTrackQueue;
-  static drivers::Bluetooth* sBluetooth;
-  static drivers::Samd* sSamd;
+  static std::shared_ptr<system_fsm::ServiceLocator> sServices;
 
  protected:
   virtual auto RegisterExtraComponents() -> void;
diff --git a/src/audio/audio_fsm.cpp b/src/audio/audio_fsm.cpp
index 6cca8211..9121cb5a 100644
--- a/src/audio/audio_fsm.cpp
+++ b/src/audio/audio_fsm.cpp
@@ -25,6 +25,7 @@
 #include "future_fetcher.hpp"
 #include "i2s_audio_output.hpp"
 #include "i2s_dac.hpp"
+#include "service_locator.hpp"
 #include "system_events.hpp"
 #include "track.hpp"
 #include "track_queue.hpp"
@@ -33,49 +34,15 @@ namespace audio {
 
 static const char kTag[] = "audio_fsm";
 
-drivers::IGpios* AudioState::sIGpios;
-std::shared_ptr<drivers::I2SDac> AudioState::sDac;
-std::weak_ptr<database::Database> AudioState::sDatabase;
+std::shared_ptr<system_fsm::ServiceLocator> AudioState::sServices;
 
 std::shared_ptr<FatfsAudioInput> AudioState::sFileSource;
 std::unique_ptr<Decoder> AudioState::sDecoder;
 std::shared_ptr<SampleConverter> AudioState::sSampleConverter;
 std::shared_ptr<IAudioOutput> AudioState::sOutput;
 
-TrackQueue* AudioState::sTrackQueue;
 std::optional<database::TrackId> AudioState::sCurrentTrack;
 
-auto AudioState::Init(drivers::IGpios* gpio_expander,
-                      std::weak_ptr<database::Database> database,
-                      std::shared_ptr<database::ITagParser> tag_parser,
-                      drivers::Bluetooth* bluetooth,
-                      TrackQueue* queue) -> bool {
-  sIGpios = gpio_expander;
-  sTrackQueue = queue;
-
-  auto dac = drivers::I2SDac::create(gpio_expander);
-  if (!dac) {
-    return false;
-  }
-  sDac.reset(dac.value());
-  sDatabase = database;
-
-  sFileSource.reset(new FatfsAudioInput(tag_parser));
-  sOutput.reset(new I2SAudioOutput(sIGpios, sDac));
-  // sOutput.reset(new BluetoothAudioOutput(bluetooth));
-
-  sSampleConverter.reset(new SampleConverter());
-  sSampleConverter->SetOutput(sOutput);
-
-  Decoder::Start(sFileSource, sSampleConverter);
-
-  return true;
-}
-
-void AudioState::react(const system_fsm::StorageMounted& ev) {
-  sDatabase = ev.db;
-}
-
 void AudioState::react(const system_fsm::KeyUpChanged& ev) {
   if (ev.falling && sOutput->AdjustVolumeUp()) {
     ESP_LOGI(kTag, "volume up!");
@@ -100,7 +67,26 @@ void AudioState::react(const system_fsm::HasPhonesChanged& ev) {
 
 namespace states {
 
-void Uninitialised::react(const system_fsm::BootComplete&) {
+void Uninitialised::react(const system_fsm::BootComplete& ev) {
+  sServices = ev.services;
+
+  auto dac = drivers::I2SDac::create(sServices->gpios());
+  if (!dac) {
+    events::System().Dispatch(system_fsm::FatalError{});
+    events::Ui().Dispatch(system_fsm::FatalError{});
+    return;
+  }
+
+  sFileSource.reset(new FatfsAudioInput(sServices->tag_parser()));
+  sOutput.reset(new I2SAudioOutput(sServices->gpios(),
+                                   std::unique_ptr<drivers::I2SDac>{*dac}));
+  // sOutput.reset(new BluetoothAudioOutput(bluetooth));
+
+  sSampleConverter.reset(new SampleConverter());
+  sSampleConverter->SetOutput(sOutput);
+
+  Decoder::Start(sFileSource, sSampleConverter);
+
   transit<Standby>();
 }
 
@@ -117,19 +103,18 @@ void Standby::react(const internal::InputFileOpened& ev) {
 }
 
 void Standby::react(const QueueUpdate& ev) {
-  auto current_track = sTrackQueue->GetCurrent();
+  auto current_track = sServices->track_queue().GetCurrent();
   if (!current_track || (sCurrentTrack && *sCurrentTrack == *current_track)) {
     return;
   }
 
   sCurrentTrack = current_track;
 
-  auto db = sDatabase.lock();
+  auto db = sServices->database().lock();
   if (!db) {
     ESP_LOGW(kTag, "database not open; ignoring play request");
     return;
   }
-
   sFileSource->SetPath(db->GetTrackPath(*current_track));
 }
 
@@ -158,7 +143,7 @@ void Playback::react(const QueueUpdate& ev) {
   if (!ev.current_changed) {
     return;
   }
-  auto current_track = sTrackQueue->GetCurrent();
+  auto current_track = sServices->track_queue().GetCurrent();
   if (!current_track) {
     sFileSource->SetPath();
     sCurrentTrack.reset();
@@ -168,7 +153,7 @@ void Playback::react(const QueueUpdate& ev) {
 
   sCurrentTrack = current_track;
 
-  auto db = sDatabase.lock();
+  auto db = sServices->database().lock();
   if (!db) {
     return;
   }
@@ -191,8 +176,8 @@ void Playback::react(const internal::InputFileClosed& ev) {}
 
 void Playback::react(const internal::InputFileFinished& ev) {
   ESP_LOGI(kTag, "finished playing file");
-  sTrackQueue->Next();
-  if (!sTrackQueue->GetCurrent()) {
+  sServices->track_queue().Next();
+  if (!sServices->track_queue().GetCurrent()) {
     transit<Standby>();
   }
 }
diff --git a/src/audio/fatfs_audio_input.cpp b/src/audio/fatfs_audio_input.cpp
index 44653624..6b032632 100644
--- a/src/audio/fatfs_audio_input.cpp
+++ b/src/audio/fatfs_audio_input.cpp
@@ -40,8 +40,7 @@ static const char* kTag = "SRC";
 
 namespace audio {
 
-FatfsAudioInput::FatfsAudioInput(
-    std::shared_ptr<database::ITagParser> tag_parser)
+FatfsAudioInput::FatfsAudioInput(database::ITagParser& tag_parser)
     : IAudioSource(),
       tag_parser_(tag_parser),
       new_stream_mutex_(),
@@ -119,7 +118,7 @@ auto FatfsAudioInput::OpenFile(const std::string& path) -> bool {
   ESP_LOGI(kTag, "opening file %s", path.c_str());
 
   database::TrackTags tags;
-  if (!tag_parser_->ReadAndParseTags(path, &tags)) {
+  if (!tag_parser_.ReadAndParseTags(path, &tags)) {
     ESP_LOGE(kTag, "failed to read tags");
     return false;
   }
diff --git a/src/audio/i2s_audio_output.cpp b/src/audio/i2s_audio_output.cpp
index 359cd4c6..927f6541 100644
--- a/src/audio/i2s_audio_output.cpp
+++ b/src/audio/i2s_audio_output.cpp
@@ -41,11 +41,11 @@ static constexpr uint16_t kDefaultVolume = 0x100;
 
 static constexpr size_t kDrainBufferSize = 8 * 1024;
 
-I2SAudioOutput::I2SAudioOutput(drivers::IGpios* expander,
-                               std::weak_ptr<drivers::I2SDac> dac)
+I2SAudioOutput::I2SAudioOutput(drivers::IGpios& expander,
+                               std::unique_ptr<drivers::I2SDac> dac)
     : IAudioOutput(kDrainBufferSize, MALLOC_CAP_INTERNAL | MALLOC_CAP_8BIT),
       expander_(expander),
-      dac_(dac.lock()),
+      dac_(std::move(dac)),
       current_config_(),
       left_difference_(0),
       current_volume_(kDefaultVolume),
diff --git a/src/audio/include/audio_fsm.hpp b/src/audio/include/audio_fsm.hpp
index cfa65551..1376feae 100644
--- a/src/audio/include/audio_fsm.hpp
+++ b/src/audio/include/audio_fsm.hpp
@@ -11,6 +11,7 @@
 #include <vector>
 
 #include "audio_sink.hpp"
+#include "service_locator.hpp"
 #include "tinyfsm.hpp"
 
 #include "audio_decoder.hpp"
@@ -32,12 +33,6 @@ namespace audio {
 
 class AudioState : public tinyfsm::Fsm<AudioState> {
  public:
-  static auto Init(drivers::IGpios* gpio_expander,
-                   std::weak_ptr<database::Database>,
-                   std::shared_ptr<database::ITagParser>,
-                   drivers::Bluetooth* bluetooth,
-                   TrackQueue* queue) -> bool;
-
   virtual ~AudioState() {}
 
   virtual void entry() {}
@@ -46,8 +41,6 @@ class AudioState : public tinyfsm::Fsm<AudioState> {
   /* Fallback event handler. Does nothing. */
   void react(const tinyfsm::Event& ev) {}
 
-  void react(const system_fsm::StorageMounted&);
-
   void react(const system_fsm::KeyUpChanged&);
   void react(const system_fsm::KeyDownChanged&);
   void react(const system_fsm::HasPhonesChanged&);
@@ -65,16 +58,13 @@ class AudioState : public tinyfsm::Fsm<AudioState> {
   virtual void react(const internal::AudioPipelineIdle&) {}
 
  protected:
-  static drivers::IGpios* sIGpios;
-  static std::shared_ptr<drivers::I2SDac> sDac;
-  static std::weak_ptr<database::Database> sDatabase;
+  static std::shared_ptr<system_fsm::ServiceLocator> sServices;
 
   static std::shared_ptr<FatfsAudioInput> sFileSource;
   static std::unique_ptr<Decoder> sDecoder;
   static std::shared_ptr<SampleConverter> sSampleConverter;
   static std::shared_ptr<IAudioOutput> sOutput;
 
-  static TrackQueue* sTrackQueue;
   static std::optional<database::TrackId> sCurrentTrack;
 };
 
diff --git a/src/audio/include/fatfs_audio_input.hpp b/src/audio/include/fatfs_audio_input.hpp
index da44d2ec..b67d29dc 100644
--- a/src/audio/include/fatfs_audio_input.hpp
+++ b/src/audio/include/fatfs_audio_input.hpp
@@ -30,7 +30,7 @@ namespace audio {
  */
 class FatfsAudioInput : public IAudioSource {
  public:
-  explicit FatfsAudioInput(std::shared_ptr<database::ITagParser> tag_parser);
+  explicit FatfsAudioInput(database::ITagParser& tag_parser);
   ~FatfsAudioInput();
 
   /*
@@ -53,7 +53,7 @@ class FatfsAudioInput : public IAudioSource {
   auto ContainerToStreamType(database::Container)
       -> std::optional<codecs::StreamType>;
 
-  std::shared_ptr<database::ITagParser> tag_parser_;
+  database::ITagParser& tag_parser_;
 
   std::mutex new_stream_mutex_;
   std::shared_ptr<codecs::IStream> new_stream_;
diff --git a/src/audio/include/i2s_audio_output.hpp b/src/audio/include/i2s_audio_output.hpp
index 0068916e..fa09deef 100644
--- a/src/audio/include/i2s_audio_output.hpp
+++ b/src/audio/include/i2s_audio_output.hpp
@@ -19,7 +19,8 @@ namespace audio {
 
 class I2SAudioOutput : public IAudioOutput {
  public:
-  I2SAudioOutput(drivers::IGpios* expander, std::weak_ptr<drivers::I2SDac> dac);
+  I2SAudioOutput(drivers::IGpios& expander,
+                 std::unique_ptr<drivers::I2SDac> dac);
   ~I2SAudioOutput();
 
   auto SetInUse(bool) -> void override;
@@ -37,8 +38,8 @@ class I2SAudioOutput : public IAudioOutput {
   I2SAudioOutput& operator=(const I2SAudioOutput&) = delete;
 
  private:
-  drivers::IGpios* expander_;
-  std::shared_ptr<drivers::I2SDac> dac_;
+  drivers::IGpios& expander_;
+  std::unique_ptr<drivers::I2SDac> dac_;
 
   std::optional<Format> current_config_;
   int_fast8_t left_difference_;
diff --git a/src/battery/battery.cpp b/src/battery/battery.cpp
index d73f4f29..9ac6ebf1 100644
--- a/src/battery/battery.cpp
+++ b/src/battery/battery.cpp
@@ -40,8 +40,8 @@ void check_voltage_cb(TimerHandle_t timer) {
   instance->Update();
 }
 
-Battery::Battery(drivers::Samd* samd, drivers::AdcBattery* adc)
-    : samd_(samd), adc_(adc) {
+Battery::Battery(drivers::Samd& samd, std::unique_ptr<drivers::AdcBattery> adc)
+    : samd_(samd), adc_(std::move(adc)) {
   timer_ = xTimerCreate("BATTERY", kBatteryCheckPeriod, true, this,
                         check_voltage_cb);
   xTimerStart(timer_, portMAX_DELAY);
@@ -56,7 +56,7 @@ Battery::~Battery() {
 auto Battery::Update() -> void {
   std::lock_guard<std::mutex> lock{state_mutex_};
 
-  auto charge_state = samd_->GetChargeStatus();
+  auto charge_state = samd_.GetChargeStatus();
   if (!charge_state || *charge_state == ChargeStatus::kNoBattery) {
     if (state_) {
       EmitEvent();
diff --git a/src/battery/include/battery.hpp b/src/battery/include/battery.hpp
index dcb9b4ea..63a8a47b 100644
--- a/src/battery/include/battery.hpp
+++ b/src/battery/include/battery.hpp
@@ -18,7 +18,7 @@ namespace battery {
 
 class Battery {
  public:
-  Battery(drivers::Samd* samd, drivers::AdcBattery* adc);
+  Battery(drivers::Samd& samd, std::unique_ptr<drivers::AdcBattery> adc);
   ~Battery();
 
   auto Update() -> void;
@@ -33,8 +33,8 @@ class Battery {
  private:
   auto EmitEvent() -> void;
 
-  drivers::Samd* samd_;
-  drivers::AdcBattery* adc_;
+  drivers::Samd& samd_;
+  std::unique_ptr<drivers::AdcBattery> adc_;
 
   TimerHandle_t timer_;
   std::mutex state_mutex_;
diff --git a/src/database/database.cpp b/src/database/database.cpp
index 2a5b3236..76c2dda1 100644
--- a/src/database/database.cpp
+++ b/src/database/database.cpp
@@ -46,9 +46,6 @@ static const char kTrackIdKey[] = "next_track_id";
 
 static std::atomic<bool> sIsDbOpen(false);
 
-static FileGathererImpl sFileGatherer;
-static TagParserImpl sTagParser;
-
 template <typename Parser>
 auto IterateAndParse(leveldb::Iterator* it, std::size_t limit, Parser p)
     -> void {
@@ -62,11 +59,7 @@ auto IterateAndParse(leveldb::Iterator* it, std::size_t limit, Parser p)
   }
 }
 
-auto Database::Open() -> cpp::result<Database*, DatabaseError> {
-  return Open(&sFileGatherer, &sTagParser);
-}
-
-auto Database::Open(IFileGatherer* gatherer, ITagParser* parser)
+auto Database::Open(IFileGatherer& gatherer, ITagParser& parser)
     -> cpp::result<Database*, DatabaseError> {
   // TODO(jacqueline): Why isn't compare_and_exchange_* available?
   if (sIsDbOpen.exchange(true)) {
@@ -79,7 +72,7 @@ auto Database::Open(IFileGatherer* gatherer, ITagParser* parser)
       tasks::Worker::Start<tasks::Type::kDatabase>());
   return worker
       ->Dispatch<cpp::result<Database*, DatabaseError>>(
-          [=]() -> cpp::result<Database*, DatabaseError> {
+          [&]() -> cpp::result<Database*, DatabaseError> {
             leveldb::DB* db;
             leveldb::Cache* cache = leveldb::NewLRUCache(24 * 1024);
             leveldb::Options options;
@@ -112,8 +105,8 @@ auto Database::Destroy() -> void {
 
 Database::Database(leveldb::DB* db,
                    leveldb::Cache* cache,
-                   IFileGatherer* file_gatherer,
-                   ITagParser* tag_parser,
+                   IFileGatherer& file_gatherer,
+                   ITagParser& tag_parser,
                    std::shared_ptr<tasks::Worker> worker)
     : db_(db),
       cache_(cache),
@@ -178,7 +171,7 @@ auto Database::Update() -> std::future<void> {
         }
 
         TrackTags tags{};
-        if (!tag_parser_->ReadAndParseTags(track->filepath(), &tags) ||
+        if (!tag_parser_.ReadAndParseTags(track->filepath(), &tags) ||
             tags.encoding() == Container::kUnsupported) {
           // We couldn't read the tags for this track. Either they were
           // malformed, or perhaps the file is missing. Either way, tombstone
@@ -215,9 +208,9 @@ auto Database::Update() -> std::future<void> {
     events::Ui().Dispatch(event::UpdateProgress{
         .stage = event::UpdateProgress::Stage::kScanningForNewTracks,
     });
-    file_gatherer_->FindFiles("", [&](const std::string& path) {
+    file_gatherer_.FindFiles("", [&](const std::string& path) {
       TrackTags tags;
-      if (!tag_parser_->ReadAndParseTags(path, &tags) ||
+      if (!tag_parser_.ReadAndParseTags(path, &tags) ||
           tags.encoding() == Container::kUnsupported) {
         // No parseable tags; skip this fiile.
         return;
@@ -287,7 +280,7 @@ auto Database::GetTrack(TrackId id) -> std::future<std::optional<Track>> {
           return {};
         }
         TrackTags tags;
-        if (!tag_parser_->ReadAndParseTags(data->filepath(), &tags)) {
+        if (!tag_parser_.ReadAndParseTags(data->filepath(), &tags)) {
           return {};
         }
         return Track(*data, tags);
@@ -628,7 +621,7 @@ auto Database::ParseRecord<Track>(const leveldb::Slice& key,
     return {};
   }
   TrackTags tags;
-  if (!tag_parser_->ReadAndParseTags(data->filepath(), &tags)) {
+  if (!tag_parser_.ReadAndParseTags(data->filepath(), &tags)) {
     return {};
   }
   return Track(*data, tags);
diff --git a/src/database/include/database.hpp b/src/database/include/database.hpp
index dd6bd7cc..559405cb 100644
--- a/src/database/include/database.hpp
+++ b/src/database/include/database.hpp
@@ -91,7 +91,7 @@ class Database {
     ALREADY_OPEN,
     FAILED_TO_OPEN,
   };
-  static auto Open(IFileGatherer* file_gatherer, ITagParser* tag_parser)
+  static auto Open(IFileGatherer& file_gatherer, ITagParser& tag_parser)
       -> cpp::result<Database*, DatabaseError>;
   static auto Open() -> cpp::result<Database*, DatabaseError>;
 
@@ -133,13 +133,13 @@ class Database {
   std::shared_ptr<tasks::Worker> worker_task_;
 
   // Not owned.
-  IFileGatherer* file_gatherer_;
-  ITagParser* tag_parser_;
+  IFileGatherer& file_gatherer_;
+  ITagParser& tag_parser_;
 
   Database(leveldb::DB* db,
            leveldb::Cache* cache,
-           IFileGatherer* file_gatherer,
-           ITagParser* tag_parser,
+           IFileGatherer& file_gatherer,
+           ITagParser& tag_parser,
            std::shared_ptr<tasks::Worker> worker);
 
   auto dbMintNewTrackId() -> TrackId;
diff --git a/src/drivers/display.cpp b/src/drivers/display.cpp
index 2d480aa6..e04de477 100644
--- a/src/drivers/display.cpp
+++ b/src/drivers/display.cpp
@@ -85,7 +85,7 @@ extern "C" void FlushDataCallback(lv_disp_drv_t* disp_drv,
   instance->OnLvglFlush(disp_drv, area, color_map);
 }
 
-auto Display::Create(IGpios* expander,
+auto Display::Create(IGpios& expander,
                      const displays::InitialisationData& init_data)
     -> Display* {
   ESP_LOGI(kTag, "Init I/O pins");
@@ -182,7 +182,7 @@ auto Display::Create(IGpios* expander,
   return display.release();
 }
 
-Display::Display(IGpios* gpio, spi_device_handle_t handle)
+Display::Display(IGpios& gpio, spi_device_handle_t handle)
     : gpio_(gpio),
       handle_(handle),
       worker_task_(tasks::Worker::Start<tasks::Type::kUiFlush>()),
diff --git a/src/drivers/i2s_dac.cpp b/src/drivers/i2s_dac.cpp
index af2125a6..bedf7ebf 100644
--- a/src/drivers/i2s_dac.cpp
+++ b/src/drivers/i2s_dac.cpp
@@ -39,7 +39,7 @@ namespace drivers {
 static const char* kTag = "i2s_dac";
 static const i2s_port_t kI2SPort = I2S_NUM_0;
 
-auto I2SDac::create(IGpios* expander) -> std::optional<I2SDac*> {
+auto I2SDac::create(IGpios& expander) -> std::optional<I2SDac*> {
   i2s_chan_handle_t i2s_handle;
   i2s_chan_config_t channel_config =
       I2S_CHANNEL_DEFAULT_CONFIG(kI2SPort, I2S_ROLE_MASTER);
@@ -77,7 +77,7 @@ auto I2SDac::create(IGpios* expander) -> std::optional<I2SDac*> {
   return dac.release();
 }
 
-I2SDac::I2SDac(IGpios* gpio, i2s_chan_handle_t i2s_handle)
+I2SDac::I2SDac(IGpios& gpio, i2s_chan_handle_t i2s_handle)
     : gpio_(gpio),
       i2s_handle_(i2s_handle),
       i2s_active_(false),
@@ -87,7 +87,7 @@ I2SDac::I2SDac(IGpios* gpio, i2s_chan_handle_t i2s_handle)
   clock_config_.clk_src = I2S_CLK_SRC_APLL;
 
   // Keep the 5V circuity off until it's needed.
-  gpio_->WriteSync(IGpios::Pin::kAmplifierEnable, false);
+  gpio_.WriteSync(IGpios::Pin::kAmplifierEnable, false);
 
   // Reset all registers back to their default values.
   wm8523::WriteRegister(wm8523::Register::kReset, 1);
@@ -103,9 +103,9 @@ I2SDac::~I2SDac() {
 auto I2SDac::Start() -> void {
   std::lock_guard<std::mutex> lock(configure_mutex_);
 
-  gpio_->WriteSync(IGpios::Pin::kAmplifierUnmute, false);
+  gpio_.WriteSync(IGpios::Pin::kAmplifierUnmute, false);
   // Ramp up the amplifier power supply.
-  gpio_->WriteSync(IGpios::Pin::kAmplifierEnable, true);
+  gpio_.WriteSync(IGpios::Pin::kAmplifierEnable, true);
 
   // Wait for voltage to stabilise
   vTaskDelay(pdMS_TO_TICKS(5));
@@ -124,7 +124,7 @@ auto I2SDac::Start() -> void {
   wm8523::WriteRegister(wm8523::Register::kPsCtrl, 0b11);
 
   vTaskDelay(pdMS_TO_TICKS(5));
-  gpio_->WriteSync(IGpios::Pin::kAmplifierUnmute, true);
+  gpio_.WriteSync(IGpios::Pin::kAmplifierUnmute, true);
 }
 
 auto I2SDac::Stop() -> void {
@@ -134,7 +134,7 @@ auto I2SDac::Stop() -> void {
   wm8523::WriteRegister(wm8523::Register::kPsCtrl, 0b10);
   vTaskDelay(pdMS_TO_TICKS(5));
   // Silence the output.
-  gpio_->WriteSync(IGpios::Pin::kAmplifierUnmute, false);
+  gpio_.WriteSync(IGpios::Pin::kAmplifierUnmute, false);
 
   vTaskDelay(pdMS_TO_TICKS(5));
 
@@ -143,7 +143,7 @@ auto I2SDac::Stop() -> void {
   i2s_channel_disable(i2s_handle_);
   i2s_active_ = false;
 
-  gpio_->WriteSync(IGpios::Pin::kAmplifierEnable, false);
+  gpio_.WriteSync(IGpios::Pin::kAmplifierEnable, false);
 }
 
 auto I2SDac::Reconfigure(Channels ch, BitsPerSample bps, SampleRate rate)
diff --git a/src/drivers/include/display.hpp b/src/drivers/include/display.hpp
index 77165c99..766fc4ea 100644
--- a/src/drivers/include/display.hpp
+++ b/src/drivers/include/display.hpp
@@ -30,10 +30,10 @@ class Display {
    * over SPI. This never fails, since unfortunately these display don't give
    * us back any kind of signal to tell us we're actually using them correctly.
    */
-  static auto Create(IGpios* expander,
+  static auto Create(IGpios& expander,
                      const displays::InitialisationData& init_data) -> Display*;
 
-  Display(IGpios* gpio, spi_device_handle_t handle);
+  Display(IGpios& gpio, spi_device_handle_t handle);
   ~Display();
 
   auto SetDisplayOn(bool) -> void;
@@ -49,7 +49,7 @@ class Display {
   Display& operator=(const Display&) = delete;
 
  private:
-  IGpios* gpio_;
+  IGpios& gpio_;
   spi_device_handle_t handle_;
 
   std::unique_ptr<tasks::Worker> worker_task_;
diff --git a/src/drivers/include/i2s_dac.hpp b/src/drivers/include/i2s_dac.hpp
index c7faed2f..6bc5b6a4 100644
--- a/src/drivers/include/i2s_dac.hpp
+++ b/src/drivers/include/i2s_dac.hpp
@@ -33,9 +33,9 @@ namespace drivers {
  */
 class I2SDac {
  public:
-  static auto create(IGpios* expander) -> std::optional<I2SDac*>;
+  static auto create(IGpios& expander) -> std::optional<I2SDac*>;
 
-  I2SDac(IGpios* gpio, i2s_chan_handle_t i2s_handle);
+  I2SDac(IGpios& gpio, i2s_chan_handle_t i2s_handle);
   ~I2SDac();
 
   auto Start() -> void;
@@ -69,7 +69,7 @@ class I2SDac {
   I2SDac& operator=(const I2SDac&) = delete;
 
  private:
-  IGpios* gpio_;
+  IGpios& gpio_;
   i2s_chan_handle_t i2s_handle_;
   bool i2s_active_;
   StreamBufferHandle_t buffer_;
diff --git a/src/drivers/include/relative_wheel.hpp b/src/drivers/include/relative_wheel.hpp
index 5e801aba..b5532a4c 100644
--- a/src/drivers/include/relative_wheel.hpp
+++ b/src/drivers/include/relative_wheel.hpp
@@ -20,11 +20,7 @@ namespace drivers {
 
 class RelativeWheel {
  public:
-  static auto Create(TouchWheel* touch) -> RelativeWheel* {
-    return new RelativeWheel(touch);
-  }
-
-  explicit RelativeWheel(TouchWheel* touch);
+  explicit RelativeWheel(TouchWheel& touch);
 
   auto Update() -> void;
   auto SetEnabled(bool) -> void;
@@ -37,7 +33,7 @@ class RelativeWheel {
   RelativeWheel& operator=(const RelativeWheel&) = delete;
 
  private:
-  TouchWheel* touch_;
+  TouchWheel& touch_;
 
   bool is_enabled_;
 
diff --git a/src/drivers/include/storage.hpp b/src/drivers/include/storage.hpp
index 65be75f1..0b0cb494 100644
--- a/src/drivers/include/storage.hpp
+++ b/src/drivers/include/storage.hpp
@@ -31,9 +31,9 @@ class SdStorage {
     FAILED_TO_MOUNT,
   };
 
-  static auto Create(IGpios* gpio) -> cpp::result<SdStorage*, Error>;
+  static auto Create(IGpios& gpio) -> cpp::result<SdStorage*, Error>;
 
-  SdStorage(IGpios* gpio,
+  SdStorage(IGpios& gpio,
             sdspi_dev_handle_t handle_,
             std::unique_ptr<sdmmc_host_t> host_,
             std::unique_ptr<sdmmc_card_t> card_,
@@ -50,7 +50,7 @@ class SdStorage {
   SdStorage& operator=(const SdStorage&) = delete;
 
  private:
-  IGpios* gpio_;
+  IGpios& gpio_;
 
   // SPI and SD driver info
   sdspi_dev_handle_t handle_;
diff --git a/src/drivers/relative_wheel.cpp b/src/drivers/relative_wheel.cpp
index 75b62ae7..c014ab5e 100644
--- a/src/drivers/relative_wheel.cpp
+++ b/src/drivers/relative_wheel.cpp
@@ -13,7 +13,7 @@
 
 namespace drivers {
 
-RelativeWheel::RelativeWheel(TouchWheel* touch)
+RelativeWheel::RelativeWheel(TouchWheel& touch)
     : touch_(touch),
       is_enabled_(true),
       is_clicking_(false),
@@ -23,8 +23,8 @@ RelativeWheel::RelativeWheel(TouchWheel* touch)
       last_angle_(0) {}
 
 auto RelativeWheel::Update() -> void {
-  touch_->Update();
-  TouchWheelData d = touch_->GetTouchWheelData();
+  touch_.Update();
+  TouchWheelData d = touch_.GetTouchWheelData();
 
   is_clicking_ = d.is_button_touched;
 
diff --git a/src/drivers/storage.cpp b/src/drivers/storage.cpp
index f253a79a..6acb6870 100644
--- a/src/drivers/storage.cpp
+++ b/src/drivers/storage.cpp
@@ -32,10 +32,10 @@ namespace drivers {
 
 const char* kStoragePath = "/sdcard";
 
-auto SdStorage::Create(IGpios* gpio) -> cpp::result<SdStorage*, Error> {
-  gpio->WriteSync(IGpios::Pin::kSdPowerEnable, 1);
-  gpio->WriteSync(IGpios::Pin::kSdMuxSwitch, IGpios::SD_MUX_ESP);
-  gpio->WriteSync(IGpios::Pin::kSdMuxDisable, 0);
+auto SdStorage::Create(IGpios& gpio) -> cpp::result<SdStorage*, Error> {
+  gpio.WriteSync(IGpios::Pin::kSdPowerEnable, 1);
+  gpio.WriteSync(IGpios::Pin::kSdMuxSwitch, IGpios::SD_MUX_ESP);
+  gpio.WriteSync(IGpios::Pin::kSdMuxDisable, 0);
 
   sdspi_dev_handle_t handle;
   FATFS* fs = nullptr;
@@ -95,7 +95,7 @@ auto SdStorage::Create(IGpios* gpio) -> cpp::result<SdStorage*, Error> {
   return new SdStorage(gpio, handle, std::move(host), std::move(card), fs);
 }
 
-SdStorage::SdStorage(IGpios* gpio,
+SdStorage::SdStorage(IGpios& gpio,
                      sdspi_dev_handle_t handle,
                      std::unique_ptr<sdmmc_host_t> host,
                      std::unique_ptr<sdmmc_card_t> card,
@@ -117,8 +117,8 @@ SdStorage::~SdStorage() {
   sdspi_host_remove_device(this->handle_);
   sdspi_host_deinit();
 
-  gpio_->WriteSync(IGpios::Pin::kSdPowerEnable, 1);
-  gpio_->WriteSync(IGpios::Pin::kSdMuxDisable, 1);
+  gpio_.WriteSync(IGpios::Pin::kSdPowerEnable, 1);
+  gpio_.WriteSync(IGpios::Pin::kSdMuxDisable, 1);
 }
 
 auto SdStorage::GetFs() -> FATFS* {
diff --git a/src/system_fsm/CMakeLists.txt b/src/system_fsm/CMakeLists.txt
index fced4093..449e14cc 100644
--- a/src/system_fsm/CMakeLists.txt
+++ b/src/system_fsm/CMakeLists.txt
@@ -3,7 +3,7 @@
 # SPDX-License-Identifier: GPL-3.0-only
 
 idf_component_register(
-  SRCS "system_fsm.cpp" "running.cpp" "booting.cpp" "idle.cpp"
+  SRCS "system_fsm.cpp" "running.cpp" "booting.cpp" "idle.cpp" "service_locator.cpp"
   INCLUDE_DIRS "include"
   REQUIRES "tinyfsm" "drivers" "database" "ui" "result" "events" "audio" "app_console" "battery")
 target_compile_options(${COMPONENT_LIB} PRIVATE ${EXTRA_WARNINGS})
diff --git a/src/system_fsm/booting.cpp b/src/system_fsm/booting.cpp
index a988c622..006ed395 100644
--- a/src/system_fsm/booting.cpp
+++ b/src/system_fsm/booting.cpp
@@ -6,8 +6,10 @@
 
 #include <stdint.h>
 
+#include "adc.hpp"
 #include "assert.h"
 #include "audio_fsm.hpp"
+#include "battery.hpp"
 #include "bluetooth.hpp"
 #include "core/lv_obj.h"
 #include "display_init.hpp"
@@ -23,6 +25,7 @@
 #include "nvs.hpp"
 #include "relative_wheel.hpp"
 #include "samd.hpp"
+#include "service_locator.hpp"
 #include "spi.hpp"
 #include "system_events.hpp"
 #include "system_fsm.hpp"
@@ -40,65 +43,55 @@ static const char kTag[] = "BOOT";
 
 auto Booting::entry() -> void {
   ESP_LOGI(kTag, "beginning tangara boot");
-  ESP_LOGI(kTag, "installing early drivers");
+  sServices.reset(new ServiceLocator());
 
+  ESP_LOGI(kTag, "installing early drivers");
   // I2C and SPI are both always needed. We can't even power down or show an
   // error without these.
   ESP_ERROR_CHECK(drivers::init_spi());
-  sGpios.reset(drivers::Gpios::Create());
-
-  sSamd.reset(drivers::Samd::Create());
-  sAdc.reset(drivers::AdcBattery::Create());
-  sNvs.reset(drivers::NvsStorage::OpenSync());
-  assert(sSamd.get() && sAdc.get() && sNvs.get());
+  sServices->gpios(std::unique_ptr<drivers::Gpios>(drivers::Gpios::Create()));
 
-  sBattery.reset(new battery::Battery(sSamd.get(), sAdc.get()));
-
-  // Start bringing up LVGL now, since we have all of its prerequisites.
-  sTrackQueue.reset(new audio::TrackQueue());
   ESP_LOGI(kTag, "starting ui");
-  if (!ui::UiState::Init(sGpios.get(), sNvs, sTrackQueue.get(), sBattery)) {
+  if (!ui::UiState::InitBootSplash(sServices->gpios())) {
     events::System().Dispatch(FatalError{});
     return;
   }
 
-  // Install everything else that is certain to be needed.
   ESP_LOGI(kTag, "installing remaining drivers");
-  sTagParser.reset(new database::TagParserImpl());
+  sServices->samd(std::unique_ptr<drivers::Samd>(drivers::Samd::Create()));
+  sServices->nvs(
+      std::unique_ptr<drivers::NvsStorage>(drivers::NvsStorage::OpenSync()));
+  sServices->touchwheel(
+      std::unique_ptr<drivers::TouchWheel>{drivers::TouchWheel::Create()});
+
+  auto adc = drivers::AdcBattery::Create();
+  sServices->battery(std::make_unique<battery::Battery>(
+      sServices->samd(), std::unique_ptr<drivers::AdcBattery>(adc)));
+
+  sServices->track_queue(std::make_unique<audio::TrackQueue>());
+  sServices->tag_parser(std::make_unique<database::TagParserImpl>());
 
   // ESP_LOGI(kTag, "starting bluetooth");
   // sBluetooth.reset(new drivers::Bluetooth(sNvs.get()));
   // sBluetooth->Enable();
 
-  // At this point we've done all of the essential boot tasks. Start remaining
-  // state machines and inform them that the system is ready.
-
-  ESP_LOGI(kTag, "starting audio");
-  if (!audio::AudioState::Init(sGpios.get(), sDatabase, sTagParser,
-                               sBluetooth.get(), sTrackQueue.get())) {
-    events::System().Dispatch(FatalError{});
-    events::Ui().Dispatch(FatalError{});
-    return;
-  }
-
-  events::System().Dispatch(BootComplete{});
-  events::Audio().Dispatch(BootComplete{});
-  events::Ui().Dispatch(BootComplete{});
+  BootComplete ev{.services = sServices};
+  events::Audio().Dispatch(ev);
+  events::Ui().Dispatch(ev);
+  events::System().Dispatch(ev);
 }
 
 auto Booting::exit() -> void {
   // TODO(jacqueline): Gate this on something. Debug flag? Flashing mode?
   sAppConsole = new console::AppConsole();
-  sAppConsole->sTrackQueue = sTrackQueue.get();
-  sAppConsole->sBluetooth = sBluetooth.get();
-  sAppConsole->sSamd = sSamd.get();
+  sAppConsole->sServices = sServices;
   sAppConsole->Launch();
 }
 
 auto Booting::react(const BootComplete& ev) -> void {
   ESP_LOGI(kTag, "bootup completely successfully");
 
-  if (sGpios->Get(drivers::Gpios::Pin::kKeyLock)) {
+  if (sServices->gpios().Get(drivers::Gpios::Pin::kKeyLock)) {
     transit<Running>();
   } else {
     transit<Idle>();
diff --git a/src/system_fsm/idle.cpp b/src/system_fsm/idle.cpp
index 7cc1fa39..bd327134 100644
--- a/src/system_fsm/idle.cpp
+++ b/src/system_fsm/idle.cpp
@@ -64,30 +64,32 @@ void Idle::react(const internal::IdleTimeout& ev) {
 
   // FIXME: It would be neater to just free a bunch of our pointers, deinit the
   // other state machines, etc.
-  if (sTouch) {
-    sTouch->PowerDown();
+  auto touchwheel = sServices->touchwheel();
+  if (touchwheel) {
+    touchwheel.value()->PowerDown();
   }
 
+  auto& gpios = sServices->gpios();
   // Pull down to turn things off
-  sGpios->WriteBuffered(drivers::IGpios::Pin::kAmplifierEnable, false);
-  sGpios->WriteBuffered(drivers::IGpios::Pin::kSdPowerEnable, false);
-  sGpios->WriteBuffered(drivers::IGpios::Pin::kDisplayEnable, false);
+  gpios.WriteBuffered(drivers::IGpios::Pin::kAmplifierEnable, false);
+  gpios.WriteBuffered(drivers::IGpios::Pin::kSdPowerEnable, false);
+  gpios.WriteBuffered(drivers::IGpios::Pin::kDisplayEnable, false);
 
   // Leave up to match the external pullups
-  sGpios->WriteBuffered(drivers::IGpios::Pin::kSdMuxSwitch, true);
-  sGpios->WriteBuffered(drivers::IGpios::Pin::kSdMuxDisable, true);
+  gpios.WriteBuffered(drivers::IGpios::Pin::kSdMuxSwitch, true);
+  gpios.WriteBuffered(drivers::IGpios::Pin::kSdMuxDisable, true);
 
   // Pull down to prevent sourcing current uselessly from input pins.
-  sGpios->WriteBuffered(drivers::IGpios::Pin::kSdCardDetect, false);
-  sGpios->WriteBuffered(drivers::IGpios::Pin::kKeyUp, false);
-  sGpios->WriteBuffered(drivers::IGpios::Pin::kKeyDown, false);
+  gpios.WriteBuffered(drivers::IGpios::Pin::kSdCardDetect, false);
+  gpios.WriteBuffered(drivers::IGpios::Pin::kKeyUp, false);
+  gpios.WriteBuffered(drivers::IGpios::Pin::kKeyDown, false);
 
-  sGpios->Flush();
+  gpios.Flush();
 
   // Retry shutting down in case of a transient failure with the SAMD. e.g. i2c
   // timeouts. This guards against a buggy SAMD firmware preventing idle.
   for (;;) {
-    sSamd->PowerDown();
+    sServices->samd().PowerDown();
     vTaskDelay(pdMS_TO_TICKS(1000));
   }
 }
diff --git a/src/system_fsm/include/service_locator.hpp b/src/system_fsm/include/service_locator.hpp
new file mode 100644
index 00000000..00285ed5
--- /dev/null
+++ b/src/system_fsm/include/service_locator.hpp
@@ -0,0 +1,113 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#pragma once
+
+#include <memory>
+
+#include "battery.hpp"
+#include "bluetooth.hpp"
+#include "database.hpp"
+#include "gpios.hpp"
+#include "nvs.hpp"
+#include "samd.hpp"
+#include "tag_parser.hpp"
+#include "touchwheel.hpp"
+#include "track_queue.hpp"
+
+namespace system_fsm {
+
+class ServiceLocator {
+ public:
+  static auto instance() -> ServiceLocator&;
+
+  auto gpios() -> drivers::Gpios& {
+    assert(gpios_ != nullptr);
+    return *gpios_;
+  }
+
+  auto gpios(std::unique_ptr<drivers::Gpios> i) { gpios_ = std::move(i); }
+
+  auto samd() -> drivers::Samd& {
+    assert(samd_ != nullptr);
+    return *samd_;
+  }
+
+  auto samd(std::unique_ptr<drivers::Samd> i) { samd_ = std::move(i); }
+
+  auto nvs() -> drivers::NvsStorage& {
+    assert(nvs_ != nullptr);
+    return *nvs_;
+  }
+
+  auto nvs(std::unique_ptr<drivers::NvsStorage> i) { nvs_ = std::move(i); }
+
+  auto bluetooth() -> drivers::Bluetooth& {
+    assert(bluetooth_ != nullptr);
+    return *bluetooth_;
+  }
+
+  auto bluetooth(std::unique_ptr<drivers::Bluetooth> i) {
+    bluetooth_ = std::move(i);
+  }
+
+  auto battery() -> battery::Battery& {
+    assert(battery_ != nullptr);
+    return *battery_;
+  }
+
+  auto battery(std::unique_ptr<battery::Battery> i) { battery_ = std::move(i); }
+
+  auto touchwheel() -> std::optional<drivers::TouchWheel*> {
+    if (!touchwheel_) {
+      return {};
+    }
+    return touchwheel_.get();
+  }
+
+  auto touchwheel(std::unique_ptr<drivers::TouchWheel> i) {
+    touchwheel_ = std::move(i);
+  }
+
+  auto database() -> std::weak_ptr<database::Database> { return database_; }
+
+  auto database(std::unique_ptr<database::Database> i) {
+    database_ = std::move(i);
+  }
+
+  auto tag_parser() -> database::ITagParser& {
+    assert(tag_parser_ != nullptr);
+    return *tag_parser_;
+  }
+
+  auto tag_parser(std::unique_ptr<database::ITagParser> i) {
+    tag_parser_ = std::move(i);
+  }
+
+  auto track_queue() -> audio::TrackQueue& {
+    assert(queue_ != nullptr);
+    return *queue_;
+  }
+
+  auto track_queue(std::unique_ptr<audio::TrackQueue> i) {
+    queue_ = std::move(i);
+  }
+
+ private:
+  std::unique_ptr<drivers::Gpios> gpios_;
+  std::unique_ptr<drivers::Samd> samd_;
+  std::unique_ptr<drivers::NvsStorage> nvs_;
+  std::unique_ptr<drivers::TouchWheel> touchwheel_;
+  std::unique_ptr<drivers::Bluetooth> bluetooth_;
+
+  std::unique_ptr<audio::TrackQueue> queue_;
+  std::unique_ptr<battery::Battery> battery_;
+
+  std::shared_ptr<database::Database> database_;
+  std::unique_ptr<database::ITagParser> tag_parser_;
+};
+
+}  // namespace system_fsm
diff --git a/src/system_fsm/include/system_events.hpp b/src/system_fsm/include/system_events.hpp
index 64cbd393..e22fe2ae 100644
--- a/src/system_fsm/include/system_events.hpp
+++ b/src/system_fsm/include/system_events.hpp
@@ -9,6 +9,7 @@
 #include <memory>
 
 #include "database.hpp"
+#include "service_locator.hpp"
 #include "tinyfsm.hpp"
 
 namespace system_fsm {
@@ -19,7 +20,9 @@ struct DisplayReady : tinyfsm::Event {};
  * Sent by SysState when the system has finished with its boot and self-test,
  * and is now ready to run normally.
  */
-struct BootComplete : tinyfsm::Event {};
+struct BootComplete : tinyfsm::Event {
+  std::shared_ptr<ServiceLocator> services;
+};
 
 /*
  * May be sent by any component to indicate that the system has experienced an
@@ -33,9 +36,7 @@ struct OnIdle : tinyfsm::Event {};
 /*
  * Sent by SysState when the system storage has been successfully mounted.
  */
-struct StorageMounted : tinyfsm::Event {
-  std::weak_ptr<database::Database> db;
-};
+struct StorageMounted : tinyfsm::Event {};
 
 struct StorageError : tinyfsm::Event {};
 
diff --git a/src/system_fsm/include/system_fsm.hpp b/src/system_fsm/include/system_fsm.hpp
index 371e5527..28448e5a 100644
--- a/src/system_fsm/include/system_fsm.hpp
+++ b/src/system_fsm/include/system_fsm.hpp
@@ -18,6 +18,7 @@
 #include "nvs.hpp"
 #include "relative_wheel.hpp"
 #include "samd.hpp"
+#include "service_locator.hpp"
 #include "storage.hpp"
 #include "tag_parser.hpp"
 #include "tinyfsm.hpp"
@@ -60,22 +61,8 @@ class SystemState : public tinyfsm::Fsm<SystemState> {
  protected:
   auto IdleCondition() -> bool;
 
-  static std::shared_ptr<drivers::Gpios> sGpios;
-  static std::shared_ptr<drivers::Samd> sSamd;
-  static std::shared_ptr<drivers::NvsStorage> sNvs;
-
-  static std::shared_ptr<drivers::TouchWheel> sTouch;
-  static std::shared_ptr<drivers::RelativeWheel> sRelativeTouch;
-  static std::shared_ptr<drivers::AdcBattery> sAdc;
-  static std::shared_ptr<battery::Battery> sBattery;
-  static std::shared_ptr<drivers::SdStorage> sStorage;
-  static std::shared_ptr<drivers::Display> sDisplay;
-  static std::shared_ptr<drivers::Bluetooth> sBluetooth;
-
-  static std::shared_ptr<database::Database> sDatabase;
-  static std::shared_ptr<database::TagParserImpl> sTagParser;
-
-  static std::shared_ptr<audio::TrackQueue> sTrackQueue;
+  static std::shared_ptr<ServiceLocator> sServices;
+  static std::unique_ptr<drivers::SdStorage> sStorage;
 
   static console::AppConsole* sAppConsole;
 };
diff --git a/src/system_fsm/running.cpp b/src/system_fsm/running.cpp
index 3fc5493f..e42429e7 100644
--- a/src/system_fsm/running.cpp
+++ b/src/system_fsm/running.cpp
@@ -6,6 +6,7 @@
 
 #include "app_console.hpp"
 #include "audio_events.hpp"
+#include "database.hpp"
 #include "file_gatherer.hpp"
 #include "freertos/projdefs.h"
 #include "result.hpp"
@@ -31,7 +32,7 @@ static database::IFileGatherer* sFileGatherer;
 void Running::entry() {
   ESP_LOGI(kTag, "mounting sd card");
   vTaskDelay(pdMS_TO_TICKS(250));
-  auto storage_res = drivers::SdStorage::Create(sGpios.get());
+  auto storage_res = drivers::SdStorage::Create(sServices->gpios());
   if (storage_res.has_error()) {
     ESP_LOGW(kTag, "failed to mount!");
 
@@ -41,11 +42,11 @@ void Running::entry() {
     return;
   }
   sStorage.reset(storage_res.value());
-  vTaskDelay(pdMS_TO_TICKS(250));
 
   ESP_LOGI(kTag, "opening database");
   sFileGatherer = new database::FileGathererImpl();
-  auto database_res = database::Database::Open(sFileGatherer, sTagParser.get());
+  auto database_res =
+      database::Database::Open(*sFileGatherer, sServices->tag_parser());
   if (database_res.has_error()) {
     ESP_LOGW(kTag, "failed to open!");
     events::System().Dispatch(StorageError{});
@@ -53,18 +54,18 @@ void Running::entry() {
     events::Ui().Dispatch(StorageError{});
     return;
   }
-  sDatabase.reset(database_res.value());
-  console::AppConsole::sDatabase = sDatabase;
+  sServices->database(
+      std::unique_ptr<database::Database>{database_res.value()});
 
   ESP_LOGI(kTag, "storage loaded okay");
-  StorageMounted ev{.db = sDatabase};
+  StorageMounted ev{};
   events::System().Dispatch(ev);
   events::Audio().Dispatch(ev);
   events::Ui().Dispatch(ev);
 }
 
 void Running::exit() {
-  sDatabase.reset();
+  sServices->database({});
   sStorage.reset();
 }
 
diff --git a/src/system_fsm/service_locator.cpp b/src/system_fsm/service_locator.cpp
new file mode 100644
index 00000000..1d4d8a65
--- /dev/null
+++ b/src/system_fsm/service_locator.cpp
@@ -0,0 +1,21 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "service_locator.hpp"
+
+#include <memory>
+
+#include "nvs.hpp"
+#include "touchwheel.hpp"
+
+namespace system_fsm {
+
+auto ServiceLocator::instance() -> ServiceLocator& {
+  static ServiceLocator sInstance{};
+  return sInstance;
+}
+
+}  // namespace system_fsm
diff --git a/src/system_fsm/system_fsm.cpp b/src/system_fsm/system_fsm.cpp
index d21e8bcb..e048cec7 100644
--- a/src/system_fsm/system_fsm.cpp
+++ b/src/system_fsm/system_fsm.cpp
@@ -9,6 +9,7 @@
 #include "event_queue.hpp"
 #include "gpios.hpp"
 #include "relative_wheel.hpp"
+#include "service_locator.hpp"
 #include "system_events.hpp"
 #include "tag_parser.hpp"
 #include "track_queue.hpp"
@@ -17,22 +18,8 @@ static const char kTag[] = "system";
 
 namespace system_fsm {
 
-std::shared_ptr<drivers::Gpios> SystemState::sGpios;
-std::shared_ptr<drivers::Samd> SystemState::sSamd;
-std::shared_ptr<drivers::NvsStorage> SystemState::sNvs;
-
-std::shared_ptr<drivers::TouchWheel> SystemState::sTouch;
-std::shared_ptr<drivers::RelativeWheel> SystemState::sRelativeTouch;
-std::shared_ptr<drivers::AdcBattery> SystemState::sAdc;
-std::shared_ptr<battery::Battery> SystemState::sBattery;
-std::shared_ptr<drivers::SdStorage> SystemState::sStorage;
-std::shared_ptr<drivers::Display> SystemState::sDisplay;
-std::shared_ptr<drivers::Bluetooth> SystemState::sBluetooth;
-
-std::shared_ptr<database::Database> SystemState::sDatabase;
-std::shared_ptr<database::TagParserImpl> SystemState::sTagParser;
-
-std::shared_ptr<audio::TrackQueue> SystemState::sTrackQueue;
+std::shared_ptr<ServiceLocator> SystemState::sServices;
+std::unique_ptr<drivers::SdStorage> SystemState::sStorage;
 
 console::AppConsole* SystemState::sAppConsole;
 
@@ -43,17 +30,18 @@ void SystemState::react(const FatalError& err) {
 }
 
 void SystemState::react(const internal::GpioInterrupt&) {
-  bool prev_key_up = sGpios->Get(drivers::Gpios::Pin::kKeyUp);
-  bool prev_key_down = sGpios->Get(drivers::Gpios::Pin::kKeyDown);
-  bool prev_key_lock = sGpios->Get(drivers::Gpios::Pin::kKeyLock);
-  bool prev_has_headphones = !sGpios->Get(drivers::Gpios::Pin::kPhoneDetect);
+  auto& gpios = sServices->gpios();
+  bool prev_key_up = gpios.Get(drivers::Gpios::Pin::kKeyUp);
+  bool prev_key_down = gpios.Get(drivers::Gpios::Pin::kKeyDown);
+  bool prev_key_lock = gpios.Get(drivers::Gpios::Pin::kKeyLock);
+  bool prev_has_headphones = !gpios.Get(drivers::Gpios::Pin::kPhoneDetect);
 
-  sGpios->Read();
+  gpios.Read();
 
-  bool key_up = sGpios->Get(drivers::Gpios::Pin::kKeyUp);
-  bool key_down = sGpios->Get(drivers::Gpios::Pin::kKeyDown);
-  bool key_lock = sGpios->Get(drivers::Gpios::Pin::kKeyLock);
-  bool has_headphones = !sGpios->Get(drivers::Gpios::Pin::kPhoneDetect);
+  bool key_up = gpios.Get(drivers::Gpios::Pin::kKeyUp);
+  bool key_down = gpios.Get(drivers::Gpios::Pin::kKeyDown);
+  bool key_lock = gpios.Get(drivers::Gpios::Pin::kKeyLock);
+  bool has_headphones = !gpios.Get(drivers::Gpios::Pin::kPhoneDetect);
 
   if (key_up != prev_key_up) {
     KeyUpChanged ev{.falling = prev_key_up};
@@ -77,14 +65,15 @@ void SystemState::react(const internal::GpioInterrupt&) {
 }
 
 void SystemState::react(const internal::SamdInterrupt&) {
-  auto prev_charge_status = sSamd->GetChargeStatus();
-  auto prev_usb_status = sSamd->GetUsbStatus();
+  auto& samd = sServices->samd();
+  auto prev_charge_status = samd.GetChargeStatus();
+  auto prev_usb_status = samd.GetUsbStatus();
 
-  sSamd->UpdateChargeStatus();
-  sSamd->UpdateUsbStatus();
+  samd.UpdateChargeStatus();
+  samd.UpdateUsbStatus();
 
-  auto charge_status = sSamd->GetChargeStatus();
-  auto usb_status = sSamd->GetUsbStatus();
+  auto charge_status = samd.GetChargeStatus();
+  auto usb_status = samd.GetUsbStatus();
 
   if (charge_status != prev_charge_status) {
     ChargingStatusChanged ev{};
@@ -97,7 +86,7 @@ void SystemState::react(const internal::SamdInterrupt&) {
 }
 
 auto SystemState::IdleCondition() -> bool {
-  return !sGpios->Get(drivers::IGpios::Pin::kKeyLock) &&
+  return !sServices->gpios().Get(drivers::IGpios::Pin::kKeyLock) &&
          audio::AudioState::is_in_state<audio::states::Standby>();
 }
 
diff --git a/src/ui/include/lvgl_task.hpp b/src/ui/include/lvgl_task.hpp
index 7e60c4b4..6b7e446e 100644
--- a/src/ui/include/lvgl_task.hpp
+++ b/src/ui/include/lvgl_task.hpp
@@ -12,15 +12,38 @@
 
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"
+#include "freertos/timers.h"
 
 #include "display.hpp"
 #include "relative_wheel.hpp"
+#include "screen.hpp"
 #include "themes.hpp"
 #include "touchwheel.hpp"
+#include "wheel_encoder.hpp"
 
 namespace ui {
 
-auto StartLvgl(std::weak_ptr<drivers::RelativeWheel> touch_wheel,
-               std::weak_ptr<drivers::Display> display) -> void;
+class UiTask {
+ public:
+  static auto Start() -> UiTask*;
+
+  ~UiTask();
+
+  // FIXME: Once we have more input devices, this function should accept a more
+  // generic interface.
+  auto SetInputDevice(std::shared_ptr<TouchWheelEncoder> dev) -> void;
+
+ private:
+  UiTask();
+
+  auto Main() -> void;
+
+  std::shared_ptr<TouchWheelEncoder> input_device_;
+  std::shared_ptr<Screen> current_screen_;
+
+  std::atomic<bool> quit_;
+  SemaphoreHandle_t frame_semaphore_;
+  TimerHandle_t frame_timer_;
+};
 
 }  // namespace ui
diff --git a/src/ui/include/screen_playing.hpp b/src/ui/include/screen_playing.hpp
index c684ddff..f2998c88 100644
--- a/src/ui/include/screen_playing.hpp
+++ b/src/ui/include/screen_playing.hpp
@@ -29,7 +29,7 @@ namespace screens {
 class Playing : public Screen {
  public:
   explicit Playing(std::weak_ptr<database::Database> db,
-                   audio::TrackQueue* queue);
+                   audio::TrackQueue& queue);
   ~Playing();
 
   auto Tick() -> void override;
@@ -51,7 +51,7 @@ class Playing : public Screen {
   auto ApplyNextUp(const std::vector<database::Track>& tracks) -> void;
 
   std::weak_ptr<database::Database> db_;
-  audio::TrackQueue* queue_;
+  audio::TrackQueue& queue_;
 
   std::optional<database::Track> track_;
   std::vector<database::Track> next_tracks_;
diff --git a/src/ui/include/screen_settings.hpp b/src/ui/include/screen_settings.hpp
index 61375fa9..0ec96d26 100644
--- a/src/ui/include/screen_settings.hpp
+++ b/src/ui/include/screen_settings.hpp
@@ -37,14 +37,14 @@ class Headphones : public MenuScreen {
 
 class Appearance : public MenuScreen {
  public:
-  Appearance(drivers::NvsStorage* nvs, drivers::Display* display);
+  Appearance(drivers::NvsStorage& nvs, drivers::Display& display);
 
   auto ChangeBrightness(uint_fast8_t) -> void;
   auto CommitBrightness() -> void;
 
  private:
-  drivers::NvsStorage* nvs_;
-  drivers::Display* display_;
+  drivers::NvsStorage& nvs_;
+  drivers::Display& display_;
 
   lv_obj_t* current_brightness_label_;
   uint_fast8_t current_brightness_;
diff --git a/src/ui/include/ui_fsm.hpp b/src/ui/include/ui_fsm.hpp
index 1fa6bf26..12fe5c69 100644
--- a/src/ui/include/ui_fsm.hpp
+++ b/src/ui/include/ui_fsm.hpp
@@ -11,9 +11,12 @@
 
 #include "audio_events.hpp"
 #include "battery.hpp"
+#include "gpios.hpp"
+#include "lvgl_task.hpp"
 #include "nvs.hpp"
 #include "relative_wheel.hpp"
 #include "screen_playing.hpp"
+#include "service_locator.hpp"
 #include "tinyfsm.hpp"
 
 #include "display.hpp"
@@ -24,15 +27,13 @@
 #include "touchwheel.hpp"
 #include "track_queue.hpp"
 #include "ui_events.hpp"
+#include "wheel_encoder.hpp"
 
 namespace ui {
 
 class UiState : public tinyfsm::Fsm<UiState> {
  public:
-  static auto Init(drivers::IGpios*,
-                   std::shared_ptr<drivers::NvsStorage>,
-                   audio::TrackQueue*,
-                   std::shared_ptr<battery::Battery>) -> bool;
+  static auto InitBootSplash(drivers::IGpios&) -> bool;
 
   virtual ~UiState() {}
 
@@ -46,7 +47,7 @@ class UiState : public tinyfsm::Fsm<UiState> {
   /* Fallback event handler. Does nothing. */
   void react(const tinyfsm::Event& ev) {}
 
-  void react(const system_fsm::BatteryStateChanged&);
+  virtual void react(const system_fsm::BatteryStateChanged&);
 
   virtual void react(const audio::PlaybackStarted&) {}
   virtual void react(const audio::PlaybackUpdate&) {}
@@ -76,15 +77,10 @@ class UiState : public tinyfsm::Fsm<UiState> {
   void PopScreen();
   void UpdateTopBar();
 
-  static drivers::IGpios* sIGpios;
-  static audio::TrackQueue* sQueue;
-
-  static std::shared_ptr<drivers::TouchWheel> sTouchWheel;
-  static std::shared_ptr<drivers::RelativeWheel> sRelativeWheel;
-  static std::shared_ptr<drivers::Display> sDisplay;
-  static std::shared_ptr<battery::Battery> sBattery;
-  static std::shared_ptr<drivers::NvsStorage> sNvs;
-  static std::weak_ptr<database::Database> sDb;
+  static std::unique_ptr<UiTask> sTask;
+  static std::shared_ptr<system_fsm::ServiceLocator> sServices;
+  static std::unique_ptr<drivers::Display> sDisplay;
+  static std::shared_ptr<TouchWheelEncoder> sEncoder;
 
   static std::stack<std::shared_ptr<Screen>> sScreens;
   static std::shared_ptr<Screen> sCurrentScreen;
@@ -97,6 +93,7 @@ class Splash : public UiState {
  public:
   void exit() override;
   void react(const system_fsm::BootComplete&) override;
+  void react(const system_fsm::BatteryStateChanged&) override{};
   using UiState::react;
 };
 
diff --git a/src/ui/include/wheel_encoder.hpp b/src/ui/include/wheel_encoder.hpp
index c49e5929..fcac5edd 100644
--- a/src/ui/include/wheel_encoder.hpp
+++ b/src/ui/include/wheel_encoder.hpp
@@ -17,7 +17,7 @@ namespace ui {
 
 class TouchWheelEncoder {
  public:
-  explicit TouchWheelEncoder(std::weak_ptr<drivers::RelativeWheel> wheel);
+  explicit TouchWheelEncoder(std::unique_ptr<drivers::RelativeWheel> wheel);
 
   auto Read(lv_indev_data_t* data) -> void;
   auto registration() -> lv_indev_t* { return registration_; }
@@ -27,7 +27,7 @@ class TouchWheelEncoder {
   lv_indev_t* registration_;
 
   lv_key_t last_key_;
-  std::weak_ptr<drivers::RelativeWheel> wheel_;
+  std::unique_ptr<drivers::RelativeWheel> wheel_;
 };
 
 }  // namespace ui
diff --git a/src/ui/lvgl_task.cpp b/src/ui/lvgl_task.cpp
index 9952d0bb..a0f14f7d 100644
--- a/src/ui/lvgl_task.cpp
+++ b/src/ui/lvgl_task.cpp
@@ -48,67 +48,74 @@
 
 namespace ui {
 
-static const char* kTag = "lv_task";
+static const char* kTag = "ui_task";
 static const TickType_t kMaxFrameRate = pdMS_TO_TICKS(100);
 
-static int sTimerId;
-static SemaphoreHandle_t sFrameSemaphore;
-
-auto next_frame(TimerHandle_t) {
-  xSemaphoreGive(sFrameSemaphore);
+static auto next_frame(TimerHandle_t t) {
+  SemaphoreHandle_t sem =
+      reinterpret_cast<SemaphoreHandle_t>(pvTimerGetTimerID(t));
+  xSemaphoreGive(sem);
 }
 
-void LvglMain(std::weak_ptr<drivers::RelativeWheel> weak_touch_wheel,
-              std::weak_ptr<drivers::Display> weak_display) {
-  ESP_LOGI(kTag, "init lvgl");
-  lv_init();
-
-  sFrameSemaphore = xSemaphoreCreateBinary();
-  auto timer =
-      xTimerCreate("lvgl_frame", kMaxFrameRate, pdTRUE, &sTimerId, next_frame);
-  xTimerStart(timer, portMAX_DELAY);
-
-  lv_theme_t* base_theme = lv_theme_basic_init(NULL);
-  lv_disp_set_theme(NULL, base_theme);
-  themes::Theme::instance()->Apply();
+UiTask::UiTask()
+    : quit_(false),
+      frame_semaphore_(xSemaphoreCreateBinary()),
+      frame_timer_(xTimerCreate("ui_frame",
+                                kMaxFrameRate,
+                                pdTRUE,
+                                frame_semaphore_,
+                                next_frame)) {
+  xTimerStart(frame_timer_, portMAX_DELAY);
+}
 
-  TouchWheelEncoder encoder(weak_touch_wheel);
+UiTask::~UiTask() {
+  assert(false);
+}
 
-  std::shared_ptr<Screen> current_screen;
+auto UiTask::Main() -> void {
+  ESP_LOGI(kTag, "start ui task");
   lv_group_t* current_group = nullptr;
   auto* events = events::queues::Ui();
-  while (1) {
+  while (true) {
     while (events->Service(0)) {
     }
 
     std::shared_ptr<Screen> screen = UiState::current_screen();
-    if (screen != current_screen && screen != nullptr) {
-      // TODO(jacqueline): animate this sometimes
+    if (screen != current_screen_ && screen != nullptr) {
       lv_scr_load(screen->root());
-      lv_indev_set_group(encoder.registration(), screen->group());
-      current_screen = screen;
+      if (input_device_) {
+        lv_indev_set_group(input_device_->registration(), screen->group());
+      }
+      current_screen_ = screen;
     }
 
-    if (current_screen->group() != current_group) {
-      current_group = current_screen->group();
-      lv_indev_set_group(encoder.registration(), current_group);
+    if (input_device_ && current_screen_->group() != current_group) {
+      current_group = current_screen_->group();
+      lv_indev_set_group(input_device_->registration(), current_group);
     }
 
-    if (current_screen) {
-      current_screen->Tick();
+    if (current_screen_) {
+      current_screen_->Tick();
     }
 
     lv_task_handler();
 
     // Wait for the signal to loop again.
-    xSemaphoreTake(sFrameSemaphore, portMAX_DELAY);
+    xSemaphoreTake(frame_semaphore_, portMAX_DELAY);
+  }
+}
+
+auto UiTask::SetInputDevice(std::shared_ptr<TouchWheelEncoder> dev) -> void {
+  input_device_ = std::move(dev);
+  if (current_screen_ && input_device_) {
+    lv_indev_set_group(input_device_->registration(), current_screen_->group());
   }
 }
 
-auto StartLvgl(std::weak_ptr<drivers::RelativeWheel> touch_wheel,
-               std::weak_ptr<drivers::Display> display) -> void {
-  tasks::StartPersistent<tasks::Type::kUi>(
-      0, [=]() { LvglMain(touch_wheel, display); });
+auto UiTask::Start() -> UiTask* {
+  UiTask* ret = new UiTask();
+  tasks::StartPersistent<tasks::Type::kUi>(0, [=]() { ret->Main(); });
+  return ret;
 }
 
 }  // namespace ui
diff --git a/src/ui/screen_playing.cpp b/src/ui/screen_playing.cpp
index 7538d093..2eb4e09e 100644
--- a/src/ui/screen_playing.cpp
+++ b/src/ui/screen_playing.cpp
@@ -104,7 +104,7 @@ auto Playing::next_up_label(lv_obj_t* parent, const std::string& text)
   return button;
 }
 
-Playing::Playing(std::weak_ptr<database::Database> db, audio::TrackQueue* queue)
+Playing::Playing(std::weak_ptr<database::Database> db, audio::TrackQueue& queue)
     : db_(db),
       queue_(queue),
       track_(),
@@ -204,7 +204,7 @@ Playing::Playing(std::weak_ptr<database::Database> db, audio::TrackQueue* queue)
 Playing::~Playing() {}
 
 auto Playing::OnTrackUpdate() -> void {
-  auto current = queue_->GetCurrent();
+  auto current = queue_.GetCurrent();
   if (!current) {
     return;
   }
@@ -230,7 +230,7 @@ auto Playing::OnPlaybackUpdate(uint32_t pos_seconds, uint32_t new_duration)
 
 auto Playing::OnQueueUpdate() -> void {
   OnTrackUpdate();
-  auto current = queue_->GetUpcoming(kMaxUpcoming);
+  auto current = queue_.GetUpcoming(kMaxUpcoming);
   auto db = db_.lock();
   if (!db) {
     return;
diff --git a/src/ui/screen_settings.cpp b/src/ui/screen_settings.cpp
index 6bafb9a8..01f40cb5 100644
--- a/src/ui/screen_settings.cpp
+++ b/src/ui/screen_settings.cpp
@@ -161,7 +161,7 @@ static auto brightness_str(uint_fast8_t percent) -> std::string {
   return std::to_string(percent) + "%";
 }
 
-Appearance::Appearance(drivers::NvsStorage* nvs, drivers::Display* display)
+Appearance::Appearance(drivers::NvsStorage& nvs, drivers::Display& display)
     : MenuScreen("Appearance"), nvs_(nvs), display_(display) {
   lv_obj_t* toggle_container = settings_container(content_);
   lv_obj_t* toggle_label = lv_label_create(toggle_container);
@@ -170,7 +170,7 @@ Appearance::Appearance(drivers::NvsStorage* nvs, drivers::Display* display)
   lv_obj_t* toggle = lv_switch_create(toggle_container);
   lv_group_add_obj(group_, toggle);
 
-  uint_fast8_t initial_brightness = nvs_->ScreenBrightness().get();
+  uint_fast8_t initial_brightness = nvs_.ScreenBrightness().get();
 
   lv_obj_t* brightness_label = lv_label_create(content_);
   lv_label_set_text(brightness_label, "Brightness");
@@ -192,13 +192,13 @@ Appearance::Appearance(drivers::NvsStorage* nvs, drivers::Display* display)
 
 auto Appearance::ChangeBrightness(uint_fast8_t new_level) -> void {
   current_brightness_ = new_level;
-  display_->SetBrightness(new_level);
+  display_.SetBrightness(new_level);
   lv_label_set_text(current_brightness_label_,
                     brightness_str(new_level).c_str());
 }
 
 auto Appearance::CommitBrightness() -> void {
-  nvs_->ScreenBrightness(current_brightness_);
+  nvs_.ScreenBrightness(current_brightness_);
 }
 
 InputMethod::InputMethod() : MenuScreen("Input Method") {
diff --git a/src/ui/ui_fsm.cpp b/src/ui/ui_fsm.cpp
index 1febd1c7..0054db23 100644
--- a/src/ui/ui_fsm.cpp
+++ b/src/ui/ui_fsm.cpp
@@ -32,6 +32,7 @@
 #include "touchwheel.hpp"
 #include "track_queue.hpp"
 #include "ui_events.hpp"
+#include "wheel_encoder.hpp"
 #include "widget_top_bar.hpp"
 
 namespace ui {
@@ -40,51 +41,25 @@ static constexpr char kTag[] = "ui_fsm";
 
 static const std::size_t kRecordsPerPage = 15;
 
-drivers::IGpios* UiState::sIGpios;
-audio::TrackQueue* UiState::sQueue;
-
-std::shared_ptr<drivers::TouchWheel> UiState::sTouchWheel;
-std::shared_ptr<drivers::RelativeWheel> UiState::sRelativeWheel;
-std::shared_ptr<drivers::Display> UiState::sDisplay;
-std::shared_ptr<battery::Battery> UiState::sBattery;
-std::shared_ptr<drivers::NvsStorage> UiState::sNvs;
-std::weak_ptr<database::Database> UiState::sDb;
+std::unique_ptr<UiTask> UiState::sTask;
+std::shared_ptr<system_fsm::ServiceLocator> UiState::sServices;
+std::unique_ptr<drivers::Display> UiState::sDisplay;
+std::shared_ptr<TouchWheelEncoder> UiState::sEncoder;
 
 std::stack<std::shared_ptr<Screen>> UiState::sScreens;
 std::shared_ptr<Screen> UiState::sCurrentScreen;
 std::shared_ptr<Modal> UiState::sCurrentModal;
 
-auto UiState::Init(drivers::IGpios* gpio_expander,
-                   std::shared_ptr<drivers::NvsStorage> nvs,
-                   audio::TrackQueue* queue,
-                   std::shared_ptr<battery::Battery> battery) -> bool {
-  sIGpios = gpio_expander;
-  sNvs = nvs;
-  sQueue = queue;
-  sBattery = battery;
-
+auto UiState::InitBootSplash(drivers::IGpios& gpios) -> bool {
+  // Init LVGL first, since the display driver registers itself with LVGL.
   lv_init();
-  sDisplay.reset(
-      drivers::Display::Create(gpio_expander, drivers::displays::kST7735R));
+  sDisplay.reset(drivers::Display::Create(gpios, drivers::displays::kST7735R));
   if (sDisplay == nullptr) {
     return false;
   }
-  sDisplay->SetBrightness(nvs->ScreenBrightness().get());
-
-  sTouchWheel.reset(drivers::TouchWheel::Create());
-  if (sTouchWheel != nullptr) {
-    sRelativeWheel.reset(new drivers::RelativeWheel(sTouchWheel.get()));
-  }
 
   sCurrentScreen.reset(new screens::Splash());
-
-  // Start the UI task even if init ultimately failed, so that we can show some
-  // kind of error screen to the user.
-  StartLvgl(sRelativeWheel, sDisplay);
-
-  if (sTouchWheel == nullptr) {
-    return false;
-  }
+  sTask.reset(UiTask::Start());
   return true;
 }
 
@@ -107,7 +82,8 @@ void UiState::PopScreen() {
 
 void UiState::react(const system_fsm::KeyLockChanged& ev) {
   sDisplay->SetDisplayOn(ev.falling);
-  sRelativeWheel->SetEnabled(ev.falling);
+  sTask->SetInputDevice(ev.falling ? sEncoder
+                                   : std::shared_ptr<TouchWheelEncoder>());
 }
 
 void UiState::react(const system_fsm::BatteryStateChanged&) {
@@ -115,8 +91,8 @@ void UiState::react(const system_fsm::BatteryStateChanged&) {
 }
 
 void UiState::UpdateTopBar() {
-  auto battery_state = sBattery->State();
-  bool has_queue = sQueue->GetCurrent().has_value();
+  auto battery_state = sServices->battery().State();
+  bool has_queue = sServices->track_queue().GetCurrent().has_value();
   bool is_playing = audio::AudioState::is_in_state<audio::states::Playback>();
 
   widgets::TopBar::State state{
@@ -140,19 +116,40 @@ namespace states {
 
 void Splash::exit() {
   if (sDisplay != nullptr) {
-    sDisplay->SetDisplayOn(sIGpios->Get(drivers::IGpios::Pin::kKeyLock));
+    sDisplay->SetDisplayOn(
+        sServices->gpios().Get(drivers::IGpios::Pin::kKeyLock));
   }
 }
 
 void Splash::react(const system_fsm::BootComplete& ev) {
+  sServices = ev.services;
+
+  // The system has finished booting! We now need to prepare to show real UI.
+  // This basically just involves reading and applying the user's preferences.
+
+  lv_theme_t* base_theme = lv_theme_basic_init(NULL);
+  lv_disp_set_theme(NULL, base_theme);
+  themes::Theme::instance()->Apply();
+
+  sDisplay->SetBrightness(sServices->nvs().ScreenBrightness().get());
+
+  auto touchwheel = sServices->touchwheel();
+  if (touchwheel) {
+    auto relative_wheel =
+        std::make_unique<drivers::RelativeWheel>(**touchwheel);
+    sEncoder = std::make_shared<TouchWheelEncoder>(std::move(relative_wheel));
+    sTask->SetInputDevice(sEncoder);
+  } else {
+    ESP_LOGE(kTag, "no input devices initialised!");
+  }
+
   transit<Browse>();
 }
 
 void Browse::entry() {}
 
 void Browse::react(const system_fsm::StorageMounted& ev) {
-  sDb = ev.db;
-  auto db = ev.db.lock();
+  auto db = sServices->database().lock();
   if (!db) {
     // TODO(jacqueline): Hmm.
     return;
@@ -177,7 +174,7 @@ void Browse::react(const internal::ShowSettingsPage& ev) {
       screen.reset(new screens::Headphones());
       break;
     case internal::ShowSettingsPage::Page::kAppearance:
-      screen.reset(new screens::Appearance(sNvs.get(), sDisplay.get()));
+      screen.reset(new screens::Appearance(sServices->nvs(), *sDisplay));
       break;
     case internal::ShowSettingsPage::Page::kInput:
       screen.reset(new screens::InputMethod());
@@ -198,7 +195,7 @@ void Browse::react(const internal::ShowSettingsPage& ev) {
 }
 
 void Browse::react(const internal::RecordSelected& ev) {
-  auto db = sDb.lock();
+  auto db = sServices->database().lock();
   if (!db) {
     return;
   }
@@ -206,9 +203,10 @@ void Browse::react(const internal::RecordSelected& ev) {
   auto record = ev.page->values().at(ev.record);
   if (record.track()) {
     ESP_LOGI(kTag, "selected track '%s'", record.text()->c_str());
-    sQueue->Clear();
-    sQueue->IncludeLast(std::make_shared<playlist::IndexRecordSource>(
-        sDb, ev.initial_page, 0, ev.page, ev.record));
+    auto& queue = sServices->track_queue();
+    queue.Clear();
+    queue.IncludeLast(std::make_shared<playlist::IndexRecordSource>(
+        sServices->database(), ev.initial_page, 0, ev.page, ev.record));
     transit<Playing>();
   } else {
     ESP_LOGI(kTag, "selected record '%s'", record.text()->c_str());
@@ -218,21 +216,21 @@ void Browse::react(const internal::RecordSelected& ev) {
     }
     auto query = db->GetPage(&cont.value());
     std::string title = record.text().value_or("TODO");
-    PushScreen(
-        std::make_shared<screens::TrackBrowser>(sDb, title, std::move(query)));
+    PushScreen(std::make_shared<screens::TrackBrowser>(
+        sServices->database(), title, std::move(query)));
   }
 }
 
 void Browse::react(const internal::IndexSelected& ev) {
-  auto db = sDb.lock();
+  auto db = sServices->database().lock();
   if (!db) {
     return;
   }
 
   ESP_LOGI(kTag, "selected index %s", ev.index.name.c_str());
   auto query = db->GetTracksByIndex(ev.index, kRecordsPerPage);
-  PushScreen(std::make_shared<screens::TrackBrowser>(sDb, ev.index.name,
-                                                     std::move(query)));
+  PushScreen(std::make_shared<screens::TrackBrowser>(
+      sServices->database(), ev.index.name, std::move(query)));
 }
 
 void Browse::react(const internal::BackPressed& ev) {
@@ -242,7 +240,8 @@ void Browse::react(const internal::BackPressed& ev) {
 static std::shared_ptr<screens::Playing> sPlayingScreen;
 
 void Playing::entry() {
-  sPlayingScreen.reset(new screens::Playing(sDb, sQueue));
+  sPlayingScreen.reset(
+      new screens::Playing(sServices->database(), sServices->track_queue()));
   PushScreen(sPlayingScreen);
 }
 
diff --git a/src/ui/wheel_encoder.cpp b/src/ui/wheel_encoder.cpp
index a0e12b7f..2f2e7f68 100644
--- a/src/ui/wheel_encoder.cpp
+++ b/src/ui/wheel_encoder.cpp
@@ -22,8 +22,8 @@ void encoder_feedback(lv_indev_drv_t* drv, uint8_t event_code) {
 }
 
 TouchWheelEncoder::TouchWheelEncoder(
-    std::weak_ptr<drivers::RelativeWheel> wheel)
-    : last_key_(0), wheel_(wheel) {
+    std::unique_ptr<drivers::RelativeWheel> wheel)
+    : last_key_(0), wheel_(std::move(wheel)) {
   lv_indev_drv_init(&driver_);
   driver_.type = LV_INDEV_TYPE_ENCODER;
   driver_.read_cb = encoder_read;
@@ -34,16 +34,11 @@ TouchWheelEncoder::TouchWheelEncoder(
 }
 
 auto TouchWheelEncoder::Read(lv_indev_data_t* data) -> void {
-  auto lock = wheel_.lock();
-  if (lock == nullptr) {
-    return;
-  }
+  wheel_->Update();
 
-  lock->Update();
-
-  data->enc_diff = lock->ticks();
+  data->enc_diff = wheel_->ticks();
   data->state =
-      lock->is_clicking() ? LV_INDEV_STATE_PRESSED : LV_INDEV_STATE_RELEASED;
+      wheel_->is_clicking() ? LV_INDEV_STATE_PRESSED : LV_INDEV_STATE_RELEASED;
 }
 
 }  // namespace ui