mpd: revamped to event-driven, single-threaded

Fix MPD connection issues by converting/rewriting module into a
state-machine driven system. It is fully single-threaded and uses
events for transitioning between states. It supports all features
and functionality of the previous MPD module.

Signed-off-by: Joseph Benden <joe@benden.us>

include/modules/mpd.hpp

@@ -1,74 +0,0 @@
-#pragma once
-
-#include <fmt/format.h>
-#include <mpd/client.h>
-#include <condition_variable>
-#include <thread>
-#include "ALabel.hpp"
-
-namespace waybar::modules {
-
-class MPD : public ALabel {
- public:
-  MPD(const std::string&, const Json::Value&);
-  auto update() -> void;
-
- private:
-  std::thread periodic_updater();
-  std::string getTag(mpd_tag_type type, unsigned idx = 0);
-  void        setLabel();
-  std::string getStateIcon();
-  std::string getOptionIcon(std::string optionName, bool activated);
-
-  std::thread event_listener();
-
-  // Assumes `connection_lock_` is locked
-  void tryConnect();
-  // If checking errors on the main connection, make sure to lock it using
-  // `connection_lock_` before calling checkErrors
-  void checkErrors(mpd_connection* conn);
-
-  // Assumes `connection_lock_` is locked
-  void fetchState();
-  void waitForEvent();
-
-  bool handlePlayPause(GdkEventButton* const&);
-
-  bool stopped();
-  bool playing();
-  bool paused();
-
-  const std::string module_name_;
-
-  using unique_connection = std::unique_ptr<mpd_connection, decltype(&mpd_connection_free)>;
-  using unique_status = std::unique_ptr<mpd_status, decltype(&mpd_status_free)>;
-  using unique_song = std::unique_ptr<mpd_song, decltype(&mpd_song_free)>;
-
-  // Not using unique_ptr since we don't manage the pointer
-  // (It's either nullptr, or from the config)
-  const char*    server_;
-  const unsigned port_;
-
-  unsigned timeout_;
-
-  // We need a mutex here because we can trigger updates from multiple thread:
-  // the event based updates, the periodic updates needed for the elapsed time,
-  // and the click play/pause feature
-  std::mutex        connection_lock_;
-  unique_connection connection_;
-  // The alternate connection will be used to wait for events: since it will
-  // be blocking (idle) we can't send commands via this connection
-  //
-  // No lock since only used in the event listener thread
-  unique_connection alternate_connection_;
-
-  // Protect them using the `connection_lock_`
-  unique_status status_;
-  mpd_state     state_;
-  unique_song   song_;
-
-  // To make sure the previous periodic_updater stops before creating a new one
-  std::mutex periodic_lock_;
-};
-
-}  // namespace waybar::modules