It's working more or less...

include/controller.h

@@ -1,13 +1,25 @@
 #pragma once
 
 #include <Arduino.h>
+#include <MFRC522v2.h>
+#include <MFRC522Debug.h>
+#include "esmp3.h"
+#include "playlist.h"
 
 class Controller {
 	private:
 	void handle_buttons();
 	void handle_rfid();
+	bool is_button_pressed(uint8_t pin);
+	Playlist current_playlist;
+	bool is_rfid_present = false;
+	unsigned long last_rfid_check = 0;
 
 	public:
 	void handle();
-	
+	void next_track();
+	void prev_track();
+	void play();
+	void play(String rfid_id);
+	void stop();
 };

include/esmp3.h

@@ -1,11 +1,26 @@
 #pragma once
-#include "controller.h"
 
-#define PIN_CS_SD     16
-#define PIN_CS_RFID   17
+#include "controller.h"
+#include "playlist_manager.h"
+#include <Audio.h>
+
+#define PIN_CS_SD     22
+#define PIN_CS_RFID   21
+
+#define PIN_BTN_VOL_UP 32
+#define PIN_BTN_VOL_DOWN 33
+#define PIN_BTN_TRACK_NEXT 34
+#define PIN_BTN_TRACK_PREV 35
 
 #define I2S_DOUT      25
-#define I2S_BCLK      27
-#define I2S_LRC       26
+#define I2S_BCLK      26
+#define I2S_LRC       27
 
-extern Controller controller;
+class Controller;
+
+extern Controller controller;
+extern Audio audio;
+extern PlaylistManager* pm;
+extern MFRC522* rfid;
+
+void save_audio_current_time();

include/playlist.h

@@ -7,9 +7,19 @@ class Playlist {
 	private:
 	std::vector<String> files;
 	uint8_t current_file = 0;
-	uint16_t current_time = 0;
+	uint32_t current_time = 0;
+	void set_current_position(uint8_t file, uint32_t position=0);
+	String rfid_id;
 
 	public:
+	Playlist(String rfid_id="");
 	void add_file(String filename);
 	void sort();
+	String get_rfid_id();
+	String get_current_file_name();
+	bool next_track();
+	bool prev_track();
+	void restart();
+	void set_current_time(uint32_t time);
+	uint32_t get_current_time();
 };

include/playlist_manager.h

@@ -16,6 +16,7 @@ class PlaylistManager {
 	std::vector<String> dirs;
 	std::map<String, String> map;
 	Playlist get_playlist(String rfid_id);
+	bool has_playlist(String rfid_id);
 	Playlist current_playlist;
 	void set_audio_current_time(uint32_t time);
 };