Version 0.4.1-dev: added mDNS responder for better discovery, added telling the mDNS name via TTS at startup; and API endpoints to control these two new features

README.md

@@ -3,7 +3,7 @@
 [![License: Unlicense](https://img.shields.io/badge/License-Unlicense-blue.svg?style=for-the-badge)](https://unlicense.org/)
 [![Open Source](https://img.shields.io/badge/Open_Source-gray?style=for-the-badge&logo=opensourceinitiative&logoColor=3DA639)](https://opensource.org/)
 [![ESP32](https://img.shields.io/badge/ESP32-FCC624?style=for-the-badge&logo=esphome&logoColor=black)](https://www.espressif.com/en/products/socs/esp32)
-[![State: Unstable](https://img.shields.io/badge/State-Unstable-red.svg?style=for-the-badge)]()
+[![State: Development](https://img.shields.io/badge/State-Development-orange.svg?style=for-the-badge)]()
 
 
 NetSpeaker is a project that aims to make it easier to build your own sound system, just like sqeezebox, for example.
@@ -16,6 +16,15 @@ via the constant operation_mode. Valid choices are:
 
 Any questions? Hopefully a look into the **Wiki** will help.
 
+## API demo
+
+One thing I have learnt while developing NetSpeaker is that implementing a web server 
+which servers hundreds of lines of html is... well sort of dumb (there previously was an API demo running
+directly on the NetSpeaker machine which took loads of resources when requested).
+You can see all this in [that commit](https://git.privacynerd.de/NetSpeaker/NetSpeaker/commit/35138308ef90ea1fccbf1b292eeb69a7d4e8a084).
+This local API demo has been replaced by another [repository](https://git.privacynerd.de/NetSpeaker/NetSpeaker-API-Demo) containing 
+the Demo as HTML files (you can just open these in your web browser and type in you NetSpeaker's IP address and start playing).
+
 
 ## Audio compatibility
 
@@ -28,6 +37,7 @@ Features, already implemented, or still in progress for the v1.0.0 release!
 
 - [x] SD card support for playing audio files
 - [x] Two operating modes, standalone mode fully implemented
+- [x] two further operation modes to choose whether to run as standalone or interconnected at startup by pressing buttons
 - [x] API in mode 0
 - [x] API methods:
     - [X] /api/v1/playback/toggle
@@ -39,6 +49,8 @@ Features, already implemented, or still in progress for the v1.0.0 release!
     - [ ] /api/v1/playback/id3_image
     - [X] /api/v1/playback/<index>
     - [X] /api/v1/playlist/get
+    - [X] /api/v1/playlist/create
+    - [X] /api/v1/playlist/play
     - [X] /api/v1/volume/get
     - [X] /api/v1/volume/get_max
     - [X] /api/v1/volume/up
@@ -61,19 +73,24 @@ Features, already implemented, or still in progress for the v1.0.0 release!
     - [X] /api/v1/system/restart/
     - [X] /api/v1/system/name
     - [X] /api/v1/system/name/change
+    - [X] /api/v1/system/network_name
+    - [X] /api/v1/system/network_name/change
     - [X] /api/v1/system/restore_state/{on,off,get}
     - [X] /api/v1/system/restore_playing/{on,off,get}
+    - [X] /api/v1/system/tell_address/{on,off,get}
     - [X] /api/v1/system/version
     - [X] /api/v1/system/wifi/change
     - [X] /api/v1/system/wifi/get_ssid
+    - [X] /api/v1/system/wifi/get_ap_creds
     - [ ] /api/v1/files/get
     - [ ] /api/v1/files/upload
 - [X] Automatic WiFi connection
 - [X] Access Point opened when no WiFi connection could be established
-- [ ] Implement a simple web interface running on location /
 - [X] Improve the volume endpoint handler (currently pretty undynamic - not anymore :)
 - [ ] Add better encoding as umlauts are not displayed correctly **sometimes**
 
+Please note that all API endpoints may not end with a `/`.
+
 
 ## Credits & Acknowledgements
 
@@ -82,7 +99,6 @@ Thanks to...
 - the makers of Arduino IDE
 - schreibfaul1 (github) for creating the audio library used in this project
 - espressif for making the best microprocessor I've ever seen
-- the authors of Bootstrap which is being used for the simple web UI
 
 External librarys used:
 
@@ -90,6 +106,13 @@ External librarys used:
 - Arduino ESP32-specific librarys (https://github.com/espressif/arduino-esp32/ as of 2023/12)
 
 
+## Helpful links
+
+- [Seperate audio task example which may solve the issue that when running the API server no IO is accesible (no buttons, status led, ...)](https://github.com/schreibfaul1/ESP32-audioI2S/tree/master/examples/separate_audiotask)
+- [Wiki of the projects Audio library](https://github.com/schreibfaul1/ESP32-audioI2S/wiki)
+- [API demo showing how to use the NetSpeaker's API](https://git.privacynerd.de/NetSpeaker/NetSpeaker-API-Demo)
+
+
 ## Contributing
 
 Pull requests are welcome. For major changes, please open an issue first
@@ -114,4 +137,3 @@ successors. We intend this dedication to be an overt act of relinquishment in pe
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 For more information, please refer to <http://unlicense.org/>
-

initial_config.ino

@@ -0,0 +1,18 @@
+#import <Preferences.h>
+
+const char PREFERENCES_KEY_WIFI_SSID[] = "wifi_ssid";              // preferences key name for wifi ssid; DO NOT CHANGE
+const char PREFERENCES_KEY_WIFI_PSK[] = "wifi_psk";                // preferences key name for wifi psk;  DO NOT CHANGE
+const char WIFI_SSID[] = "";                                       // type in the wifi's ssid here
+const char WIFI_PSK[] = "";                                        // and the wifi's passkey
+Preferences config;
+
+void setup() {
+  config.begin("netspeaker", false);
+  config.clear();
+  config.putString(PREFERENCES_KEY_WIFI_SSID, WIFI_SSID);
+  config.putString(PREFERENCES_KEY_WIFI_PSK, WIFI_PSK);
+}
+
+void loop() {
+  // empty loop
+}

src/NetSpeaker/NetSpeaker.ino

@@ -1,12 +1,18 @@
 /*
 This is free and unencumbered software released into the public domain.
 
-Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in 
+source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
 
-In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and
-successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
+In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and 
+all copyright interest in the software to the public domain. We make this dedication for the benefit of 
+the public at large and to the detriment of our heirs and successors. We intend this dedication to be an 
+overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED 
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 
+THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR 
+OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 For more information, please refer to <http://unlicense.org/>
 */
@@ -19,11 +25,15 @@ For more information, please refer to <http://unlicense.org/>
 #include <WebServer.h>      // https://github.com/espressif/arduino-esp32/tree/master/libraries/WebServer
 #include <uri/UriBraces.h>  // https://github.com/espressif/arduino-esp32/tree/master/libraries/WebServer
 #include <Preferences.h>    // https://github.com/espressif/arduino-esp32/tree/master/libraries/Preferences/
+#include <ESPmDNS.h>        // https://github.com/espressif/arduino-esp32/blob/master/libraries/ESPmDNS/
 
 
 // define all constants
-const String version = "NetSpeaker v0.3.3-dev";                    // version string used e.g. for access point ssid when wifi couldn't connect
-const int operation_mode = 0;                                      // 0: interconnected (no buttons, but api and wifi); 1: standalone (no wifi; no api)
+const String version_tag = "v0.4.1-dev";                                // version tag (with -dev appendix for dev versions)
+const String version = "NetSpeaker " + version_tag;                     // version string used e.g. for access point ssid when wifi couldn't connect
+const int operation_mode = 3;                                           // 0: interconnected (no buttons, but api and wifi); 1: standalone (no wifi; no api);
+                                                                        // 2: choose by pressing any button at startup (not pressed: interconnected; pressed: standalone)
+                                                                        // 3: same as 2 but if not pressed: standalone; pressed: interconnected
 const int SD_CS = 5;                                                    // BOARD SPECIFIC
 const int SPI_MISO = 19;                                                // BOARD SPECIFIC
 const int SPI_MOSI = 23;                                                // BOARD SPECIFIC
@@ -33,7 +43,7 @@ const int I2S_BLCK = 4;                                            // can be cha
 const int I2S_LRC = 15;                                                 // can be changed on need
 const int sdCardEjectPin = 13;                                          // pin which is used to tell the program to eject the sd card (so that the file system doesn't brake)
 const int audioVolumePin = 25;                                          // pin where the poti is connected to (wired as voltage divider)
-const int pausePlaybackPin = 12;                                   // switch (the switching is done digitally, a button has to be connected, NO switch) between play and pause
+const int pausePlaybackPin = 12;                                        // switch (the switching is done digitally, a button has to be connected, NO switch) between play and pause)
 const int forwardButtonPin = 14;                                        // pin for forward button
 const int backwardButtonPin = 27;                                       // pin for backward btn
 const int waitOnSDCardEject = 5000;                                     // defines how long to wait (in ms) after the button for SD card eject was pressed (on pin 'sdCardEjectPin'!)
@@ -42,15 +52,18 @@ const int readyPin = 32;                                           // for an LED
 const int webport_api = 80;                                             // port for the api (can't be the same as 'webport_config', will throw an error)
 const int maxVolume = 100;                                              // defines the volume steps (max. 255)
 const int EEPROM_WRITE_INTERVAL = 10000;                                // how long to wait until the next EEPROM saving process, in ms
+const int WEB_RESTART_DELAY = 5000;                                     // how long (in ms) to wait when a restart is requested by the api
+const int startupChooserWaitTime = 5000;                                // how long to wait for user to choose the mode (in operation_modes 2 and 3)
+const int startupChooserBlinkDelay = 500;                               // how long to wait for user to choose the mode (in operation_modes 2 and 3)
 const String playlistExtension = ".m3u";                                // extension for playlist files
 const String directoryPlaylistName = ".directory";                      // name for directory playlists (not a path, just a filename without ext.!)
-const String wifiConfigPath = "/.wifi.conf";                       // MAX LENGTH: 32 resp. 63 chars; path to configuration file; content: <WiFi SSID>\n<WiFi PSK> (ssid and password divided by an newline)
 const String apSSID = version;                                          // ssid of access point opened when not able to connect to wifi
 const String apPSK = "aA16161Aa";                                       // pre-shared-key of access point opened when not able to connect to wifi
 const char PREFERENCES_NAMESPACE[] = "netspeaker";                      // namespace for preferences library (stores config data in the ESP32's built-in EEPROM)
 const char PREFERENCES_KEY_WIFI_SSID[] = "wifi_ssid";                   // preferences key name for wifi ssid
 const char PREFERENCES_KEY_WIFI_PSK[] = "wifi_psk";                     // preferences key name for wifi psk
 const char PREFERENCES_KEY_FRIENDLY_NAME[] = "friendly_name";           // preferences key name for the NetSpeaker's friendly name
+const char PREFERENCES_KEY_NETWORK_NAME[] = "network_name";             // preferences key name for the NetSpeaker's network name (<Network name>.local)
 const char PREFERENCES_KEY_RESTORE_OLD_STATE[] = "restore_state";       // preferences key name for getting if the old state should be restored or not
 const char PREFERENCES_KEY_RESTORE_PLAYING[] = "restore_playing";       // preferences key name for getting if the old state should be restored or not
 const char PREFERENCES_KEY_VOLUME[] = "volume";                         // preferences key name for old volume (for state restore)
@@ -62,6 +75,7 @@ const char PREFERENCES_KEY_PLAYING[] = "playing";                  // preference
 const char PREFERENCES_KEY_MUTED[] = "muted";                           // preferences key name for info if currently muted
 const char PREFERENCES_KEY_PLAYLIST_PATH[] = "playlist";                // preferences key name for playlist path (for state restore)
 const char PREFERENCES_KEY_PLAYLIST_INDEX[] = "pl-index";               // preferences key name for current playlist index (for state restore)
+const char PREFERENCES_KEY_TELL_ADDRESS_AT_STARTUP[] = "tell_address";  // preferences key name for current playlist index (for state restore)
 
 // all other variables needed
 Audio audio;                                                                                       // Audio object (for playing audio, decoding mp3, ...)
@@ -72,6 +86,10 @@ int currentWiFiMode = 0;
 bool apON = false;                                                                                 // DON'T CHANGE IF NOT KNOWING WHAT YOU'RE DOING; is the access point opened?
 Preferences configuration;
 long lastTimeEEPROMwritten = 0;              // used to limit the number of eeprom write cycles
+int operationModeChosen = operation_mode;    // if in operation modes 2 or 3, you can choose between "interconnected" (= 0) and "standalone" (=1). This variable is used to store the decision (made at startup!)
+bool eof_speech_reached = false;             // used to recognize the end of an tts speech (e.g. used for telling the address of the netspeaker)
+bool wait_after_eof_speech = false;          // used for the audio_eof_speech handler to determine what to do after reaching eof_speach
+String default_network_name = "netspeaker";  // default network name (the part of the mDNS domain before .local (<networkName>.local will be registered))
 
 // create all variables for playback (will be set in 'void setup()' by 'restoreLastState();' call)
 int currentVolume = 100;                     // variable where current volume (0...maxVolume) is stored
@@ -84,12 +102,12 @@ bool audioPlaying = false;                 // play song or not?; don't play by s
 String currentSongPath;                      // path to currently playing song
 String currentPlaylist = defaultPlaylist;    // path to current playlist
 int currentPlaylistPosition = -1;            // the current position in the current playlist
-bool restore_old_state;                    // restore the old state of EEPROM?
+
 
 // struct for playback info (especially when playing mp3 files with id3 tags)
 struct playbackInfo {
   String title;         // e.g. Big Buck Bunny
-  String type;          // e.g. local
+  String type;          // e.g. local/google-tts/http
   String resourcePath;  // e.g. /audio/XXX.mp3
   String artist;        // e.g. Blender Foundation
   String track;         // e.g. 01/02 or 01
@@ -97,40 +115,127 @@ struct playbackInfo {
   String year;          // id3 tag year
   String genre;         // id3 tag content type
   String copyright;     // id3 tag (special)
+  String tts_language;  // text-to-speech language
 };
-struct playbackInfo pbInfo = { "", "", "", "", "", "", "", "", "" };
+struct playbackInfo pbInfo = { "", "", "", "", "", "", "", "", "", "" };
+
+
+// general helper when an system-halting error occurs (to show this, the LED blinks fast)
+bool indicate_system_error() {
+  pinMode(readyPin, OUTPUT);
+
+  while(true) {
+    digitalWrite(readyPin, LOW);
+    delay(150);
+    digitalWrite(readyPin, HIGH);
+    delay(150);
+  }
+}
+
+// helper for operation mode 2 and 3
+bool wait_for_btn_press_and_blink(int blink_pin, int blink_delay, int wait_time) {  // returns true for button pressed and false for button not pressed
+  pinMode(sdCardEjectPin, INPUT);
+  pinMode(backwardButtonPin, INPUT);
+  pinMode(pausePlaybackPin, INPUT);
+  pinMode(forwardButtonPin, INPUT);
+  pinMode(readyPin, OUTPUT);
+
+  int wait_timer_start = millis();
+  int blink_timer_start;
+
+  while ((millis() - wait_timer_start) < wait_time) {  // wait_time in milliseconds!
+    // turn led on and wait for blink_delay while checking for button presses
+    digitalWrite(blink_pin, HIGH);  // turn the LED on (HIGH is the voltage level)
+    blink_timer_start = millis();
+    while((millis() - blink_timer_start) < blink_delay) {  // wait a given time period (delay in milliseconds!)
+      if(analogRead(sdCardEjectPin) > 4000 || analogRead(pausePlaybackPin) > 4000 || analogRead(forwardButtonPin) > 4000 || analogRead(backwardButtonPin) > 4000) return true;
+    }
+
+    // turn led off and wait for blink_delay while checking for button presses
+    digitalWrite(blink_pin, LOW);
+    blink_timer_start = millis();
+    while((millis() - blink_timer_start) < blink_delay) {
+      if(analogRead(sdCardEjectPin) > 4000 || analogRead(pausePlaybackPin) > 4000 || analogRead(forwardButtonPin) > 4000 || analogRead(backwardButtonPin) > 4000) return true;
+    }
+  }
+  return false;
+}
 
 void setup() {
   Serial.begin(115200);                               // setup Serial console (over USB) with baud 115200
   configuration.begin(PREFERENCES_NAMESPACE, false);  // Initialize preferences library in RW mode
 
   // restore process if configured so
-  restore_old_state = configuration.getBool(PREFERENCES_KEY_RESTORE_OLD_STATE, true);
-  if (restore_old_state) restoreLastState();  // standard of restore = true
+  if (configuration.getBool(PREFERENCES_KEY_RESTORE_OLD_STATE, true)) restoreLastState();  // standard of restore = true
 
   // connect to sd card reader
-  Serial.println("[SETUP]              Setting up SD-Card reader");
+  Serial.println(F("[SETUP]              Setting up SD-Card reader"));
   while (!setupSD(SD_CS, SPI_MISO, SPI_MOSI, SPI_SCK)) {
     Serial.printf("[SETUP]              Can't connect to SD card reader! Waiting for %d milliseconds...\n", retrySDMountTreshold);
     delay(retrySDMountTreshold);
   }
 
-  if (operation_mode == 0) {  // things only need to be done if in interconnected mode
-    setupWiFi();
-    setupWeb();
-  } else if (operation_mode == 1) {  // things only need to be done if in standalone mode
+  setupAudio();  // setup audio library
+
+
+  // DEPENDING ON THE OPERATION MODE, DIFFERENT OPERATIONS NEED TO BE DONE
+  // BEFORE STARTING. This is what the following code does.
+
+  // operation_mode 0: see below
+  if (operation_mode == 1) {  // things only need to be done if in standalone mode
     // setup all pins (not SPI and other buses!)
     pinMode(sdCardEjectPin, INPUT);
     pinMode(backwardButtonPin, INPUT);
     pinMode(pausePlaybackPin, INPUT);
     pinMode(forwardButtonPin, INPUT);
     pinMode(readyPin, OUTPUT);
+  } else if (operation_mode == 2) {  // if enabled choosing  (mode 2: no press = interconnected, press = standalone)
+    bool runStandalone = wait_for_btn_press_and_blink(readyPin, startupChooserBlinkDelay, startupChooserWaitTime);
+    
+    if (runStandalone) {
+      Serial.println(F("[SETUP]              User pressed button; Running in 'Standalone' mode now!"));
+      operationModeChosen = 1;
+      digitalWrite(readyPin, HIGH);
     } else {
-    Serial.println("[FATAL] PLEASE CHOOSE A OPERATION MODE! VALID OPTIONS: 0; 1. SLEEPING FOREVER.");
-    while (true) delay(100);
+      Serial.println(F("[SETUP]              User didn't press any button; Running in 'Interconnected' mode now!"));
+      operationModeChosen = 0;
+      digitalWrite(readyPin, HIGH);
     }
 
-  setupAudio();                                        // setup audio library
+  } else if (operation_mode == 3) {  // if enabled choosing  (mode 3: no press = standalone, press = interconnected)
+    bool runInterconnected = wait_for_btn_press_and_blink(readyPin, startupChooserBlinkDelay, startupChooserWaitTime);
+    
+    if (runInterconnected) {
+      Serial.println(F("[SETUP]              User pressed button; Running in 'Interconnected' mode now!"));
+      operationModeChosen = 0;
+      digitalWrite(readyPin, HIGH);
+    } else {
+      Serial.println(F("[SETUP]              User didn't press any button; Running in 'Standalone' mode now!"));
+      operationModeChosen = 1;
+      digitalWrite(readyPin, HIGH);
+    }
+  }
+
+  // this function is placed here because it could be that the operation mode is chosen to be interconnected - then this check needs to run afterwards!
+  if (operation_mode == 0 || operationModeChosen == 0) {  // things only need to be done if in - or choosen to - interconnected mode
+    setupWiFi(); 
+
+    // set up the mDNS responder
+    setupMDNS();
+
+    // set up the API web server
+    setupWeb();
+
+    // now tell the address (can be turned off using the web API, state stored in the EEPROM)
+    tellAddressInfo();  // helper which uses google TTS to tell the address
+  } 
+  if (operation_mode != 0 && operation_mode != 1 && operation_mode != 2 && operation_mode != 3) {
+    Serial.println(F("[FATAL] PLEASE CHOOSE A OPERATION MODE! VALID OPTIONS: 0; 1; 2; 3. SLEEPING FOREVER."));
+    indicate_system_error();  // halt system and blink readyPin
+  }
+
+  // AND start the current track (if restored from EEPROM, only nextAudio is doing something important)
+  // TODO: move createPlaylistFromDirectory to some place where it fits better and is not called uselessly
   createPlaylistFromDirectory(defaultPlaylistFolder);  // create playlist from default dir
   nextAudio();                                         // play first element of the playlist
   digitalWrite(readyPin, HIGH);                        // show that startup is done and everything works fine
@@ -138,13 +243,14 @@ void setup() {
 
 
 void loop() {
-  if (operation_mode == 0) {               // things only need to be done if in interconnected mode
+  if (operation_mode == 0 || operationModeChosen == 0) {  // things only need to be done if in interconnected mode
     setupWiFi();                           // if connection was lost
     if (audioPlaying) audio.loop();        // play audio if not paused
     if (esp_timer_get_time() % 60 == 0) {  // REALLY NEEDED; audio playing won't work else!
       api_server.handleClient();           // listen on http ports all 60 ms
     }
-  } else if (operation_mode == 1) {  // things only need to be done if in standalone mode
+  }
+  if (operation_mode == 1 || operationModeChosen == 1) {  // things only need to be done if in standalone mode
     if (audioPlaying) audio.loop();  // play audio if not paused
 
     loopBtnListeners();

src/NetSpeaker/audio.ino

@@ -1,12 +1,18 @@
 /*
 This is free and unencumbered software released into the public domain.
 
-Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in 
+source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
 
-In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and
-successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
+In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and 
+all copyright interest in the software to the public domain. We make this dedication for the benefit of 
+the public at large and to the detriment of our heirs and successors. We intend this dedication to be an 
+overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED 
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 
+THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR 
+OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 For more information, please refer to <http://unlicense.org/>
 */
@@ -21,30 +27,43 @@ void setupAudio() {
   Serial.printf("[SETUP]              Set up audio card successfully (Pins: BLCK %d | LRC %d | DOUT %d)\n", I2S_BLCK, I2S_LRC, I2S_DOUT);
 }
 
+void tellAddressInfo() {
+  // TODO: make this Preference accessible via the Web API
+  if(configuration.getBool(PREFERENCES_KEY_TELL_ADDRESS_AT_STARTUP, true) && apON == false) {  // only tell the name if the key is set (do it by default) and connected to wifi (for internet)
+    String tell_address_string = "Connected. Head over to " + WiFi.localIP().toString() + " or " + configuration.getString(PREFERENCES_KEY_NETWORK_NAME, default_network_name) + " dot local";
+    Serial.printf("[SETUP]              Telling address now. String: %s\n", tell_address_string);
+    audio.connecttospeech(tell_address_string.c_str(), "en");
+    wait_after_eof_speech = true;  // to prevent the eof_speech handler of the Audio.h library (defined below) to play next audio (as there's none at startup!)
+    while(!eof_speech_reached) { audio.loop(); }  // wait till end of speech
+    wait_after_eof_speech = false;  // turn calling nextAudio on again (the default behaviour)
+    eof_speech_reached = false;  // reset the variable
+    Serial.println("[SETUP]              Told the address.");
+  } else {
+    Serial.println("[SETUP]              Did not tell my address because either not connected to WiFi or it's not configured so.");
+  }
+}
+
 String nextAudio() {
   String url;
 
   currentPlaylistPosition++;  // increment once
   url = getURLFromPlaylist(currentPlaylist, currentPlaylistPosition);
 
-  if (url == "") {                 // if the end of the playlist is reached go to start
+  if (url == "") {                 // if the end of the playlist is reached go to start (typically)
+    if(getURLFromPlaylist(currentPlaylist, 0) == "") {  // untypically: prevent infinite loop if playlist doesn't exist
+      Serial.println(F("[ERROR]              It seems like the current playlist does not exist! Defaulting to the default playlist!"));
+      currentPlaylist = defaultPlaylist;
+      currentPlaylistPosition = 0;
+      return "";
+    }
     currentPlaylistPosition = -1;  // the next time "nextAudio()" is called it will increment to 0
     nextAudio();                   // recursive call
     return "";                     // exit
   }
 
-  if (url.startsWith("http")) {
-    Serial.printf("[INFO]               Starting stream from playlist (ID: %d, URL: %s)\n", currentPlaylistPosition, url.c_str());
-    audio.connecttohost(url.c_str());
-  } else if (url.startsWith("/")) {
-    Serial.printf("[INFO]               Starting audio from playlist (ID: %d, Path: %s)\n", currentPlaylistPosition, url.c_str());
-    audio.connecttoFS(SD, url.c_str());      // play the next song
-  } else if (url.startsWith("speech://")) {  // format: speech://CC@TEXT where CC is the country code, e.g. en or de
-    Serial.printf("[INFO]               Starting speech from playlist (ID: %d, Language: %s, Text: %s)\n", currentPlaylistPosition, url.substring(9, 11).c_str(), url.substring(12).c_str());
-    audio.connecttospeech(url.substring(12).c_str(), url.substring(9, 11).c_str());
-  }
+
   // clear everything (if a file hadn't got id3 tags so that there won't keep the old names)
-  // these attributes are set by the audio_id3data function
+  // these attributes are set by the audio_id3data function (and the nextAudio and previousAudio functions)
   pbInfo.title = "";
   pbInfo.type = "";
   pbInfo.resourcePath = "";
@@ -54,9 +73,29 @@ String nextAudio() {
   pbInfo.year = "";
   pbInfo.genre = "";
   pbInfo.copyright = "";
+  pbInfo.tts_language = "";
 
   pbInfo.resourcePath = url;
+  pbInfo.type = "";
+
+
+  if (url.startsWith("http")) {
+    Serial.printf("[INFO]               Starting stream from playlist (ID: %d, URL: %s)\n", currentPlaylistPosition, url.c_str());
+    audio.connecttohost(url.c_str());
+    pbInfo.type = "http";
+  } else if (url.startsWith("/")) {
+    Serial.printf("[INFO]               Starting audio from playlist (ID: %d, Path: %s)\n", currentPlaylistPosition, url.c_str());
+    audio.connecttoFS(SD, url.c_str());      // play the next song
     pbInfo.type = "local";
+  } else if (url.startsWith("speech://")) {  // format: speech://CC@TEXT where CC is the country code, e.g. en or de
+    String language = url.substring(9, 11).c_str();
+    String speech_path = url.substring(12).c_str();
+    Serial.printf("[INFO]               Starting speech from playlist (ID: %d, Language: %s, Text: %s)\n", currentPlaylistPosition, language, speech_path);
+    audio.connecttospeech(url.substring(12).c_str(), url.substring(9, 11).c_str());
+    pbInfo.type = "google-tts";
+    pbInfo.track = speech_path;
+    pbInfo.tts_language = language;
+  }
 
   return url;
 }
@@ -68,18 +107,9 @@ String previousAudio() {
   if (currentPlaylistPosition < 0) currentPlaylistPosition = 0;
 
   url = getURLFromPlaylist(currentPlaylist, currentPlaylistPosition);
-  if (url.startsWith("http")) {
-    Serial.printf("[INFO]               Starting stream from playlist (ID: %d, URL: %s)\n", currentPlaylistPosition, url.c_str());
-    audio.connecttohost(url.c_str());
-  } else if (url.startsWith("/")) {
-    Serial.printf("[INFO]               Starting audio from playlist (ID: %d, Path: %s)\n", currentPlaylistPosition, url.c_str());
-    audio.connecttoFS(SD, url.c_str());      // play the next song
-  } else if (url.startsWith("speech://")) {  // format: speech://CC@TEXT where CC is the country code, e.g. en or de
-    Serial.printf("[INFO]               Starting speech from playlist (ID: %d, Language: %s, Text: %s)\n", currentPlaylistPosition, url.substring(9, 11).c_str(), url.substring(12).c_str());
-    audio.connecttospeech(url.substring(12).c_str(), url.substring(9, 11).c_str());
-  }
+
   // clear everything (if a file hadn't got id3 tags so that there won't keep the old names)
-  // these attributes are set by the audio_id3data function
+  // these attributes are set by the audio_id3data function (and the nextAudio and previousAudio functions)
   pbInfo.title = "";
   pbInfo.type = "";
   pbInfo.resourcePath = "";
@@ -89,9 +119,28 @@ String previousAudio() {
   pbInfo.year = "";
   pbInfo.genre = "";
   pbInfo.copyright = "";
+  pbInfo.tts_language = "";
 
   pbInfo.resourcePath = url;
+  pbInfo.type = "";
+
+  if (url.startsWith("http")) {
+    Serial.printf("[INFO]               Starting stream from playlist (ID: %d, URL: %s)\n", currentPlaylistPosition, url.c_str());
+    audio.connecttohost(url.c_str());
+    pbInfo.type = "http";
+  } else if (url.startsWith("/")) {
+    Serial.printf("[INFO]               Starting audio from playlist (ID: %d, Path: %s)\n", currentPlaylistPosition, url.c_str());
+    audio.connecttoFS(SD, url.c_str());      // play the next song
     pbInfo.type = "local";
+  } else if (url.startsWith("speech://")) {  // format: speech://CC@TEXT where CC is the country code, e.g. en or de
+    String language = url.substring(9, 11).c_str();
+    String speech_path = url.substring(12).c_str();
+    Serial.printf("[INFO]               Starting speech from playlist (ID: %d, Language: %s, Text: %s)\n", currentPlaylistPosition, language, speech_path);
+    audio.connecttospeech(url.substring(12).c_str(), url.substring(9, 11).c_str());
+    pbInfo.type = "google-tts";
+    pbInfo.track = speech_path;
+    pbInfo.tts_language = language;
+  }
 
   return url;
 }
@@ -145,12 +194,17 @@ void audio_eof_mp3(const char *info) {  // MUST HAVE THIS NAME (audio_eof_mp3) b
 }
 void audio_eof_speech(const char *info) {
   Serial.printf("[Audio.h] EOF_Speech %s\n", info);
+  
+  if (wait_after_eof_speech) {
+    eof_speech_reached = true;
+  } else {
     nextAudio();
   }
+}
 void audio_info(const char *info) {
   Serial.printf("[Audio.h] Info       %s\n", info);
 
-  if (String(info).startsWith("End of webstream")) {
+  if (String(info).startsWith(F("End of webstream"))) {
     nextAudio();
   }
 }
@@ -161,17 +215,17 @@ void audio_id3data(const char *info) {  // id3 metadata
   String info_str = String(info);
   if (info_str.startsWith("Album: ")) {
     pbInfo.album = info_str.substring(7);
-  } else if (info_str.startsWith("Title: ")) {
+  } else if (info_str.startsWith(F("Title: "))) {
     pbInfo.title = info_str.substring(7);
-  } else if (info_str.startsWith("Track: ")) {
+  } else if (info_str.startsWith(F("Track: "))) {
     pbInfo.track = info_str.substring(7);
-  } else if (info_str.startsWith("Artist: ")) {
+  } else if (info_str.startsWith(F("Artist: "))) {
     pbInfo.artist = info_str.substring(8);
-  } else if (info_str.startsWith("ContentType: ")) {
+  } else if (info_str.startsWith(F("ContentType: "))) {
     pbInfo.genre = info_str.substring(13);
-  } else if (info_str.startsWith("Year: ")) {
+  } else if (info_str.startsWith(F("Year: "))) {
     pbInfo.year = info_str.substring(6);
-  } else if (info_str.startsWith("Copyright: ")) {
+  } else if (info_str.startsWith(F("Copyright: "))) {
     pbInfo.copyright = info_str.substring(11);
   }
 }

src/NetSpeaker/fs.ino

@@ -1,12 +1,18 @@
 /*
 This is free and unencumbered software released into the public domain.
 
-Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in 
+source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
 
-In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and
-successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
+In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and 
+all copyright interest in the software to the public domain. We make this dedication for the benefit of 
+the public at large and to the detriment of our heirs and successors. We intend this dedication to be an 
+overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED 
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 
+THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR 
+OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 For more information, please refer to <http://unlicense.org/>
 */
@@ -22,7 +28,7 @@ int setupSD(int SD_CS, int SPI_MISO, int SPI_MOSI, int SPI_SCK) {
 
 // write preferences via the Preferences.h library
 void writeLastState() {
-  if (restore_old_state) {  // only save if restoration is wanted (to avoid unnecessary write cycles on eeprom)
+  if (configuration.getBool(PREFERENCES_KEY_RESTORE_OLD_STATE, true)) {  // only save if restoration is wanted (to avoid unnecessary write cycles on eeprom)
     // always check if the value is different on the EEPROM so that it has to be updated
     Serial.printf("[RESTORE]            Saving last state to EEPROM.\n");
     if (configuration.getInt(PREFERENCES_KEY_VOLUME, maxVolume) != currentVolume) configuration.putInt(PREFERENCES_KEY_VOLUME, currentVolume);
@@ -54,11 +60,14 @@ void restoreLastState() {
   Serial.printf("[RESTORE]            PREFERENCES_KEY_PLAYING = %s\n", audioPlaying ? "true" : "false");
   muted = configuration.getBool(PREFERENCES_KEY_MUTED, false);
   Serial.printf("[RESTORE]            PREFERENCES_KEY_MUTED = %s\n", muted ? "true" : "false");
+  if( operation_mode == 0 ) {  // only restore playlist if in interconnected mode (operation_mode = 0)
     currentPlaylist = configuration.getString(PREFERENCES_KEY_PLAYLIST_PATH, defaultPlaylist);  // default folder
     Serial.printf("[RESTORE]            PREFERENCES_KEY_PLAYLIST_PATH = %s\n", currentPlaylist.c_str());
+  }
   currentPlaylistPosition = configuration.getInt(PREFERENCES_KEY_PLAYLIST_INDEX, 0) - 1;  // -1 as default playlist position (is incremented with the first nextAudio() call)
   Serial.printf("[RESTORE]            PREFERENCES_KEY_PLAYLIST_INDEX = %i\n", currentPlaylistPosition);
-  Serial.println("[RESTORE]            Restored.");
+  
+  Serial.println(F("[RESTORE]            Restored."));
 }
 
 bool createPlaylistFromDirectory(String folderpath) {  // create a .m3u playlist from all directory contents (the directory 'folderpath' is used)
@@ -66,7 +75,7 @@ bool createPlaylistFromDirectory(String folderpath) {  // create a .m3u playlist
   File playlist;
 
   if (folderpath[folderpath.length() - 1] == '/' && folderpath.length() > 1) {  // check if file is ending with a "/" - because it wont work otherwise
-    Serial.printf("[ERROR]              Can't use a folder path with trailing /\n");
+    Serial.println(F("[ERROR]              Can't use a folder path with trailing /"));
     return false;
   }
 

src/NetSpeaker/webserver.ino

@@ -1,17 +1,23 @@
 /*
 This is free and unencumbered software released into the public domain.
 
-Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in 
+source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
 
-In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and
-successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
+In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and 
+all copyright interest in the software to the public domain. We make this dedication for the benefit of 
+the public at large and to the detriment of our heirs and successors. We intend this dedication to be an 
+overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED 
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 
+THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR 
+OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 For more information, please refer to <http://unlicense.org/>
 */
 
-String generate_api_json(bool success, String content, bool plain) {
+String send_api_json(bool success, String content, bool plain) {
   String json = "{\"success\": ";  // success
   json += success ? "true" : "false";
   json += ", ";
@@ -24,13 +30,15 @@ String generate_api_json(bool success, String content, bool plain) {
   }
   json += "}";
 
+  api_server.sendHeader("Access-Control-Allow-Origin", "*");
+  api_server.send(200, "application/json", json);
   return json;
 }
-String generate_api_json(bool success) {  // if you just want the basic json frame with the basic info
-  return generate_api_json(success, "", true);
+String send_api_json(bool success) {  // if you just want the basic json frame with the basic info
+  return send_api_json(success, "", true);
 }
-String generate_api_json(bool success, String content) {  // when info is to be embedded
-  return generate_api_json(success, content, false);
+String send_api_json(bool success, String content) {  // when info is to be embedded
+  return send_api_json(success, content, false);
 }
 bool isStringConvertable2Int(String toIntStr) {
   for (int i = 0; i < toIntStr.length(); i++) {  // check if a non-digit character is in the given string
@@ -39,319 +47,67 @@ bool isStringConvertable2Int(String toIntStr) {
   return true;
 }
 
-
-
-void api_root() {
-  Serial.println("[HTTP] [Config]      200 - GET '/'");
-
-  String html = "<!doctype html>";
-  html += "<html><head>";
-  html += "<meta charset='utf-8'><meta name='viewport' content='width=device-width,initial-scale=1'>";
-  html += "<title>Web UI | " + version + "</title>";
-  html += "<link href='https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/css/bootstrap.min.css' rel='stylesheet' integrity='sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN' crossorigin='anonymous'>";
-  html += "</head><body data-bs-theme='dark'>";
-  html += "<div class='text-center container-sm' style='padding: 4em 0em'>";
-
-  html += "<p>Welcome to</p>";
-  html += "<h1>" + configuration.getString(PREFERENCES_KEY_FRIENDLY_NAME, "NetSpeaker") + "</h1>";
-  html += "<code>" + version + "</code>";
-
-  html += "<hr style='margin: 3em 0em;'>";
-
-  // informations accordion
-  html += "<div class='accordion text-start' id='accordion-info'>";
-  html += "  <div class='accordion-item'>";
-  html += "    <h2 class='accordion-header'>";
-  html += "      <button class='accordion-button collapsed' type='button' data-bs-toggle='collapse' data-bs-target='#accordion-info-playback' aria-expanded='true' aria-controls='accordion-info-playback'>";
-  html += "        Playback information";
-  html += "      </button>";
-  html += "    </h2>";
-  html += "    <div id='accordion-info-playback' class='accordion-collapse collapse' data-bs-parent='#accordion-info'>";
-  html += "      <div class='accordion-body'>";
-  html += "        <table class='table table-striped'><tbody><tr>";
-  html += "              <td>Playing</td>";
-  html += "              <td class='text-end'>";
-  html +=                  audioPlaying ? "yes" : "no";
-  html += "              </td>";
-  html += "            </tr><tr>";
-  html += "              <td>Volume</td>";
-  html += "              <td class='text-end'>" + String(currentVolume) + "/" + String(maxVolume) + "%</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Muted</td>";
-  html += "              <td class='text-end'>";
-  html +=                  muted ? "yes" : "no";
-  html += "              </td>";
-  html += "            </tr><tr>";
-  html += "              <td>Equalizer Low</td>";
-  html += "              <td class='text-end'>" + String(eqLow-40) + "dB</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Equalizer Mid</td>";
-  html += "              <td class='text-end'>" + String(eqMid-40) + "dB</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Equalizer High</td>";
-  html += "              <td class='text-end'>" + String(eqHigh-40) + "dB</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Balance (range -16 | +16)</td>";
-  html += "              <td class='text-end'>" + String(balanceLevel-16) + "</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Path to playlist</td>";
-  html += "              <td class='text-end'>" + currentPlaylist + "</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Index in playlist (starting from 0)</td>";
-  html += "              <td class='text-end'>" + String(currentPlaylistPosition) + "</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Resource type</td>";
-  html += "              <td class='text-end'>" + pbInfo.type + "</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Resource title</td>";
-  html += "              <td class='text-end'>" + pbInfo.title + "</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Resource album</td>";
-  html += "              <td class='text-end'>" + pbInfo.album + "</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Resource artist</td>";
-  html += "              <td class='text-end'>" + pbInfo.artist + "</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Resource track number</td>";
-  html += "              <td class='text-end'>" + pbInfo.track + "</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Resource year</td>";
-  html += "              <td class='text-end'>" + pbInfo.year + "</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Resource genre</td>";
-  html += "              <td class='text-end'>" + pbInfo.genre + "</td>";
-  html += "        </tr></tbody></table>";
-  html += "      </div>";
-  html += "    </div>";
-  html += "  </div>";  
-  html += "  <div class='accordion-item'>";
-  html += "    <h2 class='accordion-header'>";
-  html += "      <button class='accordion-button collapsed' type='button' data-bs-toggle='collapse' data-bs-target='#accordion-info-general' aria-expanded='true' aria-controls='accordion-info-general'>";
-  html += "        General information";
-  html += "      </button>";
-  html += "    </h2>";
-  html += "    <div id='accordion-info-general' class='accordion-collapse collapse' data-bs-parent='#accordion-info'>";
-  html += "      <div class='accordion-body'>";
-  html += "        <table class='table table-striped'><tbody><tr>";
-  html += "              <td>Version</td>";
-  html += "              <td class='text-end'>" + version + "</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Friendly name</td>";
-  html += "              <td class='text-end'>" + configuration.getString(PREFERENCES_KEY_FRIENDLY_NAME, "<not_given>") + "</td>";
-  html += "            </tr><tr>";
-  html += "              <td>Save & Restore state</td>";
-  html += "              <td class='text-end'>";
-  html +=                  configuration.getBool(PREFERENCES_KEY_RESTORE_OLD_STATE, false) ? "yes" : "no";
-  html += "              </td>";
-  html += "            </tr><tr>";
-  html += "              <td>Save & Restore playing state (default no)</td>";
-  html += "              <td class='text-end'>";
-  html +=                  configuration.getBool(PREFERENCES_KEY_RESTORE_PLAYING, false) ? "yes" : "no";
-  html += "              </td>";
-  html += "            </tr><tr>";
-  html += "              <td>WiFi SSID</td>";
-  html += "              <td class='text-end'>" + configuration.getString(PREFERENCES_KEY_WIFI_SSID, "") + "</td>";
-  html += "        </tr></tbody></table>";
-  html += "      </div>";
-  html += "    </div>";
-  html += "  </div>";
-  html += "</div>";
-
-  html += "<hr style='margin: 3em 0em;'>";
-
-  // api functions accordion
-  html += "<div class='accordion text-start' id='accordion'>";
-  html += "  <div class='accordion-item'>";
-  html += "    <h2 class='accordion-header'>";
-  html += "      <button class='accordion-button collapsed' type='button' data-bs-toggle='collapse' data-bs-target='#accordion-collapse-playback' aria-expanded='true' aria-controls='accordion-collapse-playback'>";
-  html += "        Playback";
-  html += "        &nbsp;<span class='badge text-bg-success'>/api/v1/playback/</span>";
-  html += "      </button>";
-  html += "    </h2>";
-  html += "    <div id='accordion-collapse-playback' class='accordion-collapse collapse' data-bs-parent='#accordion'>";
-  html += "      <div class='accordion-body'>";
-  html += "        <strong>Work in progress</strong>";
-  html += "      </div>";
-  html += "    </div>";
-  html += "  </div>";
-
-  html += "  <div class='accordion-item'>";
-  html += "    <h2 class='accordion-header'>";
-  html += "      <button class='accordion-button collapsed' type='button' data-bs-toggle='collapse' data-bs-target='#accordion-collapse-volume' aria-expanded='true' aria-controls='accordion-collapse-volume'>";
-  html += "        Volume";
-  html += "        &nbsp;<span class='badge text-bg-info'>/api/v1/volume/</span>";
-  html += "      </button>";
-  html += "    </h2>";
-  html += "    <div id='accordion-collapse-volume' class='accordion-collapse collapse' data-bs-parent='#accordion'>";
-  html += "      <div class='accordion-body'>";
-  html += "        <strong>Work in progress</strong>";
-  html += "      </div>";
-  html += "    </div>";
-  html += "  </div>";
-
-  html += "  <div class='accordion-item'>";
-  html += "    <h2 class='accordion-header'>";
-  html += "      <button class='accordion-button collapsed' type='button' data-bs-toggle='collapse' data-bs-target='#accordion-collapse-playlist' aria-expanded='true' aria-controls='accordion-collapse-playlist'>";
-  html += "        Playlist";
-  html += "        &nbsp;<span class='badge text-bg-success'>/api/v1/playlist/</span>";
-  html += "      </button>";
-  html += "    </h2>";
-  html += "    <div id='accordion-collapse-playlist' class='accordion-collapse collapse' data-bs-parent='#accordion'>";
-  html += "      <div class='accordion-body'>";
-  html += "        <strong>Work in progress</strong>";
-  html += "      </div>";
-  html += "    </div>";
-  html += "  </div>";
-
-  html += "  <div class='accordion-item'>";
-  html += "    <h2 class='accordion-header'>";
-  html += "      <button class='accordion-button collapsed' type='button' data-bs-toggle='collapse' data-bs-target='#accordion-collapse-balance' aria-expanded='true' aria-controls='accordion-collapse-balance'>";
-  html += "        Balance";
-  html += "        &nbsp;<span class='badge text-bg-info'>/api/v1/balance/</span>";
-  html += "      </button>";
-  html += "    </h2>";
-  html += "    <div id='accordion-collapse-balance' class='accordion-collapse collapse' data-bs-parent='#accordion'>";
-  html += "      <div class='accordion-body'>";
-  html += "        <strong>Work in progress</strong>";
-  html += "      </div>";
-  html += "    </div>";
-  html += "  </div>";
-
-  html += "  <div class='accordion-item'>";
-  html += "    <h2 class='accordion-header'>";
-  html += "      <button class='accordion-button collapsed' type='button' data-bs-toggle='collapse' data-bs-target='#accordion-collapse-eq' aria-expanded='true' aria-controls='accordion-collapse-eq'>";
-  html += "        Equalizer";
-  html += "        &nbsp;<span class='badge text-bg-info'>/api/v1/eq/</span>";
-  html += "      </button>";
-  html += "    </h2>";
-  html += "    <div id='accordion-collapse-eq' class='accordion-collapse collapse' data-bs-parent='#accordion'>";
-  html += "      <div class='accordion-body'>";
-  html += "        <strong>Work in progress</strong>";
-  html += "      </div>";
-  html += "    </div>";
-  html += "  </div>";
-
-  html += "  <div class='accordion-item'>";
-  html += "    <h2 class='accordion-header'>";
-  html += "      <button class='accordion-button collapsed' type='button' data-bs-toggle='collapse' data-bs-target='#accordion-collapse-frname' aria-expanded='true' aria-controls='accordion-collapse-frname'>";
-  html += "        Friendly name";
-  html += "        &nbsp;<span class='badge text-bg-warning'>/api/v1/system/name</span>";  // explicitly no trailing / as there are the two endpoints /name and /name/change
-  html += "      </button>";
-  html += "    </h2>";
-  html += "    <div id='accordion-collapse-frname' class='accordion-collapse collapse' data-bs-parent='#accordion'>";
-  html += "      <div class='accordion-body'>";
-  html += "        <strong>Work in progress</strong>";
-  html += "      </div>";
-  html += "    </div>";
-  html += "  </div>";
-
-  html += "  <div class='accordion-item'>";
-  html += "    <h2 class='accordion-header'>";
-  html += "      <button class='accordion-button collapsed' type='button' data-bs-toggle='collapse' data-bs-target='#accordion-collapse-wifi' aria-expanded='true' aria-controls='accordion-collapse-wifi'>";
-  html += "        WiFi configuration";
-  html += "        &nbsp;<span class='badge text-bg-warning'>/api/v1/system/wifi/</span>";
-  html += "      </button>";
-  html += "    </h2>";
-  html += "    <div id='accordion-collapse-wifi' class='accordion-collapse collapse' data-bs-parent='#accordion'>";
-  html += "      <div class='accordion-body'>";
-  html += "        <strong>Work in progress</strong>";
-  html += "      </div>";
-  html += "    </div>";
-  html += "  </div>";
-
-  html += "  <div class='accordion-item'>";
-  html += "    <h2 class='accordion-header'>";
-  html += "      <button class='accordion-button collapsed' type='button' data-bs-toggle='collapse' data-bs-target='#accordion-collapse-restore' aria-expanded='true' aria-controls='accordion-collapse-restore'>";
-  html += "        Save & Restore";
-  html += "        &nbsp;<span class='badge text-bg-warning'>/api/v1/system/restore_state/</span>";
-  html += "        &nbsp;<span class='badge text-bg-warning'>/api/v1/system/restore_playing/</span>";
-  html += "      </button>";
-  html += "    </h2>";
-  html += "    <div id='accordion-collapse-restore' class='accordion-collapse collapse' data-bs-parent='#accordion'>";
-  html += "      <div class='accordion-body'>";
-  html += "        <strong>Work in progress</strong>";
-  html += "      </div>";
-  html += "    </div>";
-  html += "  </div>";
-
-  html += "  <div class='accordion-item'>";
-  html += "    <h2 class='accordion-header'>";
-  html += "      <button class='accordion-button collapsed' type='button' data-bs-toggle='collapse' data-bs-target='#accordion-collapse-restart' aria-expanded='true' aria-controls='accordion-collapse-restart'>";
-  html += "        Restart";
-  html += "        &nbsp;<span class='badge text-bg-danger'>/api/v1/system/restart</span>";
-  html += "      </button>";
-  html += "    </h2>";
-  html += "    <div id='accordion-collapse-restart' class='accordion-collapse collapse' data-bs-parent='#accordion'>";
-  html += "      <div class='accordion-body'>";
-  html += "        <strong>Work in progress</strong>";
-  html += "      </div>";
-  html += "    </div>";
-  html += "  </div>";
-
-  html += "</div></div>";
-  html += "<script src='https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js' integrity='sha384-C6RzsynM9kWDrMNeT87bh95OGNyZPhcTNXj1NW7RuBCsyN/o0jlpcV8Qyq46cDfL' crossorigin='anonymous'></script>";
-  html += "</body></html>";
-
-  api_server.send(200, "text/html", html);
-}
+/* ----------------------
+----  API FUNCTIONS  ----
+-----------------------*/
 
 void api_v1_playback_toggle() {
-  Serial.println("[HTTP] [API]         200 - GET '/api/v1/playback/toggle'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/playback/toggle'");
 
   audioPlaying = !audioPlaying;
   Serial.printf("[INFO]               Playback has switched: %s\n", audioPlaying ? "Playing" : "Paused");
 
-  api_server.send(200, "application/json", generate_api_json(true));
+  send_api_json(true);
 }
 
 void api_v1_playback_play() {
-  Serial.println("[HTTP] [API]         200 - GET '/_api/v1/playback/play'");
+  Serial.println("[HTTP] [API]         200 - '/_api/v1/playback/play'");
 
   audioPlaying = true;
   Serial.printf("[INFO]               Playback has switched: Playing\n");
 
-  api_server.send(200, "application/json", generate_api_json(true));
+  send_api_json(true);
 }
 
 void api_v1_playback_pause() {
-  Serial.println("[HTTP] [API]         200 - GET '/api/v1/playback/pause'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/playback/pause'");
 
   audioPlaying = false;
   Serial.printf("[INFO]               Playback has switched: Paused\n");
 
-  api_server.send(200, "application/json", generate_api_json(true));
+  send_api_json(true);
 }
 
 void api_v1_playback_next() {
-  Serial.println("[HTTP] [API]         200 - GET '/api/v1/playback/next'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/playback/next'");
 
   nextAudio();
   String content = "\"resource_playlist_index\": ";
   content += String(currentPlaylistPosition);
 
-  api_server.send(200, "application/json", generate_api_json(true, content));
+  send_api_json(true, content);
 }
 
 void api_v1_playback_previous() {
-  Serial.println("[HTTP] [API]         200 - GET '/api/v1/playback/previous'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/playback/previous'");
 
   previousAudio();
   String content = "\"resource_playlist_index\": ";
   content += String(currentPlaylistPosition);
 
-  api_server.send(200, "application/json", generate_api_json(true, content));
+  send_api_json(true, content);
 }
 
 void api_v1_playback_byindex() {
   String option = api_server.pathArg(0);
   String toIntStr;
-  Serial.printf("[HTTP] [API]         200 - GET '/api/v1/playback/%s'\n", option);
+  Serial.printf("[HTTP] [API]         200 - '/api/v1/playback/%s'\n", option);
 
   // convert string to int
   for (int i = 0; i < option.length(); i++) {
     if (isDigit((char)option[i])) toIntStr += option[i];
     else {
-      api_server.send(200, "application/json", generate_api_json(false));
+      send_api_json(false);
       return;
     }
   }
@@ -361,18 +117,18 @@ void api_v1_playback_byindex() {
     currentPlaylistPosition = index - 1;
     nextAudio();  // the clean way of playing the next resource
   } else {
-    api_server.send(200, "application/json", generate_api_json(false));
+    send_api_json(false);
   }
 
   String content = "\"resource_playlist_index\": ";
   content += String(currentPlaylistPosition);
-  api_server.send(200, "application/json", generate_api_json(true, content));
+  send_api_json(true, content);
 }
 
 void api_v1_volume() {
   String option = api_server.pathArg(0);
   bool success = true;
-  Serial.printf("[HTTP] [API]         200 - GET '/api/v1/volume/%s'\n", option);
+  Serial.printf("[HTTP] [API]         200 - '/api/v1/volume/%s'\n", option);
 
   if (option == "up") {
     currentVolume++;
@@ -384,10 +140,12 @@ void api_v1_volume() {
     muted = true;
   } else if (option == "unmute") {
     muted = false;
+  } else if (option == "toggle_mute") {
+    muted = !muted;
   } else if (option == "get") {
     // just here that no 'success: false' is sent
   } else if (option == "get_max") {
-    api_server.send(200, "application/json", generate_api_json(success, "\"volume_max\": " + String(maxVolume)));
+    send_api_json(success, "\"volume_max\": " + String(maxVolume));
   } else {
     String toIntStr;
     int volumeLevel;
@@ -407,13 +165,14 @@ void api_v1_volume() {
   content += String(currentVolume);
   content += ", \"muted\": ";
   content += muted ? "true" : "false";
-  api_server.send(200, "application/json", generate_api_json(success, content));  // generate json and send it
+  content += ", \"volume_max\": " + String(maxVolume);
+  send_api_json(success, content);  // generate json and send it
 }
 
 void api_v1_balance() {
   String option = api_server.pathArg(0);
   bool success = true;
-  Serial.printf("[HTTP] [API]         200 - GET '/api/v1/balance/%s'\n", option);
+  Serial.printf("[HTTP] [API]         200 - '/api/v1/balance/%s'\n", option);
 
   if (option == "right") {
     balanceLevel--;
@@ -438,11 +197,11 @@ void api_v1_balance() {
 
   String content = "\"balance\": ";  // prepare the http response
   content += String(balanceLevel);
-  api_server.send(200, "application/json", generate_api_json(success, content));  // generate json and send it
+  send_api_json(success, content);  // generate json and send it
 }
 
 void api_v1_eq_get() {
-  Serial.println("[HTTP] [API]         200 - GET '/api/v1/eq/get");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/eq/get");
 
   String content = "\"equalizer_low\": ";  // prepare the http response
   content += String(eqLow);
@@ -451,11 +210,11 @@ void api_v1_eq_get() {
   content += ", \"equalizer_high\": ";  // prepare the http response
   content += String(eqHigh);
 
-  api_server.send(200, "application/json", generate_api_json(true, content));  // generate json and send it
+  send_api_json(true, content);  // generate json and send it
 }
 
 void api_v1_eq_reset() {
-  Serial.println("[HTTP] [API]         200 - GET '/api/v1/eq/reset");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/eq/reset");
 
   eqLow = 0;
   eqMid = 0;
@@ -471,13 +230,13 @@ void api_v1_eq_reset() {
   content += ", \"equalizer_high\": ";  // prepare the http response
   content += String(eqHigh);
 
-  api_server.send(200, "application/json", generate_api_json(true, content));  // generate json and send it
+  send_api_json(true, content);  // generate json and send it
 }
 
 void api_v1_eq_low() {
   String option = api_server.pathArg(0);
   bool success = true;
-  Serial.printf("[HTTP] [API]         200 - GET '/api/v1/eq/low/%s'\n", option);
+  Serial.printf("[HTTP] [API]         200 - '/api/v1/eq/low/%s'\n", option);
 
   if (option == "get") {
     // just here to make /get available
@@ -489,7 +248,7 @@ void api_v1_eq_low() {
       success = false;
     } else {
       eqLow = res - 40;
-      Serial.printf("[INFO]               Set balance to %ddB | %ddB | %ddB!\n", eqLow, eqMid, eqHigh);
+      Serial.printf("[INFO]               Set equalizer to %ddB | %ddB | %ddB!\n", eqLow, eqMid, eqHigh);
     }
   } else success = false;
 
@@ -497,12 +256,12 @@ void api_v1_eq_low() {
 
   String content = "\"equalizer_low\": ";  // prepare the http response
   content += String(eqLow);
-  api_server.send(200, "application/json", generate_api_json(success, content));  // generate json and send it
+  send_api_json(success, content);  // generate json and send it
 }
 void api_v1_eq_mid() {
   String option = api_server.pathArg(0);
   bool success = true;
-  Serial.printf("[HTTP] [API]         200 - GET '/api/v1/eq/mid/%s'\n", option);
+  Serial.printf("[HTTP] [API]         200 - '/api/v1/eq/mid/%s'\n", option);
 
   if (option == "get") {
     // just here to make /get available
@@ -514,7 +273,7 @@ void api_v1_eq_mid() {
       success = false;
     } else {
       eqMid = res - 40;
-      Serial.printf("[INFO]               Set balance to %ddB | %ddB | %ddB!\n", eqLow, eqMid, eqHigh);
+      Serial.printf("[INFO]               Set equalizer to %ddB | %ddB | %ddB!\n", eqLow, eqMid, eqHigh);
     }
   } else success = false;
 
@@ -522,12 +281,12 @@ void api_v1_eq_mid() {
 
   String content = "\"equalizer_mid\": ";  // prepare the http response
   content += String(eqMid);
-  api_server.send(200, "application/json", generate_api_json(success, content));  // generate json and send it
+  send_api_json(success, content);  // generate json and send it
 }
 void api_v1_eq_high() {
   String option = api_server.pathArg(0);
   bool success = true;
-  Serial.printf("[HTTP] [API]         200 - GET '/api/v1/eq/high/%s'\n", option);
+  Serial.printf("[HTTP] [API]         200 - '/api/v1/eq/high/%s'\n", option);
 
   if (option == "get") {
     // just here to make /get available
@@ -539,7 +298,7 @@ void api_v1_eq_high() {
       success = false;
     } else {
       eqHigh = res - 40;
-      Serial.printf("[INFO]               Set balance to %dB | %ddB | %ddB!\n", eqLow, eqMid, eqHigh);
+      Serial.printf("[INFO]               Set equalizer to %dB | %ddB | %ddB!\n", eqLow, eqMid, eqHigh);
     }
   } else success = false;
 
@@ -547,11 +306,11 @@ void api_v1_eq_high() {
 
   String content = "\"equalizer_high\": ";  // prepare the http response
   content += String(eqHigh);
-  api_server.send(200, "application/json", generate_api_json(success, content));  // generate json and send it
+  send_api_json(success, content);  // generate json and send it
 }
 
 void api_v1_playback_info() {
-  Serial.println("[HTTP] [API]         200 - GET '/api/v1/playback/info'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/playback/info'");
   String content = "\"resource_path\": \"" + pbInfo.resourcePath + "\", ";       // resource's path
   content += "\"resource_type\": \"" + pbInfo.type + "\", ";                     // type
   content += "\"resource_title\": \"" + pbInfo.title + "\", ";                   // title
@@ -561,14 +320,15 @@ void api_v1_playback_info() {
   content += "\"resource_year\": \"" + pbInfo.year + "\", ";                     // year
   content += "\"resource_genre\": \"" + pbInfo.genre + "\", ";                   // genre
   content += "\"resource_copyright\": \"" + pbInfo.copyright + "\", ";           // copyright
+  content += "\"resource_tts_language\": \"" + pbInfo.tts_language + "\", ";     // language
   content += "\"resource_playlist_path\": \"" + currentPlaylist + "\", ";        // playlist path
   content += "\"resource_playlist_index\": " + String(currentPlaylistPosition);  // playlist index (starting from 0)
 
-  api_server.send(200, "application/json", generate_api_json(true, content));
+  send_api_json(true, content);
 }
 
 void api_v1_playlist_get() {
-  Serial.println("[HTTP] [API]         200 - GET '/api/v1/playlist/get'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/playlist/get'");
 
   int index = 0;
   String content = "\"playlist\": {";
@@ -592,16 +352,16 @@ void api_v1_playlist_get() {
   }
   content += "}";
 
-  api_server.send(200, "application/json", generate_api_json(true, content));
+  send_api_json(true, content);
 }
 
 void api_v1_playlist_create() {
-  Serial.println("[HTTP] [API]         200 - POST '/api/v1/playlist/create'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/playlist/create'");
 
   // get the right POST param
   String folderPath;
   for (int i = 0; i < api_server.args(); i++) {
-    if (api_server.argName(i) == "folderPath") {
+    if (api_server.argName(i) == "folder_path") {
       folderPath = api_server.arg(i);
       break;
     }
@@ -611,53 +371,54 @@ void api_v1_playlist_create() {
   if (code) {  // if creating the playlist was successful
     String playlistPath = folderPath + "/" + directoryPlaylistName + playlistExtension;
     String content = "\"playlist_path\": \"" + playlistPath + "\"";
-    api_server.send(200, "application/json", generate_api_json(true, content));
+    send_api_json(true, content);
   } else {
-    api_server.send(200, "application/json", generate_api_json(false));
+    send_api_json(false);
   }
 }
 
 void api_v1_playlist_play() {
-  Serial.println("[HTTP] [API]         200 - POST '/api/v1/playlist/play'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/playlist/play'");
 
   // get the right POST param
   String playlistPath;
   for (int i = 0; i < api_server.args(); i++) {
-    if (api_server.argName(i) == "playlistPath") {
+    if (api_server.argName(i) == "playlist_path") {
       playlistPath = api_server.arg(i);
       break;
     }
   }
 
-  if (getURLFromPlaylist(playlistPath, 0) == "") {                       // if playlist is empty or nonexistent
-    api_server.send(200, "application/json", generate_api_json(false));  // send no success info
+  if (getURLFromPlaylist(playlistPath, 0) == "") {                       // get the first item from the playlist to check whether the pl is empty or nonexistent
+    send_api_json(false);  // send no success info
   } else {
     currentPlaylist = playlistPath;
     currentPlaylistPosition = -1;
     nextAudio();
-    api_server.send(200, "application/json", generate_api_json(true));  // just return the success info
+    send_api_json(true);  // just return the success info
   }
 }
 
 void api_v1_system_restart() {
-  Serial.println("[HTTP] [API]         200 - GET '/api/v1/system/restart'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/system/restart'");
 
   SD.end();           // delete SD object and sync its cache to flash
   WiFi.disconnect();  // disconnect wifi
   Serial.printf("[INFO]               Restarting after 5000ms.\n", waitOnSDCardEject, retrySDMountTreshold);
+  api_server.sendHeader("Access-Control-Allow-Origin", "*");
   api_server.send(200, "application/json", "{\"restart\": true, \"wait_time\": 5000}");
-  delay(5000);
+  delay(WEB_RESTART_DELAY);
   ESP.restart();  // reset everything and restart the program
 }
 
 void api_v1_system_friendlyname_get() {
-  Serial.println("[HTTP] [API]         200 - GET '/api/v1/system/name'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/system/name'");
 
-  api_server.send(200, "application/json", generate_api_json(true, "\"friendly_name\": \"" + configuration.getString(PREFERENCES_KEY_FRIENDLY_NAME) + "\""));
+  send_api_json(true, "\"friendly_name\": \"" + configuration.getString(PREFERENCES_KEY_FRIENDLY_NAME) + "\"");
 }
 
 void api_v1_system_friendlyname_change() {
-  Serial.println("[HTTP] [API]         200 - POST '/api/v1/system/name/change'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/system/name/change'");
 
   String currentFriendlyName = configuration.getString(PREFERENCES_KEY_FRIENDLY_NAME, "");
   String newFriendlyName;
@@ -672,23 +433,60 @@ void api_v1_system_friendlyname_change() {
   }
   // define what to do if nothing really changed (or no argument was given)
   if (newFriendlyName == currentFriendlyName || !arg_given) {
-    String content;
-    content = "\"friendly_name\": \"" + currentFriendlyName + "\"";
-    api_server.send(200, "application/json", generate_api_json(false, content));  // return with no success ("false")
+    send_api_json(false, "\"friendly_name\": \"" + currentFriendlyName + "\"");  // return with no success ("false")
     return;
   }
 
-
   configuration.putString(PREFERENCES_KEY_FRIENDLY_NAME, newFriendlyName);
-  Serial.printf("[INFO]               Changed friendly name from \"%s\" to \"%s\".\n", currentFriendlyName.c_str(), newFriendlyName.c_str());
+  Serial.printf("[INFO]               Changed friendly name from \"%s\" to \"%s\".\n", currentFriendlyName, newFriendlyName);
 
-  api_server.send(200, "application/json", generate_api_json(true, "\"friendly_name\": \"" + newFriendlyName + "\""));
+  send_api_json(true, "\"friendly_name\": \"" + newFriendlyName + "\"");
+}
+
+void api_v1_system_networkname_get() {
+  Serial.println("[HTTP] [API]         200 - '/api/v1/system/network_name'");
+
+  send_api_json(true, "\"network_name\": \"" + configuration.getString(PREFERENCES_KEY_NETWORK_NAME, default_network_name) + "\"");
+}
+
+void api_v1_system_networkname_change() {
+  Serial.println("[HTTP] [API]         200 - '/api/v1/system/network_name/change'");
+
+  String currentNetworkName = configuration.getString(PREFERENCES_KEY_NETWORK_NAME, default_network_name);
+  String newNetworkName;
+  bool arg_given = false;
+  bool apply_changes = false;  // whether changes should be applied directly
+  // get the right post param (by key)
+  for (int i = 0; i < api_server.args(); i++) {
+    if (api_server.argName(i) == "apply_changes") {
+      apply_changes = true;
+    }
+    if (api_server.argName(i) == "network_name") {
+      arg_given = true;
+      newNetworkName = api_server.arg(i);
+      break;
+    }
+  }
+  // define what to do if nothing really changed (or no argument was given)
+  if (newNetworkName == currentNetworkName || !arg_given) {
+    send_api_json(false, "\"network_name\": \"" + currentNetworkName + "\", \"apply_changes\": false");  // return with no success ("false")
+    return;
+  }
+
+  configuration.putString(PREFERENCES_KEY_NETWORK_NAME, newNetworkName);
+  Serial.printf("[INFO]               Changed network name from \"%s\" to \"%s\".\n", currentNetworkName, newNetworkName);
+
+  if(apply_changes) {
+    setupMDNS();
+  }
+
+  send_api_json(true, "\"network_name\": \"" + newNetworkName + "\", \"apply_changes\": " + (apply_changes ? "true" : "false"));
 }
 
 void api_v1_system_restore_state() {
   String option = api_server.pathArg(0);
   bool success = true;
-  Serial.printf("[HTTP] [API]         200 - GET '/api/v1/system/restore_state/%s'\n", option);
+  Serial.printf("[HTTP] [API]         200 - '/api/v1/system/restore_state/%s'\n", option);
 
   if (option == "get") {
     // just here that calling .../get wont respond 404
@@ -696,19 +494,21 @@ void api_v1_system_restore_state() {
     configuration.putBool(PREFERENCES_KEY_RESTORE_OLD_STATE, true);
   } else if (option == "off") {
     configuration.putBool(PREFERENCES_KEY_RESTORE_OLD_STATE, false);
+  } else if (option == "toggle") {  // toggle; default to true
+    configuration.putBool(PREFERENCES_KEY_RESTORE_OLD_STATE, !configuration.getBool(PREFERENCES_KEY_RESTORE_OLD_STATE, false));
   } else {
     success = false;
   }
 
   String content = "\"restore_state\": ";  // prepare the http response
   content += configuration.getBool(PREFERENCES_KEY_RESTORE_OLD_STATE, false) ? "true" : "false";
-  api_server.send(200, "application/json", generate_api_json(success, content));  // generate json and send it
+  send_api_json(success, content);  // generate json and send it
 }
 
 void api_v1_system_restore_playing() {
   String option = api_server.pathArg(0);
   bool success = true;
-  Serial.printf("[HTTP] [API]         200 - GET '/api/v1/system/restore_playing/%s'\n", option);
+  Serial.printf("[HTTP] [API]         200 - '/api/v1/system/restore_playing/%s'\n", option);
 
   if (option == "get") {
     // just here that calling .../get wont respond 404
@@ -716,29 +516,59 @@ void api_v1_system_restore_playing() {
     configuration.putBool(PREFERENCES_KEY_RESTORE_PLAYING, true);
   } else if (option == "off") {
     configuration.putBool(PREFERENCES_KEY_RESTORE_PLAYING, false);
+  } else if (option == "toggle") {  // toggle; default to false (do not restore playing by default)
+    configuration.putBool(PREFERENCES_KEY_RESTORE_PLAYING, !configuration.getBool(PREFERENCES_KEY_RESTORE_PLAYING, true));
   } else {
     success = false;
   }
 
   String content = "\"restore_playing\": ";  // prepare the http response
   content += configuration.getBool(PREFERENCES_KEY_RESTORE_PLAYING, false) ? "true" : "false";
-  api_server.send(200, "application/json", generate_api_json(success, content));  // generate json and send it
+  send_api_json(success, content);  // generate json and send it
+}
+void api_v1_system_tell_address() {
+  String option = api_server.pathArg(0);
+  bool success = true;
+  Serial.printf("[HTTP] [API]         200 - '/api/v1/system/tell_address/%s'\n", option);
+
+  if (option == "get") {
+    // just here that calling .../get wont respond 404
+  } else if (option == "on") {
+    configuration.putBool(PREFERENCES_KEY_TELL_ADDRESS_AT_STARTUP, true);
+  } else if (option == "off") {
+    configuration.putBool(PREFERENCES_KEY_TELL_ADDRESS_AT_STARTUP, false);
+  } else if (option == "toggle") {  // toggle; default to true (tell by default)
+    configuration.putBool(PREFERENCES_KEY_TELL_ADDRESS_AT_STARTUP, !configuration.getBool(PREFERENCES_KEY_TELL_ADDRESS_AT_STARTUP, false));
+  } else {
+    success = false;
+  }
+
+  String content = "\"tell_address\": ";  // prepare the http response
+  content += configuration.getBool(PREFERENCES_KEY_TELL_ADDRESS_AT_STARTUP, true) ? "true" : "false";
+  send_api_json(success, content);  // generate json and send it
 }
 
 void api_v1_system_version() {
-  Serial.printf("[HTTP] [API]         200 - GET '/api/v1/system/version'\n");
+  Serial.printf("[HTTP] [API]         200 - '/api/v1/system/version'\n");
 
-  api_server.send(200, "application/json", generate_api_json(true, "\"version\": \"" + version + "\""));
+  send_api_json(true, "\"version\": \"" + version + "\", " + "\"version_tag\": \"" + version_tag + "\"");
 }
 
 void api_v1_system_wifi_getssid() {
-  Serial.println("[HTTP] [API]         200 - GET '/api/v1/system/wifi/get_ssid'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/system/wifi/get_ssid'");
 
-  api_server.send(200, "application/json", generate_api_json(true, "\"wifi_ssid\": \"" + configuration.getString(PREFERENCES_KEY_WIFI_SSID) + "\""));
+  send_api_json(true, "\"wifi_ssid\": \"" + configuration.getString(PREFERENCES_KEY_WIFI_SSID) + "\"");
+}
+
+void 
+api_v1_system_wifi_get_ap_creds() {
+  Serial.println("[HTTP] [API]         200 - '/api/v1/system/wifi/get_ap_creds'");
+
+  send_api_json(true, "\"ap_ssid\": \"" + apSSID + "\", \"ap_psk\": \"" + apPSK + "\"");
 }
 
 void api_v1_system_wifi_change() {
-  Serial.println("[HTTP] [API]         200 - POST '/api/v1/system/wifi/change'");
+  Serial.println("[HTTP] [API]         200 - '/api/v1/system/wifi/change'");
 
   // get the right POST params
   String ssid = "";
@@ -764,20 +594,26 @@ void api_v1_system_wifi_change() {
   } else if (ssid == "" && psk != "") {  // just the psk is given
     configuration.putString(PREFERENCES_KEY_WIFI_PSK, psk);
   } else {  // none of ssid or psk is given
-    api_server.send(200, "application/json", generate_api_json(false));
+    send_api_json(false);
     return;
   }
 
   Serial.printf("[INFO]               Changed wifi credentials (SSID: '%s' | PSK: '%s')\n", ssid.c_str(), psk.c_str());
-  api_server.send(200, "application/json", generate_api_json(true, "\"ssid\": \"" + ssid + "\", \"psk\": \"" + psk + "\""));
+  send_api_json(true, "\"ssid\": \"" + ssid + "\", \"psk\": \"" + psk + "\"");
 }
 
 void setupWeb() {
-  api_server.on("/", api_root);
+  api_server.on("/", []() {
+    Serial.println("[HTTP] [API]         200 - '/'");
+    char message[] = "{\"message\": \"Welcome to your NetSpeaker's API! More info can be found at https://git.privacynerd.de/NetSpeaker/NetSpeaker\"}";
+    api_server.sendHeader("Access-Control-Allow-Origin", "*");
+    api_server.send(200, "application/json", message);
+  });  // on /
   api_server.onNotFound([]() {
     Serial.println("[HTTP] [API]         404: Not Found");
+    api_server.sendHeader("Access-Control-Allow-Origin", "*");
     api_server.send(404, "application/json", "{\"code\": 404, \"message\": \"Resource not found.\"}");
-  });
+  });  // on NotFound (the fallback if nothing else configured for the requested URL)
   api_server.on("/api/v1/playback/toggle", api_v1_playback_toggle);
   api_server.on("/api/v1/playback/play", api_v1_playback_play);
   api_server.on("/api/v1/playback/pause", api_v1_playback_pause);
@@ -791,18 +627,22 @@ void setupWeb() {
   api_server.on(UriBraces("/api/v1/volume/{}"), api_v1_volume);
   api_server.on(UriBraces("/api/v1/balance/{}"), api_v1_balance);
   api_server.on("/api/v1/eq/get", api_v1_eq_get);
-  api_server.on(UriBraces("/api/v1/eq/reset"), api_v1_eq_reset);
+  api_server.on("/api/v1/eq/reset", api_v1_eq_reset);
   api_server.on(UriBraces("/api/v1/eq/low/{}"), api_v1_eq_low);
   api_server.on(UriBraces("/api/v1/eq/mid/{}"), api_v1_eq_mid);
   api_server.on(UriBraces("/api/v1/eq/high/{}"), api_v1_eq_high);
   api_server.on("/api/v1/system/restart", api_v1_system_restart);
   api_server.on("/api/v1/system/name", api_v1_system_friendlyname_get);
   api_server.on("/api/v1/system/name/change", api_v1_system_friendlyname_change);
+  api_server.on("/api/v1/system/network_name", api_v1_system_networkname_get);
+  api_server.on("/api/v1/system/network_name/change", api_v1_system_networkname_change);
   api_server.on(UriBraces("/api/v1/system/restore_state/{}"), api_v1_system_restore_state);
   api_server.on(UriBraces("/api/v1/system/restore_playing/{}"), api_v1_system_restore_playing);
+  api_server.on(UriBraces("/api/v1/system/tell_address/{}"), api_v1_system_tell_address);
   api_server.on("/api/v1/system/version", api_v1_system_version);
   api_server.on("/api/v1/system/wifi/change", api_v1_system_wifi_change);
   api_server.on("/api/v1/system/wifi/get_ssid", api_v1_system_wifi_getssid);
+  api_server.on("/api/v1/system/wifi/get_ap_creds", api_v1_system_wifi_get_ap_creds);
 
   Serial.println("[HTTP] [API]         Starting API server (http) on port " + String(webport_api));
   api_server.begin();

src/NetSpeaker/wifi.ino

@@ -1,22 +1,27 @@
 /*
 This is free and unencumbered software released into the public domain.
 
-Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in 
+source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
 
-In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and
-successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
+In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and 
+all copyright interest in the software to the public domain. We make this dedication for the benefit of 
+the public at large and to the detriment of our heirs and successors. We intend this dedication to be an 
+overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED 
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 
+THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR 
+OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 For more information, please refer to <http://unlicense.org/>
 */
 
-
 void setupWiFi() {
   if(WiFi.status() == WL_CONNECTED) { return; }  // return if not connected
   switch(currentWiFiMode) {
     case 0: {
-        Serial.println("[WiFi]               Connecting to WiFi...");
+        Serial.println(F("[WiFi]               Connecting to WiFi..."));
         String WiFiSSID = configuration.getString(PREFERENCES_KEY_WIFI_SSID);
         String WiFiPSK = configuration.getString(PREFERENCES_KEY_WIFI_PSK);
         if(WiFiPSK == String() || WiFiSSID == String()) { 
@@ -49,9 +54,23 @@ void setupWiFi() {
           WiFi.mode(WIFI_AP);
           WiFi.softAP(apSSID, apPSK);
           apON = true;
-          Serial.printf("[WiFi]               Opened AP successfully\n");
+          Serial.println(F("[WiFi]               Opened AP successfully"));
         }
       }
       break;
   }
 }
+
+void setupMDNS() {
+  MDNS.end();
+  // start the mDNS responder
+  Serial.println(F("[SETUP]              Starting mDNS responder"));
+  if (!MDNS.begin(configuration.getString(PREFERENCES_KEY_NETWORK_NAME, default_network_name))) {  // get network name from EEPROM (default to default_network_name)
+    Serial.println(F("[SETUP]              Error setting up mDNS responder!"));
+    indicate_system_error();  // halt system and blink readyPin
+  }
+  Serial.println(F("[SETUP]              Started mDNS responder"));  
+
+  // Add service to MDNS-SD
+  MDNS.addService("http", "tcp", 80);
+}