From 00048face420b050b40c0545d2ba2da10649173a Mon Sep 17 00:00:00 2001
From: Stefan Ostermann <stefan@ostermail.de>
Date: Wed, 30 Jul 2025 11:00:57 +0200
Subject: [PATCH] String optimizations

---
 src/DirectoryNode.cpp |  5 ++--
 src/main.cpp          | 69 +++++++++++++++++++++++++++----------------
 2 files changed, 46 insertions(+), 28 deletions(-)

diff --git a/src/DirectoryNode.cpp b/src/DirectoryNode.cpp
index e616160..d72d512 100644
--- a/src/DirectoryNode.cpp
+++ b/src/DirectoryNode.cpp
@@ -455,7 +455,8 @@ DirectoryNode *DirectoryNode::advanceToNextMP3(const String *currentGlobal)
 String DirectoryNode::getDirectoryStructureHTML() const
 {
     String html;
-    html.reserve(1024); // Reserve memory for better performance
+    html.reserve(512);
+    
     if (name == "/")
     {
         html += "<ul>\n";
@@ -487,7 +488,7 @@ void DirectoryNode::appendIndentation(String &html, int level) const
 {
     for (int i = 0; i < level; i++)
     {
-        html += "  ";
+        html.concat("  ");
     }
 }
 
diff --git a/src/main.cpp b/src/main.cpp
index af79e7e..53704e6 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -481,7 +481,7 @@ void playNextMp3()
 {
   stop();
   continuousMode = true;
-  if (currentNode == NULL)
+  if (currentNode == nullptr)
   {
     currentNode = rootNode.findFirstDirectoryWithMP3s();
     if (currentNode)
@@ -494,14 +494,14 @@ void playNextMp3()
     currentNode = rootNode.advanceToNextMP3(currentNode->getCurrentPlaying());
   }
 
-  if (currentNode != NULL)
+  if (currentNode != nullptr)
   {
     currentNode->setSecondsPlayed(0);
   }
 
-  Serial.print("Now advancing to ");
+  Serial.print("Advancing to ");
   String mp3File = currentNode->getCurrentPlayingFilePath();
-  Serial.println(mp3File.c_str());
+  Serial.println(mp3File);
   deactivateRFID();
   activateSD();
   playFile(mp3File.c_str());
@@ -620,6 +620,12 @@ String getState()
 {
   // Use static buffer to avoid repeated allocations
   static DynamicJsonDocument jsonState(512);
+  static String output;
+
+  output.reserve(512); // Pre-allocate string buffer
+  output.clear();
+
+
   jsonState.clear(); // Clear previous data
 
   jsonState["playing"] = audio.isRunning();
@@ -627,7 +633,7 @@ String getState()
   if (currentNode != nullptr)
     jsonState["title"] = *currentNode->getCurrentPlaying();
   else
-    jsonState["title"] = "Angehalten";
+    jsonState["title"] = "Stopped";
 
   if (currentNode != nullptr)
     jsonState["filepath"] = currentNode->getCurrentPlayingFilePath();
@@ -641,8 +647,7 @@ String getState()
   jsonState["uid"] = lastUid;
   jsonState["heap"] = free_heap;
 
-  String output;
-  output.reserve(512); // Pre-allocate string buffer
+
   serializeJson(jsonState, output);
 
   return output;
@@ -656,7 +661,9 @@ void saveMappingToFile(const String filename)
   {
     for (const auto &pair : rfid_map)
     {
-      file.println(pair.first + "=" + pair.second);
+      file.print(pair.first);
+      file.print("="); // Using F() macro
+      file.println(pair.second);
     }
     file.close();
     Serial.println("Mapping saved to file.");
@@ -751,12 +758,18 @@ String processor(const String &var)
       }
       return out;
     };
-    String html = "<table style='width:100%;border-collapse:collapse;'><tr><th style='border:1px solid #ccc;padding:4px;'>RFID</th><th style='border:1px solid #ccc;padding:4px;'>Song</th></tr>";
+    String html;
+    html.reserve(256);
+    html.concat(F("<table style='width:100%;border-collapse:collapse;'><tr><th style='border:1px solid #ccc;padding:4px;'>RFID</th><th style='border:1px solid #ccc;padding:4px;'>Song</th></tr>"));
     for (const auto &pair : rfid_map)
     {
-      html += "<tr><td style='border:1px solid #ccc;padding:4px;'>" + htmlEscape(pair.first) + "</td><td style='border:1px solid #ccc;padding:4px;'>" + htmlEscape(pair.second) + "</td></tr>";
+      html.concat(F("<tr><td style='border:1px solid #ccc;padding:4px;'>"));
+      html.concat(htmlEscape(pair.first));
+      html.concat(F("</td><td style='border:1px solid #ccc;padding:4px;'>"));
+      html.concat(htmlEscape(pair.second));
+      html.concat("</td></tr>");
     }
-    html += "</table>";
+    html.concat("</table>");
     return html;
   }
 
@@ -886,12 +899,12 @@ void previous()
       }
       else
       {
-        Serial.println("previous(): Global previous song is null");
+        Serial.println("prev: Global previous song is null");
       }
     }
     else
     {
-      Serial.println("previous(): No previous song found globally - at beginning of playlist");
+      Serial.println("prev: No previous song found, beginning again");
       // Optionally restart current song or do nothing
       audio.setAudioPlayPosition(0);
       currentNode->setSecondsPlayed(0);
@@ -1006,7 +1019,7 @@ void setup()
   // Optimize audio buffer size to save memory (ESP32-audioI2S optimization)
   audio.setBufferSize(8192); // Reduced from default large buffer (saves 40-600KB!)
 
-  Serial.println("Audio initialized.");
+  Serial.println("Audio init");
 
   lastVoltage = getBatteryVoltageMv();
 
@@ -1045,7 +1058,7 @@ void setup()
                 else
                 {
                   // Fallback: serve minimal error if file not found
-                  request->send(404, "text/plain", "ERROR: /system/index.html on SD Card not found!");
+                  request->send(404, "text/plain", "ERROR: /system/index.html not found!");
                 }
                 webrequestActive = false;
               });
@@ -1061,7 +1074,7 @@ void setup()
                 else
                 {
                   // Fallback: serve minimal CSS if file not found
-                  request->send(404, "text/plain", "ERROR: /system/style.css on SD Card not found!");
+                  request->send(404, "text/plain", "ERROR: /system/style.css ot found!");
                 }
                 webrequestActive = false;
               });
@@ -1079,7 +1092,7 @@ void setup()
                 else
                 {
                   // Fallback: serve minimal JS if file not found
-                  request->send(404, "text/plain", "ERROR: /system/script.js on SD Card not found!");
+                  request->send(404, "text/plain", "ERROR: /system/script.js not found!");
                 }
                 webrequestActive = false;
               });
@@ -1135,11 +1148,11 @@ void setup()
     server.on("/delete_file", HTTP_GET, handleDeleteFile);
 
     server.begin();
-    Serial.println("Wifi initialized.");
+    Serial.println("Wifi init");
   }
   else
   {
-    Serial.println("Wifi timed out. Fallback no Wifi.");
+    Serial.println("Wifi timed out. Fallback.");
   }
 
   Serial.println("Activating Brownout detector...");
@@ -1155,13 +1168,11 @@ void setup()
       0);         /* Core where the task should run */
 
   lastInteraction = millis();
-  Serial.println("initialization done.");
+  Serial.println("Init done.");
 }
 
 void id_song_action(AsyncWebServerRequest *request)
 {
-  Serial.println("song by id!");
-
   int params = request->params();
   for (int i = 0; i < params; i++)
   {
@@ -1209,7 +1220,13 @@ void volume_action(AsyncWebServerRequest *request)
 
 const String getSysDir(const String filename)
 {
-  return "/" + sys_dir + "/" + filename;
+  static String st_sys_str(96);
+  st_sys_str.clear();
+  st_sys_str.concat("/");
+  st_sys_str.concat(sys_dir);
+  st_sys_str.concat("/");
+  st_sys_str.concat(filename);
+  return st_sys_str;
 }
 
 void loop()
@@ -1252,7 +1269,7 @@ void loop()
   {
     sleepSoundPlayed = true;
     prepareSleepMode = true;
-    if (currentNode != NULL)
+    if (currentNode != nullptr)
     {
       String progressPath = getSysDir(progress_file);
       writeSongProgress(progressPath.c_str(), currentNode->getCurrentPlayingId(), currentNode->getSecondsPlayed());
@@ -1264,7 +1281,7 @@ void loop()
 
   if (now - lastInteraction > config.sleepDelay)
   {
-    Serial.println("entering deep sleep...");
+    Serial.println("entering deep sleep..");
     deactivateRFID();
     deactivateSD();
     esp_deep_sleep_start();
@@ -1332,7 +1349,7 @@ void loop()
     {
       if (voltage_threshold_counter > 3)
       {
-        Serial.println("entering deep sleep due to low voltage...");
+        Serial.println("deep sleep due to low volts..");
         lastInteraction = millis() - config.sleepMessageDelay;
         voltage_threshold_counter = 0;
       }