Fix crash on loading malformed settings, option to load partial configuration

code/espurna/settings.ino

@@ -375,19 +375,30 @@ size_t settingsMaxSize() {
 
 bool settingsRestoreJson(JsonObject& data) {
 
+    // Check this is an ESPurna configuration file (must have "app":"ESPURNA")
     const char* app = data["app"];
-    if (strcmp(app, APP_NAME) != 0) return false;
+    if (!app || strcmp(app, APP_NAME) != 0) {
+        DEBUG_MSG_P(PSTR("[SETTING] Wrong or missing 'app' key\n"));
+        return false;
+    }
 
-    for (unsigned int i = EEPROM_DATA_END; i < SPI_FLASH_SEC_SIZE; i++) {
-        EEPROMr.write(i, 0xFF);
+    // Clear settings
+    bool is_backup = data["backup"];
+    if (is_backup) {
+        for (unsigned int i = EEPROM_DATA_END; i < SPI_FLASH_SEC_SIZE; i++) {
+            EEPROMr.write(i, 0xFF);
+        }
     }
 
+    // Dump settings to memory buffer
     for (auto element : data) {
         if (strcmp(element.key, "app") == 0) continue;
         if (strcmp(element.key, "version") == 0) continue;
+        if (strcmp(element.key, "backup") == 0) continue;
         setSetting(element.key, element.value.as<char*>());
     }
 
+    // Persist to EEPROM
     saveSettings();
 
     DEBUG_MSG_P(PSTR("[SETTINGS] Settings restored successfully\n"));

code/espurna/web.ino

@@ -123,14 +123,17 @@ void _onGetConfig(AsyncWebServerRequest *request) {
     response->addHeader("X-Content-Type-Options", "nosniff");
     response->addHeader("X-Frame-Options", "deny");
 
-    response->printf("{\n  \"app\": \"%s\",\n  \"version\": \"%s\"", APP_NAME, APP_VERSION);
+    response->printf("{\n\"app\": \"%s\"", APP_NAME);
+    response->printf(",\n\"version\": \"%s\"", APP_VERSION);
+    response->printf(",\n\"backup\": \"1\"");
+    response->printf(",\n\"timestamp\": \"%s\"", ntpDateTime().c_str());
 
     // Write the keys line by line (not sorted)
     unsigned long count = settingsKeyCount();
     for (unsigned int i=0; i<count; i++) {
         String key = settingsKeyName(i);
         String value = getSetting(key);
-        response->printf(",\n  \"%s\": \"%s\"", key.c_str(), value.c_str());
+        response->printf(",\n\"%s\": \"%s\"", key.c_str(), value.c_str());
     }
     response->printf("\n}");