feat: add SD-backed stats archive and dedicated /stats web console

src/helpers/web/WebPrefs.cpp

@@ -0,0 +1,68 @@
+#include "WebPrefs.h"
+
+#include <string.h>
+
+void WebPrefsStore::setDefaults(WebPrefs& prefs) {
+  memset(&prefs, 0, sizeof(prefs));
+  prefs.magic = kMagic;
+  prefs.web_enabled = 1;
+  prefs.web_stats_enabled = 1;
+}
+
+bool WebPrefsStore::load(FILESYSTEM* fs, WebPrefs& prefs) {
+  setDefaults(prefs);
+  if (fs == nullptr) {
+    return false;
+  }
+
+  if (!fs->exists(kFilename)) {
+    save(fs, prefs);
+    return false;
+  }
+
+#if defined(RP2040_PLATFORM)
+  File file = fs->open(kFilename, "r");
+#else
+  File file = fs->open(kFilename);
+#endif
+  if (!file) {
+    return false;
+  }
+
+  WebPrefs persisted{};
+  size_t bytes_to_read = min(static_cast<size_t>(file.size()), sizeof(persisted));
+  bool ok = bytes_to_read >= sizeof(persisted.magic) &&
+            file.read(reinterpret_cast<uint8_t*>(&persisted), bytes_to_read) == bytes_to_read;
+  file.close();
+
+  if (!ok || persisted.magic != kMagic) {
+    fs->remove(kFilename);
+    save(fs, prefs);
+    return false;
+  }
+
+  prefs = persisted;
+  prefs.web_enabled = prefs.web_enabled ? 1 : 0;
+  prefs.web_stats_enabled = prefs.web_stats_enabled ? 1 : 0;
+  return true;
+}
+
+bool WebPrefsStore::save(FILESYSTEM* fs, const WebPrefs& prefs) {
+  if (fs == nullptr) {
+    return false;
+  }
+  if (fs->exists(kFilename) && !fs->remove(kFilename)) {
+    return false;
+  }
+#if defined(RP2040_PLATFORM)
+  File file = fs->open(kFilename, "w");
+#else
+  File file = fs->open(kFilename, "w", true);
+#endif
+  if (!file) {
+    return false;
+  }
+  bool ok = file.write(reinterpret_cast<const uint8_t*>(&prefs), sizeof(prefs)) == sizeof(prefs);
+  file.close();
+  return ok;
+}