feat: Connect to last wifi by default (#752)

## Summary

* **What is the goal of this PR?** 

Use last connected network as default

* **What changes are included?**

- Refactor how an action type of Settings are handled
- Add a new System Settings option → Network
- Add the ability to forget a network in the Network Selection Screen
- Add the ability to Refresh network list
- Save the last connected network SSID
- Use the last connection whenever network is needed (OPDS, Koreader
sync, update etc)

## Additional Context

* Add any other information that might be helpful for the reviewer
(e.g., performance implications, potential risks,
  specific areas to focus on).


![IMG_6504](https://github.com/user-attachments/assets/e48fb013-b5c3-45c0-b284-e183e6fd5a68)

![IMG_6503](https://github.com/user-attachments/assets/78c4b6b6-4e7b-4656-b356-19d65ff6aa12)




https://github.com/user-attachments/assets/95bf34a8-44ce-4279-8cd8-f78524ce745b





---

### AI Usage

Did you use AI tools to help write this code? _** PARTIALLY: I wrote
most of it but I also used Gemini as assist.

---------

Co-authored-by: Eliz Kilic <elizk@google.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

src/WifiCredentialStore.cpp

@@ -9,7 +9,7 @@ WifiCredentialStore WifiCredentialStore::instance;
 
 namespace {
 // File format version
-constexpr uint8_t WIFI_FILE_VERSION = 1;
+constexpr uint8_t WIFI_FILE_VERSION = 2;  // Increased version
 
 // WiFi credentials file path
 constexpr char WIFI_FILE[] = "/.crosspoint/wifi.bin";
@@ -38,6 +38,7 @@ bool WifiCredentialStore::saveToFile() const {
 
   // Write header
   serialization::writePod(file, WIFI_FILE_VERSION);
+  serialization::writeString(file, lastConnectedSsid);  // Save last connected SSID
   serialization::writePod(file, static_cast<uint8_t>(credentials.size()));
 
   // Write each credential
@@ -67,12 +68,18 @@ bool WifiCredentialStore::loadFromFile() {
   // Read and verify version
   uint8_t version;
   serialization::readPod(file, version);
-  if (version != WIFI_FILE_VERSION) {
+  if (version > WIFI_FILE_VERSION) {
     Serial.printf("[%lu] [WCS] Unknown file version: %u\n", millis(), version);
     file.close();
     return false;
   }
 
+  if (version >= 2) {
+    serialization::readString(file, lastConnectedSsid);
+  } else {
+    lastConnectedSsid.clear();
+  }
+
   // Read credential count
   uint8_t count;
   serialization::readPod(file, count);
@@ -128,6 +135,9 @@ bool WifiCredentialStore::removeCredential(const std::string& ssid) {
   if (cred != credentials.end()) {
     credentials.erase(cred);
     Serial.printf("[%lu] [WCS] Removed credentials for: %s\n", millis(), ssid.c_str());
+    if (ssid == lastConnectedSsid) {
+      clearLastConnectedSsid();
+    }
     return saveToFile();
   }
   return false;  // Not found
@@ -146,8 +156,25 @@ const WifiCredential* WifiCredentialStore::findCredential(const std::string& ssi
 
 bool WifiCredentialStore::hasSavedCredential(const std::string& ssid) const { return findCredential(ssid) != nullptr; }
 
+void WifiCredentialStore::setLastConnectedSsid(const std::string& ssid) {
+  if (lastConnectedSsid != ssid) {
+    lastConnectedSsid = ssid;
+    saveToFile();
+  }
+}
+
+const std::string& WifiCredentialStore::getLastConnectedSsid() const { return lastConnectedSsid; }
+
+void WifiCredentialStore::clearLastConnectedSsid() {
+  if (!lastConnectedSsid.empty()) {
+    lastConnectedSsid.clear();
+    saveToFile();
+  }
+}
+
 void WifiCredentialStore::clearAll() {
   credentials.clear();
+  lastConnectedSsid.clear();
   saveToFile();
   Serial.printf("[%lu] [WCS] Cleared all WiFi credentials\n", millis());
 }

src/WifiCredentialStore.h

@@ -16,6 +16,7 @@ class WifiCredentialStore {
  private:
   static WifiCredentialStore instance;
   std::vector<WifiCredential> credentials;
+  std::string lastConnectedSsid;
 
   static constexpr size_t MAX_NETWORKS = 8;
 
@@ -48,6 +49,11 @@ class WifiCredentialStore {
   // Check if a network is saved
   bool hasSavedCredential(const std::string& ssid) const;
 
+  // Last connected network
+  void setLastConnectedSsid(const std::string& ssid);
+  const std::string& getLastConnectedSsid() const;
+  void clearLastConnectedSsid();
+
   // Clear all credentials
   void clearAll();
 };

src/activities/network/WifiSelectionActivity.cpp

@@ -21,7 +21,8 @@ void WifiSelectionActivity::onEnter() {
 
   renderingMutex = xSemaphoreCreateMutex();
 
-  // Load saved WiFi credentials - SD card operations need lock as we use SPI for both
+  // Load saved WiFi credentials - SD card operations need lock as we use SPI
+  // for both
   xSemaphoreTake(renderingMutex, portMAX_DELAY);
   WIFI_STORE.loadFromFile();
   xSemaphoreGive(renderingMutex);
@@ -37,6 +38,7 @@ void WifiSelectionActivity::onEnter() {
   usedSavedPassword = false;
   savePromptSelection = 0;
   forgetPromptSelection = 0;
+  autoConnecting = false;
 
   // Cache MAC address for display
   uint8_t mac[6];
@@ -46,9 +48,7 @@ void WifiSelectionActivity::onEnter() {
            mac[5]);
   cachedMacAddress = std::string(macStr);
 
-  // Trigger first update to show scanning message
+  // Task creation
-  updateRequired = true;
-
   xTaskCreate(&WifiSelectionActivity::taskTrampoline, "WifiSelectionTask",
               4096,               // Stack size (larger for WiFi operations)
               this,               // Parameters
@@ -56,7 +56,26 @@ void WifiSelectionActivity::onEnter() {
               &displayTaskHandle  // Task handle
   );
 
-  // Start WiFi scan
+  // Attempt to auto-connect to the last network
+  if (allowAutoConnect) {
+    const std::string lastSsid = WIFI_STORE.getLastConnectedSsid();
+    if (!lastSsid.empty()) {
+      const auto* cred = WIFI_STORE.findCredential(lastSsid);
+      if (cred) {
+        Serial.printf("[%lu] [WIFI] Attempting to auto-connect to %s\n", millis(), lastSsid.c_str());
+        selectedSSID = cred->ssid;
+        enteredPassword = cred->password;
+        selectedRequiresPassword = !cred->password.empty();
+        usedSavedPassword = true;
+        autoConnecting = true;
+        attemptConnection();
+        updateRequired = true;
+        return;
+      }
+    }
+  }
+
+  // Fallback to scanning
   startWifiScan();
 }
 
@@ -70,15 +89,17 @@ void WifiSelectionActivity::onExit() {
   WiFi.scanDelete();
   Serial.printf("[%lu] [WIFI] [MEM] Free heap after scanDelete: %d bytes\n", millis(), ESP.getFreeHeap());
 
-  // Note: We do NOT disconnect WiFi here - the parent activity (CrossPointWebServerActivity)
+  // Note: We do NOT disconnect WiFi here - the parent activity
-  // manages WiFi connection state. We just clean up the scan and task.
+  // (CrossPointWebServerActivity) manages WiFi connection state. We just clean
+  // up the scan and task.
 
   // Acquire mutex before deleting task to ensure task isn't using it
   // This prevents hangs/crashes if the task holds the mutex when deleted
   Serial.printf("[%lu] [WIFI] Acquiring rendering mutex before task deletion...\n", millis());
   xSemaphoreTake(renderingMutex, portMAX_DELAY);
 
-  // Delete the display task (we now hold the mutex, so task is blocked if it needs it)
+  // Delete the display task (we now hold the mutex, so task is blocked if it
+  // needs it)
   Serial.printf("[%lu] [WIFI] Deleting display task...\n", millis());
   if (displayTaskHandle) {
     vTaskDelete(displayTaskHandle);
@@ -96,6 +117,7 @@ void WifiSelectionActivity::onExit() {
 }
 
 void WifiSelectionActivity::startWifiScan() {
+  autoConnecting = false;
   state = WifiSelectionState::SCANNING;
   networks.clear();
   updateRequired = true;
@@ -181,6 +203,7 @@ void WifiSelectionActivity::selectNetwork(const int index) {
   selectedRequiresPassword = network.isEncrypted;
   usedSavedPassword = false;
   enteredPassword.clear();
+  autoConnecting = false;
 
   // Check if we have saved credentials for this network
   const auto* savedCred = WIFI_STORE.findCredential(selectedSSID);
@@ -223,7 +246,7 @@ void WifiSelectionActivity::selectNetwork(const int index) {
 }
 
 void WifiSelectionActivity::attemptConnection() {
-  state = WifiSelectionState::CONNECTING;
+  state = autoConnecting ? WifiSelectionState::AUTO_CONNECTING : WifiSelectionState::CONNECTING;
   connectionStartTime = millis();
   connectedIP.clear();
   connectionError.clear();
@@ -239,7 +262,7 @@ void WifiSelectionActivity::attemptConnection() {
 }
 
 void WifiSelectionActivity::checkConnectionStatus() {
-  if (state != WifiSelectionState::CONNECTING) {
+  if (state != WifiSelectionState::CONNECTING && state != WifiSelectionState::AUTO_CONNECTING) {
     return;
   }
 
@@ -251,6 +274,13 @@ void WifiSelectionActivity::checkConnectionStatus() {
     char ipStr[16];
     snprintf(ipStr, sizeof(ipStr), "%d.%d.%d.%d", ip[0], ip[1], ip[2], ip[3]);
     connectedIP = ipStr;
+    autoConnecting = false;
+
+    // Save this as the last connected network - SD card operations need lock as
+    // we use SPI for both
+    xSemaphoreTake(renderingMutex, portMAX_DELAY);
+    WIFI_STORE.setLastConnectedSsid(selectedSSID);
+    xSemaphoreGive(renderingMutex);
 
     // If we entered a new password, ask if user wants to save it
     // Otherwise, immediately complete so parent can start web server
@@ -260,7 +290,10 @@ void WifiSelectionActivity::checkConnectionStatus() {
       updateRequired = true;
     } else {
       // Using saved password or open network - complete immediately
-      Serial.printf("[%lu] [WIFI] Connected with saved/open credentials, completing immediately\n", millis());
+      Serial.printf(
+          "[%lu] [WIFI] Connected with saved/open credentials, "
+          "completing immediately\n",
+          millis());
       onComplete(true);
     }
     return;
@@ -299,7 +332,7 @@ void WifiSelectionActivity::loop() {
   }
 
   // Check connection progress
-  if (state == WifiSelectionState::CONNECTING) {
+  if (state == WifiSelectionState::CONNECTING || state == WifiSelectionState::AUTO_CONNECTING) {
     checkConnectionStatus();
     return;
   }
@@ -368,17 +401,16 @@ void WifiSelectionActivity::loop() {
         }
       }
       // Go back to network list (whether Cancel or Forget network was selected)
-      state = WifiSelectionState::NETWORK_LIST;
+      startWifiScan();
-      updateRequired = true;
     } else if (mappedInput.wasPressed(MappedInputManager::Button::Back)) {
       // Skip forgetting, go back to network list
-      state = WifiSelectionState::NETWORK_LIST;
+      startWifiScan();
-      updateRequired = true;
     }
     return;
   }
 
-  // Handle connected state (should not normally be reached - connection completes immediately)
+  // Handle connected state (should not normally be reached - connection
+  // completes immediately)
   if (state == WifiSelectionState::CONNECTED) {
     // Safety fallback - immediately complete
     onComplete(true);
@@ -389,12 +421,14 @@ void WifiSelectionActivity::loop() {
   if (state == WifiSelectionState::CONNECTION_FAILED) {
     if (mappedInput.wasPressed(MappedInputManager::Button::Back) ||
         mappedInput.wasPressed(MappedInputManager::Button::Confirm)) {
-      // If we used saved credentials, offer to forget the network
+      // If we were auto-connecting or using a saved credential, offer to forget
-      if (usedSavedPassword) {
+      // the network
+      if (autoConnecting || usedSavedPassword) {
+        autoConnecting = false;
         state = WifiSelectionState::FORGET_PROMPT;
         forgetPromptSelection = 0;  // Default to "Cancel"
       } else {
-        // Go back to network list on failure
+        // Go back to network list on failure for non-saved credentials
         state = WifiSelectionState::NETWORK_LIST;
       }
       updateRequired = true;
@@ -420,6 +454,23 @@ void WifiSelectionActivity::loop() {
       return;
     }
 
+    if (mappedInput.wasPressed(MappedInputManager::Button::Right)) {
+      startWifiScan();
+      return;
+    }
+
+    const bool leftPressed = mappedInput.wasPressed(MappedInputManager::Button::Left);
+    if (leftPressed) {
+      const bool hasSavedPassword = !networks.empty() && networks[selectedNetworkIndex].hasSavedPassword;
+      if (hasSavedPassword) {
+        selectedSSID = networks[selectedNetworkIndex].ssid;
+        state = WifiSelectionState::FORGET_PROMPT;
+        forgetPromptSelection = 0;  // Default to "Cancel"
+        updateRequired = true;
+        return;
+      }
+    }
+
     // Handle navigation
     buttonNavigator.onNext([this] {
       selectedNetworkIndex = ButtonNavigator::nextIndex(selectedNetworkIndex, networks.size());
@@ -479,6 +530,9 @@ void WifiSelectionActivity::render() const {
   renderer.clearScreen();
 
   switch (state) {
+    case WifiSelectionState::AUTO_CONNECTING:
+      renderConnecting();
+      break;
     case WifiSelectionState::SCANNING:
       renderConnecting();  // Reuse connecting screen with different message
       break;
@@ -582,7 +636,11 @@ void WifiSelectionActivity::renderNetworkList() const {
 
   // Draw help text
   renderer.drawText(SMALL_FONT_ID, 20, pageHeight - 75, "* = Encrypted | + = Saved");
-  const auto labels = mappedInput.mapLabels("« Back", "Connect", "", "");
+
+  const bool hasSavedPassword = !networks.empty() && networks[selectedNetworkIndex].hasSavedPassword;
+  const char* forgetLabel = hasSavedPassword ? "Forget" : "";
+
+  const auto labels = mappedInput.mapLabels("« Back", "Connect", forgetLabel, "Refresh");
   GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 }
 
@@ -686,8 +744,7 @@ void WifiSelectionActivity::renderForgetPrompt() const {
   const auto height = renderer.getLineHeight(UI_10_FONT_ID);
   const auto top = (pageHeight - height * 3) / 2;
 
-  renderer.drawCenteredText(UI_12_FONT_ID, top - 40, "Connection Failed", true, EpdFontFamily::BOLD);
+  renderer.drawCenteredText(UI_12_FONT_ID, top - 40, "Forget Network", true, EpdFontFamily::BOLD);
-
   std::string ssidInfo = "Network: " + selectedSSID;
   if (ssidInfo.length() > 28) {
     ssidInfo.replace(25, ssidInfo.length() - 25, "...");

src/activities/network/WifiSelectionActivity.h

@@ -22,6 +22,7 @@ struct WifiNetworkInfo {
 
 // WiFi selection states
 enum class WifiSelectionState {
+  AUTO_CONNECTING,    // Trying to connect to the last known network
   SCANNING,           // Scanning for networks
   NETWORK_LIST,       // Displaying available networks
   PASSWORD_ENTRY,     // Entering password for selected network
@@ -70,6 +71,12 @@ class WifiSelectionActivity final : public ActivityWithSubactivity {
   // Whether network was connected using a saved password (skip save prompt)
   bool usedSavedPassword = false;
 
+  // Whether to attempt auto-connect on entry
+  const bool allowAutoConnect;
+
+  // Whether we are attempting to auto-connect
+  bool autoConnecting = false;
+
   // Save/forget prompt selection (0 = Yes, 1 = No)
   int savePromptSelection = 0;
   int forgetPromptSelection = 0;
@@ -98,8 +105,10 @@ class WifiSelectionActivity final : public ActivityWithSubactivity {
 
  public:
   explicit WifiSelectionActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
-                                 const std::function<void(bool connected)>& onComplete)
+                                 const std::function<void(bool connected)>& onComplete, bool autoConnect = true)
-      : ActivityWithSubactivity("WifiSelection", renderer, mappedInput), onComplete(onComplete) {}
+      : ActivityWithSubactivity("WifiSelection", renderer, mappedInput),
+        onComplete(onComplete),
+        allowAutoConnect(autoConnect) {}
   void onEnter() override;
   void onExit() override;
   void loop() override;

src/activities/settings/SettingsActivity.cpp

@@ -11,6 +11,7 @@
 #include "MappedInputManager.h"
 #include "OtaUpdateActivity.h"
 #include "SettingsList.h"
+#include "activities/network/WifiSelectionActivity.h"
 #include "components/UITheme.h"
 #include "fontIds.h"
 
@@ -46,11 +47,13 @@ void SettingsActivity::onEnter() {
   }
 
   // Append device-only ACTION items
-  controlsSettings.insert(controlsSettings.begin(), SettingInfo::Action("Remap Front Buttons"));
+  controlsSettings.insert(controlsSettings.begin(),
-  systemSettings.push_back(SettingInfo::Action("KOReader Sync"));
+                          SettingInfo::Action("Remap Front Buttons", SettingAction::RemapFrontButtons));
-  systemSettings.push_back(SettingInfo::Action("OPDS Browser"));
+  systemSettings.push_back(SettingInfo::Action("Network", SettingAction::Network));
-  systemSettings.push_back(SettingInfo::Action("Clear Cache"));
+  systemSettings.push_back(SettingInfo::Action("KOReader Sync", SettingAction::KOReaderSync));
-  systemSettings.push_back(SettingInfo::Action("Check for updates"));
+  systemSettings.push_back(SettingInfo::Action("OPDS Browser", SettingAction::OPDSBrowser));
+  systemSettings.push_back(SettingInfo::Action("Clear Cache", SettingAction::ClearCache));
+  systemSettings.push_back(SettingInfo::Action("Check for updates", SettingAction::CheckForUpdates));
 
   // Reset selection to first category
   selectedCategoryIndex = 0;
@@ -178,46 +181,45 @@ void SettingsActivity::toggleCurrentSetting() {
       SETTINGS.*(setting.valuePtr) = currentValue + setting.valueRange.step;
     }
   } else if (setting.type == SettingType::ACTION) {
-    if (strcmp(setting.name, "Remap Front Buttons") == 0) {
+    auto enterSubActivity = [this](Activity* activity) {
       xSemaphoreTake(renderingMutex, portMAX_DELAY);
       exitActivity();
-      enterNewActivity(new ButtonRemapActivity(renderer, mappedInput, [this] {
+      enterNewActivity(activity);
+      xSemaphoreGive(renderingMutex);
+    };
+
+    auto onComplete = [this] {
       exitActivity();
       updateRequired = true;
-      }));
+    };
-      xSemaphoreGive(renderingMutex);
+
-    } else if (strcmp(setting.name, "KOReader Sync") == 0) {
+    auto onCompleteBool = [this](bool) {
-      xSemaphoreTake(renderingMutex, portMAX_DELAY);
-      exitActivity();
-      enterNewActivity(new KOReaderSettingsActivity(renderer, mappedInput, [this] {
       exitActivity();
       updateRequired = true;
-      }));
+    };
-      xSemaphoreGive(renderingMutex);
+
-    } else if (strcmp(setting.name, "OPDS Browser") == 0) {
+    switch (setting.action) {
-      xSemaphoreTake(renderingMutex, portMAX_DELAY);
+      case SettingAction::RemapFrontButtons:
-      exitActivity();
+        enterSubActivity(new ButtonRemapActivity(renderer, mappedInput, onComplete));
-      enterNewActivity(new CalibreSettingsActivity(renderer, mappedInput, [this] {
+        break;
-        exitActivity();
+      case SettingAction::KOReaderSync:
-        updateRequired = true;
+        enterSubActivity(new KOReaderSettingsActivity(renderer, mappedInput, onComplete));
-      }));
+        break;
-      xSemaphoreGive(renderingMutex);
+      case SettingAction::OPDSBrowser:
-    } else if (strcmp(setting.name, "Clear Cache") == 0) {
+        enterSubActivity(new CalibreSettingsActivity(renderer, mappedInput, onComplete));
-      xSemaphoreTake(renderingMutex, portMAX_DELAY);
+        break;
-      exitActivity();
+      case SettingAction::Network:
-      enterNewActivity(new ClearCacheActivity(renderer, mappedInput, [this] {
+        enterSubActivity(new WifiSelectionActivity(renderer, mappedInput, onCompleteBool, false));
-        exitActivity();
+        break;
-        updateRequired = true;
+      case SettingAction::ClearCache:
-      }));
+        enterSubActivity(new ClearCacheActivity(renderer, mappedInput, onComplete));
-      xSemaphoreGive(renderingMutex);
+        break;
-    } else if (strcmp(setting.name, "Check for updates") == 0) {
+      case SettingAction::CheckForUpdates:
-      xSemaphoreTake(renderingMutex, portMAX_DELAY);
+        enterSubActivity(new OtaUpdateActivity(renderer, mappedInput, onComplete));
-      exitActivity();
+        break;
-      enterNewActivity(new OtaUpdateActivity(renderer, mappedInput, [this] {
+      case SettingAction::None:
-        exitActivity();
+        // Do nothing
-        updateRequired = true;
+        break;
-      }));
-      xSemaphoreGive(renderingMutex);
     }
   } else {
     return;

src/activities/settings/SettingsActivity.h

@@ -14,11 +14,22 @@ class CrossPointSettings;
 
 enum class SettingType { TOGGLE, ENUM, ACTION, VALUE, STRING };
 
+enum class SettingAction {
+  None,
+  RemapFrontButtons,
+  KOReaderSync,
+  OPDSBrowser,
+  Network,
+  ClearCache,
+  CheckForUpdates,
+};
+
 struct SettingInfo {
   const char* name;
   SettingType type;
   uint8_t CrossPointSettings::* valuePtr = nullptr;
   std::vector<std::string> enumValues;
+  SettingAction action = SettingAction::None;
 
   struct ValueRange {
     uint8_t min;
@@ -63,10 +74,11 @@ struct SettingInfo {
     return s;
   }
 
-  static SettingInfo Action(const char* name) {
+  static SettingInfo Action(const char* name, SettingAction action) {
     SettingInfo s;
     s.name = name;
     s.type = SettingType::ACTION;
+    s.action = action;
     return s;
   }