main.cpp

#include <Arduino.h>
#include <BoardConfig.h>
#include <Epub.h>
#include <FontCacheManager.h>
#include <FontDecompressor.h>
#include <GfxRenderer.h>
#include <HalClock.h>
#include <HalDisplay.h>
#include <HalFrontlight.h>
#include <HalGPIO.h>
#include <HalPowerManager.h>
#include <HalStorage.h>
#include <HalSystem.h>
#include <HalTiltSensor.h>
#include <I18n.h>
#include <Logging.h>
#include <SPI.h>
#include <WiFi.h>
#include <XteinkDetect.h>
#include <builtinFonts/all.h>
#if FREEINK_CAP_TOUCH
#include <esp_sntp.h>
#endif

#include <cstring>

#include "CrossPointSettings.h"
#include "CrossPointState.h"
#include "KOReaderCredentialStore.h"
#include "MappedInputManager.h"
#include "OpdsServerStore.h"
#include "RecentBooksStore.h"
#include "SdCardFontSystem.h"
#include "activities/Activity.h"
#include "activities/ActivityManager.h"
#include "activities/settings/SdFirmwareUpdateActivity.h"
#include "components/UITheme.h"
#include "fontIds.h"
#include "images/LoadingIcon.h"
#include "util/ButtonNavigator.h"
#include "util/ScreenshotUtil.h"

GfxRenderer renderer(display);
MappedInputManager mappedInputManager(gpio, renderer);
ActivityManager activityManager(renderer, mappedInputManager);
FontDecompressor fontDecompressor;
SdCardFontSystem sdFontSystem;
FontCacheManager fontCacheManager(renderer.getFontMap(), renderer.getSdCardFonts());
static unsigned long allowSleepAt = 0;
static unsigned long lastX4ProPowerClickAt = 0;

namespace {
constexpr unsigned long X4PRO_POWER_DOUBLE_CLICK_MS = 500;
constexpr unsigned long X4PRO_POWER_CLICK_MAX_HOLD_MS = 300;
constexpr unsigned long X4PRO_RECOVERY_SETTLE_MS = 20;
constexpr unsigned long DEFAULT_RECOVERY_SETTLE_MS = 500;
}  // namespace

// A wake hold must never become an in-app power-button action.  Boot may continue
// while the button is held; swallow the one release that ends that wake gesture.
static bool wakePowerReleasePending = false;

// Fonts
EpdFont notoserif14RegularFont(&notoserif_14_regular);
EpdFont notoserif14BoldFont(&notoserif_14_bold);
EpdFont notoserif14ItalicFont(&notoserif_14_italic);
EpdFont notoserif14BoldItalicFont(&notoserif_14_bolditalic);
EpdFontFamily notoserif14FontFamily(&notoserif14RegularFont, &notoserif14BoldFont, &notoserif14ItalicFont,
                                    &notoserif14BoldItalicFont);
#ifndef OMIT_FONTS
EpdFont notoserif12RegularFont(&notoserif_12_regular);
EpdFont notoserif12BoldFont(&notoserif_12_bold);
EpdFont notoserif12ItalicFont(&notoserif_12_italic);
EpdFont notoserif12BoldItalicFont(&notoserif_12_bolditalic);
EpdFontFamily notoserif12FontFamily(&notoserif12RegularFont, &notoserif12BoldFont, &notoserif12ItalicFont,
                                    &notoserif12BoldItalicFont);
EpdFont notoserif16RegularFont(&notoserif_16_regular);
EpdFont notoserif16BoldFont(&notoserif_16_bold);
EpdFont notoserif16ItalicFont(&notoserif_16_italic);
EpdFont notoserif16BoldItalicFont(&notoserif_16_bolditalic);
EpdFontFamily notoserif16FontFamily(&notoserif16RegularFont, &notoserif16BoldFont, &notoserif16ItalicFont,
                                    &notoserif16BoldItalicFont);
EpdFont notoserif18RegularFont(&notoserif_18_regular);
EpdFont notoserif18BoldFont(&notoserif_18_bold);
EpdFont notoserif18ItalicFont(&notoserif_18_italic);
EpdFont notoserif18BoldItalicFont(&notoserif_18_bolditalic);
EpdFontFamily notoserif18FontFamily(&notoserif18RegularFont, &notoserif18BoldFont, &notoserif18ItalicFont,
                                    &notoserif18BoldItalicFont);

EpdFont notosans12RegularFont(&notosans_12_regular);
EpdFont notosans12BoldFont(&notosans_12_bold);
EpdFont notosans12ItalicFont(&notosans_12_italic);
EpdFont notosans12BoldItalicFont(&notosans_12_bolditalic);
EpdFontFamily notosans12FontFamily(&notosans12RegularFont, &notosans12BoldFont, &notosans12ItalicFont,
                                   &notosans12BoldItalicFont);
EpdFont notosans14RegularFont(&notosans_14_regular);
EpdFont notosans14BoldFont(&notosans_14_bold);
EpdFont notosans14ItalicFont(&notosans_14_italic);
EpdFont notosans14BoldItalicFont(&notosans_14_bolditalic);
EpdFontFamily notosans14FontFamily(&notosans14RegularFont, &notosans14BoldFont, &notosans14ItalicFont,
                                   &notosans14BoldItalicFont);
EpdFont notosans16RegularFont(&notosans_16_regular);
EpdFont notosans16BoldFont(&notosans_16_bold);
EpdFont notosans16ItalicFont(&notosans_16_italic);
EpdFont notosans16BoldItalicFont(&notosans_16_bolditalic);
EpdFontFamily notosans16FontFamily(&notosans16RegularFont, &notosans16BoldFont, &notosans16ItalicFont,
                                   &notosans16BoldItalicFont);
EpdFont notosans18RegularFont(&notosans_18_regular);
EpdFont notosans18BoldFont(&notosans_18_bold);
EpdFont notosans18ItalicFont(&notosans_18_italic);
EpdFont notosans18BoldItalicFont(&notosans_18_bolditalic);
EpdFontFamily notosans18FontFamily(&notosans18RegularFont, &notosans18BoldFont, &notosans18ItalicFont,
                                   &notosans18BoldItalicFont);

#endif  // OMIT_FONTS

EpdFont smallFont(&notosans_8_regular);
EpdFontFamily smallFontFamily(&smallFont);

EpdFont ui10RegularFont(&ubuntu_10_regular);
EpdFont ui10BoldFont(&ubuntu_10_bold);
EpdFontFamily ui10FontFamily(&ui10RegularFont, &ui10BoldFont);

EpdFont ui12RegularFont(&ubuntu_12_regular);
EpdFont ui12BoldFont(&ubuntu_12_bold);
EpdFontFamily ui12FontFamily(&ui12RegularFont, &ui12BoldFont);

// measurement of power button press duration calibration value
unsigned long t1 = 0;
unsigned long t2 = 0;

// Definitions for SilentRestart.h. RTC_NOINIT survives ESP.restart() but not power loss.
RTC_NOINIT_ATTR uint32_t silentRebootMagic;
RTC_NOINIT_ATTR uint32_t silentRebootTarget;
constexpr uint32_t SILENT_REBOOT_MAGIC = 0xC1EAB007;
constexpr uint32_t SILENT_REBOOT_TARGET_HOME = 0;
constexpr uint32_t SILENT_REBOOT_TARGET_READER = 1;

// How the device is coming back to life, resolved once at boot. Both resume
// flows suppress the splash and leave the panel holding its pre-boot frame; a
// plain boot shows the splash. See setup() for the resolution.
enum class BootResume : uint8_t {
  Splash,          // cold boot, flash, panic, or plain reboot
  Silent,          // heap-defrag ESP.restart() (RTC flag; lost on power loss)
  SplashlessWake,  // wake from deep sleep with the splash suppressed by the SD flag
};

// Latched true once enterDeepSleep() commits to sleeping, before it tears down
// the current activity. WiFi activities call silentRestart() in onExit() to
// clear heap fragmentation on the way out, but deep sleep is a full chip reset
// on wake and already clears the heap, so rebooting here would just power the
// device back up against the user's sleep gesture. Never cleared:
// startDeepSleep() does not return, so a set latch only ends at the wakeup reset.
static bool deepSleepInProgress = false;

#if FREEINK_CAP_TOUCH
static bool finishWifiSessionWithoutRestart() {
  if (!BoardConfig::hasTouch()) return false;

  // A software reset does not cycle externally powered touch/frontlight rails.
  // Shut down the network stack in place so those peripherals retain state.
  if (esp_sntp_enabled()) {
    esp_sntp_stop();
  }
  WiFi.mode(WIFI_OFF);
  delay(100);
  LOG_DBG("MAIN", "WiFi stopped without restart on touch device");
  return true;
}
#endif

void silentRestart() {
  if (deepSleepInProgress) return;  // sleeping supersedes the heap-defrag reboot
#if FREEINK_CAP_TOUCH
  if (finishWifiSessionWithoutRestart()) return;
#endif
  silentRebootTarget = SILENT_REBOOT_TARGET_HOME;
  silentRebootMagic = SILENT_REBOOT_MAGIC;
  LOG_DBG("MAIN", "Silent restart (target=home)");
  // E-ink retains the previous frame until Home's first paint lands (~2-3s).
  // Without an overlay, users don't see the reboot and fire input through to
  // Home. Select on the default selectorIndex=0 then opens the most-recent
  // book, looking like a trampoline back to the reader they just exited.
  GUI.drawPopup(renderer, tr(STR_LOADING_POPUP));
  delay(50);
  ESP.restart();
}

void silentRestartToReader() {
  if (deepSleepInProgress) return;  // sleeping supersedes the heap-defrag reboot
#if FREEINK_CAP_TOUCH
  if (finishWifiSessionWithoutRestart()) return;
#endif
  silentRebootTarget = SILENT_REBOOT_TARGET_READER;
  silentRebootMagic = SILENT_REBOOT_MAGIC;
  LOG_DBG("MAIN", "Silent restart (target=reader)");
  GUI.drawPopup(renderer, tr(STR_LOADING_POPUP));
  delay(50);
  ESP.restart();
}

bool handleX4ProFrontlightDoubleClick() {
  if (!BoardConfig::isX4Pro() || !gpio.wasReleased(HalGPIO::BTN_POWER)) {
    return false;
  }

  const unsigned long now = millis();
  if (gpio.getPowerButtonHeldTime() > X4PRO_POWER_CLICK_MAX_HOLD_MS) {
    lastX4ProPowerClickAt = 0;
    return false;
  }

  if (lastX4ProPowerClickAt == 0 || now - lastX4ProPowerClickAt > X4PRO_POWER_DOUBLE_CLICK_MS) {
    lastX4ProPowerClickAt = now;
    return false;
  }

  lastX4ProPowerClickAt = 0;
  const bool lightOn = !Frontlight.isOn();
  Frontlight.setOn(lightOn);
  SETTINGS.frontlightOn = lightOn ? 1 : 0;
  SETTINGS.saveToFile();
  LOG_INF("LIGHT", "Frontlight toggled %s by power-button double-click", lightOn ? "on" : "off");
  return true;
}

constexpr char SLEEP_FRAME_FILE[] = "/.crosspoint/sleep_frame.bin";

static void saveSleepFrameBuffer() {
  HalFile file;
  if (!Storage.openFileForWrite("SLP", SLEEP_FRAME_FILE, file)) return;
  file.write(renderer.getFrameBuffer(), renderer.getBufferSize());
  file.close();
}

static bool loadSleepFrameBuffer() {
  HalFile file;
  if (!Storage.openFileForRead("SLP", SLEEP_FRAME_FILE, file)) return false;
  const size_t bufferSize = display.getBufferSize();
  const size_t bytesRead = file.read(display.getFrameBuffer(), bufferSize);
  file.close();
  if (bytesRead != bufferSize) {
    Storage.remove(SLEEP_FRAME_FILE);
    return false;
  }
  Storage.remove(SLEEP_FRAME_FILE);
  return true;
}

// Enter deep sleep mode
void enterDeepSleep(bool fromTimeout = false) {
  HalPowerManager::Lock powerLock;  // Ensure we are at normal CPU frequency for sleep preparation
  APP_STATE.lastSleepFromReader = activityManager.isReaderActivity();

  const bool isQuickResumeSleep =
      SETTINGS.sleepScreen == CrossPointSettings::SLEEP_SCREEN_MODE::QUICK_RESUME ||
      (fromTimeout &&
       SETTINGS.quickResumeSleepScreen == CrossPointSettings::QUICK_RESUME_SLEEP_SCREEN::QUICK_RESUME_AFTER_TIMEOUT);
  // Every sleep mode leaves a complete retained frame on the e-ink panel. Keep
  // it visible until the first useful reader or home paint replaces it.
  APP_STATE.showBootScreen = false;

  APP_STATE.saveToFile();

  // Commit to sleeping before goToSleep() runs the outgoing activity's onExit():
  // a WiFi activity would otherwise silentRestart() here and reboot instead.
  deepSleepInProgress = true;
  activityManager.goToSleep(fromTimeout);

  if (isQuickResumeSleep) {
    saveSleepFrameBuffer();
  } else if (Storage.exists(SLEEP_FRAME_FILE)) {
    // A stale Quick Resume frame must not replace the selected sleep screen during wake.
    Storage.remove(SLEEP_FRAME_FILE);
  }

  // Tear down WiFi so the modem power domain isn't held alive across deep sleep.
  // Wake from deep sleep is effectively a chip reset, so no state needs to survive.
  if (WiFi.getMode() != WIFI_MODE_NULL) {
    WiFi.disconnect(true);
    WiFi.mode(WIFI_OFF);
  }

  halTiltSensor.deepSleep();
  display.deepSleep();
  LOG_DBG("MAIN", "Entering deep sleep");

  powerManager.startDeepSleep(gpio);
}

void setupDisplayAndFonts(bool seamless = false) {
#if !FREEINK_MCU_C3
  // C3 resolves its controller in HalGPIO::begin() before SPI claims the
  // display pins. X4 Pro skips that C3-only path, so probe here before
  // display.begin() selects and initializes its panel driver.
  static bool controllerResolved = false;
  if (!controllerResolved) {
    controllerResolved = true;
    if (freeink::applyXteinkDisplayController()) {
      LOG_DBG("MAIN", "Panel controller: UltraChip UC81xx variant detected");
    }
  }
#endif

  display.begin(seamless);
  renderer.begin();
  activityManager.begin();
  LOG_DBG("MAIN", "Display initialized");

  // Initialize font decompressor for compressed reader fonts
  if (!fontDecompressor.init()) {
    LOG_ERR("MAIN", "Font decompressor init failed");
  }
  fontCacheManager.setFontDecompressor(&fontDecompressor);
  renderer.setFontCacheManager(&fontCacheManager);
  renderer.insertFont(NOTOSERIF_14_FONT_ID, notoserif14FontFamily);
#ifndef OMIT_FONTS
  renderer.insertFont(NOTOSERIF_12_FONT_ID, notoserif12FontFamily);
  renderer.insertFont(NOTOSERIF_16_FONT_ID, notoserif16FontFamily);
  renderer.insertFont(NOTOSERIF_18_FONT_ID, notoserif18FontFamily);

  renderer.insertFont(NOTOSANS_12_FONT_ID, notosans12FontFamily);
  renderer.insertFont(NOTOSANS_14_FONT_ID, notosans14FontFamily);
  renderer.insertFont(NOTOSANS_16_FONT_ID, notosans16FontFamily);
  renderer.insertFont(NOTOSANS_18_FONT_ID, notosans18FontFamily);
#endif  // OMIT_FONTS
  renderer.insertFont(UI_10_FONT_ID, ui10FontFamily);
  renderer.insertFont(UI_12_FONT_ID, ui12FontFamily);
  renderer.insertFont(SMALL_FONT_ID, smallFontFamily);

  // Discover and load SD card fonts
  sdFontSystem.begin(renderer);

  LOG_DBG("MAIN", "Fonts setup");
}

void setup() {
  BoardConfig::holdPowerRails();

  t1 = millis();

#ifdef ENABLE_SERIAL_LOG
  // Earliest possible Serial setup. The 250 ms stall before begin() lets the
  // USB Serial/JTAG peripheral finish power-on and lets the host complete USB
  // enumeration before we touch the CDC state — otherwise cold boot races
  // and the host has to be physically replugged for logs to flow. Warm reboot
  // worked without the delay because USB was already enumerated.
  delay(250);
  Serial.begin(115200);
#if LOG_SERIAL_HAS_TX_TIMEOUT
  logSerial.setTxTimeoutMs(1);  // This is a load-bearing 1. Do not modify.
#endif
#endif

  HalSystem::begin();
  // checkPanic() clears the watchdog capture marker after a successful SD
  // dump, so retain the boot classification for the later activity route.
  const bool rebootedFromPanic = HalSystem::isRebootFromPanic();

  // Read-and-clear so a panic later in setup() doesn't loop into silent reboot.
  // Bound the target range too — RTC_NOINIT memory is uninitialized on cold boot.
  const bool isSilentReboot = (silentRebootMagic == SILENT_REBOOT_MAGIC);
  const uint32_t snapshotTarget =
      (isSilentReboot && silentRebootTarget <= SILENT_REBOOT_TARGET_READER) ? silentRebootTarget : 0;
  silentRebootMagic = 0;
  silentRebootTarget = 0;

  gpio.begin();
  powerManager.begin();
  halTiltSensor.begin();
  halClock.begin();

  const auto wakeupReason = gpio.getWakeupReason();

  // Latch the recovery chord before SD and settings I/O. X4 Pro uses a plain
  // digital button with 5 ms debounce; other Xteink inputs retain their legacy
  // settling window. BTN_DOWN avoids the X4 Pro's GPIO0 boot-strap pin.
  bool recoveryFirmwareMode = false;
  if (wakeupReason == HalGPIO::WakeupReason::PowerButton) {
    const unsigned long settleMs = BoardConfig::isX4Pro() ? X4PRO_RECOVERY_SETTLE_MS : DEFAULT_RECOVERY_SETTLE_MS;
    const unsigned long settleStart = millis();
    while (millis() - settleStart < settleMs) {
      gpio.update();
      delay(10);
    }

    const uint8_t recoveryButton = BoardConfig::isX4Pro() ? HalGPIO::BTN_DOWN : HalGPIO::BTN_UP;
    if (gpio.isPressed(recoveryButton)) {
      recoveryFirmwareMode = true;
      LOG_INF("MAIN", "Recovery firmware mode (%s + POWER held at boot)", BoardConfig::isX4Pro() ? "DOWN" : "UP");
    }
  }

#if FREEINK_DEVICE_X4 || FREEINK_DEVICE_X3
  LOG_INF("MAIN", "Hardware detect: %s", gpio.deviceIsX3() ? "X3" : "X4");
#else
  LOG_INF("MAIN", "Device: %s", BoardConfig::ACTIVE.name);
#endif

  // SD Card Initialization
  // We need 6 open files concurrently when parsing a new chapter
  if (!Storage.begin()) {
    LOG_ERR("MAIN", "SD card initialization failed");
    setupDisplayAndFonts(isSilentReboot);
    activityManager.goToFullScreenMessage("SD card error", EpdFontFamily::BOLD);
    return;
  }

  HalSystem::checkPanic();

  SETTINGS.loadFromFile();
  APP_STATE.loadFromFile();
  RECENT_BOOKS.loadFromFile();
  I18N.setLanguage(static_cast<Language>(SETTINGS.language));
  KOREADER_STORE.loadFromFile();
  OPDS_STORE.loadFromFile();
  UITheme::getInstance().reload();
  ButtonNavigator::setMappedInputManager(mappedInputManager);

  // Brightness and warmth are always restored. A normal wake starts with the
  // light off unless Restore Light on Wake is enabled; silent maintenance
  // reboots preserve the live state so they do not unexpectedly go dark.
  const bool restoreLightOn = SETTINGS.frontlightOn != 0 && (SETTINGS.frontlightRestoreOnWake != 0 || isSilentReboot);
  Frontlight.begin(SETTINGS.frontlightBrightness, SETTINGS.frontlightWarmth, restoreLightOn);

  switch (wakeupReason) {
    case HalGPIO::WakeupReason::PowerButton:
      LOG_DBG("MAIN", "Verifying power button press duration");
      if (!gpio.verifyPowerButtonWakeup(SETTINGS.getPowerButtonDuration(),
                                        SETTINGS.shortPwrBtn == CrossPointSettings::SHORT_PWRBTN::SLEEP)) {
        powerManager.startDeepSleep(gpio);
      }
      wakePowerReleasePending = true;
      break;
    case HalGPIO::WakeupReason::AfterUSBPower:
      // If USB power caused a cold boot, go back to sleep
      LOG_DBG("MAIN", "Wakeup reason: After USB Power");
#if FREEINK_DEVICE_PAPERMONO
      // There is no armable GPIO wake because the button is behind the PMIC.
      // Sleeping here would strand the device in a USB-replug boot loop.
      break;
#else
      powerManager.startDeepSleep(gpio);
      break;
#endif
    case HalGPIO::WakeupReason::AfterFlash:
      // After flashing, just proceed to boot
    case HalGPIO::WakeupReason::Other:
    default:
      break;
  }

  // First serial output only here to avoid timing inconsistencies for power button press duration verification
  LOG_DBG("MAIN", "Starting CrossPoint version " CROSSPOINT_VERSION);

  // Resolve the single boot-presentation decision. Skipping the splash also
  // skips the panel-clearing pass and the X3 initial-full-sync arming (see
  // HalDisplay::begin), so the first paint is FAST_REFRESH (~500ms) over the
  // retained frame and input dispatches against a visible UI.
  // Only a verified deep-sleep wake may use the one-shot persisted flag.
  // Otherwise a stale flag could suppress the splash on a cold boot.
  const bool isSleepWake = wakeupReason == HalGPIO::WakeupReason::PowerButton;
  const BootResume resume = isSilentReboot                             ? BootResume::Silent
                            : isSleepWake && !APP_STATE.showBootScreen ? BootResume::SplashlessWake
                                                                       : BootResume::Splash;
  bool allowFastInitialReaderRefresh = false;
  bool needsWakeRefresh = false;

  setupDisplayAndFonts(resume != BootResume::Splash);

  switch (resume) {
    case BootResume::Silent:
      // Splash skipped: the routing block below picks the target activity; the
      // panel keeps showing the pre-reboot popup until that first paint lands.
      break;
    case BootResume::SplashlessWake:
      // One-shot flag: re-arm the splash for the next ordinary boot. Save
      // before any painting so a hang in the blocking paint path can't strand
      // us in a splashless-with-no-frame loop on the next boot.
      APP_STATE.showBootScreen = true;
      APP_STATE.saveToFile();
      if (Storage.exists(SLEEP_FRAME_FILE) && loadSleepFrameBuffer()) {
        const bool useDifferentialRefresh = gpio.deviceIsX3();
        if (useDifferentialRefresh) {
          // begin() clears the X3 controller RAM, so restore the saved frame as
          // the baseline before replacing the moon with the loading icon.
          renderer.cleanupGrayscaleWithFrameBuffer();
        }

        const auto pageHeight = renderer.getScreenHeight();
        renderer.drawImage(LoadingIcon, 0, pageHeight - LOADINGICON_HEIGHT, LOADINGICON_WIDTH, LOADINGICON_HEIGHT);
        if (useDifferentialRefresh) {
          renderer.displayGrayscaleBase(HalDisplay::FAST_REFRESH);
          allowFastInitialReaderRefresh = true;
        } else {
          renderer.displayBuffer(HalDisplay::HALF_REFRESH);
        }
      } else {
        // The first Home/Reader paint is followed by an explicit clean refresh
        // because the panel still physically shows the sleep image.
        needsWakeRefresh = true;
      }
      break;
    case BootResume::Splash:
      activityManager.goToBoot();
      break;
  }

  // Output polarity is resolved per render by ActivityManager (night mode
  // inverts only the reading surfaces), so nothing to restore here.

  if (recoveryFirmwareMode) {
    // Skip normal home/reader routing: jump straight into the SD firmware picker.
    activityManager.replaceActivity(
        std::make_unique<SdFirmwareUpdateActivity>(renderer, mappedInputManager, /*recoveryMode=*/true));
  } else if (rebootedFromPanic) {
    // If we rebooted from a panic, go to crash report screen to show the panic info
    activityManager.goToCrashReport();
  } else if (resume == BootResume::Silent && snapshotTarget == SILENT_REBOOT_TARGET_READER &&
             !APP_STATE.openEpubPath.empty()) {
    activityManager.goToReader(APP_STATE.openEpubPath);
  } else if (resume == BootResume::Silent) {
    // target == home (or reader with no open book): land on home — don't fall
    // through to the sleep-wake "resume reader" logic, which fires on stale
    // openEpubPath + lastSleepFromReader from a prior session.
    activityManager.goHome();
  } else if (APP_STATE.openEpubPath.empty() || !APP_STATE.lastSleepFromReader ||
             mappedInputManager.isPressed(MappedInputManager::Button::Back) || APP_STATE.readerActivityLoadCount > 0) {
    // Boot to home screen if no book is open, last sleep was not from reader, back button is held, or reader activity
    // crashed (indicated by readerActivityLoadCount > 0)
    activityManager.goHome(HomeMenuItem::NONE, needsWakeRefresh);
  } else {
    // Clear app state to avoid getting into a boot loop if the epub doesn't load
    const auto path = APP_STATE.openEpubPath;
    APP_STATE.openEpubPath = "";
    APP_STATE.readerActivityLoadCount++;
    APP_STATE.saveToFile();
    activityManager.goToReader(path, allowFastInitialReaderRefresh);
  }

  if (resume == BootResume::Silent) {
    // Block until the first paint physically completes. refreshDisplay()
    // waits on the panel BUSY pin so when this returns the user can see the
    // new activity. Without the wait, an edge captured by gpio.update()
    // during boot dispatches against an invisible Home and the default
    // selectorIndex=0 opens the most-recent book.
    activityManager.requestUpdateAndWait();
    // Absorb any button held at this point into currentState as a non-edge:
    // two gpio.update() calls separated by > InputManager's 5ms debounce
    // transition the held bit through lastDebounceTime into currentState
    // without setting pressedEvents, so the first loop()'s own gpio.update()
    // sees state == currentState and emits nothing.
    gpio.update();
    delay(10);
    gpio.update();
  }

  allowSleepAt = millis() + 2000;
}

void loop() {
  static unsigned long maxLoopDuration = 0;
  const unsigned long loopStartTime = millis();
  static unsigned long lastMemPrint = 0;

  gpio.setSharedConfirmPowerShortPressEmitsPower(SETTINGS.shortPwrBtn == CrossPointSettings::SHORT_PWRBTN::SLEEP);
  gpio.update();
  halTiltSensor.update(SETTINGS.tiltPageTurn, SETTINGS.orientation, activityManager.isReaderActivity());

  renderer.setFadingFix(SETTINGS.fadingFix);

  if (Serial && millis() - lastMemPrint >= 10000) {
    LOG_INF("MEM", "Free: %d bytes, Total: %d bytes, Min Free: %d bytes, MaxAlloc: %d bytes", ESP.getFreeHeap(),
            ESP.getHeapSize(), ESP.getMinFreeHeap(), ESP.getMaxAllocHeap());
    lastMemPrint = millis();
  }

  // Handle incoming serial commands,
  // nb: we use logSerial from logging to avoid deprecation warnings
  if (logSerial.available() > 0) {
    String line = logSerial.readStringUntil('\n');
    if (line.startsWith("CMD:")) {
      String cmd = line.substring(4);
      cmd.trim();
      if (cmd == "SCREENSHOT") {
        const uint32_t bufferSize = display.getBufferSize();
        logSerial.printf("SCREENSHOT_START:%d\n", bufferSize);
        uint8_t* buf = display.getFrameBuffer();
        logSerial.write(buf, bufferSize);
        logSerial.printf("SCREENSHOT_END\n");
      }
    }
  }

  // Check for any user activity (button press or release) or active background work
  static unsigned long lastActivityTime = millis();
  if (gpio.wasAnyPressed() || gpio.wasAnyReleased() || gpio.wasTouchActivity() || halTiltSensor.hadActivity() ||
      activityManager.preventAutoSleep()) {
    lastActivityTime = millis();         // Reset inactivity timer
    powerManager.setPowerSaving(false);  // Restore normal CPU frequency on user activity
  }

  // Let wake continue as soon as its hold has been verified. The release can
  // arrive after setup, so consume that one input frame rather than making it
  // a page turn, refresh, or other short power-button action.
  if (wakePowerReleasePending && !gpio.isPressed(HalGPIO::BTN_POWER)) {
    wakePowerReleasePending = false;
    return;
  }

  static bool screenshotButtonsReleased = true;
  static bool screenshotComboActive = false;
  if (gpio.isPressed(HalGPIO::BTN_POWER) && gpio.isPressed(HalGPIO::BTN_DOWN)) {
    screenshotComboActive = true;
    if (screenshotButtonsReleased) {
      screenshotButtonsReleased = false;
      {
        RenderLock lock;
        ScreenshotUtil::takeScreenshot(renderer);
      }
    }
    return;
  }
  if (screenshotComboActive) {
    if (gpio.isPressed(HalGPIO::BTN_POWER)) return;
    if (gpio.wasReleased(HalGPIO::BTN_POWER)) {
      screenshotButtonsReleased = true;
      screenshotComboActive = false;
      return;
    }
    screenshotButtonsReleased = true;
    screenshotComboActive = false;
  }

  // Consume the second X4 Pro power-button release so it does not also run a
  // configured short-power action after toggling the frontlight.
  if (handleX4ProFrontlightDoubleClick()) {
    return;
  }

#if FREEINK_CAP_TOUCH
  // A single X4 Pro power click becomes Confirm only after the frontlight
  // double-click window expires without a second click.
  mappedInputManager.setPowerConfirmClickFrame(false);
  if (SETTINGS.shortPwrBtn == CrossPointSettings::SHORT_PWRBTN::PWR_CONFIRM && BoardConfig::isX4Pro() &&
      lastX4ProPowerClickAt != 0 && millis() - lastX4ProPowerClickAt > X4PRO_POWER_DOUBLE_CLICK_MS) {
    lastX4ProPowerClickAt = 0;
    mappedInputManager.setPowerConfirmClickFrame(true);
  }
#endif

  const unsigned long sleepTimeoutMs = SETTINGS.getSleepTimeoutMs();
  if (sleepTimeoutMs > 0 && millis() - lastActivityTime >= sleepTimeoutMs) {
    LOG_DBG("SLP", "Auto-sleep triggered after %lu ms of inactivity", sleepTimeoutMs);
    enterDeepSleep(true);
    // This should never be hit as `enterDeepSleep` calls esp_deep_sleep_start
    return;
  }

  // A hold that woke the device must be released before it can count as a new
  // in-app long press. Otherwise a user who keeps holding after wake would put
  // the device straight back to sleep once allowSleepAt expires.
  static bool powerReleasedSinceWake = false;
  if (!gpio.isPressed(HalGPIO::BTN_POWER)) powerReleasedSinceWake = true;

  if (powerReleasedSinceWake && millis() >= allowSleepAt && gpio.isPressed(HalGPIO::BTN_POWER) &&
      gpio.getPowerButtonHeldTime() > SETTINGS.getPowerButtonDuration()) {
    // If the screenshot combination is potentially being pressed, don't sleep
    if (gpio.isPressed(HalGPIO::BTN_DOWN)) {
      return;
    }
    enterDeepSleep();
    // This should never be hit as `enterDeepSleep` calls esp_deep_sleep_start
    return;
  }

#if FREEINK_DEVICE_PAPERMONO
  // Paper Mono reports the PMIC power button as a one-tick click, so the held
  // path above cannot fire. With the default Ignore action, retain the normal
  // power-button meaning and shut down; explicit alternate bindings still win.
  if ((SETTINGS.shortPwrBtn == CrossPointSettings::SHORT_PWRBTN::SLEEP ||
       SETTINGS.shortPwrBtn == CrossPointSettings::SHORT_PWRBTN::IGNORE) &&
      millis() >= allowSleepAt && mappedInputManager.wasReleased(MappedInputManager::Button::Power)) {
    enterDeepSleep();
    return;
  }
#endif

  // Refresh screen when power button is short-pressed with FORCE_REFRESH setting.
  if (SETTINGS.shortPwrBtn == CrossPointSettings::SHORT_PWRBTN::FORCE_REFRESH &&
      mappedInputManager.wasReleased(MappedInputManager::Button::Power)) {
    LOG_DBG("MAIN", "Manual screen refresh triggered");
    if (!activityManager.handleForcedRefresh()) {
      RenderLock lock;
      renderer.displayBuffer(HalDisplay::HALF_REFRESH);
    }
  }

  // Refresh the battery icon when USB is plugged or unplugged.
  // Placed after sleep guards so we never queue a render that won't be processed.
  if (gpio.wasUsbStateChanged()) {
    activityManager.requestUpdate();
  }

  const unsigned long activityStartTime = millis();
  activityManager.loop();
  const unsigned long activityDuration = millis() - activityStartTime;

  const unsigned long loopDuration = millis() - loopStartTime;
  if (loopDuration > maxLoopDuration) {
    maxLoopDuration = loopDuration;
    if (maxLoopDuration > 50) {
      LOG_DBG("LOOP", "New max loop duration: %lu ms (activity: %lu ms)", maxLoopDuration, activityDuration);
    }
  }

  // Add delay at the end of the loop to prevent tight spinning
  // When an activity requests skip loop delay (e.g., webserver running), use yield() for faster response
  // Otherwise, use longer delay to save power
  if (activityManager.skipLoopDelay()) {
    powerManager.setPowerSaving(false);  // Make sure we're at full performance when skipLoopDelay is requested
    yield();                             // Give FreeRTOS a chance to run tasks, but return immediately
  } else {
    if (millis() - lastActivityTime >= HalPowerManager::IDLE_POWER_SAVING_MS) {
      // If we've been inactive for a while, increase the delay to save power
      powerManager.setPowerSaving(true);  // Lower CPU frequency after extended inactivity
      delay(50);
    } else {
      // Short delay to prevent tight loop while still being responsive
      delay(10);
    }
  }
}