crosspoint-reader/src/activities/boot_sleep/SleepActivity.cpp

#include "SleepActivity.h"

#include <Epub.h>
#include <GfxRenderer.h>
#include <SDCardManager.h>
#include <Txt.h>
#include <Xtc.h>

#include <cmath>

#include "BookManager.h"
#include "CrossPointSettings.h"
#include "CrossPointState.h"
#include "fontIds.h"
#include "images/CrossLarge.h"
#include "util/StringUtils.h"

namespace {
// Edge luminance cache file format (per-BMP):
// - 4 bytes: uint32_t file size (for cache invalidation)
// - 4 bytes: EdgeLuminance (top, bottom, left, right)
constexpr size_t EDGE_CACHE_SIZE = 8;

// Book-level edge cache file format (stored in book's cache directory):
// - 4 bytes: uint32_t cover BMP file size (for cache invalidation)
// - 4 bytes: EdgeLuminance (top, bottom, left, right)
// - 1 byte: cover mode (0=FIT, 1=CROP) - for EPUB mode invalidation
constexpr size_t BOOK_EDGE_CACHE_SIZE = 9;
}  // namespace

void SleepActivity::onEnter() {
  Activity::onEnter();
  renderPopup("Entering Sleep...");

  if (SETTINGS.sleepScreen == CrossPointSettings::SLEEP_SCREEN_MODE::BLANK) {
    return renderBlankSleepScreen();
  }

  if (SETTINGS.sleepScreen == CrossPointSettings::SLEEP_SCREEN_MODE::CUSTOM) {
    return renderCustomSleepScreen();
  }

  if (SETTINGS.sleepScreen == CrossPointSettings::SLEEP_SCREEN_MODE::COVER) {
    return renderCoverSleepScreen();
  }

  renderDefaultSleepScreen();
}

void SleepActivity::renderPopup(const char* message) const {
  const int textWidth = renderer.getTextWidth(UI_12_FONT_ID, message, EpdFontFamily::BOLD);
  constexpr int margin = 20;
  const int x = (renderer.getScreenWidth() - textWidth - margin * 2) / 2;
  constexpr int y = 117;
  const int w = textWidth + margin * 2;
  const int h = renderer.getLineHeight(UI_12_FONT_ID) + margin * 2;
  // renderer.clearScreen();
  renderer.fillRect(x - 5, y - 5, w + 10, h + 10, true);
  renderer.fillRect(x + 5, y + 5, w - 10, h - 10, false);
  renderer.drawText(UI_12_FONT_ID, x + margin, y + margin, message, true, EpdFontFamily::BOLD);
  renderer.displayBuffer();
}

void SleepActivity::renderCustomSleepScreen() const {
  // Check if we have a /sleep directory
  auto dir = SdMan.open("/sleep");
  if (dir && dir.isDirectory()) {
    std::vector<std::string> files;
    char name[500];
    // collect all valid BMP files
    for (auto file = dir.openNextFile(); file; file = dir.openNextFile()) {
      if (file.isDirectory()) {
        file.close();
        continue;
      }
      file.getName(name, sizeof(name));
      auto filename = std::string(name);
      if (filename[0] == '.') {
        file.close();
        continue;
      }

      if (filename.substr(filename.length() - 4) != ".bmp") {
        Serial.printf("[%lu] [SLP] Skipping non-.bmp file name: %s\n", millis(), name);
        file.close();
        continue;
      }
      Bitmap bitmap(file);
      if (bitmap.parseHeaders() != BmpReaderError::Ok) {
        Serial.printf("[%lu] [SLP] Skipping invalid BMP file: %s\n", millis(), name);
        file.close();
        continue;
      }
      files.emplace_back(filename);
      file.close();
    }
    const auto numFiles = files.size();
    if (numFiles > 0) {
      // Generate a random number between 1 and numFiles
      auto randomFileIndex = random(numFiles);
      // If we picked the same image as last time, reroll
      while (numFiles > 1 && randomFileIndex == APP_STATE.lastSleepImage) {
        randomFileIndex = random(numFiles);
      }
      APP_STATE.lastSleepImage = randomFileIndex;
      APP_STATE.saveToFile();
      const auto bmpPath = "/sleep/" + files[randomFileIndex];
      FsFile file;
      if (SdMan.openFileForRead("SLP", bmpPath, file)) {
        Serial.printf("[%lu] [SLP] Randomly loading: /sleep/%s\n", millis(), files[randomFileIndex].c_str());
        delay(100);
        Bitmap bitmap(file, true);
        if (bitmap.parseHeaders() == BmpReaderError::Ok) {
          renderBitmapSleepScreen(bitmap, bmpPath);
          dir.close();
          return;
        }
      }
    }
  }
  if (dir) dir.close();

  // Look for sleep.bmp on the root of the sd card to determine if we should
  // render a custom sleep screen instead of the default.
  FsFile file;
  const std::string rootSleepPath = "/sleep.bmp";
  if (SdMan.openFileForRead("SLP", rootSleepPath, file)) {
    Bitmap bitmap(file, true);
    if (bitmap.parseHeaders() == BmpReaderError::Ok) {
      Serial.printf("[%lu] [SLP] Loading: /sleep.bmp\n", millis());
      renderBitmapSleepScreen(bitmap, rootSleepPath);
      return;
    }
  }

  renderDefaultSleepScreen();
}

void SleepActivity::renderDefaultSleepScreen() const {
  const auto pageWidth = renderer.getScreenWidth();
  const auto pageHeight = renderer.getScreenHeight();

  renderer.clearScreen();
  renderer.drawImage(CrossLarge, (pageWidth - 128) / 2, (pageHeight - 128) / 2, 128, 128);
  renderer.drawCenteredText(UI_10_FONT_ID, pageHeight / 2 + 70, "CrossPoint", true, EpdFontFamily::BOLD);
  renderer.drawCenteredText(SMALL_FONT_ID, pageHeight / 2 + 95, "SLEEPING");

  // Make sleep screen dark unless light is selected in settings
  if (SETTINGS.sleepScreen != CrossPointSettings::SLEEP_SCREEN_MODE::LIGHT) {
    renderer.invertScreen();
  }

  renderer.displayBuffer(EInkDisplay::HALF_REFRESH);
}

void SleepActivity::renderBitmapSleepScreen(const Bitmap& bitmap, const std::string& bmpPath) const {
  int x, y;
  const auto pageWidth = renderer.getScreenWidth();
  const auto pageHeight = renderer.getScreenHeight();
  float cropX = 0, cropY = 0;
  int drawWidth = pageWidth;
  int drawHeight = pageHeight;
  int fillWidth = pageWidth;   // Actual area the image will occupy
  int fillHeight = pageHeight;

  Serial.printf("[%lu] [SLP] bitmap %d x %d, screen %d x %d\n", millis(), bitmap.getWidth(), bitmap.getHeight(),
                pageWidth, pageHeight);

  const float bitmapRatio = static_cast<float>(bitmap.getWidth()) / static_cast<float>(bitmap.getHeight());
  const float screenRatio = static_cast<float>(pageWidth) / static_cast<float>(pageHeight);
  Serial.printf("[%lu] [SLP] bitmap ratio: %f, screen ratio: %f\n", millis(), bitmapRatio, screenRatio);

  const auto coverMode = SETTINGS.sleepScreenCoverMode;

  if (coverMode == CrossPointSettings::SLEEP_SCREEN_COVER_MODE::ACTUAL) {
    // ACTUAL mode: Show image at actual size, centered (no scaling)
    x = (pageWidth - bitmap.getWidth()) / 2;
    y = (pageHeight - bitmap.getHeight()) / 2;
    // Don't constrain to screen dimensions - drawBitmap will clip
    drawWidth = 0;
    drawHeight = 0;
    fillWidth = bitmap.getWidth();
    fillHeight = bitmap.getHeight();
    Serial.printf("[%lu] [SLP] ACTUAL mode: centering at %d, %d\n", millis(), x, y);
  } else if (coverMode == CrossPointSettings::SLEEP_SCREEN_COVER_MODE::CROP) {
    // CROP mode: Scale to fill screen completely (may crop edges)
    // Calculate crop values to fill the screen while maintaining aspect ratio
    if (bitmapRatio > screenRatio) {
      // Image is wider than screen ratio - crop horizontally
      cropX = 1.0f - (screenRatio / bitmapRatio);
      Serial.printf("[%lu] [SLP] CROP mode: cropping x by %f\n", millis(), cropX);
    } else if (bitmapRatio < screenRatio) {
      // Image is taller than screen ratio - crop vertically
      cropY = 1.0f - (bitmapRatio / screenRatio);
      Serial.printf("[%lu] [SLP] CROP mode: cropping y by %f\n", millis(), cropY);
    }
    // After cropping, the image should fill the screen exactly
    x = 0;
    y = 0;
    fillWidth = pageWidth;
    fillHeight = pageHeight;
    Serial.printf("[%lu] [SLP] CROP mode: drawing at 0, 0 with crop %f, %f\n", millis(), cropX, cropY);
  } else {
    // FIT mode (default): Scale to fit entire image within screen (may have letterboxing)
    // Calculate the scaled dimensions
    float scale;
    if (bitmapRatio > screenRatio) {
      // Image is wider than screen ratio - fit to width
      scale = static_cast<float>(pageWidth) / static_cast<float>(bitmap.getWidth());
    } else {
      // Image is taller than screen ratio - fit to height
      scale = static_cast<float>(pageHeight) / static_cast<float>(bitmap.getHeight());
    }
    // Use ceil to ensure fill area covers all drawn pixels
    fillWidth = static_cast<int>(std::ceil(bitmap.getWidth() * scale));
    fillHeight = static_cast<int>(std::ceil(bitmap.getHeight() * scale));

    // Center the scaled image
    x = (pageWidth - fillWidth) / 2;
    y = (pageHeight - fillHeight) / 2;
    Serial.printf("[%lu] [SLP] FIT mode: scale %f, scaled size %d x %d, position %d, %d\n", millis(), scale,
                  fillWidth, fillHeight, x, y);
  }

  // Get edge luminance values (from cache or calculate)
  const EdgeLuminance edges = getEdgeLuminance(bitmap, bmpPath);
  const uint8_t topGray = quantizeGray(edges.top);
  const uint8_t bottomGray = quantizeGray(edges.bottom);
  const uint8_t leftGray = quantizeGray(edges.left);
  const uint8_t rightGray = quantizeGray(edges.right);

  Serial.printf("[%lu] [SLP] Edge luminance: T=%d B=%d L=%d R=%d -> gray levels T=%d B=%d L=%d R=%d\n",
                millis(), edges.top, edges.bottom, edges.left, edges.right,
                topGray, bottomGray, leftGray, rightGray);

  // Check if greyscale pass should be used (PR #476: skip if filter is applied)
  const bool hasGreyscale = bitmap.hasGreyscale() &&
                            SETTINGS.sleepScreenCoverFilter == CrossPointSettings::SLEEP_SCREEN_COVER_FILTER::NO_FILTER;

  // Clear screen to white first (default background)
  renderer.clearScreen(0xFF);

  // Fill letterbox regions with edge colors (BW pass)
  // Top letterbox
  if (y > 0) {
    renderer.fillRectGray(0, 0, pageWidth, y, topGray);
  }
  // Bottom letterbox
  if (y + fillHeight < pageHeight) {
    renderer.fillRectGray(0, y + fillHeight, pageWidth, pageHeight - y - fillHeight, bottomGray);
  }
  // Left letterbox
  if (x > 0) {
    renderer.fillRectGray(0, y, x, fillHeight, leftGray);
  }
  // Right letterbox
  if (x + fillWidth < pageWidth) {
    renderer.fillRectGray(x + fillWidth, y, pageWidth - x - fillWidth, fillHeight, rightGray);
  }

  Serial.printf("[%lu] [SLP] drawing bitmap at %d, %d\n", millis(), x, y);
  renderer.drawBitmap(bitmap, x, y, drawWidth, drawHeight, cropX, cropY);

  // PR #476: Apply inverted B&W filter if selected
  if (SETTINGS.sleepScreenCoverFilter == CrossPointSettings::SLEEP_SCREEN_COVER_FILTER::INVERTED_BLACK_AND_WHITE) {
    renderer.invertScreen();
  }

  renderer.displayBuffer(EInkDisplay::HALF_REFRESH);

  if (hasGreyscale) {
    // Grayscale LSB pass
    bitmap.rewindToData();
    renderer.clearScreen(0x00);
    renderer.setRenderMode(GfxRenderer::GRAYSCALE_LSB);

    // Fill letterbox regions for LSB pass
    if (y > 0) renderer.fillRectGray(0, 0, pageWidth, y, topGray);
    if (y + fillHeight < pageHeight)
      renderer.fillRectGray(0, y + fillHeight, pageWidth, pageHeight - y - fillHeight, bottomGray);
    if (x > 0) renderer.fillRectGray(0, y, x, fillHeight, leftGray);
    if (x + fillWidth < pageWidth)
      renderer.fillRectGray(x + fillWidth, y, pageWidth - x - fillWidth, fillHeight, rightGray);

    renderer.drawBitmap(bitmap, x, y, drawWidth, drawHeight, cropX, cropY);
    renderer.copyGrayscaleLsbBuffers();

    // Grayscale MSB pass
    bitmap.rewindToData();
    renderer.clearScreen(0x00);
    renderer.setRenderMode(GfxRenderer::GRAYSCALE_MSB);

    // Fill letterbox regions for MSB pass
    if (y > 0) renderer.fillRectGray(0, 0, pageWidth, y, topGray);
    if (y + fillHeight < pageHeight)
      renderer.fillRectGray(0, y + fillHeight, pageWidth, pageHeight - y - fillHeight, bottomGray);
    if (x > 0) renderer.fillRectGray(0, y, x, fillHeight, leftGray);
    if (x + fillWidth < pageWidth)
      renderer.fillRectGray(x + fillWidth, y, pageWidth - x - fillWidth, fillHeight, rightGray);

    renderer.drawBitmap(bitmap, x, y, drawWidth, drawHeight, cropX, cropY);
    renderer.copyGrayscaleMsbBuffers();

    renderer.displayGrayBuffer();
    renderer.setRenderMode(GfxRenderer::BW);
  }
}

void SleepActivity::renderCoverSleepScreen() const {
  if (APP_STATE.openEpubPath.empty()) {
    return renderDefaultSleepScreen();
  }

  const bool cropped = SETTINGS.sleepScreenCoverMode == CrossPointSettings::SLEEP_SCREEN_COVER_MODE::CROP;

  // Try to use cached edge data to skip book metadata loading
  if (tryRenderCachedCoverSleep(APP_STATE.openEpubPath, cropped)) {
    return;
  }

  // Cache miss - need to load book metadata and generate cover
  Serial.printf("[%lu] [SLP] Cache miss, loading book metadata\n", millis());

  std::string coverBmpPath;

  // Check if the current book is XTC, TXT, or EPUB
  if (StringUtils::checkFileExtension(APP_STATE.openEpubPath, ".xtc") ||
      StringUtils::checkFileExtension(APP_STATE.openEpubPath, ".xtch")) {
    // Handle XTC file
    Xtc lastXtc(APP_STATE.openEpubPath, "/.crosspoint");
    if (!lastXtc.load()) {
      Serial.println("[SLP] Failed to load last XTC");
      return renderDefaultSleepScreen();
    }

    if (!lastXtc.generateCoverBmp()) {
      Serial.println("[SLP] Failed to generate XTC cover bmp");
      return renderDefaultSleepScreen();
    }

    coverBmpPath = lastXtc.getCoverBmpPath();
  } else if (StringUtils::checkFileExtension(APP_STATE.openEpubPath, ".txt")) {
    // Handle TXT file - looks for cover image in the same folder
    Txt lastTxt(APP_STATE.openEpubPath, "/.crosspoint");
    if (!lastTxt.load()) {
      Serial.println("[SLP] Failed to load last TXT");
      return renderDefaultSleepScreen();
    }

    if (!lastTxt.generateCoverBmp()) {
      Serial.println("[SLP] No cover image found for TXT file");
      return renderDefaultSleepScreen();
    }

    coverBmpPath = lastTxt.getCoverBmpPath();
  } else if (StringUtils::checkFileExtension(APP_STATE.openEpubPath, ".epub")) {
    // Handle EPUB file
    Epub lastEpub(APP_STATE.openEpubPath, "/.crosspoint");
    if (!lastEpub.load()) {
      Serial.println("[SLP] Failed to load last epub");
      return renderDefaultSleepScreen();
    }

    if (!lastEpub.generateCoverBmp(cropped)) {
      Serial.println("[SLP] Failed to generate cover bmp");
      return renderDefaultSleepScreen();
    }

    coverBmpPath = lastEpub.getCoverBmpPath(cropped);
  } else {
    return renderDefaultSleepScreen();
  }

  FsFile file;
  if (SdMan.openFileForRead("SLP", coverBmpPath, file)) {
    Bitmap bitmap(file);
    if (bitmap.parseHeaders() == BmpReaderError::Ok) {
      // Render the bitmap - this will calculate and cache edge luminance per-BMP
      renderBitmapSleepScreen(bitmap, coverBmpPath);

      // Also save to book-level edge cache for faster subsequent sleeps
      const std::string edgeCachePath = getBookEdgeCachePath(APP_STATE.openEpubPath);
      if (!edgeCachePath.empty()) {
        // Get the edge luminance that was just calculated (it's now cached per-BMP)
        const EdgeLuminance edges = getEdgeLuminance(bitmap, coverBmpPath);
        const uint32_t bmpFileSize = bitmap.getFileSize();
        const uint8_t coverMode = cropped ? 1 : 0;

        FsFile cacheFile;
        if (SdMan.openFileForWrite("SLP", edgeCachePath, cacheFile)) {
          uint8_t cacheData[BOOK_EDGE_CACHE_SIZE];
          cacheData[0] = bmpFileSize & 0xFF;
          cacheData[1] = (bmpFileSize >> 8) & 0xFF;
          cacheData[2] = (bmpFileSize >> 16) & 0xFF;
          cacheData[3] = (bmpFileSize >> 24) & 0xFF;
          cacheData[4] = edges.top;
          cacheData[5] = edges.bottom;
          cacheData[6] = edges.left;
          cacheData[7] = edges.right;
          cacheData[8] = coverMode;
          cacheFile.write(cacheData, BOOK_EDGE_CACHE_SIZE);
          cacheFile.close();
          Serial.printf("[%lu] [SLP] Saved book-level edge cache to %s\n", millis(), edgeCachePath.c_str());
        }
      }
      return;
    }
  }

  renderDefaultSleepScreen();
}

void SleepActivity::renderBlankSleepScreen() const {
  renderer.clearScreen();
  renderer.displayBuffer(EInkDisplay::HALF_REFRESH);
}

std::string SleepActivity::getEdgeCachePath(const std::string& bmpPath) {
  // Convert "/dir/file.bmp" to "/dir/.file.bmp.perim"
  const size_t lastSlash = bmpPath.find_last_of('/');
  if (lastSlash == std::string::npos) {
    // No directory, just prepend dot
    return "." + bmpPath + ".perim";
  }
  const std::string dir = bmpPath.substr(0, lastSlash + 1);
  const std::string filename = bmpPath.substr(lastSlash + 1);
  return dir + "." + filename + ".perim";
}

uint8_t SleepActivity::quantizeGray(uint8_t lum) {
  // Quantize luminance (0-255) to 4-level grayscale (0-3)
  // Thresholds tuned for X4 display gray levels
  if (lum < 43) return 0;       // black
  if (lum < 128) return 1;      // dark gray
  if (lum < 213) return 2;      // light gray
  return 3;                      // white
}

EdgeLuminance SleepActivity::getEdgeLuminance(const Bitmap& bitmap, const std::string& bmpPath) const {
  const std::string cachePath = getEdgeCachePath(bmpPath);
  EdgeLuminance result = {128, 128, 128, 128};  // Default to neutral gray

  // Try to read from cache
  FsFile cacheFile;
  if (SdMan.openFileForRead("SLP", cachePath, cacheFile)) {
    uint8_t cacheData[EDGE_CACHE_SIZE];
    if (cacheFile.read(cacheData, EDGE_CACHE_SIZE) == EDGE_CACHE_SIZE) {
      // Extract cached file size
      const uint32_t cachedSize = static_cast<uint32_t>(cacheData[0]) |
                                  (static_cast<uint32_t>(cacheData[1]) << 8) |
                                  (static_cast<uint32_t>(cacheData[2]) << 16) |
                                  (static_cast<uint32_t>(cacheData[3]) << 24);

      // Get current BMP file size from already-opened bitmap
      const uint32_t currentSize = bitmap.getFileSize();

      // Validate cache
      if (cachedSize == currentSize && currentSize > 0) {
        result.top = cacheData[4];
        result.bottom = cacheData[5];
        result.left = cacheData[6];
        result.right = cacheData[7];
        Serial.printf("[%lu] [SLP] Edge cache hit for %s: T=%d B=%d L=%d R=%d\n", millis(), bmpPath.c_str(),
                      result.top, result.bottom, result.left, result.right);
        cacheFile.close();
        return result;
      }
      Serial.printf("[%lu] [SLP] Edge cache invalid (size mismatch: %lu vs %lu)\n", millis(),
                    static_cast<unsigned long>(cachedSize), static_cast<unsigned long>(currentSize));
    }
    cacheFile.close();
  }

  // Cache miss - calculate edge luminance
  Serial.printf("[%lu] [SLP] Calculating edge luminance for %s\n", millis(), bmpPath.c_str());
  result = bitmap.detectEdgeLuminance(2);  // Sample 2 pixels deep for stability
  Serial.printf("[%lu] [SLP] Edge luminance detected: T=%d B=%d L=%d R=%d\n", millis(),
                result.top, result.bottom, result.left, result.right);

  // Get BMP file size from already-opened bitmap for cache
  const uint32_t fileSize = bitmap.getFileSize();

  // Save to cache
  if (fileSize > 0 && SdMan.openFileForWrite("SLP", cachePath, cacheFile)) {
    uint8_t cacheData[EDGE_CACHE_SIZE];
    cacheData[0] = fileSize & 0xFF;
    cacheData[1] = (fileSize >> 8) & 0xFF;
    cacheData[2] = (fileSize >> 16) & 0xFF;
    cacheData[3] = (fileSize >> 24) & 0xFF;
    cacheData[4] = result.top;
    cacheData[5] = result.bottom;
    cacheData[6] = result.left;
    cacheData[7] = result.right;
    cacheFile.write(cacheData, EDGE_CACHE_SIZE);
    cacheFile.close();
    Serial.printf("[%lu] [SLP] Saved edge cache to %s\n", millis(), cachePath.c_str());
  }

  return result;
}

std::string SleepActivity::getBookEdgeCachePath(const std::string& bookPath) {
  const std::string cacheDir = BookManager::getCacheDir(bookPath);
  if (cacheDir.empty()) {
    return "";
  }
  return cacheDir + "/edge.bin";
}

std::string SleepActivity::getCoverBmpPath(const std::string& cacheDir, const std::string& bookPath, bool cropped) {
  if (cacheDir.empty()) {
    return "";
  }

  // EPUB uses different paths for fit vs crop modes
  if (StringUtils::checkFileExtension(bookPath, ".epub")) {
    return cropped ? (cacheDir + "/cover_crop.bmp") : (cacheDir + "/cover_fit.bmp");
  }

  // XTC and TXT use a single cover.bmp
  return cacheDir + "/cover.bmp";
}

bool SleepActivity::tryRenderCachedCoverSleep(const std::string& bookPath, bool cropped) const {
  // Try to render cover sleep screen using cached edge data without loading book metadata
  const std::string edgeCachePath = getBookEdgeCachePath(bookPath);
  if (edgeCachePath.empty()) {
    Serial.println("[SLP] Cannot get edge cache path");
    return false;
  }

  // Check if edge cache exists
  FsFile cacheFile;
  if (!SdMan.openFileForRead("SLP", edgeCachePath, cacheFile)) {
    Serial.println("[SLP] No edge cache file found");
    return false;
  }

  // Read cache data
  uint8_t cacheData[BOOK_EDGE_CACHE_SIZE];
  if (cacheFile.read(cacheData, BOOK_EDGE_CACHE_SIZE) != BOOK_EDGE_CACHE_SIZE) {
    Serial.println("[SLP] Edge cache file too small");
    cacheFile.close();
    return false;
  }
  cacheFile.close();

  // Extract cached values
  const uint32_t cachedBmpSize = static_cast<uint32_t>(cacheData[0]) |
                                 (static_cast<uint32_t>(cacheData[1]) << 8) |
                                 (static_cast<uint32_t>(cacheData[2]) << 16) |
                                 (static_cast<uint32_t>(cacheData[3]) << 24);
  EdgeLuminance cachedEdges;
  cachedEdges.top = cacheData[4];
  cachedEdges.bottom = cacheData[5];
  cachedEdges.left = cacheData[6];
  cachedEdges.right = cacheData[7];
  const uint8_t cachedCoverMode = cacheData[8];

  // Check if cover mode matches (for EPUB)
  const uint8_t currentCoverMode = cropped ? 1 : 0;
  if (StringUtils::checkFileExtension(bookPath, ".epub") && cachedCoverMode != currentCoverMode) {
    Serial.printf("[SLP] Cover mode changed (cached=%d, current=%d), invalidating cache\n",
                  cachedCoverMode, currentCoverMode);
    return false;
  }

  // Construct cover BMP path
  const std::string cacheDir = BookManager::getCacheDir(bookPath);
  const std::string coverBmpPath = getCoverBmpPath(cacheDir, bookPath, cropped);
  if (coverBmpPath.empty()) {
    Serial.println("[SLP] Cannot construct cover BMP path");
    return false;
  }

  // Try to open the cover BMP
  FsFile bmpFile;
  if (!SdMan.openFileForRead("SLP", coverBmpPath, bmpFile)) {
    Serial.printf("[SLP] Cover BMP not found: %s\n", coverBmpPath.c_str());
    return false;
  }

  // Check if BMP file size matches cache
  const uint32_t currentBmpSize = bmpFile.size();
  if (currentBmpSize != cachedBmpSize || currentBmpSize == 0) {
    Serial.printf("[SLP] BMP size mismatch (cached=%lu, current=%lu)\n",
                  static_cast<unsigned long>(cachedBmpSize), static_cast<unsigned long>(currentBmpSize));
    bmpFile.close();
    return false;
  }

  // Parse bitmap headers
  Bitmap bitmap(bmpFile);
  if (bitmap.parseHeaders() != BmpReaderError::Ok) {
    Serial.println("[SLP] Failed to parse cached cover BMP");
    bmpFile.close();
    return false;
  }

  Serial.printf("[%lu] [SLP] Using cached cover sleep: %s (T=%d B=%d L=%d R=%d)\n", millis(),
                coverBmpPath.c_str(), cachedEdges.top, cachedEdges.bottom, cachedEdges.left, cachedEdges.right);

  // Render the bitmap with cached edge values
  // We call renderBitmapSleepScreen which will use getEdgeLuminance internally,
  // but since the per-BMP cache should also exist (same values), it will be a cache hit
  renderBitmapSleepScreen(bitmap, coverBmpPath);
  return true;
}