/**
 * XtcReaderActivity.cpp
 *
 * XTC ebook reader activity implementation
 * Displays pre-rendered XTC pages on e-ink display
 */

#include "XtcReaderActivity.h"

#include <FsHelpers.h>
#include <GfxRenderer.h>
#include <HalStorage.h>
#include <I18n.h>

#include <algorithm>

#include "CrossPointSettings.h"
#include "CrossPointState.h"
#include "MappedInputManager.h"
#include "ReaderUtils.h"
#include "RecentBooksStore.h"
#include "XtcReaderChapterSelectionActivity.h"
#include "fontIds.h"

namespace {
constexpr unsigned long skipPageMs = 700;
constexpr unsigned long goHomeMs = 1000;
}  // namespace

void XtcReaderActivity::onEnter() {
  Activity::onEnter();

  // See ReaderUtils::InputDrainGuard — prevents wake-up power-button hold from leaking into
  // the first detectPageTurn() call as a page turn or chapter skip.
  inputDrainGuard.arm();

  if (!xtc) {
    return;
  }

  xtc->setupCacheDir();

  // Load saved progress
  loadProgress();

  // Save current XTC as last opened book and add to recent books
  APP_STATE.openEpubPath = xtc->getPath();
  APP_STATE.saveToFile();
  RECENT_BOOKS.addBook(xtc->getPath(), xtc->getTitle(), xtc->getAuthor(), "", xtc->getThumbBmpPath());

  // Trigger first update
  requestUpdate();
}

void XtcReaderActivity::onExit() {
  Activity::onExit();

  APP_STATE.readerActivityLoadCount = 0;
  APP_STATE.saveToFile();
  xtc.reset();
}

void XtcReaderActivity::loop() {
  if (inputDrainGuard.shouldDrain(mappedInput)) {
    return;
  }

  // Enter chapter selection activity
  if (mappedInput.wasReleased(MappedInputManager::Button::Confirm)) {
    if (xtc && xtc->hasChapters() && !xtc->getChapters().empty()) {
      ReaderUtils::enforceExitFullRefresh(renderer);
      startActivityForResult(
          std::make_unique<XtcReaderChapterSelectionActivity>(renderer, mappedInput, xtc, currentPage),
          [this](const ActivityResult& result) {
            if (!result.isCancelled) {
              currentPage = std::get<PageResult>(result.data).page;
            }
          });
    }
  }

  // Long press BACK (1s+) goes to home screen
  if (mappedInput.isPressed(MappedInputManager::Button::Back) && mappedInput.getHeldTime() >= goHomeMs) {
    ReaderUtils::enforceExitFullRefresh(renderer);
    onGoHome();
    return;
  }

  // Short press BACK returns to the calling activity
  if (mappedInput.wasReleased(MappedInputManager::Button::Back) && mappedInput.getHeldTime() < goHomeMs) {
    ReaderUtils::enforceExitFullRefresh(renderer);
    finish();
    return;
  }

  const bool prevTriggered = mappedInput.wasReleased(MappedInputManager::Button::PageBack) ||
                             mappedInput.wasReleased(MappedInputManager::Button::Left);
  const bool nextTriggered = mappedInput.wasReleased(MappedInputManager::Button::PageForward) ||
                             mappedInput.wasReleased(MappedInputManager::Button::Right);

  if (!prevTriggered && !nextTriggered) {
    return;
  }

  // At end of the book, forward button returns to caller and back button returns to last page
  if (currentPage >= xtc->getPageCount()) {
    if (nextTriggered) {
      finish();
    } else {
      currentPage = xtc->getPageCount() - 1;
      requestUpdate();
    }
    return;
  }

  const bool skipPages = mappedInput.getHeldTime() > skipPageMs;
  const int skipAmount = skipPages ? 10 : 1;

  if (prevTriggered) {
    if (currentPage >= static_cast<uint32_t>(skipAmount)) {
      currentPage -= skipAmount;
    } else {
      currentPage = 0;
    }
    requestUpdate();
  } else if (nextTriggered) {
    currentPage += skipAmount;
    if (currentPage >= xtc->getPageCount()) {
      currentPage = xtc->getPageCount();  // Allow showing "End of book"
    }
    requestUpdate();
  }
}

void XtcReaderActivity::render(RenderLock&&) {
  if (!xtc) {
    return;
  }

  // Bounds check
  if (currentPage >= xtc->getPageCount()) {
    // Show end of book screen
    renderer.clearScreen();
    renderer.drawCenteredText(UI_12_FONT_ID, 300, tr(STR_END_OF_BOOK), true, EpdFontFamily::BOLD);
    renderer.displayBuffer();
    return;
  }

  renderPage();
  saveProgress();
}

void XtcReaderActivity::renderPage() {
  const uint16_t pageWidth = xtc->getPageWidth();
  const uint16_t pageHeight = xtc->getPageHeight();
  const uint8_t bitDepth = xtc->getBitDepth();

  // Calculate buffer size for one page
  // XTG (1-bit): Row-major, ((width+7)/8) * height bytes
  // XTH (2-bit): Two bit planes, column-major, ((width * height + 7) / 8) * 2 bytes
  size_t pageBufferSize;
  if (bitDepth == 2) {
    pageBufferSize = ((static_cast<size_t>(pageWidth) * pageHeight + 7) / 8) * 2;
  } else {
    pageBufferSize = ((pageWidth + 7) / 8) * pageHeight;
  }

  // Allocate page buffer
  uint8_t* pageBuffer = static_cast<uint8_t*>(malloc(pageBufferSize));
  if (!pageBuffer) {
    LOG_ERR("XTR", "Failed to allocate page buffer (%lu bytes)", pageBufferSize);
    renderer.clearScreen();
    renderer.drawCenteredText(UI_12_FONT_ID, 300, tr(STR_MEMORY_ERROR), true, EpdFontFamily::BOLD);
    renderer.displayBuffer();
    return;
  }

  // Load page data
  size_t bytesRead = xtc->loadPage(currentPage, pageBuffer, pageBufferSize);
  if (bytesRead == 0) {
    LOG_ERR("XTR", "Failed to load page %lu", currentPage);
    free(pageBuffer);
    renderer.clearScreen();
    renderer.drawCenteredText(UI_12_FONT_ID, 300, tr(STR_PAGE_LOAD_ERROR), true, EpdFontFamily::BOLD);
    renderer.displayBuffer();
    return;
  }

  // Clear screen first
  renderer.clearScreen();

  // Copy page bitmap using GfxRenderer's drawPixel
  // XTC/XTCH pages are pre-rendered with status bar included, so render full page
  const uint16_t maxSrcY = pageHeight;

  if (bitDepth == 2) {
    // XTH 2-bit mode: Two bit planes, column-major order
    // - Columns scanned right to left (x = width-1 down to 0)
    // - 8 vertical pixels per byte (MSB = topmost pixel in group)
    // - First plane: Bit1, Second plane: Bit2
    // - Pixel value = (bit1 << 1) | bit2
    // - Grayscale: 0=White, 1=Dark Grey, 2=Light Grey, 3=Black

    const size_t planeSize = (static_cast<size_t>(pageWidth) * pageHeight + 7) / 8;
    const uint8_t* plane1 = pageBuffer;              // Bit1 plane
    const uint8_t* plane2 = pageBuffer + planeSize;  // Bit2 plane
    const size_t colBytes = (pageHeight + 7) / 8;    // Bytes per column (100 for 800 height)

    // Lambda to get pixel value at (x, y)
    auto getPixelValue = [&](uint16_t x, uint16_t y) -> uint8_t {
      const size_t colIndex = pageWidth - 1 - x;
      const size_t byteInCol = y / 8;
      const size_t bitInByte = 7 - (y % 8);
      const size_t byteOffset = colIndex * colBytes + byteInCol;
      const uint8_t bit1 = (plane1[byteOffset] >> bitInByte) & 1;
      const uint8_t bit2 = (plane2[byteOffset] >> bitInByte) & 1;
      return (bit1 << 1) | bit2;
    };

    // Optimized grayscale rendering without storeBwBuffer (saves 48KB peak memory)
    // Flow: BW display → LSB/MSB passes → grayscale display → re-render BW for next frame

    // Count pixel distribution for debugging
    uint32_t pixelCounts[4] = {0, 0, 0, 0};
    for (uint16_t y = 0; y < pageHeight; y++) {
      for (uint16_t x = 0; x < pageWidth; x++) {
        pixelCounts[getPixelValue(x, y)]++;
      }
    }
    LOG_DBG("XTR", "Pixel distribution: White=%lu, DarkGrey=%lu, LightGrey=%lu, Black=%lu", pixelCounts[0],
            pixelCounts[1], pixelCounts[2], pixelCounts[3]);

    // Pass 1: BW buffer - draw all non-white pixels as black
    for (uint16_t y = 0; y < pageHeight; y++) {
      for (uint16_t x = 0; x < pageWidth; x++) {
        if (getPixelValue(x, y) >= 1) {
          renderer.drawPixel(x, y, true);
        }
      }
    }

    // Display BW with conditional refresh based on pagesUntilFullRefresh
    if (pagesUntilFullRefresh <= 1) {
      renderer.displayBuffer(HalDisplay::HALF_REFRESH);
      pagesUntilFullRefresh = SETTINGS.getRefreshFrequency();
    } else {
      renderer.displayBuffer();
      pagesUntilFullRefresh--;
    }

    // Pass 2: LSB buffer - mark DARK gray only (XTH value 1)
    // In LUT: 0 bit = apply gray effect, 1 bit = untouched
    renderer.clearScreen(0x00);
    for (uint16_t y = 0; y < pageHeight; y++) {
      for (uint16_t x = 0; x < pageWidth; x++) {
        if (getPixelValue(x, y) == 1) {  // Dark grey only
          renderer.drawPixel(x, y, false);
        }
      }
    }
    renderer.copyGrayscaleLsbBuffers();

    // Pass 3: MSB buffer - mark LIGHT AND DARK gray (XTH value 1 or 2)
    // In LUT: 0 bit = apply gray effect, 1 bit = untouched
    renderer.clearScreen(0x00);
    for (uint16_t y = 0; y < pageHeight; y++) {
      for (uint16_t x = 0; x < pageWidth; x++) {
        const uint8_t pv = getPixelValue(x, y);
        if (pv == 1 || pv == 2) {  // Dark grey or Light grey
          renderer.drawPixel(x, y, false);
        }
      }
    }
    renderer.copyGrayscaleMsbBuffers();

    // Display grayscale overlay
    renderer.displayGrayBuffer();

    // Pass 4: Re-render BW to framebuffer (restore for next frame, instead of restoreBwBuffer)
    renderer.clearScreen();
    for (uint16_t y = 0; y < pageHeight; y++) {
      for (uint16_t x = 0; x < pageWidth; x++) {
        if (getPixelValue(x, y) >= 1) {
          renderer.drawPixel(x, y, true);
        }
      }
    }

    // Cleanup grayscale buffers with current frame buffer
    renderer.cleanupGrayscaleWithFrameBuffer();

    free(pageBuffer);

    LOG_DBG("XTR", "Rendered page %lu/%lu (2-bit grayscale)", currentPage + 1, xtc->getPageCount());
    return;
  } else {
    // 1-bit mode: 8 pixels per byte, MSB first
    const size_t srcRowBytes = (pageWidth + 7) / 8;  // 60 bytes for 480 width

    for (uint16_t srcY = 0; srcY < maxSrcY; srcY++) {
      const size_t srcRowStart = srcY * srcRowBytes;

      for (uint16_t srcX = 0; srcX < pageWidth; srcX++) {
        // Read source pixel (MSB first, bit 7 = leftmost pixel)
        const size_t srcByte = srcRowStart + srcX / 8;
        const size_t srcBit = 7 - (srcX % 8);
        const bool isBlack = !((pageBuffer[srcByte] >> srcBit) & 1);  // XTC: 0 = black, 1 = white

        if (isBlack) {
          renderer.drawPixel(srcX, srcY, true);
        }
      }
    }
  }
  // White pixels are already cleared by clearScreen()

  free(pageBuffer);

  // XTC pages already have status bar pre-rendered, no need to add our own

  // Display with appropriate refresh
  if (pagesUntilFullRefresh <= 1) {
    renderer.displayBuffer(HalDisplay::HALF_REFRESH);
    pagesUntilFullRefresh = SETTINGS.getRefreshFrequency();
  } else {
    renderer.displayBuffer();
    pagesUntilFullRefresh--;
  }

  LOG_DBG("XTR", "Rendered page %lu/%lu (%u-bit)", currentPage + 1, xtc->getPageCount(), bitDepth);
}

void XtcReaderActivity::saveProgress() const {
  FsFile f;
  if (Storage.openFileForWrite("XTR", xtc->getCachePath() + "/progress.bin", f)) {
    uint8_t data[5];
    data[0] = currentPage & 0xFF;
    data[1] = (currentPage >> 8) & 0xFF;
    data[2] = (currentPage >> 16) & 0xFF;
    data[3] = (currentPage >> 24) & 0xFF;
    data[4] =
        ReaderUtils::pageProgressPercentByte(static_cast<int>(currentPage), static_cast<int>(xtc->getPageCount()));
    f.write(data, 5);
    f.close();
  }
}

void XtcReaderActivity::loadProgress() {
  FsFile f;
  if (Storage.openFileForRead("XTR", xtc->getCachePath() + "/progress.bin", f)) {
    uint8_t data[4];
    if (f.read(data, 4) == 4) {
      currentPage = data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24);
      LOG_DBG("XTR", "Loaded progress: page %lu", currentPage);

      // Validate page number
      if (currentPage >= xtc->getPageCount()) {
        currentPage = 0;
      }
    }
    f.close();
  }
}

bool XtcReaderActivity::drawCurrentPageToBuffer(const std::string& filePath, GfxRenderer& renderer) {
  Xtc xtc(filePath, "/.crosspoint");
  if (!xtc.load()) {
    LOG_DBG("SLP", "XTC: failed to load %s", filePath.c_str());
    return false;
  }

  // Load saved page number
  uint32_t savedPage = 0;
  FsFile f;
  if (Storage.openFileForRead("SLP", xtc.getCachePath() + "/progress.bin", f)) {
    uint8_t data[4];
    if (f.read(data, 4) == 4) {
      savedPage = (uint32_t)data[0] | ((uint32_t)data[1] << 8) | ((uint32_t)data[2] << 16) | ((uint32_t)data[3] << 24);
    }
    f.close();
  }
  if (savedPage >= xtc.getPageCount()) savedPage = 0;

  const uint16_t pageWidth = xtc.getPageWidth();
  const uint16_t pageHeight = xtc.getPageHeight();
  const uint8_t bitDepth = xtc.getBitDepth();

  // Only use the 1-bit BW path; grayscale is not needed as a background under the overlay
  const size_t pageBufferSize = (bitDepth == 2) ? ((static_cast<size_t>(pageWidth) * pageHeight + 7) / 8) * 2
                                                : ((pageWidth + 7) / 8) * pageHeight;

  uint8_t* pageBuffer = static_cast<uint8_t*>(malloc(pageBufferSize));
  if (!pageBuffer) {
    LOG_ERR("SLP", "XTC: failed to allocate page buffer");
    return false;
  }

  if (xtc.loadPage(savedPage, pageBuffer, pageBufferSize) == 0) {
    LOG_ERR("SLP", "XTC: failed to load page %lu", savedPage);
    free(pageBuffer);
    return false;
  }

  renderer.clearScreen();

  if (bitDepth == 2) {
    // 2-bit XTH: draw all non-white pixels as black (BW pass only)
    const size_t planeSize = (static_cast<size_t>(pageWidth) * pageHeight + 7) / 8;
    const uint8_t* plane1 = pageBuffer;
    const uint8_t* plane2 = pageBuffer + planeSize;
    const size_t colBytes = (pageHeight + 7) / 8;
    for (uint16_t y = 0; y < pageHeight; y++) {
      for (uint16_t x = 0; x < pageWidth; x++) {
        const size_t colIndex = pageWidth - 1 - x;
        const size_t byteInCol = y / 8;
        const size_t bitInByte = 7 - (y % 8);
        const size_t byteOffset = colIndex * colBytes + byteInCol;
        const uint8_t bit1 = (plane1[byteOffset] >> bitInByte) & 1;
        const uint8_t bit2 = (plane2[byteOffset] >> bitInByte) & 1;
        if ((bit1 << 1) | bit2) {
          renderer.drawPixel(x, y, true);
        }
      }
    }
  } else {
    // 1-bit XTG: draw black pixels
    const size_t srcRowBytes = (pageWidth + 7) / 8;
    for (uint16_t srcY = 0; srcY < pageHeight; srcY++) {
      for (uint16_t srcX = 0; srcX < pageWidth; srcX++) {
        const bool isBlack = !((pageBuffer[srcY * srcRowBytes + srcX / 8] >> (7 - srcX % 8)) & 1);
        if (isBlack) renderer.drawPixel(srcX, srcY, true);
      }
    }
  }

  free(pageBuffer);
  return true;
}

void XtcReaderActivity::onButtonAction(const CrossPointSettings::BUTTON_ACTION action) {
  using BA = CrossPointSettings::BUTTON_ACTION;
  if (!xtc) return;
  const uint32_t pageCount = xtc->getPageCount();
  switch (action) {
    case BA::BTN_PAGE_FORWARD:
      if (currentPage + 1 < pageCount) {
        currentPage++;
        requestUpdate();
      }
      break;
    case BA::BTN_PAGE_BACK:
      if (currentPage > 0) {
        currentPage--;
        requestUpdate();
      }
      break;
    case BA::BTN_PAGE_FORWARD_10:
      currentPage = (currentPage + 10 < pageCount) ? currentPage + 10 : pageCount - 1;
      requestUpdate();
      break;
    case BA::BTN_PAGE_BACK_10:
      currentPage = (currentPage >= 10) ? currentPage - 10 : 0;
      requestUpdate();
      break;
    case BA::BTN_NEXT_SECTION:
      if (xtc->hasChapters()) {
        const auto& chapters = xtc->getChapters();
        const auto it = std::find_if(chapters.begin(), chapters.end(),
                                     [this](const auto& ch) { return ch.startPage > currentPage; });
        if (it != chapters.end()) {
          currentPage = it->startPage;
          requestUpdate();
        }
      }
      break;
    case BA::BTN_PREV_SECTION:
      if (xtc->hasChapters()) {
        const auto& chapters = xtc->getChapters();
        const auto prevChapter = std::find_if(chapters.rbegin(), chapters.rend(),
                                              [this](const auto& ch) { return ch.startPage < currentPage; });

        if (prevChapter != chapters.rend()) {
          currentPage = prevChapter->startPage;
          requestUpdate();
        }
      }
      break;
    case BA::BTN_EXIT_READER:
      ReaderUtils::enforceExitFullRefresh(renderer);
      finish();
      break;
    default:
      break;
  }
}