#include "HomeActivity.h"

#include <Bitmap.h>
#include <Epub.h>
#include <FsHelpers.h>
#include <GfxRenderer.h>
#include <HalStorage.h>
#include <I18n.h>
#include <Utf8.h>
#include <Xtc.h>

#include <algorithm>
#include <cstring>
#include <string>
#include <vector>

#include "CrossPointSettings.h"
#include "CrossPointState.h"
#include "GlobalBookmarkIndex.h"
#include "MappedInputManager.h"
#include "OpdsServerStore.h"
#include "RecentBooksStore.h"
#include "components/UITheme.h"
#include "components/themes/lyra/LyraCarouselTheme.h"
#include "fontIds.h"

// ---------------------------------------------------------------------------
// Static carousel frame cache — survives HomeActivity re-creation so that
// returning to home (e.g. after settings) doesn't re-read covers from SD.
// Freed explicitly in onSelectBook() before entering the reader.
// ---------------------------------------------------------------------------
namespace {
uint8_t* gCachedFrames[HomeActivity::kCarouselFrameCount] = {};
int gCachedFrameBookIdx[HomeActivity::kCarouselFrameCount] = {-1, -1, -1};
int gCachedFrameCount = 0;
std::string gCacheKey;

int findFrameSlot(int bookIdx) {
  for (int i = 0; i < HomeActivity::kCarouselFrameCount; ++i) {
    if (gCachedFrameBookIdx[i] == bookIdx && gCachedFrames[i] != nullptr) return i;
  }
  return -1;
}

void invalidateCarouselCache() {
  for (int i = 0; i < HomeActivity::kCarouselFrameCount; ++i) {
    if (gCachedFrames[i]) {
      free(gCachedFrames[i]);
      gCachedFrames[i] = nullptr;
    }
    gCachedFrameBookIdx[i] = -1;
  }
  gCachedFrameCount = 0;
  gCacheKey.clear();
}

constexpr int CLASSIC_MIN_RECENT_TILE_HEIGHT = 280;
constexpr int LYRA_MIN_RECENT_TILE_HEIGHT = 170;
constexpr int LYRA_3_COVERS_MIN_RECENT_TILE_HEIGHT = 200;
constexpr int CLASSIC_MIN_RECENT_TO_MENU_GAP = 2;
constexpr int LYRA_MIN_RECENT_TO_MENU_GAP = 4;

struct HomeScreenLayout {
  int recentTileHeight;
  int recentToMenuGap;
  int menuHeight;
};

bool isLyraFamilyTheme() {
  const auto theme = static_cast<CrossPointSettings::UI_THEME>(SETTINGS.uiTheme);
  return theme == CrossPointSettings::UI_THEME::LYRA || theme == CrossPointSettings::UI_THEME::LYRA_3_COVERS;
}

bool isLyraExtendedTheme() {
  return static_cast<CrossPointSettings::UI_THEME>(SETTINGS.uiTheme) == CrossPointSettings::UI_THEME::LYRA_3_COVERS;
}

int getMinRecentTileHeight() {
  if (isLyraExtendedTheme()) {
    return LYRA_3_COVERS_MIN_RECENT_TILE_HEIGHT;
  }
  if (isLyraFamilyTheme()) {
    return LYRA_MIN_RECENT_TILE_HEIGHT;
  }
  return CLASSIC_MIN_RECENT_TILE_HEIGHT;
}

int getMinRecentToMenuGap() {
  return isLyraFamilyTheme() ? LYRA_MIN_RECENT_TO_MENU_GAP : CLASSIC_MIN_RECENT_TO_MENU_GAP;
}

HomeScreenLayout computeHomeScreenLayout(const ThemeMetrics& metrics, int contentHeight, int menuItemCount) {
  HomeScreenLayout layout{metrics.homeCoverTileHeight, metrics.verticalSpacing, 0};

  const int menuRequiredHeight =
      menuItemCount * metrics.menuRowHeight + std::max(0, menuItemCount - 1) * metrics.menuSpacing;

  auto computeMenuHeight = [&]() {
    return contentHeight - (metrics.homeTopPadding + layout.recentTileHeight + layout.recentToMenuGap);
  };

  layout.menuHeight = computeMenuHeight();
  if (layout.menuHeight >= menuRequiredHeight) {
    return layout;
  }

  const int gapReduction =
      std::min(layout.recentToMenuGap - getMinRecentToMenuGap(), menuRequiredHeight - layout.menuHeight);
  if (gapReduction > 0) {
    layout.recentToMenuGap -= gapReduction;
    layout.menuHeight = computeMenuHeight();
  }

  if (layout.menuHeight >= menuRequiredHeight) {
    return layout;
  }

  const int tileReduction =
      std::min(layout.recentTileHeight - getMinRecentTileHeight(), menuRequiredHeight - layout.menuHeight);
  if (tileReduction > 0) {
    layout.recentTileHeight -= tileReduction;
    layout.menuHeight = computeMenuHeight();
  }

  layout.menuHeight = std::max(0, layout.menuHeight);
  return layout;
}

int getHomeCoverRenderHeight(const HomeScreenLayout& layout) {
  return isLyraExtendedTheme() ? std::max(120, layout.recentTileHeight - 58)
                               : std::max(120, layout.recentTileHeight - (isLyraFamilyTheme() ? 16 : 0));
}
}  // namespace

// Builds the menu entry list in display order. Single source of truth for both loop() (which
// dispatches Confirm based on action) and render() (which draws labels/icons).
void HomeActivity::rebuildMenuEntries() {
  menuEntries.clear();
  menuEntries.reserve(7);

  menuEntries.push_back({MenuAction::FileBrowser, StrId::STR_BROWSE_FILES, Folder});
  menuEntries.push_back({MenuAction::Recents, StrId::STR_MENU_RECENT_BOOKS, Recent});
  if (!GLOBAL_BOOKMARKS.isEmpty()) {
    menuEntries.push_back({MenuAction::GlobalBookmarks, StrId::STR_GLOBAL_BOOKMARKS, Book});
  }
  if (hasOpdsServers) {
    menuEntries.push_back({MenuAction::OpdsBrowser, StrId::STR_OPDS_BROWSER, Library});
  }
  menuEntries.push_back({MenuAction::FileTransfer, StrId::STR_FILE_TRANSFER, Transfer});
  if (SETTINGS.useWeather) {
    menuEntries.push_back({MenuAction::Weather, StrId::STR_WEATHER, Weather});
  }
  menuEntries.push_back({MenuAction::Settings, StrId::STR_SETTINGS_TITLE, Settings});
  menuEntriesDirty = false;
}

void HomeActivity::loadRecentBooks(int maxBooks) {
  recentBooks.clear();
  const auto& books = RECENT_BOOKS.getBooks();
  recentBooks.reserve(std::min(static_cast<int>(books.size()), maxBooks));

  for (const RecentBook& book : books) {
    // Limit to maximum number of recent books
    if (recentBooks.size() >= maxBooks) {
      break;
    }

    // Skip if file no longer exists
    if (!Storage.exists(book.path.c_str())) {
      continue;
    }

    recentBooks.push_back(book);
  }
}

void HomeActivity::loadRecentCovers(int coverHeight) {
  recentsLoading = true;

  for (; nextRecentCoverIndex < recentBooks.size(); nextRecentCoverIndex++) {
    RecentBook& book = recentBooks[nextRecentCoverIndex];
    if (!book.coverBmpPath.empty()) {
      std::string coverPath = UITheme::getCoverThumbPath(book.coverBmpPath, coverHeight);
      if (!Storage.exists(coverPath.c_str())) {
        // If epub, try to load the metadata for title/author and cover
        if (FsHelpers::hasEpubExtension(book.path)) {
          Epub epub(book.path, "/.crosspoint");
          // Skip loading css since we only need metadata here
          epub.load(false, true);

          // Try to generate thumbnail image for Continue Reading card
          bool success = epub.generateThumbBmp(coverHeight);
          if (!success) {
            RECENT_BOOKS.updateBook(book.path, book.title, book.author, book.series, "");
            book.coverBmpPath = "";
          }
          coverRendered = false;
          nextRecentCoverIndex++;
          recentsLoading = false;
          requestUpdate();
          return;
        } else if (FsHelpers::hasXtcExtension(book.path)) {
          // Handle XTC file
          Xtc xtc(book.path, "/.crosspoint");
          if (xtc.load()) {
            // Try to generate thumbnail image for Continue Reading card
            bool success = xtc.generateThumbBmp(coverHeight);
            if (!success) {
              RECENT_BOOKS.updateBook(book.path, book.title, book.author, book.series, "");
              book.coverBmpPath = "";
            }
            coverRendered = false;
            nextRecentCoverIndex++;
            recentsLoading = false;
            requestUpdate();
            return;
          }
        }
      }
    }
  }

  recentsLoaded = true;
  recentsLoading = false;
}

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

  hasOpdsServers = OPDS_STORE.hasServers();

  selectorIndex = 0;
  carouselFramesReady = false;
  recentsLoading = false;
  recentsLoaded = false;
  firstRenderDone = false;
  nextRecentCoverIndex = 0;
  coverRendered = false;
  freeCoverBuffer();

  const auto& metrics = UITheme::getInstance().getMetrics();
  loadRecentBooks(metrics.homeRecentBooksCount);
  if (recentBooks.empty()) {
    recentsLoaded = true;
  }

  // Pre-render carousel frames before first display so the fast path is ready.
  if (static_cast<CrossPointSettings::UI_THEME>(SETTINGS.uiTheme) == CrossPointSettings::UI_THEME::LYRA_CAROUSEL) {
    preRenderCarouselFrames();
  }

  // Apply focus: book path takes priority, else combined selector index (covers
  // "return to the menu entry I was on").
  bool focused = false;
  if (!focusBookPath.empty()) {
    for (size_t i = 0; i < recentBooks.size(); ++i) {
      if (recentBooks[i].path == focusBookPath) {
        selectorIndex = static_cast<int>(i);
        focused = true;
        break;
      }
    }
    focusBookPath.clear();
  }
  if (!focused && focusSelectorIndex >= 0) {
    rebuildMenuEntries();  // need menu count to clamp; rebuild is idempotent
    const int combinedSize = static_cast<int>(recentBooks.size() + menuEntries.size());
    if (combinedSize > 0) {
      selectorIndex = std::min(focusSelectorIndex, combinedSize - 1);
    }
  }
  focusSelectorIndex = -1;

  // Trigger first update
  menuEntriesDirty = true;
  requestUpdate();
}

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

  freeCoverBuffer();
  invalidateCarouselCache();
  freeCarouselFrames();
}

bool HomeActivity::storeCoverBuffer() {
  uint8_t* frameBuffer = renderer.getFrameBuffer();
  if (!frameBuffer) {
    return false;
  }

  // Free any existing buffer first
  freeCoverBuffer();

  const size_t bufferSize = renderer.getBufferSize();
  coverBuffer = static_cast<uint8_t*>(malloc(bufferSize));
  if (!coverBuffer) {
    return false;
  }

  memcpy(coverBuffer, frameBuffer, bufferSize);
  return true;
}

bool HomeActivity::restoreCoverBuffer() {
  if (!coverBuffer) {
    return false;
  }

  uint8_t* frameBuffer = renderer.getFrameBuffer();
  if (!frameBuffer) {
    return false;
  }

  const size_t bufferSize = renderer.getBufferSize();
  memcpy(frameBuffer, coverBuffer, bufferSize);
  return true;
}

void HomeActivity::freeCoverBuffer() {
  if (coverBuffer) {
    free(coverBuffer);
    coverBuffer = nullptr;
  }
  coverBufferStored = false;
}

void HomeActivity::freeCarouselFrames() {
  // Instance pointers are aliases into the static cache — do not free here.
  for (int i = 0; i < kCarouselFrameCount; ++i) carouselFrames[i] = nullptr;
  carouselFramesReady = false;
}

void HomeActivity::preRenderCarouselFrames() {
  const int bookCount = static_cast<int>(recentBooks.size());
  if (bookCount == 0) return;

  // Build cache key from book paths in order
  std::string newKey;
  newKey.reserve(128);
  for (const auto& b : recentBooks) {
    newKey += b.path;
    newKey += '\0';
  }

  // Cache hit: same books in same order — reuse without any SD reads
  if (newKey == gCacheKey && gCachedFrameCount > 0) {
    for (int i = 0; i < gCachedFrameCount; ++i) carouselFrames[i] = gCachedFrames[i];
    carouselFramesReady = true;
    coverRendered = false;
    coverBufferStored = false;
    return;
  }

  // Cache miss: free old cache and re-render
  invalidateCarouselCache();

  if (!renderer.getFrameBuffer()) return;

  const size_t bufferSize = renderer.getBufferSize();
  freeCoverBuffer();  // reclaim 48KB before allocating frames

  const int frameCount = std::min(bookCount, kCarouselFrameCount);
  for (int i = 0; i < frameCount; ++i) {
    gCachedFrames[i] = static_cast<uint8_t*>(malloc(bufferSize));
    if (!gCachedFrames[i]) {
      LOG_ERR("HOME", "preRenderCarouselFrames: malloc failed for frame %d", i);
      invalidateCarouselCache();
      return;
    }
  }

  // Render only the currently-selected cover. Adjacent frames are populated
  // lazily by updateSlidingWindowCache() after the first paint completes.
  const int selectedBookIdx = (selectorIndex < bookCount) ? selectorIndex : lastCarouselBookIndex;
  const int initialBookIdx = (selectedBookIdx >= 0 && selectedBookIdx < bookCount) ? selectedBookIdx : 0;
  renderCarouselFrame(initialBookIdx, 0);

  gCachedFrameCount = frameCount;
  gCacheKey = newKey;
  carouselFramesReady = true;
  coverRendered = false;
  coverBufferStored = false;
}

void HomeActivity::renderCarouselFrame(int bookIdx, int slotIdx) {
  uint8_t* frameBuffer = renderer.getFrameBuffer();
  if (!frameBuffer || !gCachedFrames[slotIdx]) return;

  const auto& metrics = UITheme::getInstance().getMetrics();
  const int pageWidth = renderer.getScreenWidth();
  const int bookCount = static_cast<int>(recentBooks.size());
  bool dummy1 = false, dummy2 = false, dummy3 = false;

  LyraCarouselTheme::setPreRenderIndex(bookIdx);
  renderer.clearScreen();
  GUI.drawHeader(renderer, Rect{0, metrics.topPadding, pageWidth, metrics.homeTopPadding}, nullptr);
  GUI.drawRecentBookCover(renderer, Rect{0, metrics.homeTopPadding, pageWidth, metrics.homeCoverTileHeight},
                          recentBooks, bookCount, dummy1, dummy2, dummy3, []() { return true; });

  memcpy(gCachedFrames[slotIdx], frameBuffer, renderer.getBufferSize());
  gCachedFrameBookIdx[slotIdx] = bookIdx;
  carouselFrames[slotIdx] = gCachedFrames[slotIdx];
}

void HomeActivity::updateSlidingWindowCache(int centerIdx, int bookCount) {
  if (bookCount <= kCarouselFrameCount || !carouselFramesReady) return;

  const int prevIdx = (centerIdx + bookCount - 1) % bookCount;
  const int nextIdx = (centerIdx + 1) % bookCount;

  const bool hasPrev = findFrameSlot(prevIdx) >= 0;
  const bool hasNext = findFrameSlot(nextIdx) >= 0;
  if (hasPrev && hasNext) return;

  const int missingIdx = !hasPrev ? prevIdx : nextIdx;

  int evictSlot = -1;
  int maxDist = -1;
  for (int i = 0; i < kCarouselFrameCount; ++i) {
    if (!gCachedFrames[i]) continue;
    const int bookInSlot = gCachedFrameBookIdx[i];
    if (bookInSlot == centerIdx) continue;
    if (hasPrev && bookInSlot == prevIdx) continue;
    if (hasNext && bookInSlot == nextIdx) continue;
    const int diff = std::abs(bookInSlot - centerIdx);
    const int dist = std::min(diff, bookCount - diff);
    if (dist > maxDist) {
      maxDist = dist;
      evictSlot = i;
    }
  }

  if (evictSlot >= 0) {
    LOG_DBG("HOME", "carousel: evict slot %d (book %d) -> book %d", evictSlot, gCachedFrameBookIdx[evictSlot],
            missingIdx);
    renderCarouselFrame(missingIdx, evictSlot);
  }
}

void HomeActivity::loop() {
  if (menuEntriesDirty) {
    rebuildMenuEntries();
  }

  const bool isCarousel =
      static_cast<CrossPointSettings::UI_THEME>(SETTINGS.uiTheme) == CrossPointSettings::UI_THEME::LYRA_CAROUSEL;

  if (isCarousel) {
    const int bookCount = static_cast<int>(recentBooks.size());
    const int menuItemCount = static_cast<int>(menuEntries.size());
    const bool inCarouselRow = (selectorIndex < bookCount);
    const int menuIdx = inCarouselRow ? 0 : (selectorIndex - bookCount);

    if (mappedInput.wasPressed(MappedInputManager::Button::Right)) {
      if (inCarouselRow && bookCount > 0)
        selectorIndex = (selectorIndex + 1) % bookCount;
      else if (!inCarouselRow)
        selectorIndex = bookCount + (menuIdx + 1) % menuItemCount;
      requestUpdate();
    }
    if (mappedInput.wasPressed(MappedInputManager::Button::Left)) {
      if (inCarouselRow && bookCount > 0)
        selectorIndex = (selectorIndex + bookCount - 1) % bookCount;
      else if (!inCarouselRow)
        selectorIndex = bookCount + (menuIdx + menuItemCount - 1) % menuItemCount;
      requestUpdate();
    }
    if (mappedInput.wasPressed(MappedInputManager::Button::Down)) {
      if (inCarouselRow) {
        lastCarouselBookIndex = selectorIndex;
        selectorIndex = bookCount;
      } else {
        selectorIndex = lastCarouselBookIndex;
      }
      requestUpdate();
    }
    if (mappedInput.wasPressed(MappedInputManager::Button::Up)) {
      if (inCarouselRow) {
        lastCarouselBookIndex = selectorIndex;
        selectorIndex = bookCount;
      } else {
        selectorIndex = lastCarouselBookIndex;
      }
      requestUpdate();
    }
  } else {
    const int totalItems = static_cast<int>(recentBooks.size() + menuEntries.size());

    if (firstRenderDone && !recentsLoaded && !recentsLoading) {
      const auto& metrics = UITheme::getInstance().getMetrics();
      const Rect contentRect = UITheme::getContentRect(renderer, true, false);
      const HomeScreenLayout layout =
          computeHomeScreenLayout(metrics, contentRect.height, static_cast<int>(menuEntries.size()));
      loadRecentCovers(getHomeCoverRenderHeight(layout));
      return;
    }

    buttonNavigator.onNext([this, totalItems] {
      selectorIndex = ButtonNavigator::nextIndex(selectorIndex, totalItems);
      requestUpdate();
    });

    buttonNavigator.onPrevious([this, totalItems] {
      selectorIndex = ButtonNavigator::previousIndex(selectorIndex, totalItems);
      requestUpdate();
    });
  }

  if (mappedInput.wasReleased(MappedInputManager::Button::Confirm)) {
    const int recentsCount = static_cast<int>(recentBooks.size());
    if (selectorIndex < recentsCount) {
      onSelectBook(recentBooks[selectorIndex].path);
    } else {
      const int menuIdx = selectorIndex - recentsCount;
      if (menuIdx < static_cast<int>(menuEntries.size())) {
        dispatchMenuAction(menuEntries[menuIdx].action);
      }
    }
  }
}

void HomeActivity::render(RenderLock&&) {
  const auto& metrics = UITheme::getInstance().getMetrics();
  const Rect contentRect = UITheme::getContentRect(renderer, true, false);

  renderer.clearScreen();
  bool bufferRestored = coverBufferStored && restoreCoverBuffer();

  GUI.drawHeader(renderer, Rect{contentRect.x, metrics.topPadding, contentRect.width, metrics.homeTopPadding}, nullptr);

  if (menuEntriesDirty) {
    rebuildMenuEntries();
  }

  const int totalItems = static_cast<int>(recentBooks.size() + menuEntries.size());
  if (selectorIndex >= totalItems) {
    selectorIndex = std::max(0, totalItems - 1);
  }

  const int menuCount = static_cast<int>(menuEntries.size());
  const HomeScreenLayout layout = computeHomeScreenLayout(metrics, contentRect.height, menuCount);

  GUI.drawRecentBookCover(renderer,
                          Rect{contentRect.x, metrics.homeTopPadding, contentRect.width, layout.recentTileHeight},
                          recentBooks, selectorIndex, coverRendered, coverBufferStored, bufferRestored,
                          std::bind(&HomeActivity::storeCoverBuffer, this));

  GUI.drawButtonMenu(
      renderer,
      Rect{contentRect.x, metrics.homeTopPadding + layout.recentTileHeight + layout.recentToMenuGap, contentRect.width,
           layout.menuHeight},
      menuCount, selectorIndex - static_cast<int>(recentBooks.size()),
      [this](int index) { return std::string(I18N.get(menuEntries[index].label)); },
      [this](int index) { return menuEntries[index].icon; });

  const auto labels = mappedInput.mapLabels("", tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
  GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);

  renderer.displayBuffer();

  if (!firstRenderDone) {
    firstRenderDone = true;
    requestUpdate();
  }
}

void HomeActivity::onSelectBook(const std::string& path) {
  ReturnHint hint;
  hint.target = ReturnTo::Home;
  hint.selectName = path;  // used to re-focus the book in the recents strip after return
  activityManager.replaceWithReader(path, std::move(hint));
}

void HomeActivity::dispatchMenuAction(MenuAction action) {
  // Record where the menu entry was focused so that when the launched activity exits
  // (via returnFromChild() or an empty-stack finish()), we come back to the same row.
  ReturnHint hint;
  hint.target = ReturnTo::Home;
  hint.selectIndex = selectorIndex;
  activityManager.setReturnHint(std::move(hint));

  switch (action) {
    case MenuAction::FileBrowser:
      activityManager.goToFileBrowser();
      break;
    case MenuAction::Recents:
      activityManager.goToRecentBooks();
      break;
    case MenuAction::GlobalBookmarks:
      activityManager.goToGlobalBookmarks();
      break;
    case MenuAction::OpdsBrowser:
      activityManager.goToBrowser();
      break;
    case MenuAction::FileTransfer:
      activityManager.goToFileTransfer();
      break;
    case MenuAction::Weather:
      activityManager.goToWeather();
      break;
    case MenuAction::Settings:
      activityManager.goToSettings();
      break;
    default:
      LOG_ERR("HOME", "Unexpected menu action: %d", static_cast<int>(action));
      break;
  }
}