/**
 * Sci-Fi Books Showcase Application
 * Fully offline version - uses local cover images and pre-fetched summaries.
 */

// State management
const state = {
  books: [],
  filteredBooks: [],
  currentFilter: {
    author: 'all',
    format: 'all',
    search: ''
  }
};

// DOM elements cache
const elements = {
  booksGrid: null,
  bookCount: null,
  authorFilter: null,
  formatFilter: null,
  searchInput: null,
  modal: null,
  modalContent: null
};

// Initialize the application
async function init() {
  cacheElements();
  setupUI();
  await initializeBooks();
}

function setupUI() {
  setupFilters();
  setupModal();
}

async function initializeBooks() {
  const books = await loadBooks();
  if (!books) return;

  state.books = books;
  state.filteredBooks = [...books];
  populateAuthorFilter();
  renderBooks();
}

// Cache DOM element references
function cacheElements() {
  elements.booksGrid = document.getElementById('books-grid');
  elements.bookCount = document.getElementById('book-count');
  elements.authorFilter = document.getElementById('author-filter');
  elements.formatFilter = document.getElementById('format-filter');
  elements.searchInput = document.getElementById('search-input');
  elements.modal = document.getElementById('book-modal');
  elements.modalContent = document.getElementById('modal-content');
}

// Load books from JSON file
async function loadBooks() {
  try {
    const response = await fetch('data/books.json');
    if (!response.ok) throw new Error('Failed to load books');
    const data = await response.json();
    return sortBooksByYear(data.books);
  } catch (error) {
    renderLoadError(error);
    return null;
  }
}

function renderLoadError(error) {
  console.error('Error loading books:', error);
  elements.booksGrid.innerHTML = `
    <div class="error-message">
      <p>Failed to load books. Please try refreshing the page.</p>
    </div>
  `;
}

function sortBooksByYear(books) {
  return [...books].sort((a, b) => {
    if (a.year !== b.year) return a.year - b.year;

    const authorCompare = a.author.localeCompare(b.author);
    if (authorCompare !== 0) return authorCompare;

    return a.title.localeCompare(b.title);
  });
}

// Populate author filter dropdown with unique authors
function populateAuthorFilter() {
  const authors = [...new Set(state.books.map(book => book.author))].sort();
  authors.forEach(author => {
    const option = document.createElement('option');
    option.value = author;
    option.textContent = author;
    elements.authorFilter.appendChild(option);
  });
}

// Setup filter event listeners
function setupFilters() {
  elements.authorFilter.addEventListener('change', handleFilterChange);
  elements.formatFilter.addEventListener('change', handleFilterChange);
  elements.searchInput.addEventListener('input', debounce(handleFilterChange, 300));
}

// Handle filter changes and update displayed books
function handleFilterChange() {
  state.currentFilter.author = elements.authorFilter.value;
  state.currentFilter.format = elements.formatFilter.value;
  state.currentFilter.search = elements.searchInput.value.toLowerCase().trim();

  state.filteredBooks = state.books.filter(book => {
    const matchesAuthor = state.currentFilter.author === 'all' ||
                          book.author === state.currentFilter.author;
    const matchesFormat = state.currentFilter.format === 'all' ||
                          book.format.toLowerCase() === state.currentFilter.format;
    const matchesSearch = !state.currentFilter.search ||
                          book.title.toLowerCase().includes(state.currentFilter.search) ||
                          book.author.toLowerCase().includes(state.currentFilter.search);

    return matchesAuthor && matchesFormat && matchesSearch;
  });

  renderBooks();
}

// Get cover image URL - uses local file if available, otherwise shows placeholder
function getCoverUrl(book) {
  if (book.coverLocal) {
    return book.coverLocal;
  }
  return null;
}

// Render books grid
function renderBooks() {
  if (state.filteredBooks.length === 0) {
    elements.booksGrid.innerHTML = `
      <div class="no-results">
        <p>No books found matching your filters.</p>
      </div>
    `;
    elements.bookCount.textContent = '0 books';
    return;
  }

  elements.bookCount.textContent = `${state.filteredBooks.length} book${state.filteredBooks.length !== 1 ? 's' : ''}`;

  elements.booksGrid.innerHTML = state.filteredBooks.map(book => {
    const coverUrl = getCoverUrl(book);
    return `
    <article class="book-card" tabindex="0" data-book-id="${book.id}" role="button" aria-label="View details for ${escapeHtml(book.title)}">
      <div class="cover-container">
        ${coverUrl ? `
          <img
            src="${coverUrl}"
            alt="Cover of ${escapeHtml(book.title)}"
            loading="lazy"
            onerror="this.style.display='none'; this.nextElementSibling.style.display='flex';"
          >
          <div class="cover-placeholder" style="display: none;">
            <span class="book-icon">📚</span>
            <span class="placeholder-title">${escapeHtml(book.title)}</span>
          </div>
        ` : `
          <div class="cover-placeholder">
            <span class="book-icon">📚</span>
            <span class="placeholder-title">${escapeHtml(book.title)}</span>
          </div>
        `}
      </div>
      <div class="card-info">
        <h3>${escapeHtml(book.title)}</h3>
        <p class="author">${escapeHtml(book.author)}</p>
        <div class="meta">
          <span class="format-badge ${book.format.toLowerCase()}">${book.format}</span>
          <span class="format-badge">${book.year}</span>
        </div>
      </div>
    </article>
  `}).join('');

  // Add click handlers to book cards
  document.querySelectorAll('.book-card').forEach(card => {
    card.addEventListener('click', () => openModal(parseInt(card.dataset.bookId)));
    card.addEventListener('keydown', (e) => {
      if (e.key === 'Enter' || e.key === ' ') {
        e.preventDefault();
        openModal(parseInt(card.dataset.bookId));
      }
    });
  });
}

// Setup modal functionality
function setupModal() {
  // Close on backdrop click
  elements.modal.addEventListener('click', (e) => {
    if (e.target === elements.modal) {
      closeModal();
    }
  });

  // Close on Escape key
  document.addEventListener('keydown', (e) => {
    if (e.key === 'Escape' && elements.modal.classList.contains('active')) {
      closeModal();
    }
  });
}

// Open modal with book details
function openModal(bookId) {
  const book = state.books.find(b => b.id === bookId);
  if (!book) return;

  const coverUrl = getCoverUrl(book);

  // Get summary from book data (embedded by build.js)
  const summary = book.summary;

  // Build summary section - split into paragraphs
  let summaryHtml;
  if (summary) {
    const paragraphs = summary.split(/\n\n+/).filter(p => p.trim());
    const paragraphsHtml = paragraphs.map(p => `<p>${escapeHtml(p)}</p>`).join('\n');
    summaryHtml = `
      <h3>Plot</h3>
      ${paragraphsHtml}
    `;
  } else {
    summaryHtml = `
      <h3>Plot</h3>
      <p class="no-summary">No plot summary available for this book.</p>
    `;
  }

  // Render modal content
  elements.modalContent.innerHTML = `
    <button class="modal-close" aria-label="Close modal">&times;</button>
    <div class="modal-body">
      <div class="modal-cover">
        ${coverUrl ? `
          <img
            src="${coverUrl}"
            alt="Cover of ${escapeHtml(book.title)}"
            onerror="this.style.display='none'; this.nextElementSibling.style.display='flex';"
          >
          <div class="cover-placeholder" style="display: none;">
            <span class="book-icon">📚</span>
            <span class="placeholder-title">${escapeHtml(book.title)}</span>
          </div>
        ` : `
          <div class="cover-placeholder">
            <span class="book-icon">📚</span>
            <span class="placeholder-title">${escapeHtml(book.title)}</span>
          </div>
        `}
      </div>
      <div class="modal-details">
        <h2 id="modal-title">${escapeHtml(book.title)}</h2>
        <p class="author">${escapeHtml(book.author)}</p>
        <div class="modal-meta">
          <div class="meta-item">
            <span class="label">Year</span>
            <span class="value">${book.year}</span>
          </div>
          <div class="meta-item">
            <span class="label">Format</span>
            <span class="value">${book.format}</span>
          </div>
          <div class="meta-item">
            <span class="label">Language</span>
            <span class="value">${book.language === 'de' ? 'German' : 'English'}</span>
          </div>
          ${book.isbn ? `
            <div class="meta-item">
              <span class="label">ISBN</span>
              <span class="value">${book.isbn}</span>
            </div>
          ` : ''}
        </div>
        <div class="modal-summary">
          ${summaryHtml}
        </div>
      </div>
    </div>
  `;

  // Add close button handler
  elements.modalContent.querySelector('.modal-close').addEventListener('click', closeModal);

  // Show modal
  elements.modal.classList.add('active');
  document.body.style.overflow = 'hidden';
}

// Close modal
function closeModal() {
  elements.modal.classList.remove('active');
  document.body.style.overflow = '';
}

// Utility: Escape HTML to prevent XSS
function escapeHtml(text) {
  if (!text) return '';
  const div = document.createElement('div');
  div.textContent = text;
  return div.innerHTML;
}

// Utility: Debounce function for search input
function debounce(func, wait) {
  let timeout;
  return function executedFunction(...args) {
    const later = () => {
      clearTimeout(timeout);
      func(...args);
    };
    clearTimeout(timeout);
    timeout = setTimeout(later, wait);
  };
}

// Initialize when DOM is ready
document.addEventListener('DOMContentLoaded', init);