// /app/static/js/reader.js
'use strict';

document.addEventListener('DOMContentLoaded', () => {
  const { startPage } = window.readerConfig || { startPage: 1 };

  // Elements
  // #readerContent is the actual scroll container (overflow-y: auto)
  const readerContent = document.getElementById('readerContent');
  const pageJumpSelect = document.getElementById('pageJumpSelect');
  const floatingIndicator = document.getElementById('floatingPageIndicator');
  const currentPageNum = document.getElementById('currentPageNum');
  const readerNav = document.getElementById('readerNav');
  const readerHeader = document.querySelector('.reader-header');
  const toggleNavBtn = document.getElementById('toggleNavBtn');
  const closeNavBtn = document.getElementById('closeNavBtn');
  const navThumbs = document.querySelectorAll('.reader-nav-thumb');
  const scrollToTopBtn = document.getElementById('scrollToTopBtn');
  const scrollToBottomBtn = document.getElementById('scrollToBottomBtn');
  const pages = document.querySelectorAll('.reader-page');
  const progressBar = document.getElementById('readerProgressBar');

  let currentPage = startPage;
  let isNavOpen = false;
  let headerHideTimeout = null;

  // -------------------------
  // Scroll to starting page
  // -------------------------
  if (startPage > 1) {
    const targetPage = document.getElementById('page-' + startPage);
    if (targetPage) {
      setTimeout(() => targetPage.scrollIntoView({ behavior: 'auto' }), 100);
    }
  }

  // -------------------------
  // Progress bar
  // -------------------------
  function updateProgressBar() {
    if (!progressBar || !readerContent) return;
    const scrollTop = readerContent.scrollTop;
    const scrollHeight = readerContent.scrollHeight - readerContent.clientHeight;
    const pct = scrollHeight > 0 ? (scrollTop / scrollHeight) * 100 : 0;
    progressBar.style.width = `${Math.min(pct, 100)}%`;
  }

  // -------------------------
  // Auto-hide header
  // -------------------------
  function showHeader() {
    if (!readerHeader) return;
    readerHeader.classList.remove('hidden');
    clearTimeout(headerHideTimeout);
  }

  function scheduleHideHeader() {
    clearTimeout(headerHideTimeout);
    headerHideTimeout = setTimeout(() => {
      if (readerHeader) readerHeader.classList.add('hidden');
    }, 2500);
  }

  // -------------------------
  // Current page tracking
  // -------------------------
  function updateCurrentPage() {
    if (!readerContent) return;
    const scrollTop = readerContent.scrollTop;
    const viewportCenter = scrollTop + (readerContent.clientHeight / 3);

    let newCurrentPage = currentPage;
    pages.forEach(page => {
      const pageTop = page.offsetTop;
      const pageBottom = pageTop + page.offsetHeight;
      if (viewportCenter >= pageTop && viewportCenter < pageBottom) {
        newCurrentPage = parseInt(page.dataset.page);
      }
    });

    if (newCurrentPage !== currentPage) {
      currentPage = newCurrentPage;

      // Update floating indicator
      if (currentPageNum) currentPageNum.textContent = currentPage;

      // Update jump select
      if (pageJumpSelect) pageJumpSelect.value = currentPage;

      // Update active nav thumb + scroll it into view
      navThumbs.forEach(thumb => {
        const isActive = parseInt(thumb.dataset.page) === currentPage;
        thumb.classList.toggle('active', isActive);
        if (isActive) {
          thumb.scrollIntoView({ block: 'nearest', behavior: 'smooth' });
        }
      });

      // Update URL without reload
      const url = new URL(window.location);
      url.searchParams.set('page', currentPage);
      history.replaceState({}, '', url);
    }
  }

  // -------------------------
  // Scroll handler
  // -------------------------
  let scrollTimeout = null;
  if (readerContent) {
    readerContent.addEventListener('scroll', () => {
      updateProgressBar();
      showHeader();
      scheduleHideHeader();

      if (scrollTimeout) return;
      scrollTimeout = setTimeout(() => {
        updateCurrentPage();
        scrollTimeout = null;
      }, 50);
    });
  }

  // Show header on mouse move
  document.addEventListener('mousemove', () => {
    showHeader();
    scheduleHideHeader();
  });

  // -------------------------
  // Jump to page
  // -------------------------
  if (pageJumpSelect) {
    pageJumpSelect.addEventListener('change', (e) => {
      const pageNum = parseInt(e.target.value);
      const targetPage = document.getElementById('page-' + pageNum);
      if (targetPage) targetPage.scrollIntoView({ behavior: 'smooth' });
    });
  }

  // -------------------------
  // Sidebar toggle
  // -------------------------
  if (toggleNavBtn) {
    toggleNavBtn.addEventListener('click', () => {
      isNavOpen = !isNavOpen;
      readerNav.classList.toggle('open', isNavOpen);
    });
  }

  if (closeNavBtn) {
    closeNavBtn.addEventListener('click', () => {
      isNavOpen = false;
      readerNav.classList.remove('open');
    });
  }

  // Click thumbnail to jump
  navThumbs.forEach(thumb => {
    thumb.addEventListener('click', () => {
      const pageNum = parseInt(thumb.dataset.page);
      const targetPage = document.getElementById('page-' + pageNum);
      if (targetPage) targetPage.scrollIntoView({ behavior: 'smooth' });
      if (window.innerWidth < 768) {
        isNavOpen = false;
        readerNav.classList.remove('open');
      }
    });
  });

  // -------------------------
  // Quick nav buttons
  // -------------------------
  if (scrollToTopBtn) {
    scrollToTopBtn.addEventListener('click', () => {
      readerContent.scrollTo({ top: 0, behavior: 'smooth' });
    });
  }

  if (scrollToBottomBtn) {
    scrollToBottomBtn.addEventListener('click', () => {
      readerContent.scrollTo({ top: readerContent.scrollHeight, behavior: 'smooth' });
    });
  }

  // -------------------------
  // Keyboard navigation
  // -------------------------
  document.addEventListener('keydown', (e) => {
    if (e.target.tagName === 'INPUT' || e.target.tagName === 'SELECT') return;
    if (!readerContent) return;
    showHeader();

    switch (e.key) {
      case 'Home':
        e.preventDefault();
        readerContent.scrollTo({ top: 0, behavior: 'smooth' });
        break;
      case 'End':
        e.preventDefault();
        readerContent.scrollTo({ top: readerContent.scrollHeight, behavior: 'smooth' });
        break;
      case 'PageUp':
        e.preventDefault();
        readerContent.scrollBy({ top: -readerContent.clientHeight * 0.9, behavior: 'smooth' });
        break;
      case 'PageDown':
      case ' ':
        e.preventDefault();
        readerContent.scrollBy({ top: readerContent.clientHeight * 0.9, behavior: 'smooth' });
        break;
      case 'n':
        isNavOpen = !isNavOpen;
        readerNav.classList.toggle('open', isNavOpen);
        break;
    }
  });

  // -------------------------
  // Initial state
  // -------------------------
  updateCurrentPage();
  updateProgressBar();
});