// /app/static/js/showcase.js
// JS-managed masonry with column distribution for infinite scroll

(function() {
  const container = document.getElementById('showcaseGrid');
  if (!container) return;

  // Configuration
  const DESKTOP_COLUMNS = 4;
  const MOBILE_COLUMNS = 2;
  const MOBILE_BREAKPOINT = 768;
  const SCROLL_THRESHOLD = 1500; // Load more when 1500px from bottom (about 2-3 rows ahead)
  const LOAD_BATCH_SIZE = 4;

  // State
  let columns = [];
  let columnHeights = [];
  let isLoading = false;
  let currentColumnCount = 0;

  // Initialize
  function init() {
    setupColumns();
    loadInitialImages();
    setupEventListeners();
  }

  function getColumnCount() {
    return window.innerWidth < MOBILE_BREAKPOINT ? MOBILE_COLUMNS : DESKTOP_COLUMNS;
  }

  function setupColumns() {
    const count = getColumnCount();
    if (count === currentColumnCount && columns.length > 0) return;

    currentColumnCount = count;
    container.innerHTML = '';
    columns = [];
    columnHeights = [];

    for (let i = 0; i < count; i++) {
      const col = document.createElement('div');
      col.className = 'masonry-column';
      col.dataset.column = i;
      container.appendChild(col);
      columns.push(col);
      columnHeights.push(0);
    }
  }

  function loadInitialImages() {
    const dataScript = document.getElementById('initialImages');
    if (!dataScript) return;

    try {
      const images = JSON.parse(dataScript.textContent);
      distributeImages(images, true); // Use lazy loading for initial images (some may be below fold)
    } catch (e) {
      console.error('Failed to parse initial images:', e);
    }
  }

  function setupEventListeners() {
    // Keyboard shuffle
    document.addEventListener('keydown', (e) => {
      const modal = document.getElementById('imageModal');
      if (modal && modal.classList.contains('active')) return;
      if (e.target.tagName === 'INPUT' || e.target.tagName === 'TEXTAREA') return;

      if (e.key === 'r' || e.key === 'R' || e.key === ' ') {
        e.preventDefault();
        shuffle();
      }
    });

    // Infinite scroll
    let scrollTimeout = null;
    window.addEventListener('scroll', () => {
      if (scrollTimeout) return;
      scrollTimeout = setTimeout(() => {
        scrollTimeout = null;
        checkScrollPosition();
      }, 100);
    });

    // Window resize - redistribute if column count changes
    let resizeTimeout = null;
    window.addEventListener('resize', () => {
      if (resizeTimeout) clearTimeout(resizeTimeout);
      resizeTimeout = setTimeout(() => {
        const newCount = getColumnCount();
        if (newCount !== currentColumnCount) {
          redistributeAllImages();
        }
      }, 200);
    });
  }

  function checkScrollPosition() {
    // For masonry layouts, we need to check if the SHORTEST column is near the viewport bottom,
    // not the overall page bottom. Otherwise, a tall image in one column prevents loading
    // even when other columns have empty space visible.

    // First, update accurate column heights
    updateColumnHeights();

    // Find the shortest column's bottom position relative to viewport
    const shortestColumnIndex = getShortestColumnIndex();
    const shortestColumn = columns[shortestColumnIndex];
    if (!shortestColumn) return;

    const columnRect = shortestColumn.getBoundingClientRect();
    const columnBottom = columnRect.bottom;  // Distance from viewport top to column bottom
    const viewportHeight = window.innerHeight;

    // If the shortest column's bottom is within SCROLL_THRESHOLD of the viewport bottom, load more
    // columnBottom - viewportHeight = how far below the viewport the column extends
    // If this is negative or small, the column end is visible or nearly visible
    const distanceFromViewportBottom = columnBottom - viewportHeight;

    if (distanceFromViewportBottom < SCROLL_THRESHOLD) {
      loadMore();
    }
  }

  function getShortestColumnIndex() {
    let minHeight = Infinity;
    let minIndex = 0;
    for (let i = 0; i < columnHeights.length; i++) {
      if (columnHeights[i] < minHeight) {
        minHeight = columnHeights[i];
        minIndex = i;
      }
    }
    return minIndex;
  }

  function createImageElement(img, useLazyLoading = false) {
    const item = document.createElement('div');
    item.className = 'masonry-item img-clickable';
    item.dataset.id = img.id;
    item.dataset.full = img.full_url;
    item.dataset.type = img.is_video ? 'video' : 'image';
    item.dataset.filename = img.filename;

    const imgEl = document.createElement('img');
    imgEl.src = img.thumb_url;
    imgEl.alt = img.filename;
    if (useLazyLoading) {
      imgEl.loading = 'lazy';
    }
    item.appendChild(imgEl);

    // Filter out archive tags from display (they're still visible in modal)
    const visibleTags = (img.tags || []).filter(t => t.kind !== 'archive');
    if (visibleTags.length > 0) {
      const overlay = document.createElement('div');
      overlay.className = 'tag-overlay';
      visibleTags.forEach(t => {
        const chip = document.createElement('a');
        chip.className = 'tag-chip';
        chip.href = `/gallery?tag=${encodeURIComponent(t.name)}`;
        chip.title = `Filter by ${t.name}`;
        chip.onclick = (e) => e.stopPropagation();
        chip.innerHTML = formatTag(t);
        overlay.appendChild(chip);
      });
      item.appendChild(overlay);
    }

    if (img.is_video) {
      const play = document.createElement('div');
      play.className = 'play-overlay';
      play.textContent = '▶';
      item.appendChild(play);
    }

    return item;
  }

  function distributeImages(images, useLazyLoading = false) {
    images.forEach(img => {
      const colIndex = getShortestColumnIndex();
      const item = createImageElement(img, useLazyLoading);
      columns[colIndex].appendChild(item);

      // Update height estimate (will be corrected after image loads)
      columnHeights[colIndex] += 300;

      // Correct height after image loads
      const imgEl = item.querySelector('img');
      imgEl.onload = () => {
        updateColumnHeights();
      };
    });

    document.dispatchEvent(new CustomEvent('showcaseUpdated'));
  }

  function updateColumnHeights() {
    columns.forEach((col, i) => {
      columnHeights[i] = col.offsetHeight;
    });
  }

  function redistributeAllImages() {
    // Collect all current items
    const allItems = [];
    columns.forEach(col => {
      Array.from(col.children).forEach(item => {
        allItems.push(item);
      });
    });

    // Reset columns
    setupColumns();

    // Re-add items maintaining order
    allItems.forEach(element => {
      const colIndex = getShortestColumnIndex();
      columns[colIndex].appendChild(element);
      columnHeights[colIndex] += element.offsetHeight || 300;
    });

    document.dispatchEvent(new CustomEvent('showcaseUpdated'));
  }

  async function shuffle() {
    if (isLoading) return;
    isLoading = true;
    container.classList.add('loading');

    try {
      const response = await fetch(`/api/random-images?count=20`);
      if (!response.ok) throw new Error('Failed to fetch');

      const data = await response.json();

      // Clear everything
      columns.forEach(col => col.innerHTML = '');
      columnHeights = columnHeights.map(() => 0);

      distributeImages(data.images);

      // Scroll to top
      window.scrollTo({ top: 0, behavior: 'smooth' });
    } catch (err) {
      console.error('Shuffle error:', err);
    } finally {
      container.classList.remove('loading');
      isLoading = false;
    }
  }

  async function loadMore() {
    if (isLoading) return;
    isLoading = true;

    try {
      const response = await fetch(`/api/random-images?count=${LOAD_BATCH_SIZE}`);
      if (!response.ok) throw new Error('Failed to fetch');

      const data = await response.json();

      if (data.images.length === 0) {
        return;
      }

      distributeImages(data.images);
    } catch (err) {
      console.error('Load more error:', err);
    } finally {
      isLoading = false;
    }
  }

  function formatTag(tag) {
    const escape = (s) => {
      const div = document.createElement('div');
      div.textContent = s;
      return div.innerHTML;
    };

    const icons = {
      artist: '🎨',
      archive: '🗜️',
      character: '👤',
      series: '📺',
      rating: '⚠️',
      source: '🌐',
      post: '📌'
    };

    const icon = icons[tag.kind];
    if (icon) {
      const label = tag.name.includes(':') ? tag.name.split(':', 2)[1] : tag.name;
      return `${icon} ${escape(label)}`;
    } else {
      return `#${escape(tag.name)}`;
    }
  }

  // Start
  init();
})();