document.addEventListener('DOMContentLoaded', function () {
  const filesContainer = document.getElementById('files-container');

  if (!filesContainer) return;

  // Create selection box element
  const selectionBox = document.createElement('div');
  selectionBox.className = 'selection-box';
  selectionBox.style.display = 'none';
  document.body.appendChild(selectionBox);

  // Selection variables
  let isSelecting = false;
  let startX, startY;
  let selectedItems = [];

  // Handle mouse down on container (start selection)
  filesContainer.addEventListener('mousedown', function (e) {
    // Only start selection if clicking on empty space with left mouse button
    if (e.target === filesContainer && e.button === 0) {
      isSelecting = true;
      startX = e.clientX;
      startY = e.clientY;

      // Position selection box
      selectionBox.style.left = `${startX}px`;
      selectionBox.style.top = `${startY}px`;
      selectionBox.style.width = '0px';
      selectionBox.style.height = '0px';
      selectionBox.style.display = 'block';

      // Clear existing selection if not holding shift
      if (!e.shiftKey) {
        clearSelection();
      }

      // Prevent default behavior
      e.preventDefault();
    }
  });

  // Handle mouse move (update selection box)
  document.addEventListener('mousemove', function (e) {
    if (!isSelecting) return;

    // Calculate new dimensions
    const width = Math.abs(e.clientX - startX);
    const height = Math.abs(e.clientY - startY);

    // Calculate top-left corner
    const left = e.clientX < startX ? e.clientX : startX;
    const top = e.clientY < startY ? e.clientY : startY;

    // Update selection box
    selectionBox.style.left = `${left}px`;
    selectionBox.style.top = `${top}px`;
    selectionBox.style.width = `${width}px`;
    selectionBox.style.height = `${height}px`;

    // Check which items are in the selection
    const selectionRect = selectionBox.getBoundingClientRect();
    const items = filesContainer.querySelectorAll('.file-item, .folder-item');

    items.forEach(item => {
      const itemRect = item.getBoundingClientRect();

      // Check if item intersects with selection box
      const intersects = !(
        itemRect.right < selectionRect.left ||
        itemRect.left > selectionRect.right ||
        itemRect.bottom < selectionRect.top ||
        itemRect.top > selectionRect.bottom
      );

      if (intersects) {
        item.classList.add('selected');
        if (!selectedItems.includes(item)) {
          selectedItems.push(item);
        }
      } else if (!e.shiftKey && !item.classList.contains('manually-selected')) {
        item.classList.remove('selected');
        const index = selectedItems.indexOf(item);
        if (index > -1) {
          selectedItems.splice(index, 1);
        }
      }
    });
  });

  // Handle mouse up (end selection)
  document.addEventListener('mouseup', function () {
    if (isSelecting) {
      isSelecting = false;
      selectionBox.style.display = 'none';

      // Mark selected items
      selectedItems.forEach(item => {
        item.classList.add('manually-selected');
      });

      // Update selection actions
      updateSelectionActions();
    }
  });

  // Handle item click (toggle selection)
  filesContainer.addEventListener('click', function (e) {
    const item = e.target.closest('.file-item, .folder-item');

    if (item) {
      // If holding Ctrl or Shift, toggle selection
      if (e.ctrlKey || e.shiftKey) {
        e.preventDefault();

        item.classList.toggle('selected');
        item.classList.toggle('manually-selected');

        const index = selectedItems.indexOf(item);
        if (index > -1) {
          selectedItems.splice(index, 1);
        } else {
          selectedItems.push(item);
        }

        updateSelectionActions();
      } else {
        // If not holding Ctrl/Shift, clear selection and select only this item
        if (!item.classList.contains('selected')) {
          clearSelection();
          item.classList.add('selected');
          item.classList.add('manually-selected');
          selectedItems = [item];
          updateSelectionActions();
        }
      }
    } else if (e.target === filesContainer) {
      // Clicking on empty space clears selection
      clearSelection();
    }
  });

  // Clear selection
  function clearSelection() {
    const items = filesContainer.querySelectorAll('.file-item, .folder-item');
    items.forEach(item => {
      item.classList.remove('selected', 'manually-selected');
    });
    selectedItems = [];
    updateSelectionActions();
  }

  // Update selection actions (e.g., show action bar)
  function updateSelectionActions() {
    const actionBar = document.getElementById('selection-actions');

    if (actionBar) {
      if (selectedItems.length > 0) {
        actionBar.classList.add('active');

        // Update count
        const countElement = actionBar.querySelector('.selection-count');
        if (countElement) {
          countElement.textContent = `${selectedItems.length} item(s) selected`;
        }
      } else {
        actionBar.classList.remove('active');
      }
    }
  }

  // Select all items
  window.selectAllItems = function () {
    const items = filesContainer.querySelectorAll('.file-item, .folder-item');
    items.forEach(item => {
      item.classList.add('selected', 'manually-selected');
      if (!selectedItems.includes(item)) {
        selectedItems.push(item);
      }
    });
    updateSelectionActions();
  };
});