/**
 * Plot comparison functionality
 */
export class ComparisonManager {
  constructor() {
    this.comparisonMode = false;
    this.comparisonSlot = null; // 'left' or 'right'
    this.plots = { left: null, right: null };
  }

  /**
   * Toggle comparison mode
   */
  toggleCompareMode() {
    this.comparisonMode = !this.comparisonMode;
    const compareBtn = document.getElementById('compareToggle');
    
    if (!compareBtn) return;
    
    if (this.comparisonMode) {
      compareBtn.style.background = 'var(--success-color)';
      compareBtn.title = 'Exit Compare Mode (Ctrl+C)';
      this.showComparisonOverlay();
    } else {
      compareBtn.style.background = 'var(--button-bg)';
      compareBtn.title = 'Compare Plots (Ctrl+C)';
      this.hideComparisonOverlay();
    }
  }

  /**
   * Show comparison overlay
   */
  showComparisonOverlay() {
    const overlay = document.getElementById('comparisonOverlay');
    if (overlay) overlay.classList.add('open');
  }

  /**
   * Hide comparison overlay
   */
  hideComparisonOverlay() {
    const overlay = document.getElementById('comparisonOverlay');
    if (overlay) overlay.classList.remove('open');
    this.comparisonMode = false;
    
    const compareBtn = document.getElementById('compareToggle');
    if (compareBtn) {
      compareBtn.style.background = 'var(--button-bg)';
      compareBtn.title = 'Compare Plots (Ctrl+C)';
    }
  }

  /**
   * Close comparison overlay (alias for hideComparisonOverlay)
   */
  closeComparison() {
    this.hideComparisonOverlay();
  }

  /**
   * Select plot for comparison - simple approach
   */
  selectPlotForComparison(slot) {
    this.comparisonSlot = slot;
    
    // Hide overlay temporarily by removing the 'open' class
    const overlay = document.getElementById('comparisonOverlay');
    if (overlay) overlay.classList.remove('open');
    
    // Show simple alert with instructions
    const instruction = document.createElement('div');
    instruction.id = 'comparisonInstruction';
    instruction.style.cssText = `
      position: fixed;
      top: 20px;
      left: 50%;
      transform: translateX(-50%);
      background: var(--button-bg);
      color: white;
      padding: 1rem 2rem;
      border-radius: 8px;
      z-index: 3000;
      font-size: 1.1rem;
      font-weight: 600;
      box-shadow: 0 4px 20px rgba(0,0,0,0.3);
    `;
    instruction.innerHTML = `📊 Click any plot to select for ${slot === 'left' ? 'Plot A' : 'Plot B'} (ESC to cancel)`;
    document.body.appendChild(instruction);
    
    // Add one-time click listener to all grid items
    const gridItems = document.querySelectorAll('.grid-item');
    const handleClick = (event) => {
      event.preventDefault();
      event.stopPropagation();
      
      const gridItem = event.currentTarget;
      const img = gridItem.querySelector('img');
      const nameEl = gridItem.querySelector('.plot-name');
      
      if (img && nameEl) {
        const plotInfo = {
          name: nameEl.textContent.trim(),
          imgSrc: img.src,
          pdfSrc: img.src.replace('.png', '.pdf'),
          path: window.location.pathname
        };
        
        this.addPlotToComparison(plotInfo, slot);
      }
      
      // Clean up
      instruction.remove();
      gridItems.forEach(item => item.removeEventListener('click', handleClick));
      this.comparisonSlot = null;
      if (overlay) overlay.classList.add('open');
    };
    
    gridItems.forEach(item => {
      item.style.cursor = 'pointer';
      item.style.border = '2px dashed var(--button-bg)';
      item.addEventListener('click', handleClick);
    });
    
    // ESC to cancel
    const handleEscape = (event) => {
      if (event.key === 'Escape') {
        instruction.remove();
        gridItems.forEach(item => {
          item.removeEventListener('click', handleClick);
          item.style.cursor = '';
          item.style.border = '';
        });
        this.comparisonSlot = null;
        if (overlay) overlay.classList.add('open');
        document.removeEventListener('keydown', handleEscape);
      }
    };
    document.addEventListener('keydown', handleEscape);
  }

  /**
   * Add plot to comparison panel
   */
  addPlotToComparison(plotInfo, slot) {
    this.plots[slot] = plotInfo;
    
    const container = document.getElementById(`${slot}PlotContainer`);
    const title = document.getElementById(`${slot}PlotTitle`);
    const replaceBtn = document.getElementById(`${slot}ReplaceBtn`);
    
    if (container) {
      container.innerHTML = `
        <img src="${plotInfo.imgSrc}" class="comparison-plot" alt="${plotInfo.name}" 
             onclick="window.open('${plotInfo.pdfSrc}', '_blank')" />
        <div class="comparison-plot-info">
          <strong>${plotInfo.name}</strong><br>
          <small>${plotInfo.path}</small>
        </div>
      `;
    }
    
    if (title) title.textContent = plotInfo.name;
    if (replaceBtn) replaceBtn.style.display = 'block';
    
    // Reset grid item styles
    const gridItems = document.querySelectorAll('.grid-item');
    gridItems.forEach(item => {
      item.style.cursor = '';
      item.style.border = '';
    });
  }

  /**
   * Replace plot in comparison
   */
  replacePlot(slot) {
    this.selectPlotForComparison(slot);
  }
}