document.addEventListener('DOMContentLoaded', function() {
    // Initialize GOV.UK Frontend
    window.GOVUKFrontend.initAll();

    // Taxonomy Explorer implementation
    class TaxonomyExplorer {
        constructor(containerId) {
            this.container = document.getElementById(containerId);
            this.data = null;
            this.hierarchy = null;
            this.currentNode = null;
            this.searchTerm = '';
            this.stats = { l1: 0, l2: 0, l3: 0 };
            
            this.init();
        }

        async init() {
            // Load taxonomy data
            await this.loadData();
            
            // Initialize visualization
            this.initVisualization();
            
            // Render controls
            this.renderControls();
        }

        async loadData() {
            // In a real implementation, this would load from an API
            // For now we'll use the static data structure
            this.data = this.parseMarkdown(markdownData);
            this.hierarchy = d3.hierarchy(this.data);
            this.calculateStats();
        }

        parseMarkdown(markdown) {
            // Improved parsing logic from original code
            // ... (keep existing parsing logic)
        }

        calculateStats() {
            // Calculate stats for the taxonomy
            // ... (keep existing stats logic)
        }

        initVisualization() {
            // Set up D3 visualization with improved GOV.UK styling
            const width = this.container.clientWidth;
            const height = this.container.clientHeight;

            this.svg = d3.select(this.container)
                .append('svg')
                .attr('width', width)
                .attr('height', height)
                .style('font-family', '"GDS Transport", Arial, sans-serif');

            this.g = this.svg.append('g');

            // Add zoom behavior
            this.zoom = d3.zoom()
                .scaleExtent([0.1, 2])
                .on('zoom', (event) => this.g.attr('transform', event.transform));
            
            this.svg.call(this.zoom);

            // Set up tree layout
            this.tree = d3.tree()
                .size([width - 200, height - 200])
                .separation((a, b) => a.parent === b.parent ? 1.5 : 2);

            // Initial render
            this.updateVisualization();
        }

        updateVisualization() {
            // Update the visualization based on current state
            const treeData = this.tree(this.hierarchy);
            const nodes = treeData.descendants();
            const links = treeData.links();

            // Normalize positions
            nodes.forEach(d => d.y = d.depth * 180);

            // Update nodes and links
            // ... (keep existing update logic with GOV.UK styling)
        }

        renderControls() {
            // Create control panel
            const controls = this.container.insertBefore(
                document.createElement('div'),
                this.container.firstChild
            );
            controls.className = 'taxonomy-controls';

            // Add search input
            const searchDiv = document.createElement('div');
            searchDiv.className = 'taxonomy-search';
            searchDiv.innerHTML = `
                <div class="govuk-form-group">
                    <label class="govuk-label" for="taxonomy-search">Search taxonomy</label>
                    <input class="govuk-input" id="taxonomy-search" type="text" placeholder="Search...">
                </div>
            `;
            controls.appendChild(searchDiv);

            // Add stats display
            const statsDiv = document.createElement('div');
            statsDiv.className = 'taxonomy-stats';
            statsDiv.innerHTML = `
                <div class="taxonomy-stat">
                    <div class="taxonomy-stat-value" id="stat-l1">${this.stats.l1}</div>
                    <div class="taxonomy-stat-label">L1 Categories</div>
                </div>
                <div class="taxonomy-stat">
                    <div class="taxonomy-stat-value" id="stat-l2">${this.stats.l2}</div>
                    <div class="taxonomy-stat-label">L2 Subcategories</div>
                </div>
                <div class="taxonomy-stat">
                    <div class="taxonomy-stat-value" id="stat-l3">${this.stats.l3}</div>
                    <div class="taxonomy-stat-label">L3 Topics</div>
                </div>
            `;
            controls.appendChild(statsDiv);

            // Add event listeners
            document.getElementById('taxonomy-search').addEventListener('input', (e) => {
                this.searchTerm = e.target.value.toLowerCase();
                this.highlightMatches();
            });
        }

        highlightMatches() {
            // Highlight nodes matching search term
            this.svg.selectAll('.node')
                .classed('node-highlighted', (d) => {
                    if (!this.searchTerm) return false;
                    const nameMatch = d.data.name.toLowerCase().includes(this.searchTerm);
                    const slugMatch = d.data.slug && d.data.slug.toLowerCase().includes(this.searchTerm);
                    return nameMatch || slugMatch;
                });
        }

        showDetails(node) {
            // Show details panel for selected node
            // ... (keep existing details panel logic with GOV.UK styling)
        }
    }

    // Initialize the explorer
    new TaxonomyExplorer('taxonomy-explorer');
});