/**
 * SchoolCompare.co.uk - Frontend Application
 * Interactive UK Primary School Performance Comparison
 */

const API_BASE = '';

// =============================================================================
// STATE MANAGEMENT
// =============================================================================

const state = {
    schools: [],
    selectedSchools: [],
    currentSchoolData: null,
    filters: null,  // Cached filter data
    metrics: null,  // Cached metric definitions
    pagination: { page: 1, pageSize: 50, total: 0, totalPages: 0 },
    isShowingFeatured: true,  // Whether showing featured schools vs search results
    locationSearch: {
        active: false,
        postcode: null,
        radius: 5,
    },
    loading: {
        schools: false,
        filters: false,
        rankings: false,
        comparison: false,
        modal: false,
    },
};

// Charts
let comparisonChart = null;
let schoolDetailChart = null;

// Chart colors
const CHART_COLORS = [
    '#e07256',  // coral
    '#2d7d7d',  // teal
    '#c9a227',  // gold
    '#7b68a6',  // purple
    '#3498db',  // blue
    '#27ae60',  // green
    '#e74c3c',  // red
    '#9b59b6',  // violet
];

// =============================================================================
// DOM ELEMENTS
// =============================================================================

const elements = {
    schoolSearch: document.getElementById('school-search'),
    localAuthorityFilter: document.getElementById('local-authority-filter'),
    typeFilter: document.getElementById('type-filter'),
    postcodeSearch: document.getElementById('postcode-search'),
    radiusSelect: document.getElementById('radius-select'),
    locationSearchBtn: document.getElementById('location-search-btn'),
    clearLocationBtn: document.getElementById('clear-location-btn'),
    schoolsGrid: document.getElementById('schools-grid'),
    compareSearch: document.getElementById('compare-search'),
    compareResults: document.getElementById('compare-results'),
    selectedSchools: document.getElementById('selected-schools'),
    chartsSection: document.getElementById('charts-section'),
    metricSelect: document.getElementById('metric-select'),
    comparisonChart: document.getElementById('comparison-chart'),
    comparisonTable: document.getElementById('comparison-table'),
    tableHeader: document.getElementById('table-header'),
    tableBody: document.getElementById('table-body'),
    rankingArea: document.getElementById('ranking-area'),
    rankingMetric: document.getElementById('ranking-metric'),
    rankingYear: document.getElementById('ranking-year'),
    rankingsList: document.getElementById('rankings-list'),
    modal: document.getElementById('school-modal'),
    modalClose: document.getElementById('modal-close'),
    modalSchoolName: document.getElementById('modal-school-name'),
    modalMeta: document.getElementById('modal-meta'),
    modalStats: document.getElementById('modal-stats'),
    schoolDetailChart: document.getElementById('school-detail-chart'),
    addToCompare: document.getElementById('add-to-compare'),
};

// =============================================================================
// API & CACHING
// =============================================================================

const apiCache = new Map();
const CACHE_TTL = 5 * 60 * 1000; // 5 minutes

async function fetchAPI(endpoint, options = {}) {
    const { useCache = true, showLoading = null } = options;
    const cacheKey = endpoint;
    
    // Check cache
    if (useCache && apiCache.has(cacheKey)) {
        const cached = apiCache.get(cacheKey);
        if (Date.now() - cached.timestamp < CACHE_TTL) {
            return cached.data;
        }
        apiCache.delete(cacheKey);
    }
    
    // Set loading state
    if (showLoading) {
        state.loading[showLoading] = true;
        updateLoadingUI(showLoading);
    }
    
    try {
        const response = await fetch(`${API_BASE}${endpoint}`);
        if (!response.ok) throw new Error(`HTTP ${response.status}`);
        const data = await response.json();
        
        // Cache the response
        if (useCache) {
            apiCache.set(cacheKey, { data, timestamp: Date.now() });
        }
        
        return data;
    } catch (error) {
        console.error(`API Error (${endpoint}):`, error);
        return null;
    } finally {
        if (showLoading) {
            state.loading[showLoading] = false;
            updateLoadingUI(showLoading);
        }
    }
}

function updateLoadingUI(section) {
    // Update UI based on loading state
    switch (section) {
        case 'schools':
            if (state.loading.schools) {
                elements.schoolsGrid.innerHTML = renderLoadingSkeleton(6);
            }
            break;
        case 'rankings':
            if (state.loading.rankings) {
                elements.rankingsList.innerHTML = renderLoadingSkeleton(5, 'ranking');
            }
            break;
        case 'modal':
            if (state.loading.modal) {
                elements.modalStats.innerHTML = '<div class="loading"><div class="loading-spinner"></div><p>Loading school data...</p></div>';
            }
            break;
    }
}

function renderLoadingSkeleton(count, type = 'card') {
    if (type === 'ranking') {
        return Array(count).fill(0).map(() => `
            <div class="ranking-item skeleton">
                <div class="skeleton-circle"></div>
                <div class="skeleton-content">
                    <div class="skeleton-line" style="width: 60%"></div>
                    <div class="skeleton-line short" style="width: 30%"></div>
                </div>
                <div class="skeleton-score"></div>
            </div>
        `).join('');
    }
    return Array(count).fill(0).map(() => `
        <div class="school-card skeleton">
            <div class="skeleton-line" style="width: 70%"></div>
            <div class="skeleton-line short" style="width: 40%"></div>
            <div class="skeleton-line" style="width: 90%"></div>
        </div>
    `).join('');
}

// =============================================================================
// ROUTING
// =============================================================================

const routes = {
    '/': 'dashboard',
    '/compare': 'compare',
    '/rankings': 'rankings',
};

function navigateTo(path) {
    // Update URL without reload
    window.history.pushState({}, '', path);
    handleRoute();
}

function handleRoute() {
    const path = window.location.pathname;
    const view = routes[path] || 'dashboard';
    
    // Update navigation
    document.querySelectorAll('.nav-link').forEach(link => {
        link.classList.toggle('active', link.dataset.view === view);
    });
    
    // Update view
    document.querySelectorAll('.view').forEach(v => v.classList.remove('active'));
    const viewElement = document.getElementById(`${view}-view`);
    if (viewElement) {
        viewElement.classList.add('active');
    }
}

// =============================================================================
// INITIALIZATION
// =============================================================================

document.addEventListener('DOMContentLoaded', init);

async function init() {
    // Load filters and metrics in parallel (single request for filters)
    const [filtersData, metricsData] = await Promise.all([
        fetchAPI('/api/filters', { showLoading: 'filters' }),
        fetchAPI('/api/metrics'),
    ]);
    
    // Cache and apply filters
    if (filtersData) {
        state.filters = filtersData;
        populateFilters(filtersData);
    }
    
    // Cache metrics
    if (metricsData) {
        state.metrics = metricsData.metrics;
    }
    
    // Load initial data
    await loadSchools();
    await loadRankings();
    
    setupEventListeners();
    
    // Handle initial route
    handleRoute();
    
    // Handle browser back/forward
    window.addEventListener('popstate', handleRoute);
}

function populateFilters(data) {
    // Populate local authority filter (dashboard)
    data.local_authorities.forEach(la => {
        const option = document.createElement('option');
        option.value = la;
        option.textContent = la;
        elements.localAuthorityFilter.appendChild(option);
    });

    // Populate school type filter
    data.school_types.forEach(type => {
        const option = document.createElement('option');
        option.value = type;
        option.textContent = type;
        elements.typeFilter.appendChild(option);
    });
    
    // Populate ranking area dropdown
    data.local_authorities.forEach(la => {
        const option = document.createElement('option');
        option.value = la;
        option.textContent = la;
        elements.rankingArea.appendChild(option);
    });
    
    // Populate ranking year dropdown
    elements.rankingYear.innerHTML = '';
    data.years.sort((a, b) => b - a).forEach(year => {
        const option = document.createElement('option');
        option.value = year;
        option.textContent = `${year}`;
        elements.rankingYear.appendChild(option);
    });
}

// =============================================================================
// DATA LOADING
// =============================================================================

async function loadSchools() {
    const search = elements.schoolSearch.value.trim();
    const localAuthority = elements.localAuthorityFilter.value;
    const type = elements.typeFilter.value;
    const { active: locationActive, postcode, radius } = state.locationSearch;
    
    // If no search query (or less than 2 chars) and no filters and no location search, show featured schools
    if (search.length < 2 && !localAuthority && !type && !locationActive) {
        await loadFeaturedSchools();
        return;
    }
    
    const params = new URLSearchParams();
    
    if (search.length >= 2) params.append('search', search);
    if (localAuthority) params.append('local_authority', localAuthority);
    if (type) params.append('school_type', type);
    
    // Add location search params
    if (locationActive && postcode) {
        params.append('postcode', postcode);
        params.append('radius', radius);
    }
    
    params.append('page', state.pagination.page);
    params.append('page_size', state.pagination.pageSize);
    
    const queryString = params.toString();
    const endpoint = `/api/schools?${queryString}`;
    
    // Don't cache search results (they change based on input)
    const data = await fetchAPI(endpoint, { useCache: false, showLoading: 'schools' });
    
    if (!data) {
        showEmptyState(elements.schoolsGrid, 'Unable to load schools');
        return;
    }
    
    state.schools = data.schools;
    state.pagination.total = data.total;
    state.pagination.totalPages = data.total_pages;
    state.isShowingFeatured = false;
    
    // Show location info banner if location search is active
    updateLocationInfoBanner(data.search_location);
    
    renderSchools(state.schools);
}

async function loadFeaturedSchools() {
    // Clear location info when showing featured
    updateLocationInfoBanner(null);
    
    // Load a sample of schools and pick 3 random ones
    const data = await fetchAPI('/api/schools?page_size=100', { showLoading: 'schools' });
    
    if (!data || !data.schools.length) {
        showEmptyState(elements.schoolsGrid, 'No schools available');
        return;
    }
    
    // Shuffle and pick 3 random schools
    const shuffled = data.schools.sort(() => Math.random() - 0.5);
    state.schools = shuffled.slice(0, 3);
    state.isShowingFeatured = true;
    
    renderFeaturedSchools(state.schools);
}

function updateLocationInfoBanner(searchLocation) {
    // Remove existing banner if any
    const existingBanner = document.querySelector('.location-info');
    if (existingBanner) {
        existingBanner.remove();
    }
    
    if (!searchLocation) {
        return;
    }
    
    // Create location info banner
    const banner = document.createElement('div');
    banner.className = 'location-info';
    banner.innerHTML = `
        <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
            <path d="M21 10c0 7-9 13-9 13s-9-6-9-13a9 9 0 0 1 18 0z"/>
            <circle cx="12" cy="10" r="3"/>
        </svg>
        <span>Showing schools within ${searchLocation.radius} miles of <strong>${searchLocation.postcode.toUpperCase()}</strong></span>
    `;
    
    // Insert banner before the schools grid
    elements.schoolsGrid.parentNode.insertBefore(banner, elements.schoolsGrid);
}

async function searchByLocation() {
    const postcode = elements.postcodeSearch.value.trim();
    const radius = parseFloat(elements.radiusSelect.value);
    
    if (!postcode) {
        alert('Please enter a postcode');
        return;
    }
    
    // Validate UK postcode format (basic check)
    const postcodeRegex = /^[A-Z]{1,2}[0-9][A-Z0-9]?\s*[0-9][A-Z]{2}$/i;
    if (!postcodeRegex.test(postcode)) {
        alert('Please enter a valid UK postcode (e.g. SW18 4TF)');
        return;
    }
    
    // Update state
    state.locationSearch = {
        active: true,
        postcode: postcode,
        radius: radius,
    };
    state.pagination.page = 1;
    
    // Show clear button
    elements.clearLocationBtn.style.display = 'inline-flex';
    
    // Load schools with location filter
    await loadSchools();
}

function clearLocationSearch() {
    state.locationSearch = {
        active: false,
        postcode: null,
        radius: 5,
    };
    state.pagination.page = 1;
    
    // Clear input
    elements.postcodeSearch.value = '';
    elements.radiusSelect.value = '5';
    
    // Hide clear button
    elements.clearLocationBtn.style.display = 'none';
    
    // Reload schools (will show featured if no other filters)
    loadSchools();
}

function renderFeaturedSchools(schools) {
    elements.schoolsGrid.innerHTML = `
        <div class="featured-header">
            <h3>Featured Schools</h3>
            <p>Start typing to search ${state.filters?.local_authorities?.length || ''} schools across England</p>
        </div>
        ${schools.map(school => `
            <div class="school-card featured" data-urn="${school.urn}">
                <h3 class="school-name">${escapeHtml(school.school_name)}</h3>
                <div class="school-meta">
                    <span class="school-tag">${escapeHtml(school.local_authority || '')}</span>
                    <span class="school-tag type">${escapeHtml(school.school_type || '')}</span>
                </div>
                <div class="school-address">${escapeHtml(school.address || '')}</div>
                <div class="school-stats">
                    <div class="stat">
                        <div class="stat-value">Primary</div>
                        <div class="stat-label">Phase</div>
                    </div>
                    <div class="stat">
                        <div class="stat-value">KS2</div>
                        <div class="stat-label">Data</div>
                    </div>
                </div>
            </div>
        `).join('')}
    `;
    
    // Add click handlers
    elements.schoolsGrid.querySelectorAll('.school-card').forEach(card => {
        card.addEventListener('click', () => {
            const urn = parseInt(card.dataset.urn);
            openSchoolModal(urn);
        });
    });
}

async function loadSchoolDetails(urn) {
    const data = await fetchAPI(`/api/schools/${urn}`, { showLoading: 'modal' });
    return data;
}

async function loadComparison() {
    if (state.selectedSchools.length === 0) return null;
    
    const urns = state.selectedSchools.map(s => s.urn).join(',');
    const data = await fetchAPI(`/api/compare?urns=${urns}`, { useCache: false, showLoading: 'comparison' });
    return data;
}

async function loadRankings() {
    const area = elements.rankingArea.value;
    const metric = elements.rankingMetric.value;
    const year = elements.rankingYear.value;
    
    let endpoint = `/api/rankings?metric=${metric}&limit=20`;
    if (year) endpoint += `&year=${year}`;
    if (area) endpoint += `&local_authority=${encodeURIComponent(area)}`;
    
    const data = await fetchAPI(endpoint, { useCache: false, showLoading: 'rankings' });
    
    if (!data) {
        showEmptyState(elements.rankingsList, 'Unable to load rankings');
        return;
    }
    
    renderRankings(data.rankings, metric);
}

// =============================================================================
// METRIC HELPERS
// =============================================================================

function getMetricLabel(key, short = false) {
    if (state.metrics) {
        const metric = state.metrics.find(m => m.key === key);
        if (metric) {
            return short ? metric.short_name : metric.name;
        }
    }
    // Fallback labels
    return key.replace(/_/g, ' ').replace(/\b\w/g, l => l.toUpperCase());
}

function formatMetricValue(value, metric) {
    if (value === null || value === undefined) return '-';
    
    const metricDef = state.metrics?.find(m => m.key === metric);
    const type = metricDef?.type || (metric.includes('pct') ? 'percentage' : 'score');
    
    if (metric.includes('progress')) {
        return (value >= 0 ? '+' : '') + value.toFixed(1);
    }
    if (type === 'percentage' || metric.includes('pct')) {
        return value.toFixed(0) + '%';
    }
    return value.toFixed(1);
}

// =============================================================================
// RENDER FUNCTIONS
// =============================================================================

function renderSchools(schools) {
    if (schools.length === 0) {
        const message = state.locationSearch.active 
            ? `No schools found within ${state.locationSearch.radius} miles of ${state.locationSearch.postcode}`
            : 'No primary schools found matching your criteria';
        showEmptyState(elements.schoolsGrid, message);
        return;
    }
    
    let html = schools.map(school => {
        const distanceBadge = school.distance !== undefined && school.distance !== null
            ? `<span class="distance-badge">${school.distance.toFixed(1)} mi</span>`
            : '';
        
        return `
            <div class="school-card" data-urn="${school.urn}">
                <h3 class="school-name">${escapeHtml(school.school_name)}${distanceBadge}</h3>
                <div class="school-meta">
                    <span class="school-tag">${escapeHtml(school.local_authority || '')}</span>
                    <span class="school-tag type">${escapeHtml(school.school_type || '')}</span>
                </div>
                <div class="school-address">${escapeHtml(school.address || '')}</div>
                <div class="school-stats">
                    <div class="stat">
                        <div class="stat-value">Primary</div>
                        <div class="stat-label">Phase</div>
                    </div>
                    <div class="stat">
                        <div class="stat-value">KS2</div>
                        <div class="stat-label">Data</div>
                    </div>
                </div>
            </div>
        `;
    }).join('');
    
    // Add pagination info
    if (state.pagination.totalPages > 1) {
        html += `
            <div class="pagination-info">
                <span>Showing ${schools.length} of ${state.pagination.total} schools</span>
                ${state.pagination.page < state.pagination.totalPages ? 
                    `<button class="btn-load-more" onclick="loadMoreSchools()">Load More</button>` : ''}
            </div>
        `;
    }
    
    elements.schoolsGrid.innerHTML = html;
    
    // Add click handlers
    elements.schoolsGrid.querySelectorAll('.school-card').forEach(card => {
        card.addEventListener('click', () => {
            const urn = parseInt(card.dataset.urn);
            openSchoolModal(urn);
        });
    });
}

async function loadMoreSchools() {
    state.pagination.page++;
    const params = new URLSearchParams();
    
    const search = elements.schoolSearch.value.trim();
    if (search) params.append('search', search);
    
    const localAuthority = elements.localAuthorityFilter.value;
    if (localAuthority) params.append('local_authority', localAuthority);
    
    const type = elements.typeFilter.value;
    if (type) params.append('school_type', type);
    
    params.append('page', state.pagination.page);
    params.append('page_size', state.pagination.pageSize);
    
    const data = await fetchAPI(`/api/schools?${params.toString()}`, { useCache: false });
    
    if (data && data.schools.length > 0) {
        state.schools = [...state.schools, ...data.schools];
        renderSchools(state.schools);
    }
}

function renderRankings(rankings, metric) {
    if (rankings.length === 0) {
        showEmptyState(elements.rankingsList, 'No ranking data available for this year/metric');
        return;
    }
    
    elements.rankingsList.innerHTML = rankings.map((school, index) => {
        const value = school[metric];
        if (value === null || value === undefined) return '';
        
        return `
            <div class="ranking-item" data-urn="${school.urn}">
                <div class="ranking-position ${index < 3 ? 'top-3' : ''}">${index + 1}</div>
                <div class="ranking-info">
                    <div class="ranking-name">${escapeHtml(school.school_name)}</div>
                    <div class="ranking-location">${escapeHtml(school.local_authority || '')}</div>
                </div>
                <div class="ranking-score">
                    <div class="ranking-score-value">${formatMetricValue(value, metric)}</div>
                    <div class="ranking-score-label">${getMetricLabel(metric, true)}</div>
                </div>
            </div>
        `;
    }).filter(Boolean).join('');
    
    // Add click handlers
    elements.rankingsList.querySelectorAll('.ranking-item').forEach(item => {
        item.addEventListener('click', () => {
            const urn = parseInt(item.dataset.urn);
            openSchoolModal(urn);
        });
    });
}

function renderSelectedSchools() {
    if (state.selectedSchools.length === 0) {
        elements.selectedSchools.innerHTML = `
            <div class="empty-selection">
                <div class="empty-icon">
                    <svg viewBox="0 0 48 48" fill="none" stroke="currentColor" stroke-width="1.5">
                        <rect x="6" y="10" width="36" height="28" rx="2"/>
                        <path d="M6 18h36"/>
                        <circle cx="14" cy="14" r="2" fill="currentColor"/>
                        <circle cx="22" cy="14" r="2" fill="currentColor"/>
                    </svg>
                </div>
                <p>Search and add schools to compare</p>
            </div>
        `;
        elements.chartsSection.style.display = 'none';
        return;
    }
    
    elements.selectedSchools.innerHTML = state.selectedSchools.map((school, index) => `
        <div class="selected-school-tag" style="border-left: 3px solid ${CHART_COLORS[index % CHART_COLORS.length]}">
            <span>${escapeHtml(school.school_name)}</span>
            <button class="remove" data-urn="${school.urn}" title="Remove">
                <svg viewBox="0 0 16 16" width="12" height="12" fill="none" stroke="currentColor" stroke-width="2">
                    <path d="M12 4L4 12M4 4l8 8"/>
                </svg>
            </button>
        </div>
    `).join('');
    
    // Add remove handlers
    elements.selectedSchools.querySelectorAll('.remove').forEach(btn => {
        btn.addEventListener('click', (e) => {
            e.stopPropagation();
            const urn = parseInt(btn.dataset.urn);
            removeFromComparison(urn);
        });
    });
    
    elements.chartsSection.style.display = 'block';
    updateComparisonChart();
}

async function updateComparisonChart() {
    if (state.selectedSchools.length === 0) return;
    
    const data = await loadComparison();
    if (!data) return;
    
    const metric = elements.metricSelect.value;
    
    // Prepare chart data
    const datasets = [];
    const allYears = new Set();
    
    state.selectedSchools.forEach((school, index) => {
        const schoolData = data.comparison[school.urn];
        if (!schoolData) return;
        
        const yearlyData = schoolData.yearly_data;
        yearlyData.forEach(d => allYears.add(d.year));
        
        const sortedData = yearlyData.sort((a, b) => a.year - b.year);
        
        datasets.push({
            label: schoolData.school_info.school_name,
            data: sortedData.map(d => ({ x: d.year, y: d[metric] })),
            borderColor: CHART_COLORS[index % CHART_COLORS.length],
            backgroundColor: CHART_COLORS[index % CHART_COLORS.length] + '20',
            borderWidth: 3,
            pointRadius: 5,
            pointHoverRadius: 7,
            tension: 0.3,
            fill: false,
        });
    });
    
    const years = Array.from(allYears).sort();
    
    // Destroy existing chart
    if (comparisonChart) {
        comparisonChart.destroy();
    }
    
    // Create new chart
    const ctx = elements.comparisonChart.getContext('2d');
    comparisonChart = new Chart(ctx, {
        type: 'line',
        data: {
            labels: years,
            datasets: datasets,
        },
        options: {
            responsive: true,
            maintainAspectRatio: true,
            aspectRatio: 2,
            plugins: {
                legend: {
                    position: 'bottom',
                    labels: {
                        font: { family: "'DM Sans', sans-serif", size: 12 },
                        padding: 20,
                        usePointStyle: true,
                    },
                },
                title: {
                    display: true,
                    text: getMetricLabel(metric),
                    font: { family: "'Playfair Display', serif", size: 18, weight: 600 },
                    padding: { bottom: 20 },
                },
                tooltip: {
                    backgroundColor: '#1a1612',
                    titleFont: { family: "'DM Sans', sans-serif" },
                    bodyFont: { family: "'DM Sans', sans-serif" },
                    padding: 12,
                    cornerRadius: 8,
                },
            },
            scales: {
                x: {
                    title: {
                        display: true,
                        text: 'Academic Year',
                        font: { family: "'DM Sans', sans-serif", weight: 500 },
                    },
                    grid: { display: false },
                },
                y: {
                    title: {
                        display: true,
                        text: getMetricLabel(metric),
                        font: { family: "'DM Sans', sans-serif", weight: 500 },
                    },
                    grid: { color: '#e5dfd5' },
                },
            },
            interaction: {
                intersect: false,
                mode: 'index',
            },
        },
    });
    
    // Update comparison table
    updateComparisonTable(data.comparison, metric, years);
}

function updateComparisonTable(comparison, metric, years) {
    const lastYear = years[years.length - 1];
    const prevYear = years.length > 1 ? years[years.length - 2] : null;
    
    // Build header with explicit year ranges
    let headerHtml = '<th>School</th>';
    years.forEach(year => {
        headerHtml += `<th>${year}</th>`;
    });
    if (prevYear) {
        headerHtml += `<th title="Change from ${prevYear} to ${lastYear}">Δ 1yr</th>`;
    }
    if (years.length > 2) {
        headerHtml += `<th title="Standard deviation of scores (lower = more consistent)">Variability</th>`;
    }
    elements.tableHeader.innerHTML = headerHtml;
    
    // Build body
    let bodyHtml = '';
    state.selectedSchools.forEach((school, index) => {
        const schoolData = comparison[school.urn];
        if (!schoolData) return;
        
        const yearlyMap = {};
        schoolData.yearly_data.forEach(d => {
            yearlyMap[d.year] = d[metric];
        });
        
        const lastValue = yearlyMap[lastYear];
        const prevValue = prevYear ? yearlyMap[prevYear] : null;
        
        // Calculate 1-year change
        const oneYearChange = prevValue != null && lastValue != null ? (lastValue - prevValue) : null;
        const oneYearChangeStr = oneYearChange !== null ? oneYearChange.toFixed(1) : 'N/A';
        const oneYearClass = oneYearChange !== null ? (oneYearChange >= 0 ? 'positive' : 'negative') : '';
        
        // Calculate variability (standard deviation)
        const values = years.map(y => yearlyMap[y]).filter(v => v != null && v !== 0);
        let variabilityStr = 'N/A';
        if (values.length >= 2) {
            const mean = values.reduce((a, b) => a + b, 0) / values.length;
            const squaredDiffs = values.map(v => Math.pow(v - mean, 2));
            const variance = squaredDiffs.reduce((a, b) => a + b, 0) / values.length;
            const stdDev = Math.sqrt(variance);
            variabilityStr = '±' + stdDev.toFixed(1);
        }
        
        const color = CHART_COLORS[index % CHART_COLORS.length];
        
        bodyHtml += `<tr>`;
        bodyHtml += `<td><strong style="border-left: 3px solid ${color}; padding-left: 8px;">${escapeHtml(schoolData.school_info.school_name)}</strong></td>`;
        years.forEach(year => {
            const value = yearlyMap[year];
            bodyHtml += `<td>${value != null ? formatMetricValue(value, metric) : '-'}</td>`;
        });
        if (prevYear) {
            bodyHtml += `<td class="${oneYearClass}">${oneYearChangeStr !== 'N/A' ? (oneYearChange >= 0 ? '+' : '') + oneYearChangeStr : oneYearChangeStr}</td>`;
        }
        if (years.length > 2) {
            bodyHtml += `<td>${variabilityStr}</td>`;
        }
        bodyHtml += `</tr>`;
    });
    elements.tableBody.innerHTML = bodyHtml;
}

async function openSchoolModal(urn) {
    // Show loading state immediately
    elements.modal.classList.add('active');
    document.body.style.overflow = 'hidden';
    elements.modalStats.innerHTML = '<div class="loading"><div class="loading-spinner"></div><p>Loading school data...</p></div>';
    elements.modalSchoolName.textContent = 'Loading...';
    elements.modalMeta.innerHTML = '';
    
    const data = await loadSchoolDetails(urn);
    if (!data) {
        elements.modalStats.innerHTML = '<div class="empty-state"><p>Unable to load school data</p></div>';
        return;
    }
    
    state.currentSchoolData = data;
    
    elements.modalSchoolName.textContent = data.school_info.school_name;
    elements.modalMeta.innerHTML = `
        <span class="school-tag">${escapeHtml(data.school_info.local_authority || '')}</span>
        <span class="school-tag type">${escapeHtml(data.school_info.school_type || '')}</span>
        <span class="school-tag">Primary</span>
    `;
    
    // Get latest year data with actual results
    const sortedData = data.yearly_data.sort((a, b) => b.year - a.year);
    const latest = sortedData.find(d => d.rwm_expected_pct !== null) || sortedData[0];
    
    elements.modalStats.innerHTML = `
        <div class="modal-stats-section">
            <h4>KS2 Results (${latest.year})</h4>
            <div class="modal-stats-grid">
                <div class="modal-stat">
                    <div class="modal-stat-value">${formatMetricValue(latest.rwm_expected_pct, 'rwm_expected_pct')}</div>
                    <div class="modal-stat-label">RWM Expected</div>
                </div>
                <div class="modal-stat">
                    <div class="modal-stat-value">${formatMetricValue(latest.rwm_high_pct, 'rwm_high_pct')}</div>
                    <div class="modal-stat-label">RWM Higher</div>
                </div>
                <div class="modal-stat">
                    <div class="modal-stat-value">${formatMetricValue(latest.gps_expected_pct, 'gps_expected_pct')}</div>
                    <div class="modal-stat-label">GPS Expected</div>
                </div>
                <div class="modal-stat">
                    <div class="modal-stat-value">${formatMetricValue(latest.science_expected_pct, 'science_expected_pct')}</div>
                    <div class="modal-stat-label">Science Expected</div>
                </div>
            </div>
        </div>
        <div class="modal-stats-section">
            <h4>Progress Scores</h4>
            <div class="modal-stats-grid">
                <div class="modal-stat">
                    <div class="modal-stat-value ${getProgressClass(latest.reading_progress)}">${formatMetricValue(latest.reading_progress, 'reading_progress')}</div>
                    <div class="modal-stat-label">Reading</div>
                </div>
                <div class="modal-stat">
                    <div class="modal-stat-value ${getProgressClass(latest.writing_progress)}">${formatMetricValue(latest.writing_progress, 'writing_progress')}</div>
                    <div class="modal-stat-label">Writing</div>
                </div>
                <div class="modal-stat">
                    <div class="modal-stat-value ${getProgressClass(latest.maths_progress)}">${formatMetricValue(latest.maths_progress, 'maths_progress')}</div>
                    <div class="modal-stat-label">Maths</div>
                </div>
            </div>
        </div>
        <div class="modal-stats-section">
            <h4>School Context</h4>
            <div class="modal-stats-grid">
                <div class="modal-stat">
                    <div class="modal-stat-value">${latest.total_pupils || '-'}</div>
                    <div class="modal-stat-label">Total Pupils</div>
                </div>
                <div class="modal-stat">
                    <div class="modal-stat-value">${formatMetricValue(latest.disadvantaged_pct, 'disadvantaged_pct')}</div>
                    <div class="modal-stat-label">% Disadvantaged</div>
                </div>
                <div class="modal-stat">
                    <div class="modal-stat-value">${formatMetricValue(latest.eal_pct, 'eal_pct')}</div>
                    <div class="modal-stat-label">% EAL</div>
                </div>
                <div class="modal-stat">
                    <div class="modal-stat-value">${formatMetricValue(latest.sen_support_pct, 'sen_support_pct')}</div>
                    <div class="modal-stat-label">% SEN Support</div>
                </div>
            </div>
        </div>
    `;
    
    function getProgressClass(value) {
        if (value === null || value === undefined) return '';
        return value >= 0 ? 'positive' : 'negative';
    }
    
    // Create chart
    if (schoolDetailChart) {
        schoolDetailChart.destroy();
    }
    
    const validData = sortedData.filter(d => d.rwm_expected_pct !== null).reverse();
    const years = validData.map(d => d.year);
    const ctx = elements.schoolDetailChart.getContext('2d');
    
    schoolDetailChart = new Chart(ctx, {
        type: 'bar',
        data: {
            labels: years,
            datasets: [
                {
                    label: 'Reading %',
                    data: validData.map(d => d.reading_expected_pct),
                    backgroundColor: '#2d7d7d',
                    borderRadius: 4,
                },
                {
                    label: 'Writing %',
                    data: validData.map(d => d.writing_expected_pct),
                    backgroundColor: '#c9a227',
                    borderRadius: 4,
                },
                {
                    label: 'Maths %',
                    data: validData.map(d => d.maths_expected_pct),
                    backgroundColor: '#e07256',
                    borderRadius: 4,
                },
            ],
        },
        options: {
            responsive: true,
            maintainAspectRatio: true,
            aspectRatio: 2,
            plugins: {
                legend: {
                    position: 'bottom',
                    labels: {
                        font: { family: "'DM Sans', sans-serif" },
                        usePointStyle: true,
                    },
                },
                title: {
                    display: true,
                    text: 'KS2 Attainment Over Time (% meeting expected standard)',
                    font: { family: "'Playfair Display', serif", size: 16, weight: 600 },
                },
            },
            scales: {
                y: {
                    beginAtZero: true,
                    max: 100,
                    grid: { color: '#e5dfd5' },
                },
                x: {
                    grid: { display: false },
                },
            },
        },
    });
    
    // Update add to compare button
    const isSelected = state.selectedSchools.some(s => s.urn === data.school_info.urn);
    elements.addToCompare.textContent = isSelected ? 'Remove from Compare' : 'Add to Compare';
    elements.addToCompare.dataset.urn = data.school_info.urn;
}

function closeModal() {
    elements.modal.classList.remove('active');
    document.body.style.overflow = '';
    state.currentSchoolData = null;
}

function addToComparison(school) {
    if (state.selectedSchools.some(s => s.urn === school.urn)) return;
    if (state.selectedSchools.length >= 5) {
        alert('Maximum 5 schools can be compared at once');
        return;
    }
    
    state.selectedSchools.push(school);
    renderSelectedSchools();
}

function removeFromComparison(urn) {
    state.selectedSchools = state.selectedSchools.filter(s => s.urn !== urn);
    renderSelectedSchools();
}

function showEmptyState(container, message) {
    container.innerHTML = `
        <div class="empty-state">
            <svg viewBox="0 0 48 48" fill="none" stroke="currentColor" stroke-width="1.5">
                <circle cx="24" cy="24" r="20"/>
                <path d="M16 20h16M16 28h10"/>
            </svg>
            <p>${escapeHtml(message)}</p>
        </div>
    `;
}

function escapeHtml(text) {
    if (!text) return '';
    const div = document.createElement('div');
    div.textContent = text;
    return div.innerHTML;
}

// =============================================================================
// EVENT LISTENERS
// =============================================================================

function setupEventListeners() {
    // Navigation
    document.querySelectorAll('.nav-link').forEach(link => {
        link.addEventListener('click', (e) => {
            e.preventDefault();
            const view = link.dataset.view;
            const path = view === 'dashboard' ? '/' : `/${view}`;
            navigateTo(path);
        });
    });
    
    // Search and filters
    let searchTimeout;
    elements.schoolSearch.addEventListener('input', () => {
        clearTimeout(searchTimeout);
        state.pagination.page = 1; // Reset to first page on new search
        searchTimeout = setTimeout(loadSchools, 300);
    });
    
    elements.localAuthorityFilter.addEventListener('change', () => {
        state.pagination.page = 1;
        loadSchools();
    });
    elements.typeFilter.addEventListener('change', () => {
        state.pagination.page = 1;
        loadSchools();
    });
    
    // Location search
    if (elements.locationSearchBtn) {
        elements.locationSearchBtn.addEventListener('click', searchByLocation);
    }
    if (elements.clearLocationBtn) {
        elements.clearLocationBtn.addEventListener('click', clearLocationSearch);
    }
    if (elements.postcodeSearch) {
        elements.postcodeSearch.addEventListener('keydown', (e) => {
            if (e.key === 'Enter') {
                e.preventDefault();
                searchByLocation();
            }
        });
    }
    
    // Compare search
    let compareSearchTimeout;
    let lastCompareSearchData = null;
    
    function renderCompareResults(data) {
        if (!data) return;
        lastCompareSearchData = data;
        
        const results = data.schools.filter(s => !state.selectedSchools.some(sel => sel.urn === s.urn));
        
        const headerHtml = `
            <div class="compare-results-header">
                <span>${results.length} school${results.length !== 1 ? 's' : ''} found</span>
                <button class="compare-results-close" title="Close (Esc)">
                    <svg viewBox="0 0 16 16" width="14" height="14" fill="none" stroke="currentColor" stroke-width="2">
                        <path d="M12 4L4 12M4 4l8 8"/>
                    </svg>
                </button>
            </div>
        `;
        
        if (results.length === 0) {
            elements.compareResults.innerHTML = headerHtml + '<div class="compare-result-item"><span class="name">No more schools to add</span></div>';
        } else {
            elements.compareResults.innerHTML = headerHtml + results.slice(0, 10).map(school => `
                <div class="compare-result-item" data-urn="${school.urn}" data-name="${escapeHtml(school.school_name)}">
                    <div class="name">${escapeHtml(school.school_name)}</div>
                    <div class="location">${escapeHtml(school.local_authority || '')}${school.postcode ? ' • ' + escapeHtml(school.postcode) : ''}</div>
                </div>
            `).join('');
            
            elements.compareResults.querySelectorAll('.compare-result-item').forEach(item => {
                item.addEventListener('click', () => {
                    const urn = parseInt(item.dataset.urn);
                    const school = data.schools.find(s => s.urn === urn);
                    if (school) {
                        addToComparison(school);
                        renderCompareResults(data);
                    }
                });
            });
        }
        
        // Add close button handler
        const closeBtn = elements.compareResults.querySelector('.compare-results-close');
        if (closeBtn) {
            closeBtn.addEventListener('click', () => {
                elements.compareResults.classList.remove('active');
                elements.compareSearch.value = '';
            });
        }
    }
    
    elements.compareSearch.addEventListener('input', async () => {
        clearTimeout(compareSearchTimeout);
        const query = elements.compareSearch.value.trim();
        
        if (query.length < 2) {
            elements.compareResults.classList.remove('active');
            return;
        }
        
        compareSearchTimeout = setTimeout(async () => {
            const data = await fetchAPI(`/api/schools?search=${encodeURIComponent(query)}`, { useCache: false });
            if (!data) return;
            
            renderCompareResults(data);
            elements.compareResults.classList.add('active');
        }, 300);
    });
    
    elements.compareSearch.addEventListener('focus', () => {
        if (elements.compareSearch.value.trim().length >= 2 && lastCompareSearchData) {
            renderCompareResults(lastCompareSearchData);
            elements.compareResults.classList.add('active');
        }
    });
    
    // Metric selector
    elements.metricSelect.addEventListener('change', updateComparisonChart);
    
    // Rankings
    elements.rankingArea.addEventListener('change', loadRankings);
    elements.rankingMetric.addEventListener('change', loadRankings);
    elements.rankingYear.addEventListener('change', loadRankings);
    
    // Modal
    elements.modalClose.addEventListener('click', closeModal);
    elements.modal.querySelector('.modal-backdrop').addEventListener('click', closeModal);
    
    elements.addToCompare.addEventListener('click', () => {
        if (!state.currentSchoolData) return;
        
        const urn = state.currentSchoolData.school_info.urn;
        const isSelected = state.selectedSchools.some(s => s.urn === urn);
        
        if (isSelected) {
            removeFromComparison(urn);
            elements.addToCompare.textContent = 'Add to Compare';
        } else {
            addToComparison(state.currentSchoolData.school_info);
            elements.addToCompare.textContent = 'Remove from Compare';
        }
    });
    
    // Keyboard
    document.addEventListener('keydown', (e) => {
        if (e.key === 'Escape') {
            if (elements.compareResults.classList.contains('active')) {
                elements.compareResults.classList.remove('active');
                elements.compareSearch.value = '';
                return;
            }
            closeModal();
        }
    });
}