let bgChart = null;
let bgReferenceData = null;
let bgContinuumData = null;

async function loadBgReference() {
    try {
        const resp = await fetch(`${API_BASE}/api/background/reference`);
        if (!resp.ok) return;
        bgReferenceData = await resp.json();
    } catch {}
}

async function loadBgContinuum(cps, liveTime) {
    try {
        const resp = await fetch(`${API_BASE}/api/background/continuum?cps=${cps}&live_time_s=${liveTime}`);
        if (!resp.ok) return;
        bgContinuumData = await resp.json();
    } catch {}
}

/**
 * Gaussian kernel smoothing.
 * Convolves the data with a Gaussian kernel of given sigma (in channels).
 * Preserves peak shapes while reducing statistical variation.
 */
function smoothGaussian(data, sigma) {
    if (!data || data.length === 0) return data;
    const kernelRadius = Math.ceil(sigma * 3);
    const kernel = [];
    for (let i = -kernelRadius; i <= kernelRadius; i++) {
        kernel.push(Math.exp(-0.5 * (i / sigma) ** 2));
    }

    const result = new Array(data.length);
    for (let i = 0; i < data.length; i++) {
        let sum = 0;
        let wSum = 0;
        for (let k = -kernelRadius; k <= kernelRadius; k++) {
            const idx = i + k;
            if (idx < 0 || idx >= data.length) continue;
            const w = kernel[k + kernelRadius];
            sum += data[idx] * w;
            wSum += w;
        }
        result[i] = wSum > 0 ? sum / wSum : 0;
    }
    return result;
}

async function refreshBackground() {
    try {
        const [infoResp, specResp] = await Promise.all([
            fetch(`${API_BASE}/api/background`),
            fetch(`${API_BASE}/api/background/spectrum`)
        ]);

        if (!infoResp.ok || !specResp.ok) {
            document.getElementById('bg-stats').innerHTML = '<p style="color:#888">Background non disponible</p>';
            return;
        }

        const info = await infoResp.json();
        const spec = await specResp.json();

        // Stats
        document.getElementById('bg-stats').innerHTML = `
            <div class="bg-stat"><div class="bg-stat-value">${info.elapsed_hours.toFixed(1)}h</div><div class="bg-stat-label">Durée</div></div>
            <div class="bg-stat"><div class="bg-stat-value">${info.live_time_s.toFixed(0)}s</div><div class="bg-stat-label">Live time</div></div>
            <div class="bg-stat"><div class="bg-stat-value">${info.total_counts.toFixed(0)}</div><div class="bg-stat-label">Coups</div></div>
            <div class="bg-stat"><div class="bg-stat-value">${info.cps.toFixed(2)}</div><div class="bg-stat-label">CPS</div></div>
        `;

        // Load continuum on first load
        if (!bgContinuumData && spec.live_time_s > 0) {
            await loadBgContinuum(info.cps || 6.0, spec.live_time_s);
        }

        // Chart
        updateBackgroundChart(spec);

        // Peaks table
        updatePeaksTable(info.top_peaks || []);

        // Show/hide toggles
        const refToggle = document.getElementById('show-bg-reference');
        if (refToggle) refToggle.parentElement.style.display = spec.reference_available ? 'flex' : 'none';
    } catch {}
}

function updateBackgroundChart(spec) {
 const showLog = document.getElementById('bg-scale-log')?.checked;
    const ctx = document.getElementById('background-chart').getContext('2d');
    const showRef = document.getElementById('show-bg-reference')?.checked && bgReferenceData;
    const showSmooth = document.getElementById('show-bg-smooth')?.checked;
    const showContinuum = document.getElementById('show-bg-continuum')?.checked && bgContinuumData;

    const datasets = [{
        label: 'Background (live)',
        data: spec.counts,
        borderColor: '#ff9800',
        backgroundColor: 'rgba(255, 152, 0, 0.1)',
        borderWidth: 1,
        pointRadius: 0,
        fill: true,
    }];

    if (showSmooth) {
        const smoothed = smoothGaussian(spec.counts, 8);
        datasets.push({
            label: 'Lissé',
            data: smoothed,
            borderColor: 'rgba(233, 30, 99, 0.9)',
            backgroundColor: 'rgba(233, 30, 99, 0.05)',
            borderWidth: 2,
            pointRadius: 0,
            fill: false,
        });
    }

    if (showContinuum) {
        datasets.push({
            label: 'Continuum',
            data: bgContinuumData.counts,
            borderColor: 'rgba(156, 39, 176, 0.8)',
            backgroundColor: 'rgba(156, 39, 176, 0.05)',
            borderWidth: 2,
            pointRadius: 0,
            fill: false,
            borderDash: [8, 4],
        });
    }

    if (showRef) {
        const scale = spec.live_time_s > 0 && bgReferenceData.live_time_s > 0
            ? spec.live_time_s / bgReferenceData.live_time_s
            : 1;
        datasets.push({
            label: `Référence 24h (×${scale.toFixed(1)})`,
            data: bgReferenceData.counts.map(c => c * scale),
            borderColor: 'rgba(79, 195, 247, 0.8)',
            backgroundColor: 'rgba(79, 195, 247, 0.08)',
            borderWidth: 1,
            pointRadius: 0,
            fill: true,
            borderDash: [4, 2],
        });
    }

    const chartData = {
        labels: spec.energy_kev,
        datasets: datasets,
    };

    const options = {
        responsive: true,
        maintainAspectRatio: false,
        interaction: { mode: 'index', intersect: false },
        plugins: {
            legend: { labels: { color: '#e0e0e0' } },
            tooltip: {
                enabled: true,
                mode: 'index',
                intersect: false,
                filter: (item) => item.raw != null,
                callbacks: {
                    title: (items) => `${spec.energy_kev[items[0].dataIndex]} keV`,
                    label: (item) => `${item.dataset.label}: ${item.raw.toFixed(1)} counts`
                }
            },
            zoom: {
                pan: {
                    enabled: true,
                    mode: 'x',
                    modifierKey: null,
                },
                zoom: {
                    wheel: { enabled: true },
                    pinch: { enabled: true },
                    drag: { enabled: false },
                    mode: 'x',
                    limits: { x: { min: 30, max: 3000 } },
                    onZoom: () => { document.getElementById('reset-zoom-bg').style.display = 'inline-block'; }
                }
            }
        },
        scales: {
            x: {
                type: 'linear',
                title: { display: true, text: 'Énergie (keV)', color: '#888' },
                ticks: { color: '#888', maxTicksLimit: 20 },
                grid: { color: '#333' },
            },
            y: {
                type: showLog ? 'logarithmic' : 'linear',
                title: { display: true, text: `Comptages (${showLog ? 'log' : 'lin'})`, color: '#888' },
                ...(showLog ? { min: 0.9 } : {}),
                ticks: { color: '#888' },
                grid: { color: '#333' },
            }
        }
    };

 if (bgChart) {
        bgChart.data = chartData;
        bgChart.options = options;
        bgChart.update();
    } else {
        bgChart = new Chart(ctx, { type: 'line', data: chartData, ...options });
    }
}

function updatePeaksTable(peaks) {
    const container = document.getElementById('peaks-table');
    if (!peaks || peaks.length === 0) {
        container.innerHTML = '<p style="color:#888;text-align:center;padding:8px;">Pas assez de données pour identifier les pics</p>';
        return;
    }

    let html = '<h3 style="margin-bottom:8px;color:#ff9800;">Pics détectés</h3>';
    peaks.forEach(p => {
        html += `<div class="peak-row">
            <span style="color:#4fc3f7">${p.energy_kev.toFixed(1)} keV</span>
            <span>${p.counts.toFixed(0)} cts</span>
        </div>`;
    });
    container.innerHTML = html;
}

document.querySelector('[data-tab="background"]').addEventListener('click', () => {
    refreshBackground();
    loadBgReference();
});

// Toggle handlers
document.getElementById('show-bg-reference')?.addEventListener('change', () => refreshBackground());
document.getElementById('show-bg-continuum')?.addEventListener('change', () => {
    if (document.getElementById('show-bg-continuum').checked && !bgContinuumData) {
        loadBgContinuum(6.0, 3600).then(() => refreshBackground());
    } else {
        refreshBackground();
    }
});
document.getElementById('show-bg-smooth')?.addEventListener('change', () => refreshBackground());
document.getElementById('bg-scale-log')?.addEventListener('change', () => refreshBackground());

// Reset zoom button
document.getElementById('reset-zoom-bg')?.addEventListener('click', () => {
    if (bgChart) {
        bgChart.resetZoom();
        document.getElementById('reset-zoom-bg').style.display = 'none';
    }
});

// Show/hide reset button based on zoom state — wrapped via options plugin
const _origBgOptions = options => options;