/**
 * Performance charts — real-time CPU, RAM, GPU usage with Chart.js.
 */

import { API_BASE, getHeaders } from '../core/api.js';
import { t } from '../core/i18n.js';
import { dashboardPollInterval } from '../core/state.js';

const MAX_SAMPLES = 60;
const STORAGE_KEY = 'perf_history';

let _pollTimer = null;
let _charts = {};     // { cpu: Chart, ram: Chart, gpu: Chart }
let _history = _loadHistory();
let _hasGpu = null;   // null = unknown, true/false after first fetch

function _loadHistory() {
    try {
        const raw = sessionStorage.getItem(STORAGE_KEY);
        if (raw) {
            const parsed = JSON.parse(raw);
            if (parsed.cpu && parsed.ram && parsed.gpu) return parsed;
        }
    } catch {}
    return { cpu: [], ram: [], gpu: [] };
}

function _saveHistory() {
    try { sessionStorage.setItem(STORAGE_KEY, JSON.stringify(_history)); }
    catch {}
}

/** Returns the static HTML for the perf section (canvas placeholders). */
export function renderPerfSection() {
    return `<div class="perf-charts-grid">
        <div class="perf-chart-card">
            <div class="perf-chart-header">
                <span class="perf-chart-label">${t('dashboard.perf.cpu')}</span>
                <span class="perf-chart-value cpu" id="perf-cpu-value">-</span>
            </div>
            <div class="perf-chart-wrap"><canvas id="perf-chart-cpu"></canvas></div>
        </div>
        <div class="perf-chart-card">
            <div class="perf-chart-header">
                <span class="perf-chart-label">${t('dashboard.perf.ram')}</span>
                <span class="perf-chart-value ram" id="perf-ram-value">-</span>
            </div>
            <div class="perf-chart-wrap"><canvas id="perf-chart-ram"></canvas></div>
        </div>
        <div class="perf-chart-card" id="perf-gpu-card">
            <div class="perf-chart-header">
                <span class="perf-chart-label">${t('dashboard.perf.gpu')}</span>
                <span class="perf-chart-value gpu" id="perf-gpu-value">-</span>
            </div>
            <div class="perf-chart-wrap"><canvas id="perf-chart-gpu"></canvas></div>
        </div>
    </div>`;
}

function _createChart(canvasId, color, fillColor) {
    const ctx = document.getElementById(canvasId);
    if (!ctx) return null;
    return new Chart(ctx, {
        type: 'line',
        data: {
            labels: Array(MAX_SAMPLES).fill(''),
            datasets: [{
                data: [],
                borderColor: color,
                backgroundColor: fillColor,
                borderWidth: 1.5,
                tension: 0.3,
                fill: true,
                pointRadius: 0,
            }],
        },
        options: {
            responsive: true,
            maintainAspectRatio: false,
            animation: false,
            plugins: { legend: { display: false }, tooltip: { enabled: false } },
            scales: {
                x: { display: false },
                y: { min: 0, max: 100, display: false },
            },
            layout: { padding: 0 },
        },
    });
}

/** Initialize Chart.js instances on the already-mounted canvases. */
export function initPerfCharts() {
    _destroyCharts();
    _charts.cpu = _createChart('perf-chart-cpu', '#2196F3', 'rgba(33,150,243,0.15)');
    _charts.ram = _createChart('perf-chart-ram', '#4CAF50', 'rgba(76,175,80,0.15)');
    _charts.gpu = _createChart('perf-chart-gpu', '#FF9800', 'rgba(255,152,0,0.15)');
    // Restore any existing history data into the freshly created charts
    for (const key of ['cpu', 'ram', 'gpu']) {
        if (_charts[key] && _history[key].length > 0) {
            _charts[key].data.datasets[0].data = [..._history[key]];
            _charts[key].data.labels = _history[key].map(() => '');
            _charts[key].update();
        }
    }
}

function _destroyCharts() {
    for (const key of Object.keys(_charts)) {
        if (_charts[key]) { _charts[key].destroy(); _charts[key] = null; }
    }
}

function _pushSample(key, value) {
    _history[key].push(value);
    if (_history[key].length > MAX_SAMPLES) _history[key].shift();
    const chart = _charts[key];
    if (!chart) return;
    chart.data.datasets[0].data = [..._history[key]];
    chart.data.labels = _history[key].map(() => '');
    chart.update();
}

async function _fetchPerformance() {
    try {
        const resp = await fetch(`${API_BASE}/system/performance`, { headers: getHeaders() });
        if (!resp.ok) return;
        const data = await resp.json();

        // CPU
        _pushSample('cpu', data.cpu_percent);
        const cpuEl = document.getElementById('perf-cpu-value');
        if (cpuEl) cpuEl.textContent = `${data.cpu_percent.toFixed(0)}%`;

        // RAM
        _pushSample('ram', data.ram_percent);
        const ramEl = document.getElementById('perf-ram-value');
        if (ramEl) {
            const usedGb = (data.ram_used_mb / 1024).toFixed(1);
            const totalGb = (data.ram_total_mb / 1024).toFixed(1);
            ramEl.textContent = `${usedGb}/${totalGb} GB`;
        }

        // GPU
        if (data.gpu) {
            _hasGpu = true;
            _pushSample('gpu', data.gpu.utilization);
            const gpuEl = document.getElementById('perf-gpu-value');
            if (gpuEl) gpuEl.textContent = `${data.gpu.utilization.toFixed(0)}% · ${data.gpu.temperature_c}°C`;
        } else if (_hasGpu === null) {
            _hasGpu = false;
            const card = document.getElementById('perf-gpu-card');
            if (card) {
                const canvas = card.querySelector('canvas');
                if (canvas) canvas.style.display = 'none';
                const noGpu = document.createElement('div');
                noGpu.className = 'perf-chart-unavailable';
                noGpu.textContent = t('dashboard.perf.unavailable');
                card.appendChild(noGpu);
            }
        }

        _saveHistory();
    } catch {
        // Silently ignore fetch errors (e.g., network issues, tab hidden)
    }
}

export function startPerfPolling() {
    if (_pollTimer) return;
    _fetchPerformance();
    _pollTimer = setInterval(_fetchPerformance, dashboardPollInterval);
}

export function stopPerfPolling() {
    if (_pollTimer) {
        clearInterval(_pollTimer);
        _pollTimer = null;
    }
    _saveHistory();
}