// log-panel.js — Log ring buffer DOM rendering, filter, auto-scroll
// 對齊 Design Spec v2.1 control-panel.md §4.4-4.5

const MAX_LINES = 2000;
const buffer = []; // [{ts, level, stream, line}]
let autoScroll = true;
let filterText = '';
let filterLevel = '';

// ---------- init ----------
export function initLogPanel(existing) {
    buffer.length = 0;
    if (Array.isArray(existing)) {
        for (const line of existing) buffer.push(line);
    }
    renderAll();
    updateLineCount();

    const output = document.getElementById('log-output');
    if (output) {
        output.addEventListener('scroll', () => {
            const nearBottom = output.scrollTop + output.clientHeight >= output.scrollHeight - 30;
            if (!nearBottom) {
                autoScroll = false;
                const jumpBtn = document.getElementById('btn-jump-latest');
                if (jumpBtn) jumpBtn.removeAttribute('hidden');
            } else {
                autoScroll = true;
                const jumpBtn = document.getElementById('btn-jump-latest');
                if (jumpBtn) jumpBtn.setAttribute('hidden', '');
            }
        });
    }

    const jumpBtn = document.getElementById('btn-jump-latest');
    if (jumpBtn) {
        jumpBtn.addEventListener('click', () => {
            autoScroll = true;
            const el = document.getElementById('log-output');
            if (el) el.scrollTop = el.scrollHeight;
            jumpBtn.setAttribute('hidden', '');
        });
    }

    const followCb = document.getElementById('cb-follow-tail');
    if (followCb) {
        followCb.addEventListener('change', (e) => {
            autoScroll = e.target.checked;
            if (autoScroll) scrollToBottom();
        });
    }
    const tsCb = document.getElementById('cb-show-ts');
    if (tsCb) {
        tsCb.addEventListener('change', () => renderAll());
    }
}

// ---------- append from event ----------
export function appendLogs(entries) {
    for (const e of entries) {
        buffer.push(e);
    }
    // ring buffer 裁切
    if (buffer.length > MAX_LINES) {
        buffer.splice(0, buffer.length - MAX_LINES);
    }
    renderAppend(entries);
    updateLineCount();
    if (autoScroll) scrollToBottom();
}

export function clearLog() {
    buffer.length = 0;
    const output = document.getElementById('log-output');
    if (output) output.innerHTML = '';
    updateLineCount();
}

// ---------- filter ----------
export function applyLogFilter(opts) {
    if (opts.text !== undefined) filterText = opts.text.toLowerCase();
    if (opts.level !== undefined) filterLevel = opts.level.toLowerCase();
    renderAll();
}

function matches(entry) {
    if (filterLevel && (entry.level || '').toLowerCase() !== filterLevel) return false;
    if (filterText && !((entry.line || '').toLowerCase().includes(filterText))) return false;
    return true;
}

// ---------- render ----------
function renderAll() {
    const output = document.getElementById('log-output');
    if (!output) return;
    output.innerHTML = '';
    const showTs = document.getElementById('cb-show-ts')?.checked !== false;
    const frag = document.createDocumentFragment();
    for (const e of buffer) {
        if (!matches(e)) continue;
        frag.appendChild(buildLine(e, showTs));
    }
    output.appendChild(frag);
    if (autoScroll) scrollToBottom();
}

function renderAppend(entries) {
    const output = document.getElementById('log-output');
    if (!output) return;
    const showTs = document.getElementById('cb-show-ts')?.checked !== false;
    const frag = document.createDocumentFragment();
    for (const e of entries) {
        if (!matches(e)) continue;
        frag.appendChild(buildLine(e, showTs));
    }
    output.appendChild(frag);

    // DOM 行數裁切（跟 ring buffer 同步）
    while (output.childElementCount > MAX_LINES) {
        output.removeChild(output.firstChild);
    }
}

function buildLine(entry, showTs) {
    const row = document.createElement('div');
    const level = (entry.level || '').toLowerCase();
    row.className = 'log-line level-' + (level || 'plain');

    let html = '';
    if (showTs && entry.ts) {
        const d = new Date(entry.ts);
        const hh = String(d.getHours()).padStart(2, '0');
        const mm = String(d.getMinutes()).padStart(2, '0');
        const ss = String(d.getSeconds()).padStart(2, '0');
        html += `<span class="log-ts">${hh}:${mm}:${ss}</span> `;
    }
    if (entry.level) {
        html += `<span class="log-level">${entry.level.toUpperCase().padEnd(5)}</span> `;
    }
    html += `<span class="log-msg"></span>`;
    row.innerHTML = html;
    row.querySelector('.log-msg').textContent = entry.line || '';
    return row;
}

function scrollToBottom() {
    const el = document.getElementById('log-output');
    if (el) el.scrollTop = el.scrollHeight;
}

function updateLineCount() {
    const el = document.getElementById('footer-lines');
    if (!el) return;
    el.textContent = `Lines: ${buffer.length} / ${MAX_LINES}`;
}

// ---------- 閃爍最後一條 ERROR ----------
export function flashLastError() {
    const output = document.getElementById('log-output');
    if (!output) return;
    // 找最後一條 ERROR row
    const errors = output.querySelectorAll('.log-line.level-error');
    if (errors.length === 0) {
        // fallback: 捲到最底
        scrollToBottom();
        return;
    }
    const target = errors[errors.length - 1];
    target.scrollIntoView({ block: 'center', behavior: 'smooth' });
    // flash 2 次
    target.classList.remove('flash');
    void target.offsetWidth;
    target.classList.add('flash');
    setTimeout(() => target.classList.remove('flash'), 1500);
}