const API = 'http://localhost:8000';

const urlInput      = document.getElementById('url-input');
const clearBtn      = document.getElementById('clear-btn');
const fetchBtn      = document.getElementById('fetch-btn');
const errorMsg      = document.getElementById('error-msg');
const preview       = document.getElementById('preview');
const thumbnail     = document.getElementById('thumbnail');
const videoTitle    = document.getElementById('video-title');
const uploaderEl    = document.getElementById('uploader');
const durationEl    = document.getElementById('duration');
const formatSection = document.getElementById('format-section');
const formatSelect  = document.getElementById('format-select');
const downloadBtn   = document.getElementById('download-btn');
const progressWrap  = document.getElementById('progress-wrap');
const progressFill  = document.getElementById('progress-fill');
const progressLabel = document.getElementById('progress-label');
const cancelBtn     = document.getElementById('cancel-btn');

let currentFileId   = null;
let currentAbort    = null;
let currentSse      = null;

// --- Cancel ---
cancelBtn.addEventListener('click', async (e) => {
  e.preventDefault();
  e.stopPropagation();

  // Abort the pending fetch
  if (currentAbort) { currentAbort.abort(); currentAbort = null; }
  // Close SSE
  if (currentSse)  { currentSse.close();  currentSse = null; }
  // Tell backend to kill the task and clean up
  if (currentFileId) {
    fetch(`${API}/cancel/${currentFileId}`, { method: 'POST' }).catch(() => {});
    currentFileId = null;
  }

  progressWrap.style.display = 'none';
  setProgress(0, '');
  setLoading(downloadBtn, false);
});

// --- Reset UI ---
function resetUI() {
  urlInput.value = '';
  clearBtn.style.display = 'none';
  errorMsg.style.display = 'none';
  preview.style.display = 'none';
  formatSection.style.display = 'none';
  downloadBtn.style.display = 'none';
  progressWrap.style.display = 'none';
  thumbnail.src = '';
}
window.addEventListener('pageshow', resetUI);

// --- Helpers ---
function showError(msg) {
  errorMsg.textContent = msg;
  errorMsg.style.display = 'block';
}
function hideError() { errorMsg.style.display = 'none'; }

function setLoading(btn, loading, text) {
  btn.disabled = loading;
  btn.style.opacity = loading ? '0.6' : '1';
  btn.style.cursor  = loading ? 'wait' : '';
  if (text) btn.dataset.label = btn.dataset.label || btn.textContent.trim();
  if (loading && text) {
    btn.textContent = text;
  } else if (!loading && btn.dataset.label) {
    if (btn.id === 'download-btn') {
      btn.innerHTML = `<svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5"><path d="M21 15v4a2 2 0 01-2 2H5a2 2 0 01-2-2v-4"/><polyline points="7 10 12 15 17 10"/><line x1="12" y1="15" x2="12" y2="3"/></svg> Download`;
    } else {
      btn.textContent = btn.dataset.label;
    }
    delete btn.dataset.label;
  }
}

function formatDuration(secs) {
  if (!secs) return null;
  const h = Math.floor(secs / 3600);
  const m = Math.floor((secs % 3600) / 60);
  const s = secs % 60;
  return h > 0
    ? `${h}:${String(m).padStart(2,'0')}:${String(s).padStart(2,'0')}`
    : `${m}:${String(s).padStart(2,'0')}`;
}

function formatCount(n) {
  if (n >= 1e9) return (n / 1e9).toFixed(1) + 'B';
  if (n >= 1e6) return (n / 1e6).toFixed(1) + 'M';
  if (n >= 1e3) return (n / 1e3).toFixed(1) + 'K';
  return n.toString();
}

function formatBytes(bytes) {
  if (!bytes) return null;
  if (bytes >= 1e9) return (bytes / 1e9).toFixed(1) + ' GB';
  if (bytes >= 1e6) return (bytes / 1e6).toFixed(1) + ' MB';
  return (bytes / 1e3).toFixed(0) + ' KB';
}

function formatLabel(f) {
  const parts = [];
  const res = f.resolution || '';
  if (res && res !== 'unknown') parts.push(res);
  if (f.ext) parts.push(f.ext.toUpperCase());
  const hasVideo = f.vcodec && f.vcodec !== 'none';
  const hasAudio = f.acodec && f.acodec !== 'none';
  if (!hasVideo && hasAudio) parts.push('audio only');
  if (f.fps && hasVideo) parts.push(`${f.fps}fps`);
  const size = formatBytes(f.filesize);
  if (size) parts.push(`~${size}`);
  return parts.join(' · ') || f.format_id;
}

function setProgress(pct, label) {
  progressFill.style.width = pct + '%';
  progressLabel.innerHTML = label;
}

function formatEta(secs) {
  if (secs == null || secs < 0) return '';
  if (secs < 60) return `ETA ${secs}s`;
  const m = Math.floor(secs / 60);
  const s = secs % 60;
  return `ETA ${m}m ${s}s`;
}

// --- URL input ---
urlInput.addEventListener('input', () => {
  clearBtn.style.display = urlInput.value ? 'flex' : 'none';
});
clearBtn.addEventListener('click', () => { resetUI(); urlInput.focus(); });
urlInput.addEventListener('keydown', (e) => { if (e.key === 'Enter') fetchBtn.click(); });

// --- Fetch info ---
fetchBtn.addEventListener('click', async () => {
  const url = urlInput.value.trim();
  if (!url) { showError('Please paste a video URL first.'); return; }

  hideError();
  preview.style.display = 'none';
  formatSection.style.display = 'none';
  downloadBtn.style.display = 'none';
  progressWrap.style.display = 'none';
  setLoading(fetchBtn, true, 'Fetching…');

  try {
    const res = await fetch(`${API}/info`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ url }),
    });
    const data = await res.json();
    if (!res.ok) throw new Error(data.detail || 'Failed to fetch video info.');
    renderPreview(data);
    renderFormats(data.formats || []);
    preview.style.display = 'flex';
    formatSection.style.display = 'flex';
    downloadBtn.style.display = 'flex';
  } catch (err) {
    showError(err.message);
  } finally {
    setLoading(fetchBtn, false);
  }
});

function renderPreview(info) {
  thumbnail.src = info.thumbnail || '';
  thumbnail.alt = info.title || 'Video thumbnail';
  thumbnail.style.display = info.thumbnail ? 'block' : 'none';
  videoTitle.textContent = info.title || 'Unknown title';
  uploaderEl.textContent = info.uploader || '';
  uploaderEl.style.display = info.uploader ? '' : 'none';
  const dur = formatDuration(info.duration);
  durationEl.textContent = dur || '';
  durationEl.style.display = dur ? '' : 'none';

  const viewsEl = document.getElementById('views');
  const likesEl = document.getElementById('likes');
  const dateEl  = document.getElementById('upload-date');
  viewsEl.textContent = info.view_count ? '👁 ' + formatCount(info.view_count) : '';
  viewsEl.style.display = info.view_count ? '' : 'none';
  likesEl.textContent = info.like_count ? '👍 ' + formatCount(info.like_count) : '';
  likesEl.style.display = info.like_count ? '' : 'none';
  if (info.upload_date && info.upload_date.length === 8) {
    const d = info.upload_date;
    const formatted = new Date(`${d.slice(0,4)}-${d.slice(4,6)}-${d.slice(6,8)}`).toLocaleDateString(undefined, { year: 'numeric', month: 'short', day: 'numeric' });
    dateEl.textContent = '📅 ' + formatted;
    dateEl.style.display = '';
  } else {
    dateEl.style.display = 'none';
  }
}

function renderFormats(formats) {
  formatSelect.innerHTML = '';
  const sorted = [...formats].sort((a, b) =>
    (b.height || 0) - (a.height || 0) || (b.tbr || 0) - (a.tbr || 0)
  );
  const combined  = sorted.filter(f => f.vcodec !== 'none' && f.acodec !== 'none');
  const videoOnly = sorted.filter(f => f.vcodec !== 'none' && f.acodec === 'none');
  const audioOnly = sorted.filter(f => f.vcodec === 'none' && f.acodec !== 'none');

  const addGroup = (label, items) => {
    if (!items.length) return;
    const group = document.createElement('optgroup');
    group.label = label;
    items.forEach(f => {
      const opt = document.createElement('option');
      opt.value = f.format_id;
      opt.textContent = formatLabel(f);
      group.appendChild(opt);
    });
    formatSelect.appendChild(group);
  };

  if ((videoOnly[0]?.height || 0) >= (combined[0]?.height || 0)) {
    addGroup('Video only', videoOnly);
    addGroup('Video + Audio', combined);
  } else {
    addGroup('Video + Audio', combined);
    addGroup('Video only', videoOnly);
  }
  addGroup('Audio only', audioOnly);
  if (sorted.length) formatSelect.value = sorted[0].format_id;
}

// --- Download ---
downloadBtn.addEventListener('click', async () => {
  const url = urlInput.value.trim();
  if (!url) return;

  hideError();
  setLoading(downloadBtn, true, 'Downloading…');
  progressWrap.style.display = 'block';
  setProgress(0, '<span class="meta">Starting…</span>');

  const fileId = crypto.randomUUID();
  currentFileId = fileId;

  // SSE for live progress
  const sse = new EventSource(`${API}/progress/${fileId}`);
  currentSse = sse;
  sse.onmessage = (e) => {
    const d = JSON.parse(e.data);
    if (d.status === 'downloading') {
      const pct = d.percent || 0;
      const eta = d.eta != null ? formatEta(d.eta) : '';
      const speed = d.speed != null ? `${d.speed} MB/s` : '';
      const meta = [speed, eta].filter(Boolean).join('  ·  ');
      setProgress(pct, `<span class="pct">${pct}%</span>${meta ? `&ensp;<span class="meta">${meta}</span>` : ''}`);
    } else if (d.status === 'finished') {
      setProgress(100, '<span class="pct">100%</span>&ensp;<span class="meta">Processing…</span>');
    } else if (d.status === 'cancelled') {
      sse.close();
    } else if (d.status === 'error') {
      sse.close();
      showError(d.error || 'Download failed.');
      progressWrap.style.display = 'none';
      setLoading(downloadBtn, false);
    }
  };
  sse.onerror = () => sse.close();

  // AbortController so cancel can kill the fetch
  const abort = new AbortController();
  currentAbort = abort;

  try {
    const res = await fetch(`${API}/download`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ url, format_id: formatSelect.value, file_id: fileId }),
      signal: abort.signal,
    });

    sse.close();
    currentSse = null;
    currentAbort = null;

    if (!res.ok) {
      const data = await res.json().catch(() => ({ detail: 'Download failed.' }));
      throw new Error(data.detail || 'Download failed.');
    }

    // Only trigger file download if not cancelled
    if (currentFileId === fileId) {
      setProgress(100, '<span class="pct">✓</span>&ensp;<span class="meta">Done — saving to your downloads</span>');
      // Open in new tab so current page never navigates away
      window.open(`${API}/file/${fileId}`, '_blank');
      setTimeout(() => { progressWrap.style.display = 'none'; }, 2500);
    }
  } catch (err) {
    sse.close();
    currentSse = null;
    currentAbort = null;
    if (err.name !== 'AbortError') {
      showError(err.message);
      progressWrap.style.display = 'none';
    }
  } finally {
    if (currentFileId === fileId) currentFileId = null;
    setLoading(downloadBtn, false);
  }
});