const Browse = (() => {
  const AGG_ID = '__all__';
  const AGG_LIMIT = 5;

  const state = {
    sourceId: null,
    supportsSearch: true,
    mode: 'list',
    keyword: '',
    page: 1,
    maxPage: 1,
    scrollY: 0,
    sourceList: [],
    aggToken: 0,
    gridToken: 0,
    detailToken: 0,
    activeSourceId: null,
    currentPostId: null,
    currentDetail: null
  };

  let grid, statusBar, pager, gridView, detailView, detailContent, mainEl, sourceSelect, searchInput;

  function init() {
    grid = $('grid');
    statusBar = $('statusBar');
    pager = $('pager');
    gridView = $('browseGridView');
    detailView = $('detailView');
    detailContent = $('detailContent');
    mainEl = $('main');
    sourceSelect = $('sourceSelect');
    searchInput = $('searchInput');

    $('searchBtn').onclick = doSearch;
    searchInput.addEventListener('keydown', (e) => { if (e.key === 'Enter') doSearch(); });
    $('clearSearchBtn').onclick = clearSearch;
    $('prevBtn').onclick = () => { if (state.page > 1) { state.page--; loadGrid(); } };
    $('nextBtn').onclick = () => { if (state.page < state.maxPage) { state.page++; loadGrid(); } };
    $('jumpBtn').onclick = jumpToPage;
    $('jumpInput').addEventListener('keydown', (e) => { if (e.key === 'Enter') jumpToPage(); });
    $('backBtn').onclick = showGrid;

    sourceSelect.onchange = () => {
      applySourceSelection(sourceSelect.value);
      state.mode = 'list';
      state.page = 1;
      clearSearchUi();
      loadGrid();
    };

    loadSources();
  }

  function isAgg() { return state.sourceId === AGG_ID; }

  function applySourceSelection(id) {
    state.sourceId = id;
    const opt = sourceSelect.selectedOptions[0];
    state.supportsSearch = id === AGG_ID ? true : (opt ? opt.dataset.search !== '0' : true);
    updateSearchUi();
  }

  function updateSearchUi() {
    searchInput.disabled = !state.supportsSearch;
    $('searchBtn').disabled = !state.supportsSearch;
    searchInput.placeholder = isAgg()
      ? '聚合搜索：一次查询所有已启用数据源...'
      : (state.supportsSearch ? '搜索标题 / 作者 / 关键词...' : '该源暂不支持搜索，请翻页浏览');
  }

  async function loadSources() {
    const res = await window.api.sources.list();
    const all = res.ok ? res.data : [];
    const enabled = getEnabledSources();
    const list = enabled ? all.filter((s) => enabled.includes(s.id)) : all;
    state.sourceList = list;
    const aggOpt = list.filter((s) => s.supportsSearch).length > 1
      ? `<option value="${AGG_ID}" data-search="1">🔎 聚合搜索（全部源）</option>` : '';
    sourceSelect.innerHTML = aggOpt + list.map((s) =>
      `<option value="${escapeHtml(s.id)}" data-search="${s.supportsSearch ? '1' : '0'}">${escapeHtml(s.name)}</option>`).join('');
    if (!list.length) {
      state.sourceId = null;
      grid.innerHTML = '<div class="empty">未启用任何数据源，请在设置中开启</div>';
      pager.classList.add('hidden');
      statusBar.textContent = '';
      return;
    }
    const stillValid = state.sourceId === AGG_ID ? !!aggOpt : list.some((s) => s.id === state.sourceId);
    if (!stillValid) state.sourceId = aggOpt ? AGG_ID : list[0].id;
    sourceSelect.value = state.sourceId;
    applySourceSelection(state.sourceId);
    loadGrid();
  }

  function gotoSource(sourceId, keyword) {
    sourceSelect.value = sourceId;
    applySourceSelection(sourceId);
    state.mode = 'search';
    state.keyword = keyword;
    state.page = 1;
    searchInput.value = keyword;
    $('clearSearchBtn').classList.remove('hidden');
    loadGrid();
  }

  function doSearch() {
    if (!state.supportsSearch) return;
    const kw = searchInput.value.trim();
    if (!kw) return;
    state.mode = 'search';
    state.keyword = kw;
    state.page = 1;
    $('clearSearchBtn').classList.remove('hidden');
    loadGrid();
  }

  function clearSearchUi() {
    searchInput.value = '';
    $('clearSearchBtn').classList.add('hidden');
  }

  function clearSearch() {
    state.mode = 'list';
    state.keyword = '';
    state.page = 1;
    clearSearchUi();
    loadGrid();
  }

  async function loadGrid() {
    const token = ++state.gridToken;
    state.aggToken++;
    showGrid();
    statusBar.textContent = '加载中...';
    grid.innerHTML = '';
    pager.classList.add('hidden');
    mainEl.scrollTop = 0;

    if (isAgg()) return loadAggregate();

    const sourceId = state.sourceId;
    const mode = state.mode;
    const keyword = state.keyword;
    const page = state.page;
    const res = mode === 'search'
      ? await window.api.sources.search(sourceId, keyword, page)
      : await window.api.sources.browse(sourceId, page);
    if (token !== state.gridToken) return;

    grid.className = 'grid';

    if (!res.ok) {
      const isAuth = sourceId === 'zlib' && /登录|AUTH/i.test(res.error || '');
      statusBar.innerHTML = `加载失败：${escapeHtml(res.error)} <button class="retry-btn" id="gridRetry">重试</button>`;
      if (isAuth) {
        grid.innerHTML = '<div class="empty">Z-Library 需要登录，请到"设置"页配置账号</div>';
      } else {
        grid.innerHTML = '<div class="empty">该数据源暂时不可用，可切换其它源</div>';
      }
      $('gridRetry').onclick = loadGrid;
      return;
    }

    const { items, maxPage } = res.data;
    state.maxPage = maxPage || 1;

    if (!items.length) {
      grid.innerHTML = `<div class="empty">${escapeHtml(res.data.note || '未找到相关结果')}</div>`;
      statusBar.textContent = mode === 'search' ? `搜索：${keyword}` : '';
      return;
    }

    statusBar.textContent = mode === 'search' ? `搜索：${keyword}（第 ${page} 页）` : '';

    grid.innerHTML = items.map(cardHtml).join('');
    bindCards(grid, sourceId);

    $('pageInfo').textContent = `第 ${page} / ${state.maxPage} 页`;
    $('prevBtn').disabled = page <= 1;
    $('nextBtn').disabled = page >= state.maxPage;
    const jump = $('jumpInput');
    jump.max = state.maxPage;
    jump.value = '';
    jump.placeholder = page;
    pager.classList.remove('hidden');
  }

  function cardHtml(it) {
    return `
      <div class="card" data-id="${escapeHtml(it.postId)}">
        <div class="card-cover" style="${coverStyle(it.cover)}">${it.cover ? '' : `<div class="ph">${escapeHtml(it.title)}</div>`}</div>
        <div class="card-title">${escapeHtml(it.title)}</div>
        ${it.subtitle ? `<div class="card-sub">${escapeHtml(it.subtitle)}</div>` : ''}
        ${it.date ? `<div class="card-date">${escapeHtml(it.date)}</div>` : ''}
      </div>`;
  }

  function bindCards(root, sourceId) {
    root.querySelectorAll('.card').forEach((el) => {
      el.onclick = () => openDetail(el.dataset.id, sourceId);
    });
  }

  // 聚合搜索：并发查询所有支持搜索的已启用源，按源分组展示，每组最多 AGG_LIMIT 条
  async function loadAggregate() {
    const targets = state.sourceList.filter((s) => s.supportsSearch);
    grid.className = 'agg-list';

    if (state.mode !== 'search' || !state.keyword) {
      statusBar.textContent = '';
      grid.innerHTML = `<div class="empty">聚合搜索：输入关键词后将同时查询 ${targets.length} 个数据源</div>`;
      return;
    }

    const token = ++state.aggToken;
    const keyword = state.keyword;

    statusBar.textContent = `聚合搜索「${keyword}」：0 / ${targets.length} 个源完成`;
    grid.innerHTML = targets.map((s) => `
      <section class="agg-group" id="agg-${escapeHtml(s.id)}">
        <div class="agg-head">
          <span class="agg-name">${escapeHtml(s.name)}</span>
          <span class="agg-count" data-role="count">搜索中...</span>
        </div>
        <div class="grid agg-grid" data-role="grid"><div class="agg-loading">加载中...</div></div>
      </section>`).join('');

    let done = 0;
    let hit = 0;
    let failed = 0;

    await Promise.all(targets.map(async (s) => {
      const res = await window.api.sources.search(s.id, keyword, 1);
      if (token !== state.aggToken || !grid.isConnected) return;
      const sec = $(`agg-${s.id}`);
      if (!sec) return;
      const countEl = sec.querySelector('[data-role="count"]');
      const gridEl = sec.querySelector('[data-role="grid"]');
      const headEl = sec.querySelector('.agg-head');
      done++;

      if (!res.ok) {
        failed++;
        sec.classList.add('agg-failed');
        countEl.textContent = '失败';
        countEl.classList.add('err');
        gridEl.className = 'agg-msg';
        gridEl.innerHTML = `<span class="agg-err">${escapeHtml(res.error)}</span>`;
      } else {
        const items = (res.data && res.data.items) || [];
        if (!items.length) {
          sec.classList.add('agg-empty');
          countEl.textContent = '无结果';
          gridEl.className = 'agg-msg';
          gridEl.textContent = res.data.note || '未找到相关结果';
        } else {
          hit++;
          const shown = items.slice(0, AGG_LIMIT);
          countEl.textContent = `${shown.length} 条`;
          gridEl.className = 'grid agg-grid';
          gridEl.innerHTML = shown.map(cardHtml).join('');
          bindCards(gridEl, s.id);
          if (items.length > AGG_LIMIT || (res.data.maxPage || 1) > 1) {
            const more = document.createElement('button');
            more.className = 'tb-btn ghost sm agg-more';
            more.textContent = '查看更多 →';
            more.onclick = () => gotoSource(s.id, keyword);
            headEl.appendChild(more);
          }
        }
      }
      statusBar.textContent = `聚合搜索「${keyword}」：${done} / ${targets.length} 个源完成`;
    }));

    if (token !== state.aggToken) return;
    statusBar.textContent = `聚合搜索「${keyword}」：${hit} 个源有结果${failed ? `，${failed} 个源失败` : ''}（共 ${targets.length} 个源）`;
  }

  function jumpToPage() {
    const input = $('jumpInput');
    let n = parseInt(input.value, 10);
    if (!n || n < 1) return;
    if (n > state.maxPage) n = state.maxPage;
    if (n === state.page) return;
    state.page = n;
    loadGrid();
  }

  function showGrid() {
    state.detailToken++;
    detailView.classList.add('hidden');
    gridView.classList.remove('hidden');
    if (state.scrollY) mainEl.scrollTop = state.scrollY;
  }

  async function openDetail(postId, sourceId) {
    const token = ++state.detailToken;
    state.scrollY = mainEl.scrollTop;
    state.currentPostId = postId;
    const activeSourceId = sourceId || state.sourceId;
    state.activeSourceId = activeSourceId;
    gridView.classList.add('hidden');
    detailView.classList.remove('hidden');
    mainEl.scrollTop = 0;
    detailContent.innerHTML = '<div class="dl-loading">加载中...</div>';

    const res = await window.api.sources.detail(activeSourceId, postId);
    if (token !== state.detailToken) return;
    if (!res.ok) {
      detailContent.innerHTML = `<div class="dl-error">加载失败：${escapeHtml(res.error)}<button class="retry-btn" id="detailRetry">重试</button></div>`;
      $('detailRetry').onclick = () => openDetail(postId, state.activeSourceId);
      return;
    }
    state.currentDetail = res.data;
    renderDetail(res.data);
    if (sourceDownloadsOnDemand(activeSourceId)) {
      renderOnDemandDownload(postId, activeSourceId, token);
    } else {
      loadDownload(postId, activeSourceId, token);
    }
    refreshAddButton();
  }

  function sourceNameOf(id) {
    const s = state.sourceList.find((x) => x.id === id);
    return s ? s.name : id;
  }

  function sourceDownloadsOnDemand(id) {
    const source = state.sourceList.find((item) => item.id === id);
    return !!(source && source.downloadOnDemand);
  }

  function renderDetail(d) {
    const tagsHtml = (d.tags || []).map((t) => {
      const idx = t.indexOf('：');
      if (idx > 0) return `<div class="meta-row"><b>${escapeHtml(t.slice(0, idx))}</b>${escapeHtml(t.slice(idx + 1))}</div>`;
      return `<div class="meta-row">${escapeHtml(t)}</div>`;
    }).join('');
    const authorsHtml = (d.authors && d.authors.length)
      ? `<div class="detail-authors">${escapeHtml(d.authors.join(', '))}</div>` : '';
    const briefHtml = d.brief ? `<div class="section-title">简介 / 摘要</div><div class="brief-panel">${escapeHtml(d.brief)}</div>` : '';

    detailContent.innerHTML = `
      <div class="detail-head">
        <div class="detail-cover" style="${coverStyle(d.cover)}">${d.cover ? '' : `<div class="ph">${escapeHtml(d.title)}</div>`}</div>
        <div class="detail-meta">
          <div class="detail-title">${escapeHtml(d.title)}</div>
          ${authorsHtml}
          <div class="meta-row"><b>来源</b>${escapeHtml(sourceNameOf(state.activeSourceId))}</div>
          ${d.date ? `<div class="meta-row"><b>日期</b>${escapeHtml(d.date)}</div>` : ''}
          ${tagsHtml}
          ${d.url ? `<div class="meta-row"><b>原始链接</b><a href="#" id="detailUrlLink">${escapeHtml(d.url)}</a></div>` : ''}
          <button class="tb-btn add-lib-btn" id="addLibBtn">加入我的书库</button>
        </div>
      </div>
      <div class="section-title">下载 / 全文</div>
      <div class="download-box" id="downloadBox"><div class="dl-loading">下载信息获取中...</div></div>
      ${briefHtml}
    `;

    $('addLibBtn').onclick = addToLibrary;
    const urlLink = $('detailUrlLink');
    if (urlLink) urlLink.onclick = (e) => { e.preventDefault(); window.api.openExternal(d.url); };
  }

  async function refreshAddButton() {
    const btn = $('addLibBtn');
    if (!btn) return;
    const res = await window.api.library.findBySource(state.activeSourceId, state.currentPostId);
    if (res.ok && res.data) {
      btn.textContent = '已在书库 ✓';
      btn.disabled = true;
      btn.classList.add('in-lib');
    }
  }

  async function addToLibrary() {
    const d = state.currentDetail;
    if (!d) return;
    const res = await window.api.library.add(entryMeta());
    if (res.ok) {
      const btn = $('addLibBtn');
      btn.textContent = '已加入书库 ✓';
      btn.disabled = true;
      btn.classList.add('in-lib');
      if (window.Library) window.Library.markDirty();
    }
  }

  async function loadDownload(postId, sourceId = state.activeSourceId, token = state.detailToken) {
    const box = $('downloadBox');
    if (!box) return;
    box.innerHTML = '<div class="dl-loading">下载信息获取中...</div>';
    const res = await window.api.sources.download(sourceId, postId);
    if (!box.isConnected || token !== state.detailToken) return;
    if (!res.ok) {
      box.innerHTML = `<div class="dl-error">获取失败：${escapeHtml(res.error)}<button class="retry-btn" id="dlRetry">重试</button></div>`;
      $('dlRetry').onclick = () => loadDownload(postId, sourceId, token);
      return;
    }
    renderDownloadResult(box, res.data);
  }

  function renderDownloadResult(box, d) {
    let html = '';
    const files = d.files || [];
    if (files.length) {
      html += `<div class="dl-files">${files.map((f) => `<div class="dl-file-row">
        <span class="dl-file-name" title="${escapeHtml(f.name)}">${escapeHtml(f.name)}</span>
        ${f.format ? `<span class="dl-fmt">${escapeHtml(f.format)}</span>` : ''}
        <button class="copy-btn" data-copy="${escapeHtml(f.link)}">复制</button>
        <button class="dl-btn" data-file="${escapeHtml(f.link)}" data-name="${escapeHtml(f.name)}">下载</button>
      </div>`).join('')}</div>`;
    }
    const links = d.links || [];
    if (links.length) {
      html += links.map((l) => `<div class="dl-link-row">🔗 <a href="#" data-open="${escapeHtml(l.url)}">${escapeHtml(l.name)}</a></div>`).join('');
    }
    box.innerHTML = html || '<div class="dl-error">未解析到下载信息</div>';
    box.querySelectorAll('.copy-btn').forEach((btn) => { btn.onclick = () => copyText(btn, btn.dataset.copy); });
    box.querySelectorAll('.dl-btn[data-file]').forEach((btn) => { btn.onclick = () => downloadFile(btn, btn.dataset.file); });
    box.querySelectorAll('[data-open]').forEach((a) => { a.onclick = (e) => { e.preventDefault(); window.api.openExternal(a.dataset.open); }; });
  }

  function renderOnDemandDownload(postId, sourceId, token) {
    const box = $('downloadBox');
    if (!box) return;
    box.innerHTML = `<div class="dl-files"><div class="dl-file-row">
      <span class="dl-file-name">每日免费下载额度有限，仅在点击后获取下载地址</span>
      <button class="dl-btn" id="onDemandDownloadBtn">下载</button>
    </div></div>`;
    const btn = $('onDemandDownloadBtn');
    btn.onclick = async () => {
      const oldError = box.querySelector('.dl-error');
      if (oldError) oldError.remove();
      btn.disabled = true;
      btn.textContent = '获取中...';
      const res = await window.api.sources.download(sourceId, postId);
      if (!box.isConnected || token !== state.detailToken) return;
      if (!res.ok) {
        btn.disabled = false;
        btn.textContent = '重试';
        btn.title = res.error || '获取下载地址失败';
        box.insertAdjacentHTML('beforeend', `<div class="dl-error">获取失败：${escapeHtml(res.error)}</div>`);
        return;
      }
      renderDownloadResult(box, res.data);
      const download = box.querySelector('.dl-btn[data-file]');
      if (download) download.click();
    };
  }

  // 当前条目的元数据，供下载时自动建库用
  function entryMeta() {
    const d = state.currentDetail || {};
    return {
      title: d.title || '未命名',
      authors: d.authors || [],
      cover: d.cover || '',
      date: d.date || '',
      brief: d.brief || '',
      url: d.url || '',
      sourceId: state.activeSourceId,
      sourcePostId: state.currentPostId
    };
  }

  function formatBytes(value) {
    const bytes = Math.max(0, Number(value) || 0);
    if (bytes < 1024) return `${bytes} B`;
    if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
    if (bytes < 1024 * 1024 * 1024) return `${(bytes / (1024 * 1024)).toFixed(1)} MB`;
    return `${(bytes / (1024 * 1024 * 1024)).toFixed(2)} GB`;
  }

  function createDownloadProgress(row) {
    const box = document.createElement('div');
    box.className = 'dl-progress';
    const track = document.createElement('div');
    track.className = 'dl-progress-track';
    const fill = document.createElement('div');
    fill.className = 'dl-progress-fill';
    const label = document.createElement('span');
    label.className = 'dl-progress-label';
    label.textContent = '准备下载…';
    track.appendChild(fill);
    box.append(track, label);
    row.appendChild(box);
    return { box, fill, label };
  }

  function updateDownloadProgress(progress, data) {
    const received = Number(data && data.receivedBytes) || 0;
    const total = Number(data && data.totalBytes) || 0;
    const ratio = Number(data && data.percent);
    if (data && data.percent != null && Number.isFinite(ratio)) {
      const percent = Math.max(0, Math.min(1, ratio));
      progress.box.classList.remove('indeterminate');
      progress.fill.style.width = `${Math.round(percent * 100)}%`;
      progress.label.textContent = total
        ? `${Math.round(percent * 100)}% · ${formatBytes(received)} / ${formatBytes(total)}`
        : `${Math.round(percent * 100)}% · ${formatBytes(received)}`;
    } else {
      progress.box.classList.add('indeterminate');
      progress.label.textContent = `${formatBytes(received)} 已下载`;
    }
  }

  async function downloadFile(btn, url) {
    const orig = btn.textContent;
    const sourceId = state.activeSourceId;
    const sourcePostId = state.currentPostId;
    const meta = entryMeta();
    const suggestedName = btn.dataset.name || '';
    const row = btn.closest('.dl-file-row');
    const oldProgress = row && row.querySelector('.dl-progress');
    if (oldProgress) oldProgress.remove();
    const progress = row ? createDownloadProgress(row) : null;
    btn.disabled = true;
    btn.textContent = '下载中...';

    const lib = await window.api.library.findBySource(sourceId, sourcePostId);
    const entryId = (lib.ok && lib.data) ? lib.data.id : undefined;
    // 元数据与页面内进度回调交给全局任务中心，详情页离开后下载仍由它接管
    let res;
    try {
      res = await window.DownloadCenter.start({
        key: `${sourceId}:${sourcePostId}:${suggestedName}`,
        url,
        suggestName: suggestedName,
        entryId,
        meta,
        onProgress: (data) => { if (progress) updateDownloadProgress(progress, data); }
      });
    } catch (error) {
      res = { ok: false, error: (error && error.message) || String(error) };
    }

    if (res.ok && res.data && res.data.canceled) {
      if (progress) progress.box.remove();
      btn.textContent = orig; btn.disabled = false;
      return;
    }
    if (res.ok && res.data && res.data.paused) {
      if (progress) {
        progress.box.classList.remove('indeterminate');
        progress.label.textContent = '已暂停，可在任务中心继续';
      }
      btn.textContent = '继续';
      btn.disabled = false;
      return;
    }
    if (res.ok && res.data && res.data.deleted) {
      if (progress) progress.box.remove();
      btn.textContent = orig;
      btn.disabled = false;
      return;
    }
    if (!res.ok) {
      if (progress) {
        progress.box.classList.add('failed');
        progress.label.textContent = res.error || '下载失败';
      }
      btn.textContent = '失败';
      btn.title = res.error || '';
      setTimeout(() => {
        if (progress) progress.box.remove();
        btn.textContent = orig;
        btn.disabled = false;
      }, 2000);
      return;
    }

    // 下载即入库，刷新"加入书库"按钮并就地提供打开入口
    if (window.Library) window.Library.markDirty();
    if (state.activeSourceId === sourceId && state.currentPostId === sourcePostId) {
      refreshAddButton();
    }

    const saved = res.data.path;
    if (progress) {
      updateDownloadProgress(progress, { ...res.data, percent: 1, complete: true });
      progress.label.textContent = '下载完成';
      setTimeout(() => progress.box.remove(), 900);
    }
    btn.textContent = '打开';
    btn.title = '打开已下载文件';
    btn.disabled = false;
    btn.classList.add('downloaded');
    btn.onclick = async () => {
      const r = await window.api.openPath(saved);
      if (!r.ok) await confirmModal('打开失败', r.error || '无法打开该文件');
    };

    if (row && !row.querySelector('.reveal-btn')) {
      const reveal = document.createElement('button');
      reveal.className = 'copy-btn reveal-btn';
      reveal.textContent = '定位';
      reveal.onclick = () => window.api.showItem(saved);
      row.appendChild(reveal);
    }
  }

  return { init, reloadSources: loadSources };
})();

window.Browse = Browse;