import { app, navigate, isRouteCurrent } from '../router.js';
import { api } from '../api.js';
import {
  escapeHTML, relativeTime,
  getEnvelopeType, getEnvelopeCorrelation, getEnvelopeSource, getEnvelopeTS,
  isCurrentPath, renderCopyButton, sessionsSkeleton,
} from '../utils.js';
import { subscribeWS } from '../ws.js';

let sessionsState = { sessions: [], cursor: null, total: 0, activeSessionByBackend: {} };
let sessionsPageUnsubscribe = null;

let sessionFilterMode = 'all';
let sessionSortKey = 'started_at';
let sessionSortDir = 'desc';

export function cleanup() {
  if (sessionsPageUnsubscribe) { sessionsPageUnsubscribe(); sessionsPageUnsubscribe = null; }
  if (sessionsState.timerInterval) { clearInterval(sessionsState.timerInterval); }
  sessionsState = { sessions: [], cursor: null, total: 0, activeSessionByBackend: {} };
}

function isSessionActive(s) { return !s.ended_at; }

function sortSessions(sessions) {
  return [...sessions].sort((a, b) => {
    let av = a[sessionSortKey], bv = b[sessionSortKey];
    if (sessionSortKey === 'started_at') {
      av = new Date(av).getTime();
      bv = new Date(bv).getTime();
    } else if (typeof av === 'string') {
      av = av.toLowerCase();
      bv = (bv || '').toLowerCase();
    }
    if (av == null) av = 0;
    if (bv == null) bv = 0;
    if (av < bv) return sessionSortDir === 'asc' ? -1 : 1;
    if (av > bv) return sessionSortDir === 'asc' ? 1 : -1;
    return 0;
  });
}

function groupSessionsByDate(sessions) {
  const now = new Date();
  const todayStart = new Date(now.getFullYear(), now.getMonth(), now.getDate());
  const yesterdayStart = new Date(todayStart);
  yesterdayStart.setDate(yesterdayStart.getDate() - 1);
  const weekStart = new Date(todayStart);
  weekStart.setDate(weekStart.getDate() - 6);
  const groups = [
    { label: 'Today', items: [] },
    { label: 'Yesterday', items: [] },
    { label: 'This Week', items: [] },
    { label: 'Older', items: [] },
  ];
  for (const s of sessions) {
    const d = new Date(s.started_at);
    if (d >= todayStart) groups[0].items.push(s);
    else if (d >= yesterdayStart) groups[1].items.push(s);
    else if (d >= weekStart) groups[2].items.push(s);
    else groups[3].items.push(s);
  }
  return groups.filter(g => g.items.length > 0);
}

function getSessionBackendKey(s) {
  const framework = s.framework || 'unknown';
  const backendID = s.client_id || s.host || 'unknown';
  return `${framework}|${backendID}`;
}

function sessionActivityTS(s) {
  const raw = s._lastActivityTS || Date.parse(s.started_at);
  return Number.isFinite(raw) ? raw : 0;
}

function recomputeActiveSessionByBackend() {
  const next = {};
  const bestTS = {};
  sessionsState.sessions.forEach(s => {
    if (!isSessionActive(s)) return;
    const key = getSessionBackendKey(s);
    const ts = sessionActivityTS(s);
    if (!next[key] || ts > bestTS[key]) {
      next[key] = s.session_id;
      bestTS[key] = ts;
    }
  });
  sessionsState.activeSessionByBackend = next;
}

function sessionDotState(s) {
  if (!isSessionActive(s)) return 'ended';
  const key = getSessionBackendKey(s);
  const activeSessionID = sessionsState.activeSessionByBackend[key];
  return activeSessionID === s.session_id ? 'active' : 'idle';
}

function touchSessionActivity(sessionID, ts, source) {
  const session = sessionsState.sessions.find(s => s.session_id === sessionID);
  if (!session) return null;

  const parsedTS = Date.parse(ts || '');
  const activityTS = Number.isFinite(parsedTS) ? parsedTS : Date.now();
  session._lastActivityTS = Math.max(session._lastActivityTS || 0, activityTS);

  if (source && typeof source === 'object') {
    if (source.framework) session.framework = source.framework;
    if (source.host) session.host = source.host;
    if (source.client_id) session.client_id = source.client_id;
  }

  const key = getSessionBackendKey(session);
  sessionsState.activeSessionByBackend[key] = session.session_id;
  return session;
}

function updatePaginationInfo() {
  const el = document.getElementById('pagination-info');
  if (!el) return;
  const loaded = sessionsState.sessions.length;
  const total = sessionsState.total || loaded;
  let filtered = loaded;
  if (sessionFilterMode === 'active') {
    filtered = sessionsState.sessions.filter(s => isSessionActive(s)).length;
  } else if (sessionFilterMode === 'ended') {
    filtered = sessionsState.sessions.filter(s => !isSessionActive(s)).length;
  } else if (sessionFilterMode === 'errored') {
    filtered = sessionsState.sessions.filter(s => (s._errorCount || 0) > 0).length;
  }
  if (filtered < loaded) {
    el.textContent = `Showing ${filtered} of ${loaded} loaded (${total} total)`;
  } else {
    el.textContent = `Showing ${loaded} of ${total}`;
  }
}

function refreshSessionsTable() {
  const tbody = document.getElementById('sessions-body');
  if (!tbody) return;

  // Update pill counts based on full unfiltered sessions list
  const all = sessionsState.sessions;
  const activeCount = all.filter(s => isSessionActive(s)).length;
  const endedCount = all.filter(s => !isSessionActive(s)).length;
  const erroredCount = all.filter(s => (s._errorCount || 0) > 0).length;
  const pillDefs = [
    { filter: 'all', count: all.length },
    { filter: 'active', count: activeCount },
    { filter: 'ended', count: endedCount },
    { filter: 'errored', count: erroredCount },
  ];
  pillDefs.forEach(({ filter, count }) => {
    const btn = document.querySelector(`#session-pills [data-filter="${filter}"]`);
    if (!btn) return;
    let countEl = btn.querySelector('.pill-count');
    if (!countEl) {
      countEl = document.createElement('span');
      countEl.className = 'pill-count';
      btn.appendChild(countEl);
    }
    countEl.textContent = count;
  });

  // Apply filter
  let filtered = sessionsState.sessions;
  if (sessionFilterMode === 'active') {
    filtered = filtered.filter(s => isSessionActive(s));
  } else if (sessionFilterMode === 'ended') {
    filtered = filtered.filter(s => !isSessionActive(s));
  } else if (sessionFilterMode === 'errored') {
    filtered = filtered.filter(s => (s._errorCount || 0) > 0);
  }

  const groups = groupSessionsByDate(sortSessions(filtered));
  if (groups.length === 0) {
    tbody.innerHTML = '<tr><td colspan="6" class="empty-state">No sessions found</td></tr>';
    return;
  }

  // Update sort indicator classes on headers
  document.querySelectorAll('th.sortable').forEach(th => {
    th.classList.remove('sort-asc', 'sort-desc');
    if (th.dataset.sort === sessionSortKey) {
      th.classList.add(sessionSortDir === 'asc' ? 'sort-asc' : 'sort-desc');
    }
  });
  const allFiltered = groups.flatMap(g => g.items);
  const maxDuration = Math.max(...allFiltered.map(s => {
    const start = new Date(s.started_at).getTime();
    const end = s.ended_at ? new Date(s.ended_at).getTime() : Date.now();
    return end - start;
  }), 1);
  tbody.innerHTML = groups.map(group => {
    const rows = group.items.map(s => {
      const fw = s.framework || 'unknown';
      const fwClass = fw.replace(/[^a-z0-9-]/g, '-');
      const active = isSessionActive(s);
      const dotState = sessionDotState(s);
      const dotTitle = dotState === 'active'
        ? 'Currently active session'
        : (active ? 'Open session' : 'Session ended');
      const rowClass = active ? 'clickable active-session' : 'clickable';
      const start = new Date(s.started_at).getTime();
      const end = s.ended_at ? new Date(s.ended_at).getTime() : Date.now();
      const duration = end - start;
      const barWidth = Math.max(4, (duration / maxDuration) * 80);
      const durationBar = `<span class="session-duration-bar" style="width:${barWidth.toFixed(0)}px"></span>`;
      const errorCell = (s._errorCount || 0) > 0
        ? `<span class="error-count-badge">${s._errorCount}</span>`
        : '<span style="color:var(--text-dim)">—</span>';
      return `
        <tr class="${rowClass}" data-session="${escapeHTML(s.session_id)}">
          <td class="id-cell" title="${escapeHTML(s.session_id)}">${escapeHTML(s.session_id.substring(0, 12))}…${renderCopyButton(s.session_id)}</td>
          <td><span class="fw-dot ${escapeHTML(fwClass)} ${dotState}" title="${dotTitle}"></span>${escapeHTML(fw)}</td>
          <td>${escapeHTML(s.host || '-')}</td>
          <td>${s.run_count}</td>
          <td title="${escapeHTML(s.started_at)}">${escapeHTML(relativeTime(s.started_at))}${durationBar}</td>
          <td>${errorCell}</td>
        </tr>`;
    }).join('');
    return `<tr class="session-date-group"><td colspan="6">${escapeHTML(group.label)}</td></tr>${rows}`;
  }).join('');
  tbody.querySelectorAll('tr.clickable').forEach(row => {
    row.addEventListener('click', () => navigate('/sessions/' + row.dataset.session));
  });
  updatePaginationInfo();
}


function updateSessionTimers() {
  const tbody = document.getElementById('sessions-body');
  if (!tbody) return;
  sessionsState.sessions.forEach(s => {
    const row = tbody.querySelector(`[data-session="${s.session_id}"]`);
    if (row) {
      const td = row.cells[4];
      if (td) {
        // Update only the text node, preserving the duration bar span
        const bar = td.querySelector('.session-duration-bar');
        td.textContent = relativeTime(s.started_at);
        if (bar) td.appendChild(bar);
      }
    }
  });
}

function handleSessionsWS(msg) {
  if (msg.type !== 'message') return;
  const eventType = getEnvelopeType(msg.data);
  const correlation = getEnvelopeCorrelation(msg.data);
  const source = getEnvelopeSource(msg.data);
  const ts = getEnvelopeTS(msg.data);
  const sessionId = correlation?.session_id || msg.data.event?.id;

  if (eventType === 'session.start') {
    const newSession = {
      session_id: sessionId,
      started_at: ts || new Date().toISOString(),
      framework: source.framework || 'unknown',
      client_id: source.client_id || '',
      host: source.host || '-',
      run_count: 1,
      _lastActivityTS: Date.parse(ts || '') || Date.now(),
    };
    sessionsState.sessions.unshift(newSession);
    const backendKey = getSessionBackendKey(newSession);
    sessionsState.activeSessionByBackend[backendKey] = newSession.session_id;
    refreshSessionsTable();
    return;
  }

  const tbody = document.getElementById('sessions-body');
  if (!tbody) return;

  if (sessionId) {
    touchSessionActivity(sessionId, ts, source);
  }

  if (eventType === 'run.start' && sessionId) {
    const session = sessionsState.sessions.find(s => s.session_id === sessionId);
    if (session) {
      session.run_count = (session.run_count || 0) + 1;
      const row = tbody.querySelector(`[data-session="${sessionId}"]`);
      if (row && row.cells[3]) row.cells[3].textContent = session.run_count;
    }
  }

  if (eventType === 'session.end' && sessionId) {
    const session = sessionsState.sessions.find(s => s.session_id === sessionId);
    if (session) {
      session.ended_at = new Date().toISOString();
      recomputeActiveSessionByBackend();
    }
  }

  if (eventType === 'error' && sessionId) {
    const session = sessionsState.sessions.find(s => s.session_id === sessionId);
    if (session) {
      session._errorCount = (session._errorCount || 0) + 1;
    }
  }

  refreshSessionsTable();
}

async function loadSessions(routeToken) {
  const params = new URLSearchParams();
  const from = document.getElementById('filter-from').value;
  const to = document.getElementById('filter-to').value;
  const framework = document.getElementById('filter-framework').value;
  const host = document.getElementById('filter-host').value;

  // Sync filters to URL
  const filterParams = new URLSearchParams();
  if (from) filterParams.set('from', from);
  if (to) filterParams.set('to', to);
  if (framework) filterParams.set('framework', framework);
  if (host) filterParams.set('host', host);
  const filterQS = filterParams.toString();
  const newURL = '/sessions' + (filterQS ? '?' + filterQS : '');
  if (window.location.pathname + window.location.search !== newURL) {
    history.replaceState(null, '', newURL);
  }

  if (from) params.set('from', from);
  if (to) params.set('to', to);
  if (framework) params.set('framework', framework);
  if (host) params.set('host', host);
  if (sessionsState.cursor) params.set('cursor', sessionsState.cursor);

  const data = await api('/v1/sessions?' + params.toString());
  if (routeToken && !isRouteCurrent(routeToken)) return;
  const incoming = (data.sessions || []).map(s => ({
    ...s,
    _lastActivityTS: Date.parse(s.started_at || '') || Date.now(),
  }));
  sessionsState.sessions = sessionsState.sessions.concat(incoming);
  sessionsState.cursor = data.next_cursor;
  // total is only returned on the first page (no cursor)
  if (data.total !== undefined) sessionsState.total = data.total;
  recomputeActiveSessionByBackend();

  refreshSessionsTable();
  document.getElementById('load-more').style.display = sessionsState.cursor ? 'block' : 'none';
}

export async function renderSessions(routeToken) {
  // Reset filter mode on each page visit
  sessionFilterMode = 'all';

  app.innerHTML = `
    <div class="page-header">
      <h2>Sessions</h2>
    </div>
    <div class="filters">
      <label>From <input type="date" id="filter-from"></label>
      <label>To <input type="date" id="filter-to"></label>
      <label>Framework
        <select id="filter-framework">
          <option value="">All</option>
        </select>
      </label>
      <label>Host <input type="text" id="filter-host" placeholder="hostname"></label>
    </div>
    <div class="filter-pills" id="session-pills">
      <button class="filter-pill active" data-filter="all">All</button>
      <button class="filter-pill" data-filter="active">Active</button>
      <button class="filter-pill" data-filter="ended">Ended</button>
      <button class="filter-pill" data-filter="errored">With Errors</button>
    </div>
    <div class="pagination-info" id="pagination-info"></div>
    <div class="table-container">
      <table>
        <thead>
          <tr>
            <th class="sortable" data-sort="session_id">Session <span class="sort-icon"></span></th>
            <th class="sortable" data-sort="framework">Framework <span class="sort-icon"></span></th>
            <th class="sortable" data-sort="host">Host <span class="sort-icon"></span></th>
            <th class="sortable" data-sort="run_count">Runs <span class="sort-icon"></span></th>
            <th class="sortable" data-sort="started_at">Time <span class="sort-icon"></span></th>
            <th>Errors</th>
          </tr>
        </thead>
        <tbody id="sessions-body">${sessionsSkeleton()}</tbody>
      </table>
    </div>
    <button id="load-more" class="load-more" style="display:none">Load more</button>
  `;

  // Wire up filter pill click handlers
  document.querySelectorAll('#session-pills .filter-pill').forEach(btn => {
    btn.addEventListener('click', () => {
      document.querySelectorAll('#session-pills .filter-pill').forEach(b => b.classList.remove('active'));
      btn.classList.add('active');
      sessionFilterMode = btn.dataset.filter;
      refreshSessionsTable();
    });
  });

  // Wire up sortable column headers
  document.querySelectorAll('th.sortable').forEach(th => {
    th.addEventListener('click', () => {
      const key = th.dataset.sort;
      if (sessionSortKey === key) {
        sessionSortDir = sessionSortDir === 'asc' ? 'desc' : 'asc';
      } else {
        sessionSortKey = key;
        sessionSortDir = 'desc';
      }
      refreshSessionsTable();
    });
  });

  api('/v1/stats/summary').then(data => {
    if (routeToken && !isRouteCurrent(routeToken)) return;
    const sel = document.getElementById('filter-framework');
    if (!sel || !data.by_framework) return;
    for (const fw of Object.keys(data.by_framework).sort()) {
      const opt = document.createElement('option');
      opt.value = fw;
      opt.textContent = fw;
      sel.appendChild(opt);
    }
  }).catch(() => {});

  // Restore filters from URL
  const urlParams = new URLSearchParams(window.location.search);
  if (urlParams.get('from')) document.getElementById('filter-from').value = urlParams.get('from');
  if (urlParams.get('to')) document.getElementById('filter-to').value = urlParams.get('to');
  if (urlParams.get('framework')) document.getElementById('filter-framework').value = urlParams.get('framework');
  if (urlParams.get('host')) document.getElementById('filter-host').value = urlParams.get('host');

  ['from', 'to', 'framework'].forEach(f => {
    document.getElementById('filter-' + f).addEventListener('change', () => {
      sessionsState.sessions = [];
      sessionsState.cursor = null;
      loadSessions(routeToken);
    });
  });
  let _hostDebounce = null;
  document.getElementById('filter-host').addEventListener('input', () => {
    clearTimeout(_hostDebounce);
    _hostDebounce = setTimeout(() => {
      sessionsState.sessions = [];
      sessionsState.cursor = null;
      loadSessions(routeToken);
    }, 400);
  });

  document.getElementById('load-more').addEventListener('click', () => loadSessions(routeToken));

  sessionsState = { sessions: [], cursor: null, total: 0, timerInterval: null, activeSessionByBackend: {} };
  await loadSessions(routeToken);
  if (routeToken && !isRouteCurrent(routeToken)) return;

  sessionsState.timerInterval = setInterval(updateSessionTimers, 30000);
  sessionsPageUnsubscribe = subscribeWS(handleSessionsWS);
}