'use strict';
/* ════════════════════════════════════════════════════════════════
   Constants
   ════════════════════════════════════════════════════════════════ */
const DEFAULT_CAP  = 10_000;
const TEMPORAL_CAP = 600_000;
const LTTB_MIN     = 200;    // never decimate below this many points

const TRACE_COLORS = [
  '#89b4fa','#a6e3a1','#f38ba8','#fab387','#cba6f7',
  '#94e2d5','#89dceb','#b4befe','#f9e2af','#f5c2e7',
];

/* ════════════════════════════════════════════════════════════════
   Globals
   ════════════════════════════════════════════════════════════════ */
let signals     = [];
let buffers     = {};
let plots       = [];
let nextPlotId  = 1;
let windowSec   = 5;
let globalPause = false;
let lastDataAt  = 0;

const traceColorMap = {};
let   colorIdx      = 0;
function getTraceColor(key) {
  if (!traceColorMap[key]) traceColorMap[key] = TRACE_COLORS[colorIdx++ % TRACE_COLORS.length];
  return traceColorMap[key];
}

// Sync: shared uPlot cursor crosshair across all live plots
const LIVE_SYNC = uPlot.sync('live');
const TRIG_SYNC = uPlot.sync('trig');

// Zoom guard: prevents echo on cross-plot sync calls inside onZoom.
// zoomGuard prevents the setScale hook from calling onZoom when we programmatically
// set the scale (rolling window, zoom-back, fit, resize, pan, cross-plot sync).
// All programmatic setScale calls wrap with zoomGuard=true/false so that the hook
// only fires for genuine user drag-zoom or scroll-wheel gestures.
let zoomGuard = false;

// Zoom history for Back button (global since plots are zoom-synced)
const zoomHistory = [];

// Cursors A/B — stored in x-axis units of the current mode:
//   live mode  → Unix seconds
//   trig mode  → relative seconds from trigger
const cursors = { mode: 'off', tA: null, tB: null };
let cursorsDirty = false;  // if true, redraw all plots to update cursor lines

// Layout — [label, cssClass, cols, rows]
const LAYOUTS = [
  ['1×1','l1x1',1,1],['1×2','l1x2',1,2],['2×1','l2x1',2,1],['1×3','l1x3',1,3],
  ['3×1','l3x1',3,1],['2×2','l2x2',2,2],['1×4','l1x4',1,4],['4×1','l4x1',4,1],
];
let currentLayout = 'l1x1';

/* ════════════════════════════════════════════════════════════════
   Trigger state
   ════════════════════════════════════════════════════════════════ */
const trig = {
  enabled:false, signal:'', edge:'rising', threshold:0, windowSec:1,
  prePercent:20, mode:'normal', stopped:false,
  armed:false, prevVal:null, collecting:false, trigTime:null, snapshot:null,
};
function trigPreSec()  { return trig.windowSec * trig.prePercent / 100; }
function trigPostSec() { return trig.windowSec * (100 - trig.prePercent) / 100; }

/* ════════════════════════════════════════════════════════════════
   WebSocket
   ════════════════════════════════════════════════════════════════ */
let ws = null, wsBackoff = 1000;
function connectWS() {
  ws = new WebSocket('ws://' + location.host + '/ws');
  ws.onopen  = () => { wsBackoff = 1000; setStatus('orange','Connected – waiting for data'); };
  ws.onclose = () => {
    setStatus('red','Disconnected (reconnecting…)');
    setTimeout(connectWS, wsBackoff);
    wsBackoff = Math.min(wsBackoff * 2, 30000);
  };
  ws.onerror = () => {};
  ws.onmessage = evt => {
    let msg; try { msg = JSON.parse(evt.data); } catch { return; }
    if      (msg.type === 'config') onConfig(msg);
    else if (msg.type === 'data')   onData(msg);
  };
}

/* ════════════════════════════════════════════════════════════════
   Status LED
   ════════════════════════════════════════════════════════════════ */
function setStatus(s, t) {
  document.getElementById('status-led').className  = s;
  document.getElementById('status-text').textContent = t;
}
setInterval(() => {
  const tsEl = document.getElementById('sb-tsage');
  if (ws && ws.readyState === WebSocket.OPEN && lastDataAt > 0) {
    const age = performance.now() - lastDataAt;
    // Compute minimum lag: newest buffer timestamp vs browser wall clock.
    let tsAge = null;
    const wallNow = Date.now() / 1000;
    Object.values(buffers).forEach(buf => {
      if (buf.size === 0) return;
      const newest = buf.t[(buf.head - 1 + buf.cap) % buf.cap];
      const a = wallNow - newest;
      if (tsAge === null || a < tsAge) tsAge = a;
    });
    if (tsEl && tsAge !== null) {
      const ms = tsAge * 1000;
      tsEl.textContent = '| lag: ' + (ms < 1000 ? ms.toFixed(0) + 'ms' : tsAge.toFixed(2) + 's');
    } else if (tsEl) {
      tsEl.textContent = '';
    }
    if (age > 1000) setStatus('orange', 'No data for ' + (age/1000).toFixed(1) + 's');
    else            setStatus('green',  'Streaming');
  } else if (tsEl) {
    tsEl.textContent = '';
  }
}, 500);

/* ════════════════════════════════════════════════════════════════
   Config handler
   ════════════════════════════════════════════════════════════════ */
function numElements(sig) { return (sig.numRows || 1) * (sig.numCols || 1); }
function isTemporal(sig)  { return numElements(sig) > 1 && (sig.timeMode || 0) !== 0; }

function onConfig(msg) {
  const newSigs = msg.signals || [];
  const fp = s => s.name+':'+s.typeCode+':'+(s.numRows||1)+':'+(s.numCols||1)+':'+(s.timeMode||0);
  const changed = newSigs.length !== signals.length || newSigs.some((s,i) => fp(s) !== fp(signals[i]));
  signals = newSigs;
  if (changed) {
    buffers = {};
    signals.forEach(sig => {
      const n = numElements(sig);
      if (isTemporal(sig))  { buffers[sig.name] = makeBuffer(TEMPORAL_CAP); }
      else if (n === 1)     { buffers[sig.name] = makeBuffer(); }
      else { for (let i = 0; i < n; i++) buffers[sig.name+'['+i+']'] = makeBuffer(); }
    });
    trigDisarm(); trig.snapshot = null; trig.prevVal = null;
    zoomHistory.length = 0;
    document.getElementById('btn-zoom-back').style.display = 'none';
  }
  buildSidebar();
  buildTrigSignalSelect();
}

/* ════════════════════════════════════════════════════════════════
   Data handler
   ════════════════════════════════════════════════════════════════ */
function onData(msg) {
  lastDataAt = performance.now();
  const sigs = msg.signals; if (!sigs) return;
  Object.keys(sigs).forEach(key => {
    const buf = buffers[key]; if (!buf) return;
    const sd  = sigs[key];   if (!sd || !sd.t || !sd.v) return;
    const len = Math.min(sd.t.length, sd.v.length);
    for (let i = 0; i < len; i++) pushBuffer(buf, sd.t[i], sd.v[i]);
  });
  if (trig.enabled && trig.armed && trig.signal) checkTrigger(sigs);
  if (trig.enabled && trig.collecting && (Date.now()/1000) >= trig.trigTime + trigPostSec())
    finaliseTriggerCapture();
  if (!trig.enabled) {
    plots.forEach(p => {
      if (globalPause) return;
      if (p.traces.some(t => buffers[t] !== undefined)) p.needsRedraw = true;
    });
  }
}

/* ════════════════════════════════════════════════════════════════
   Trigger logic
   ════════════════════════════════════════════════════════════════ */
function checkTrigger(sigs) {
  const sd = sigs[trig.signal]; if (!sd || !sd.v || !sd.v.length) return;
  for (let i = 0; i < sd.v.length; i++) {
    const cur = sd.v[i], prev = trig.prevVal; trig.prevVal = cur;
    if (prev === null) continue;
    const e = trig.edge, thr = trig.threshold;
    if ((e==='rising' &&prev<thr&&cur>=thr) ||
        (e==='falling'&&prev>thr&&cur<=thr) ||
        (e==='both'&&((prev<thr&&cur>=thr)||(prev>thr&&cur<=thr)))) {
      fireTrigger(sd.t ? sd.t[i] : Date.now()/1000); break;
    }
  }
}
function fireTrigger(t) {
  trig.armed=false; trig.collecting=true; trig.trigTime=t; trig.snapshot=null;
  updateTrigStatusBadge('waiting'); setAllCardsCollecting(true);
}
function finaliseTriggerCapture() {
  trig.collecting = false;
  const t0 = trig.trigTime - trigPreSec(), t1 = trig.trigTime + trigPostSec();
  const snap = {};
  Object.keys(buffers).forEach(key => {
    const sl = getBufferSliceRange(buffers[key], t0, t1);
    if (sl.t.length > 0) snap[key] = sl;
  });
  // Tag snapshot with the window parameters captured at trigger time so that
  // the render loop uses the correct bounds even if UI controls are changed later.
  snap._preS  = trigPreSec();
  snap._postS = trigPostSec();
  trig.snapshot = snap;
  setAllCardsCollecting(false); updateTrigStatusBadge('triggered');
  showRearmBtn(trig.mode === 'single');
  showStopBtn(trig.mode === 'normal');
  // Reset cursor positions (mode changed) and show cursor button now that snapshot exists
  cursors.tA = null; cursors.tB = null; updateCursorReadout();
  updateCursorBtnVisibility();
  plots.forEach(p => { p.xRange = null; p.needsRedraw = true; });
  if (trig.mode === 'normal' && !trig.stopped)
    setTimeout(() => { if (trig.enabled && trig.mode==='normal' && !trig.stopped) trigArm(); }, 200);
}
function trigArm() {
  trig.snapshot=null; trig.armed=true; trig.collecting=false; trig.prevVal=null;
  showRearmBtn(false); updateTrigStatusBadge('armed');
  cursors.tA = null; cursors.tB = null; updateCursorReadout();
  updateCursorBtnVisibility();
  plots.forEach(p => { p.xRange = null; p.needsRedraw = true; });
}
function trigDisarm() {
  trig.armed=false; trig.collecting=false; trig.trigTime=null; trig.stopped=false;
  setAllCardsCollecting(false); showRearmBtn(false); showStopBtn(false); updateTrigStatusBadge('idle');
}
function setAllCardsCollecting(on) {
  document.querySelectorAll('.plot-card').forEach(c => c.classList.toggle('trig-collecting', on));
}
function updateTrigStatusBadge(state) {
  const el = document.getElementById('trig-status-badge');
  el.className = state;
  el.textContent = {idle:'IDLE',armed:'ARMED',waiting:'COLLECTING',triggered:'TRIGGERED'}[state]||'IDLE';
}
function showRearmBtn(v) { document.getElementById('btn-trig-rearm').style.display = v?'inline-block':'none'; }
function showStopBtn(v)  { document.getElementById('btn-trig-stop').style.display  = v?'inline-block':'none'; }
function updateStopBtn() {
  const btn = document.getElementById('btn-trig-stop');
  btn.textContent = trig.stopped ? 'Resume' : 'Stop';
}

/* ════════════════════════════════════════════════════════════════
   Circular buffer
   ════════════════════════════════════════════════════════════════ */
function makeBuffer(cap) {
  cap = cap || DEFAULT_CAP;
  return { t: new Float64Array(cap), v: new Float64Array(cap), head:0, size:0, cap };
}
function pushBuffer(buf, t, v) {
  buf.t[buf.head] = t; buf.v[buf.head] = v;
  buf.head = (buf.head + 1) % buf.cap;
  if (buf.size < buf.cap) buf.size++;
}

// Binary-search range slice of circular buffer — O(log n + window_size)
function getBufferSliceRange(buf, t0, t1) {
  if (buf.size === 0) return { t: new Float64Array(0), v: new Float64Array(0) };
  const { cap, size, head } = buf;
  const start  = (size === cap) ? head : 0;
  const physAt = k => (start + k) % cap;

  let lo = 0, hi = size;
  while (lo < hi) { const m = (lo+hi)>>>1; if (buf.t[physAt(m)] < t0) lo=m+1; else hi=m; }
  const kStart = lo;
  lo = kStart; hi = size;
  while (lo < hi) { const m = (lo+hi)>>>1; if (buf.t[physAt(m)] <= t1) lo=m+1; else hi=m; }
  const kEnd = lo, len = kEnd - kStart;
  if (len <= 0) return { t: new Float64Array(0), v: new Float64Array(0) };

  const outT = new Float64Array(len), outV = new Float64Array(len);
  const physStart = physAt(kStart), tail = cap - physStart;
  if (tail >= len) {
    outT.set(buf.t.subarray(physStart, physStart + len));
    outV.set(buf.v.subarray(physStart, physStart + len));
  } else {
    outT.set(buf.t.subarray(physStart, physStart + tail));
    outT.set(buf.t.subarray(0, len - tail), tail);
    outV.set(buf.v.subarray(physStart, physStart + tail));
    outV.set(buf.v.subarray(0, len - tail), tail);
  }
  return { t: outT, v: outV };
}
// getGlobalNow returns the reference "now" for the rolling window.
// Always anchors to the newest timestamp found in any buffer so the rolling
// window tracks real data regardless of any clock skew between the Go server
// and the browser.  Falls back to Date.now()/1000 only when all buffers are
// empty (no data yet received).
function getGlobalNow() {
  let latest = -Infinity;
  Object.values(buffers).forEach(buf => {
    if (buf.size === 0) return;
    const newestT = buf.t[(buf.head - 1 + buf.cap) % buf.cap];
    if (newestT > latest) latest = newestT;
  });
  return isFinite(latest) ? latest : Date.now() / 1000;
}

// getBufferNow returns the "now" anchor for a single buffer — the buffer's own
// newest timestamp.  This avoids cross-signal interference when signals have
// different timescales or update rates.
function getBufferNow(buf) {
  if (buf.size === 0) return Date.now() / 1000;
  return buf.t[(buf.head - 1 + buf.cap) % buf.cap];
}

function getBufferSlice(buf) {
  const now = getBufferNow(buf);
  return getBufferSliceRange(buf, now - windowSec, now);
}

// Binary-search slice of a sorted contiguous Float64Array pair
function sliceTypedArrayRange(t, v, t0, t1) {
  let lo = 0, hi = t.length;
  while (lo < hi) { const m = (lo+hi)>>>1; if (t[m] < t0) lo=m+1; else hi=m; }
  const s = lo; lo = s; hi = t.length;
  while (lo < hi) { const m = (lo+hi)>>>1; if (t[m] <= t1) lo=m+1; else hi=m; }
  return { t: t.subarray(s, lo), v: v.subarray(s, lo) };
}


// Return the configured samplingRate for a buffer key.
// Temporal array signals have a meaningful SamplingRate; scalars return 0.
// Used to prefer high-freq signals as the master time grid regardless of trace order.
function getKeySamplingRate(key) {
  const direct = signals.find(s => s.name === key);
  if (direct) return direct.samplingRate || 0;
  // Array element key like "Sig[3]" — strip the index
  const sig = signals.find(s => key.startsWith(s.name + '['));
  return sig ? (sig.samplingRate || 0) : 0;
}

// LTTB decimation — O(n).  Returns {t, v} unchanged when len ≤ threshold.
function lttb(t, v, threshold) {
  const len = t.length;
  if (len <= threshold) return { t, v };
  const outT = new Float64Array(threshold), outV = new Float64Array(threshold);
  outT[0] = t[0]; outV[0] = v[0];
  outT[threshold-1] = t[len-1]; outV[threshold-1] = v[len-1];
  const every = (len - 2) / (threshold - 2);
  let a = 0;
  for (let i = 0; i < threshold - 2; i++) {
    const avgS = Math.floor((i+1)*every)+1, avgE = Math.min(Math.floor((i+2)*every)+1, len);
    let avgT = 0, avgV = 0, n = 0;
    for (let j = avgS; j < avgE; j++) { avgT += t[j]; avgV += v[j]; n++; }
    if (n) { avgT /= n; avgV /= n; }
    const rS = Math.floor(i*every)+1, rE = Math.min(Math.floor((i+1)*every)+1, len);
    let maxA = -1, next = rS;
    const aT = t[a], aV = v[a];
    for (let j = rS; j < rE; j++) {
      const area = Math.abs((aT-avgT)*(v[j]-aV) - (aT-t[j])*(avgV-aV));
      if (area > maxA) { maxA = area; next = j; }
    }
    outT[i+1] = t[next]; outV[i+1] = v[next]; a = next;
  }
  return { t: outT, v: outV };
}

/* ════════════════════════════════════════════════════════════════
   uPlot helpers
   ════════════════════════════════════════════════════════════════ */
// Format Unix seconds → HH:MM:SS.mmm  (used for live x-axis ticks)
function fmtLiveTick(u, vals) {
  return vals.map(v => {
    if (v == null) return '';
    const d = new Date(v * 1000);
    const hh = String(d.getHours()).padStart(2,'0');
    const mm = String(d.getMinutes()).padStart(2,'0');
    const ss = String(d.getSeconds()).padStart(2,'0');
    const ms = String(d.getMilliseconds()).padStart(3,'0');
    return hh+':'+mm+':'+ss+'.'+ms;
  });
}
// Format relative seconds → ±Xms or ±Xs  (used for trigger x-axis ticks)
function fmtTrigTick(u, vals) {
  return vals.map(v => {
    if (v == null) return '';
    const abs = Math.abs(v), sign = v < 0 ? '-' : '+';
    if (abs < 1) return sign + (abs*1000).toFixed(1) + 'ms';
    return sign + abs.toFixed(3) + 's';
  });
}

// Draw custom cursor A/B lines onto the canvas (called from draw hook)
function drawCursorLines(u) {
  const { ctx, bbox } = u;
  if (!bbox) return;
  const drawLine = (val, color) => {
    if (val === null) return;
    const x = u.valToPos(val, 'x', true); // canvas pixels
    if (x < bbox.left || x > bbox.left + bbox.width) return;
    ctx.save();
    ctx.strokeStyle = color;
    ctx.lineWidth = 1.5;
    ctx.setLineDash([5, 4]);
    ctx.beginPath();
    ctx.moveTo(Math.round(x), bbox.top);
    ctx.lineTo(Math.round(x), bbox.top + bbox.height);
    ctx.stroke();
    ctx.restore();
  };
  drawLine(cursors.tA, 'rgba(137,220,235,0.85)');
  drawLine(cursors.tB, 'rgba(249,226,175,0.85)');
}

// Build uPlot opts for a given plot object
function makeUPlotOpts(p, inTrigMode) {
  const seriesArr = [{}]; // time (index 0)
  p.traces.forEach(key => {
    seriesArr.push({
      label: key,
      stroke: getTraceColor(key),
      width: 1.5,
      points: { show: false },
      spanGaps: true,
    });
  });

  const xVals = inTrigMode ? (u, vals) => fmtTrigTick(u, vals)
                           : (u, vals) => fmtLiveTick(u, vals);

  return {
    width:  Math.max(p.div.clientWidth  || 100, 50),
    height: Math.max(p.div.clientHeight || 100, 50),
    cursor: {
      sync: { key: inTrigMode ? 'trig' : 'live', setSeries: false },
      drag: { x: true, y: false, setScale: true, uni: 20 },
      lock: false,
    },
    select: { show: true },
    scales: {
      x: { time: false, auto: false,
           min: p.xRange ? p.xRange[0] : 0,
           max: p.xRange ? p.xRange[1] : windowSec },
      y: { auto: true },
    },
    series: seriesArr,
    axes: [
      { stroke:'#7f849c', grid:{ stroke:'#313244', width:1 }, ticks:{ stroke:'#313244', width:1 },
        values: xVals, size: 40 },
      { stroke:'#7f849c', grid:{ stroke:'#313244', width:1 }, ticks:{ stroke:'#313244', width:1 }, size: 50 },
    ],
    legend: { show: false },
    padding: [4, 8, 0, 0],
    hooks: {
      draw: [ u => drawCursorLines(u) ],
      // Two-hook zoom detection: setSelect flags that the NEXT setScale is user-initiated.
      // uPlot fires setSelect → then immediately setScale (when drag.setScale:true).
      // All programmatic setScale calls happen without a preceding setSelect, so the
      // flag is false and onZoom is never called unintentionally.
      setSelect: [(u) => { u._userZoom = (u.select.width > 0); }],
      setScale:  [(u, key) => {
        if (key !== 'x' || !u._userZoom || !u._ready) return;
        u._userZoom = false;
        const { min, max } = u.scales.x;
        if (min == null || max == null || max <= min) return;
        onZoom(p.id, min, max);
      }],
      ready: [ u => { u._ready = true; } ],
    },
  };
}

// Create (or recreate) the uPlot instance for a plot, mounting into p.div
function createUPlot(p) {
  // Destroy previous instance
  if (p.uplot) { p.uplot.destroy(); p.uplot = null; }

  const inTrigMode = trig.enabled && trig.snapshot !== null;
  const opts = makeUPlotOpts(p, inTrigMode);
  const data = buildUPlotData(p, inTrigMode);

  // Mount into the plot body div (clear previous uPlot DOM)
  p.div.querySelectorAll('.uplot').forEach(el => el.remove());

  p.uplot = new uPlot(opts, data, p.div);

  // ── Cursor drag: place or drag A/B cursors ──────────────────────────────
  // - Near an existing cursor line (within CURSOR_SNAP_PX): drag to move it.
  // - cursor mode A or B active: click/drag places that cursor anywhere.
  // - Intercepts mousedown before uPlot zoom so the selection rect never shows.
  const CURSOR_SNAP_PX = 8;

  function _cursorAtClientX(clientX) {
    const rect = p.uplot.over.getBoundingClientRect();
    const { min, max } = p.uplot.scales.x;
    const toX = val => rect.left + ((val - min) / (max - min)) * rect.width;
    if (cursors.tA !== null && Math.abs(clientX - toX(cursors.tA)) <= CURSOR_SNAP_PX) return 'A';
    if (cursors.tB !== null && Math.abs(clientX - toX(cursors.tB)) <= CURSOR_SNAP_PX) return 'B';
    return null;
  }

  function _cursorValFromEvent(e) {
    const rect = p.uplot.over.getBoundingClientRect();
    const pct = Math.max(0, Math.min(1, (e.clientX - rect.left) / rect.width));
    const { min, max } = p.uplot.scales.x;
    return min + pct * (max - min);
  }

  // Update pointer style based on what's under the mouse
  p.uplot.over.addEventListener('mousemove', e => {
    const snap = _cursorAtClientX(e.clientX);
    p.uplot.over.style.cursor = snap ? 'ew-resize' : '';
  });
  p.uplot.over.addEventListener('mouseleave', () => {
    p.uplot.over.style.cursor = '';
  });

  // Mousedown: start drag (intercept before uPlot to suppress zoom selection)
  p.uplot.over.addEventListener('mousedown', e => {
    if (e.button !== 0 || e.shiftKey) return; // shift is pan
    const snap   = _cursorAtClientX(e.clientX);
    const target = snap || (cursors.mode !== 'off' ? cursors.mode : null);
    if (!target) return;

    e.stopImmediatePropagation(); // prevent uPlot drag-zoom
    e.preventDefault();

    // Set cursor position immediately on mousedown
    if (target === 'A') cursors.tA = _cursorValFromEvent(e);
    else                cursors.tB = _cursorValFromEvent(e);
    updateCursorReadout();
    cursorsDirty = true;

    const onMove = ev => {
      if (target === 'A') cursors.tA = _cursorValFromEvent(ev);
      else                cursors.tB = _cursorValFromEvent(ev);
      updateCursorReadout();
      cursorsDirty = true;
    };
    const onUp = () => {
      document.removeEventListener('mousemove', onMove);
      document.removeEventListener('mouseup',   onUp);
    };
    document.addEventListener('mousemove', onMove);
    document.addEventListener('mouseup',   onUp);
  }, true); // capture:true so we fire before uPlot's own handlers

  // Pan support: Shift+left-drag pans the current view (synced across all plots).
  // Works in both zoomed mode (xRange set) and rolling mode (freezes the window first).
  let _panActive = false, _panAnchorX = 0, _panAnchorMin = 0, _panAnchorMax = 0;
  p.uplot.over.addEventListener('mousedown', e => {
    if (e.button !== 0 || !e.shiftKey) return;
    e.stopImmediatePropagation();
    e.preventDefault();
    _panActive = true;
    _panAnchorX = e.clientX;
    const xr = p.xRange;
    if (xr) {
      _panAnchorMin = xr[0];
      _panAnchorMax = xr[1];
    } else {
      // Rolling mode: capture the current window position and freeze it so we
      // have a stable anchor to pan from.
      let now = -Infinity;
      p.traces.forEach(key => {
        const buf = buffers[key];
        if (buf && buf.size > 0) {
          const t = buf.t[(buf.head - 1 + buf.cap) % buf.cap];
          if (t > now) now = t;
        }
      });
      if (!isFinite(now)) now = Date.now() / 1000;
      _panAnchorMin = now - windowSec;
      _panAnchorMax = now;
      // Freeze all plots at this position immediately.
      const pMin = _panAnchorMin, pMax = _panAnchorMax;
      zoomGuard = true;
      plots.forEach(q => {
        q.xRange = [pMin, pMax];
        if (q.uplot) q.uplot.setScale('x', { min: pMin, max: pMax });
      });
      zoomGuard = false;
      if (!syncLocked) {
        syncLocked = true;
        const btnR = document.getElementById('btn-sync-resume');
        if (btnR) btnR.style.display = '';
      }
    }
  }, true);
  const _onPanMove = e => {
    if (!_panActive || !p.uplot) return;
    const w = p.uplot.over.getBoundingClientRect().width;
    const span = _panAnchorMax - _panAnchorMin;
    const dt = -((e.clientX - _panAnchorX) / w) * span;
    const newMin = _panAnchorMin + dt;
    const newMax = _panAnchorMax + dt;
    zoomGuard = true;
    plots.forEach(q => {
      q.xRange = [newMin, newMax];
      if (q.uplot) q.uplot.setScale('x', { min: newMin, max: newMax });
      q.needsRedraw = true;
    });
    zoomGuard = false;
  };
  const _onPanEnd = () => { _panActive = false; };
  document.addEventListener('mousemove', _onPanMove);
  document.addEventListener('mouseup', _onPanEnd);

  // Resize observer so the uPlot fills its container.
  // zoomGuard prevents setSize → setScale → hook from calling onZoom.
  if (p.ro) { p.ro.disconnect(); }
  p.ro = new ResizeObserver(() => {
    if (!p.uplot) return;
    const w = Math.max(p.div.clientWidth  || 50, 50);
    const h = Math.max(p.div.clientHeight || 50, 50);
    zoomGuard = true;
    p.uplot.setSize({ width: w, height: h });
    zoomGuard = false;
  });
  p.ro.observe(p.div);
}

// Build the uPlot data array from buffers / trigger snapshot
function buildUPlotData(p, inTrigMode) {
  if (p.traces.length === 0) return [new Float64Array(0)];

  // When trigger is enabled but no snapshot yet (armed/waiting), return
  // the last-rendered data so the plot stays frozen.
  if (trig.enabled && !inTrigMode) {
    if (!p.uplot || !p.uplot.data || !p.uplot.data[0]) return [new Float64Array(0)];
    return p.uplot.data;
  }

  if (inTrigMode && trig.snapshot) return buildTrigData(p);
  return buildLiveData(p);
}

// Resample (vSrc) from times (tSrc) onto target times (tDst) using linear interpolation.
// tSrc must be sorted ascending.  Values outside tSrc range are clamped to the nearest
// endpoint (extrapolation is not safe for streaming data).
function resampleLinear(tSrc, vSrc, tDst) {
  const n = tDst.length;
  const out = new Float64Array(n);
  if (tSrc.length === 0) return out; // all zeros
  if (tSrc.length === 1) { out.fill(vSrc[0]); return out; }
  let j = 0;
  for (let i = 0; i < n; i++) {
    const td = tDst[i];
    // Advance j so that tSrc[j] <= td < tSrc[j+1] (or j at last index)
    while (j < tSrc.length - 2 && tSrc[j + 1] < td) j++;
    if (td <= tSrc[0]) {
      out[i] = vSrc[0];
    } else if (td >= tSrc[tSrc.length - 1]) {
      out[i] = vSrc[vSrc.length - 1];
    } else {
      const t0 = tSrc[j], t1 = tSrc[j + 1];
      const frac = (td - t0) / (t1 - t0);
      out[i] = vSrc[j] + frac * (vSrc[j + 1] - vSrc[j]);
    }
  }
  return out;
}

function buildLiveData(p) {
  if (p.traces.length === 0) return [new Float64Array(0)];

  // plotNow = newest timestamp across ALL traces
  let plotNow = -Infinity;
  p.traces.forEach(key => {
    const buf = buffers[key];
    if (buf && buf.size > 0) {
      const t = buf.t[(buf.head - 1 + buf.cap) % buf.cap];
      if (t > plotNow) plotNow = t;
    }
  });
  if (!isFinite(plotNow)) plotNow = Date.now() / 1000;

  const t0 = p.xRange ? p.xRange[0] : plotNow - windowSec;
  const t1 = p.xRange ? p.xRange[1] : plotNow;

  // Pixel-adaptive LTTB target: 2× plot width so zooming in automatically
  // raises the effective sample cap and reveals full resolution.
  const targetPts = Math.max(LTTB_MIN, ((p.uplot ? p.uplot.width : p.div.clientWidth) || 600) * 2);

  // Slice all traces once; pick the master time grid using configured samplingRate
  // as the primary criterion (unambiguous, independent of buffer fill / trace order).
  // Fall back to raw sample count for signals without a configured rate.
  const slices = {};
  let masterKey = p.traces[0], masterCount = -1, masterRate = -1;
  for (const key of p.traces) {
    const buf = buffers[key];
    if (!buf || buf.size === 0) continue;
    const sl = getBufferSliceRange(buf, t0, t1);
    slices[key] = sl;
    const rate = getKeySamplingRate(key);
    if (rate > masterRate || (rate === masterRate && sl.t.length > masterCount)) {
      masterRate = rate; masterCount = sl.t.length; masterKey = key;
    }
  }

  const masterRaw = slices[masterKey];
  if (!masterRaw || masterRaw.t.length === 0)
    return [new Float64Array(0), ...p.traces.map(() => new Float64Array(0))];

  // Decimate master with pixel-adaptive LTTB, use resulting grid for all others
  const dec = lttb(masterRaw.t, masterRaw.v, targetPts);
  const sharedT = dec.t;

  const yArrays = [];
  for (const key of p.traces) {
    if (key === masterKey) { yArrays.push(dec.v); continue; }
    const sl = slices[key];
    if (!sl || sl.t.length === 0) { yArrays.push(new Float64Array(sharedT.length)); continue; }
    yArrays.push(resampleLinear(sl.t, sl.v, sharedT));
  }

  return [sharedT, ...yArrays];
}

function buildTrigData(p) {
  const trigT = trig.trigTime;
  const preS  = trig.snapshot._preS  !== undefined ? trig.snapshot._preS  : trigPreSec();
  const postS = trig.snapshot._postS !== undefined ? trig.snapshot._postS : trigPostSec();

  if (p.traces.length === 0) return [new Float64Array(0)];

  const t0 = p.xRange ? trigT + p.xRange[0] : trigT - preS;
  const t1 = p.xRange ? trigT + p.xRange[1] : trigT + postS;

  const targetPts = Math.max(LTTB_MIN, ((p.uplot ? p.uplot.width : p.div.clientWidth) || 600) * 2);

  // Slice all traces; pick master by samplingRate first, then sample count
  const slices = {};
  let masterKey = p.traces[0], masterCount = -1, masterRate = -1;
  for (const key of p.traces) {
    const snap = trig.snapshot[key];
    if (!snap) continue;
    const sl = sliceTypedArrayRange(snap.t, snap.v, t0, t1);
    slices[key] = sl;
    const rate = getKeySamplingRate(key);
    if (rate > masterRate || (rate === masterRate && sl.t.length > masterCount)) {
      masterRate = rate; masterCount = sl.t.length; masterKey = key;
    }
  }

  const masterRaw = slices[masterKey];
  if (!masterRaw || masterRaw.t.length === 0)
    return [new Float64Array(0), ...p.traces.map(() => new Float64Array(0))];

  const dec = lttb(masterRaw.t, masterRaw.v, targetPts);
  // Convert absolute → relative seconds
  const sharedT = new Float64Array(dec.t.length);
  for (let i = 0; i < dec.t.length; i++) sharedT[i] = dec.t[i] - trigT;

  const yArrays = [];
  for (const key of p.traces) {
    if (key === masterKey) { yArrays.push(dec.v); continue; }
    const sl = slices[key];
    if (!sl || sl.t.length === 0) { yArrays.push(new Float64Array(sharedT.length)); continue; }
    const relT = new Float64Array(sl.t.length);
    for (let i = 0; i < sl.t.length; i++) relT[i] = sl.t[i] - trigT;
    yArrays.push(resampleLinear(relT, sl.v, sharedT));
  }

  return [sharedT, ...yArrays];
}

/* ════════════════════════════════════════════════════════════════
   Zoom sync
   ════════════════════════════════════════════════════════════════ */
let syncLocked = false;

function onZoom(sourcePlotId, min, max) {
  // Push current range to history before applying new zoom
  const prevRange = plots[0] && plots[0].xRange ? [...plots[0].xRange] : null;
  zoomHistory.push(prevRange);
  if (zoomHistory.length > 30) zoomHistory.shift();
  document.getElementById('btn-zoom-back').style.display = '';

  // Store zoom on source plot
  const src = plots.find(p => p.id === sourcePlotId);
  if (src) src.xRange = [min, max];

  // Show Auto button in live mode
  if (!trig.enabled && !syncLocked) {
    syncLocked = true;
    document.getElementById('btn-sync-resume').style.display = '';
  }

  // Propagate to other plots
  zoomGuard = true;
  plots.forEach(p => {
    if (p.id === sourcePlotId) return;
    p.xRange = [min, max];
    if (p.uplot) p.uplot.setScale('x', { min, max });
  });
  zoomGuard = false;

  // Mark all plots dirty (re-slice data to the new range for full resolution)
  plots.forEach(p => { p.needsRedraw = true; });
}

// Undo last zoom/pan action
function zoomBack() {
  if (!zoomHistory.length) return;
  const prev = zoomHistory.pop();
  if (!zoomHistory.length) document.getElementById('btn-zoom-back').style.display = 'none';

  if (prev === null) {
    // Was at auto/rolling state before the zoom
    resetZoom();
  } else {
    zoomGuard = true;
    plots.forEach(p => {
      p.xRange = [...prev];
      if (p.uplot) p.uplot.setScale('x', { min: prev[0], max: prev[1] });
      p.needsRedraw = true;
    });
    zoomGuard = false;
  }
}

// Reset to auto/rolling window (clears all zoom)
function resetZoom() {
  syncLocked = false;
  document.getElementById('btn-sync-resume').style.display = 'none';
  if (trig.enabled && trig.snapshot) {
    const preS  = trig.snapshot._preS  || trigPreSec();
    const postS = trig.snapshot._postS || trigPostSec();
    zoomGuard = true;
    plots.forEach(p => {
      p.xRange = null;
      if (p.uplot) p.uplot.setScale('x', { min: -preS, max: postS });
      p.needsRedraw = true;
    });
    zoomGuard = false;
  } else {
    // Back to rolling window — setScale to current window, render loop keeps it moving
    plots.forEach(p => {
      p.xRange = null;
      if (!globalPause) p.needsRedraw = true;
    });
  }
}

// Fit x-axis to all data currently in buffers (or full trigger snapshot)
function zoomFit() {
  if (trig.enabled && trig.snapshot) {
    resetZoom(); // "Fit" in trigger mode = show full trigger window
    return;
  }
  // Find oldest/newest timestamps across all visible signals
  let gMin = Infinity, gMax = -Infinity;
  plots.forEach(p => {
    p.traces.forEach(key => {
      const buf = buffers[key]; if (!buf || buf.size === 0) return;
      const startIdx = (buf.size === buf.cap) ? buf.head : 0;
      const oldestT  = buf.t[startIdx];
      const newestT  = buf.t[(buf.head - 1 + buf.cap) % buf.cap];
      if (oldestT < gMin) gMin = oldestT;
      if (newestT > gMax) gMax = newestT;
    });
  });
  if (!isFinite(gMin) || gMin >= gMax) return;

  // Push to history
  const prevRange = plots[0] && plots[0].xRange ? [...plots[0].xRange] : null;
  zoomHistory.push(prevRange);
  document.getElementById('btn-zoom-back').style.display = '';
  if (!syncLocked) { syncLocked = true; document.getElementById('btn-sync-resume').style.display = ''; }

  zoomGuard = true;
  plots.forEach(p => {
    p.xRange = [gMin, gMax];
    if (p.uplot) p.uplot.setScale('x', { min: gMin, max: gMax });
    p.needsRedraw = true;
  });
  zoomGuard = false;
}

// Auto = return to rolling window / full trigger window
function exitSyncLock() { resetZoom(); }

document.getElementById('btn-sync-resume').addEventListener('click', resetZoom);
document.getElementById('btn-zoom-back').addEventListener('click', zoomBack);
document.getElementById('btn-zoom-fit').addEventListener('click',  zoomFit);

/* ════════════════════════════════════════════════════════════════
   Cursor controls
   ════════════════════════════════════════════════════════════════ */
const CURSOR_LABELS = { off:'Cursor', A:'Cursor A', B:'Cursor B' };

// Show the cursor button only when paused or in trigger-snapshot mode.
// Hides and clears cursors whenever neither condition holds.
function updateCursorBtnVisibility() {
  const canUseCursors = globalPause || (trig.enabled && trig.snapshot !== null);
  const btn = document.getElementById('btn-cursor');
  btn.style.display = canUseCursors ? '' : 'none';
  if (!canUseCursors && cursors.mode !== 'off') {
    cursors.mode = 'off';
    cursors.tA = null; cursors.tB = null;
    btn.textContent = CURSOR_LABELS.off;
    btn.className = 'ctrl-btn';
    document.getElementById('cursor-readout').classList.remove('visible');
    cursorsDirty = true;
  }
}
const CURSOR_MODES  = ['off','A','B'];

document.getElementById('btn-cursor').addEventListener('click', () => {
  cursors.mode = CURSOR_MODES[(CURSOR_MODES.indexOf(cursors.mode)+1) % 3];
  const btn = document.getElementById('btn-cursor');
  btn.textContent = CURSOR_LABELS[cursors.mode];
  btn.className = 'ctrl-btn'
    + (cursors.mode==='A' ? ' cursor-a' : cursors.mode==='B' ? ' cursor-b' : '');
  if (cursors.mode === 'off') {
    cursors.tA = null; cursors.tB = null;
    document.getElementById('cursor-readout').classList.remove('visible');
    cursorsDirty = true;
  } else {
    document.getElementById('cursor-readout').classList.add('visible');
  }
});

function updateCursorReadout() {
  const ro = document.getElementById('cursor-readout');
  const active = cursors.mode !== 'off' || cursors.tA !== null || cursors.tB !== null;
  ro.classList.toggle('visible', active);
  if (!active) return;

  // Format depends on mode: live = HH:MM:SS.mmm, trigger = ±Xms
  const fmt = v => {
    if (v === null) return '—';
    if (trig.enabled && trig.snapshot) {
      const abs = Math.abs(v), sign = v < 0 ? '-' : '+';
      return abs < 1 ? sign+(abs*1000).toFixed(3)+'ms' : sign+abs.toFixed(6)+'s';
    }
    const d = new Date(v * 1000);
    return String(d.getHours()).padStart(2,'0') + ':'
         + String(d.getMinutes()).padStart(2,'0') + ':'
         + String(d.getSeconds()).padStart(2,'0') + '.'
         + String(d.getMilliseconds()).padStart(3,'0');
  };
  document.getElementById('cur-ta').textContent = 'A: ' + fmt(cursors.tA);
  document.getElementById('cur-tb').textContent = 'B: ' + fmt(cursors.tB);
  if (cursors.tA !== null && cursors.tB !== null) {
    const dt = cursors.tB - cursors.tA, abs = Math.abs(dt);
    const s = dt >= 0 ? '+' : '-';
    const str = abs < 1 ? s+(abs*1000).toFixed(3)+'ms' : s+abs.toFixed(6)+'s';
    document.getElementById('cur-dt').textContent = 'ΔT: ' + str;
  } else {
    document.getElementById('cur-dt').textContent = 'ΔT: —';
  }
}

/* ════════════════════════════════════════════════════════════════
   Trigger bar controls
   ════════════════════════════════════════════════════════════════ */
function openTrigBar(open) {
  trig.enabled = open;
  document.getElementById('trigbar').classList.toggle('open', open);
  document.getElementById('btn-trigger').classList.toggle('trig-active', open);
  document.documentElement.style.setProperty('--trigbar-h', open ? '48px' : '0px');
  // Streaming-only controls are irrelevant while the trigger is active
  const none = open ? 'none' : '';
  document.getElementById('btn-pause-global').style.display = none;
  document.getElementById('window-select').style.display = none;
  document.getElementById('lbl-window').style.display = none;
  if (!open) {
    trigDisarm(); trig.snapshot = null;
    cursors.tA = null; cursors.tB = null; updateCursorReadout();
    updateCursorBtnVisibility();
    zoomHistory.length = 0;
    document.getElementById('btn-zoom-back').style.display = 'none';
    plots.forEach(p => { p.xRange = null; p.needsRedraw = true; });
  } else {
    cursors.tA = null; cursors.tB = null; updateCursorReadout();
    updateCursorBtnVisibility();
    zoomHistory.length = 0;
    document.getElementById('btn-zoom-back').style.display = 'none';
    resetZoom();
    if (trig.signal) trigArm(); else updateTrigStatusBadge('idle');
  }
  // Resize uPlot instances after trigbar height changes
  setTimeout(() => { plots.forEach(p => {
    if (!p.uplot) return;
    p.uplot.setSize({ width: p.div.clientWidth, height: p.div.clientHeight });
  }); }, 220);
}
document.getElementById('btn-trigger').addEventListener('click', () => openTrigBar(!trig.enabled));
document.getElementById('trig-signal').addEventListener('change', e => {
  trig.signal = e.target.value; trig.prevVal = null;
  if (trig.enabled && trig.signal) trigArm(); else if (!trig.signal) trigDisarm();
});
document.getElementById('trig-edge').addEventListener('change',     e => { trig.edge      = e.target.value; if (trig.armed) trig.prevVal = null; });
document.getElementById('trig-threshold').addEventListener('change', e => { trig.threshold = parseFloat(e.target.value)||0; if (trig.armed) trig.prevVal = null; });
document.getElementById('trig-window').addEventListener('change',   e => { trig.windowSec  = parseFloat(e.target.value); });
document.getElementById('trig-pre').addEventListener('input', e => {
  trig.prePercent = parseInt(e.target.value, 10);
  document.getElementById('trig-pre-val').textContent = trig.prePercent + '%';
});
document.getElementById('trig-mode').addEventListener('change', e => { trig.mode = e.target.value; });
document.getElementById('btn-trig-rearm').addEventListener('click', () => { if (trig.enabled) trigArm(); });
document.getElementById('btn-trig-stop').addEventListener('click', () => {
  if (!trig.enabled || trig.mode !== 'normal') return;
  trig.stopped = !trig.stopped;
  updateStopBtn();
  if (!trig.stopped) trigArm(); // resume: re-arm immediately
});

/* ════════════════════════════════════════════════════════════════
   Trigger signal selector
   ════════════════════════════════════════════════════════════════ */
function buildTrigSignalSelect() {
  const sel = document.getElementById('trig-signal'), cur = sel.value;
  sel.innerHTML = '<option value="">— none —</option>';
  signals.forEach(sig => {
    const n = numElements(sig);
    if (isTemporal(sig) || n === 1) {
      const o = document.createElement('option'); o.value = sig.name; o.textContent = sig.name; sel.appendChild(o);
    } else {
      for (let i = 0; i < n; i++) {
        const key = sig.name+'['+i+']', o = document.createElement('option');
        o.value = key; o.textContent = key; sel.appendChild(o);
      }
    }
  });
  if (cur && [...sel.options].some(o => o.value === cur)) sel.value = cur;
  trig.signal = sel.value;
}

/* ════════════════════════════════════════════════════════════════
   Sidebar
   ════════════════════════════════════════════════════════════════ */
function buildSidebar() {
  const list = document.getElementById('signal-list');
  list.innerHTML = '';
  if (!signals.length) {
    list.innerHTML = '<div style="padding:20px 14px;color:var(--overlay0);font-size:12px;text-align:center;">No signals</div>';
    return;
  }
  const typeNames = ['u8','i8','u16','i16','u32','i32','u64','i64','f32','f64'];
  signals.forEach(sig => {
    const n = numElements(sig), temporal = isTemporal(sig);
    const typeName = typeNames[sig.typeCode] || '?';
    if (n === 1 || temporal) {
      list.appendChild(makeDraggable(sig.name, sig.name, temporal?'['+n+'] '+typeName:typeName, sig.unit||''));
    } else {
      const group = document.createElement('div'); group.className = 'array-group';
      const header = document.createElement('div'); header.className = 'array-header';
      header.innerHTML = '<span class="array-arrow">&#x25B6;</span><span class="sig-name">'+escHtml(sig.name)+'</span>'
        + (sig.unit?'<span class="sig-unit">'+escHtml(sig.unit)+'</span>':'')
        + '<span class="type-badge">['+n+'] '+typeName+'</span>';
      header.addEventListener('click', () => header.classList.toggle('open'));
      const children = document.createElement('div'); children.className = 'array-children';
      for (let i = 0; i < n; i++) {
        const key = sig.name+'['+i+']', child = makeDraggable(key, key, typeName, sig.unit||'');
        child.className = 'array-child'; children.appendChild(child);
      }
      group.appendChild(header); group.appendChild(children); list.appendChild(group);
    }
  });
}
function makeDraggable(key, label, typeName, unit) {
  const item = document.createElement('div');
  item.className = 'sig-item'; item.draggable = true;
  item.innerHTML = '<span class="sig-name">'+escHtml(label)+'</span>'
    + (unit?'<span class="sig-unit">'+escHtml(unit)+'</span>':'')
    + '<span class="type-badge">'+escHtml(typeName)+'</span>';
  item.addEventListener('dragstart', e => {
    e.dataTransfer.setData('signal', key); e.dataTransfer.effectAllowed = 'copy';
    requestAnimationFrame(() => item.classList.add('dragging'));
  });
  item.addEventListener('dragend', () => item.classList.remove('dragging'));
  return item;
}

/* ════════════════════════════════════════════════════════════════
   Layout management
   ════════════════════════════════════════════════════════════════ */
// Returns the number of plot cells in a layout (cols × rows).
function layoutPlotCount(cls) {
  const m = cls.match(/^l(\d+)x(\d+)$/);
  return m ? parseInt(m[1]) * parseInt(m[2]) : 1;
}

// Build a small SVG grid thumbnail for a given cols×rows layout.
function layoutSVG(cols, rows) {
  const W = 40, H = 28, GAP = 2, PAD = 2;
  const cw = (W - PAD * 2 - GAP * (cols - 1)) / cols;
  const ch = (H - PAD * 2 - GAP * (rows - 1)) / rows;
  let rects = '';
  for (let r = 0; r < rows; r++) {
    for (let c = 0; c < cols; c++) {
      const x = (PAD + c * (cw + GAP)).toFixed(1);
      const y = (PAD + r * (ch + GAP)).toFixed(1);
      rects += `<rect x="${x}" y="${y}" width="${cw.toFixed(1)}" height="${ch.toFixed(1)}" rx="1.5"/>`;
    }
  }
  return `<svg xmlns="http://www.w3.org/2000/svg" width="${W}" height="${H}" viewBox="0 0 ${W} ${H}">`
       + `<g fill="currentColor">${rects}</g></svg>`;
}

// Apply a new layout: switch the grid class and auto-add/remove plots.
// Plots with traces are preserved; empty plots are removed first when shrinking.
function applyLayout(cls) {
  const entry = LAYOUTS.find(l => l[1] === cls);
  if (!entry) return;
  const [label,, cols, rows] = entry;
  currentLayout = cls;
  document.getElementById('plot-grid').className = cls;

  // Update button label
  const btn = document.getElementById('btn-layout');
  if (btn) btn.innerHTML = layoutSVG(cols, rows) + ' <span>' + label + '</span> ▾';

  // Update active state in menu
  document.querySelectorAll('.layout-menu-item')
    .forEach(el => el.classList.toggle('active', el.dataset.layout === cls));

  const needed = layoutPlotCount(cls);

  // Remove excess plots — prefer empty ones to preserve trace assignments.
  while (plots.length > needed) {
    let removeId = plots[plots.length - 1].id;
    for (let i = plots.length - 1; i >= 0; i--) {
      if (plots[i].traces.length === 0) { removeId = plots[i].id; break; }
    }
    deletePlot(removeId);
  }

  // Add missing plots.
  while (plots.length < needed) addPlot();

  setTimeout(() => plots.forEach(p => {
    if (p.uplot) p.uplot.setSize({ width: p.div.clientWidth, height: p.div.clientHeight });
  }), 120);
}

function buildLayoutMenu() {
  const menu = document.getElementById('layout-menu');

  LAYOUTS.forEach(([label, cls, cols, rows]) => {
    const item = document.createElement('button');
    item.className = 'layout-menu-item' + (cls === currentLayout ? ' active' : '');
    item.dataset.layout = cls;
    item.innerHTML = layoutSVG(cols, rows) + '<span>' + label + '</span>';
    item.addEventListener('click', () => {
      applyLayout(cls);
      menu.classList.remove('open');
    });
    menu.appendChild(item);
  });

  // Toggle menu open/close
  document.getElementById('btn-layout').addEventListener('click', e => {
    e.stopPropagation();
    const r = e.currentTarget.getBoundingClientRect();
    menu.style.left = r.left + 'px';
    menu.style.top  = (r.bottom + 4) + 'px';
    menu.classList.toggle('open');
  });

  // Close when clicking outside
  document.addEventListener('click', e => {
    if (!e.target.closest('#layout-menu') && !e.target.closest('#btn-layout'))
      menu.classList.remove('open');
  });
}

/* ════════════════════════════════════════════════════════════════
   Export CSV (all plots)
   ════════════════════════════════════════════════════════════════ */
function exportAllCSV() {
  const inTrigMode = trig.enabled && trig.snapshot !== null;
  // Collect unique signal keys across all plots (preserving order)
  const keys = [];
  plots.forEach(p => p.traces.forEach(k => { if (!keys.includes(k)) keys.push(k); }));
  if (!keys.length) return;

  const slices = keys.map(key => {
    if (inTrigMode) {
      const raw = trig.snapshot[key] || { t: new Float64Array(0), v: new Float64Array(0) };
      return { t: Array.from(raw.t).map(ts => ts - trig.trigTime), v: Array.from(raw.v) };
    }
    const buf = buffers[key]; if (!buf) return { t: [], v: [] };
    const sl = getBufferSlice(buf);
    return { t: Array.from(sl.t), v: Array.from(sl.v) };
  });

  const allT = new Set(); slices.forEach(s => s.t.forEach(t => allT.add(t)));
  const sortedT = Array.from(allT).sort((a, b) => a - b);
  const lookups = slices.map(s => { const m = new Map(); s.t.forEach((t, i) => m.set(t, s.v[i])); return m; });
  const hdr  = [(inTrigMode ? 'time_rel_s' : 'time_s'), ...keys].join(',');
  const rows = sortedT.map(t => [t.toFixed(9), ...lookups.map(lk => lk.has(t) ? lk.get(t) : '')].join(','));
  const blob = new Blob([hdr + '\n' + rows.join('\n')], { type: 'text/csv' });
  const a = document.createElement('a');
  a.href = URL.createObjectURL(blob); a.download = 'signals_' + Date.now() + '.csv';
  a.click(); URL.revokeObjectURL(a.href);
}

/* ════════════════════════════════════════════════════════════════
   Plot management
   ════════════════════════════════════════════════════════════════ */
function addPlot() {
  const id = nextPlotId++;
  const card = document.createElement('div');
  card.className = 'plot-card'; card.dataset.plotId = id;
  card.innerHTML = `
    <div class="plot-card-header">
      <div class="plot-title" contenteditable="true" spellcheck="false">Plot ${id}</div>
      <div class="sig-badges" id="badges-${id}"></div>
    </div>
    <div class="plot-body" id="pbody-${id}">
      <div class="drop-hint" id="hint-${id}">Drop signals here</div>
      <div class="trig-collect-overlay"><span class="trig-collect-text">⚡ Collecting…</span></div>
    </div>`;

  card.addEventListener('dragover',  e => { e.preventDefault(); e.dataTransfer.dropEffect='copy'; card.classList.add('drag-over'); });
  card.addEventListener('dragleave', () => card.classList.remove('drag-over'));
  card.addEventListener('drop', e => {
    e.preventDefault(); card.classList.remove('drag-over');
    const key = e.dataTransfer.getData('signal'); if (key) addTraceTo(id, key);
  });

  document.getElementById('plot-grid').appendChild(card);

  const plotBody = card.querySelector('#pbody-'+id);
  const p = { id, traces:[], div: plotBody, needsRedraw:false, xRange:null, uplot:null, ro:null };
  plots.push(p);

  // Create the uPlot instance (empty) — deferred so DOM has settled
  requestAnimationFrame(() => { createUPlot(p); });
  return id;
}

function addTraceTo(plotId, signalKey) {
  const p = plots.find(p => p.id === plotId); if (!p) return;
  if (p.traces.includes(signalKey)) return;
  p.traces.push(signalKey);
  document.querySelector('#hint-'+plotId).style.display = 'none';
  addBadge(plotId, signalKey);
  // Recreate uPlot with new series list
  createUPlot(p);
  p.needsRedraw = true;
}

function removeTraceFrom(plotId, signalKey) {
  const p = plots.find(p => p.id === plotId); if (!p) return;
  p.traces = p.traces.filter(t => t !== signalKey);
  removeBadge(plotId, signalKey);
  createUPlot(p);
  p.needsRedraw = true;
  if (!p.traces.length) document.querySelector('#hint-'+plotId).style.display = '';
}

function addBadge(plotId, key) {
  const c = document.getElementById('badges-'+plotId); if (!c) return;
  if (c.querySelector('[data-key="'+CSS.escape(key)+'"]')) return;
  const color = getTraceColor(key);
  const badge = document.createElement('span');
  badge.className = 'sig-badge'; badge.dataset.key = key;
  const dot = document.createElement('span'); dot.className = 'trace-dot'; dot.style.background = color;
  const x   = document.createElement('span'); x.className = 'sig-badge-x'; x.title = 'Remove'; x.textContent = '×';
  x.addEventListener('click', () => removeTraceFrom(plotId, key));
  badge.appendChild(dot); badge.appendChild(document.createTextNode(key)); badge.appendChild(x);
  c.appendChild(badge);
}
function removeBadge(plotId, key) {
  const c = document.getElementById('badges-'+plotId); if (!c) return;
  const b = c.querySelector('[data-key="'+CSS.escape(key)+'"]'); if (b) b.remove();
}


function deletePlot(plotId) {
  const idx = plots.findIndex(p => p.id === plotId); if (idx === -1) return;
  const p = plots[idx];
  if (p.ro) p.ro.disconnect();
  if (p.uplot) p.uplot.destroy();
  plots.splice(idx, 1);
  document.querySelector('[data-plot-id="'+plotId+'"]').remove();
}

/* ════════════════════════════════════════════════════════════════
   Render loop
   ════════════════════════════════════════════════════════════════ */
let _dbgTick = 0;
function renderDirtyPlots() {
  const inTrigMode = trig.enabled && trig.snapshot !== null;

  // Diagnostic: every ~5 s print buffer state to the browser console.
  // Open DevTools → Console to see timestamps and sizes.
  if (++_dbgTick % 300 === 0) {
    const wallNow = Date.now() / 1000;
    let anyData = false;
    Object.entries(buffers).forEach(([k, b]) => {
      if (b.size === 0) return;
      anyData = true;
      const newest = b.t[(b.head - 1 + b.cap) % b.cap];
      const oldest = b.t[(b.size === b.cap ? b.head : 0) % b.cap];
      const sliceLen = getBufferSlice(b).t.length;
      console.log(`[buf] ${k}: size=${b.size} oldest=${oldest.toFixed(3)} newest=${newest.toFixed(3)} wallNow=${wallNow.toFixed(3)} ts-age=${(wallNow-newest).toFixed(3)}s slice(${windowSec}s)=${sliceLen}pts`);
    });
    if (!anyData) console.log('[buf] all buffers empty — no data received yet');
    plots.forEach(p => console.log(`[plot${p.id}] traces=${JSON.stringify(p.traces)} xRange=${JSON.stringify(p.xRange)} needsRedraw=${p.needsRedraw}`));
  }

  // Rolling-window mode: detect stale xRange (buffer has scrolled past a frozen
  // zoom window) and clear it back to rolling.  Run unconditionally before the
  // data-rebuild loop so the stale plot is correctly handled this frame.
  if (!trig.enabled && !globalPause) {
    plots.forEach(p => {
      if (!p.uplot || !p.xRange) return;
      const hasData = p.traces.some(k => buffers[k] && buffers[k].size > 0);
      if (!hasData) return;
      const stale = p.traces.every(key => {
        const buf = buffers[key];
        if (!buf || buf.size === 0) return true;
        const oldest = buf.t[buf.size === buf.cap ? buf.head : 0];
        return p.xRange[1] < oldest;
      });
      if (stale) {
        p.xRange = null;
        syncLocked = false;
        const btnR = document.getElementById('btn-sync-resume');
        if (btnR) btnR.style.display = 'none';
      }
    });
  }

  // Fast path: cursor-only redraw (no data rebuild needed)
  if (cursorsDirty) {
    cursorsDirty = false;
    plots.forEach(p => { if (p.uplot) p.uplot.redraw(false); });
  }

  // Rolling-window plots: mark dirty every frame for smooth continuous scrolling.
  // setScale is called AFTER setData inside the rebuild loop so the viewport and
  // data slice are always computed with the same plotNow anchor.
  if (!trig.enabled && !globalPause) {
    plots.forEach(p => {
      if (!p.uplot || p.xRange) return;
      p.needsRedraw = true;
    });
  }

  plots.forEach(p => {
    if (!p.needsRedraw || !p.uplot) return;
    p.needsRedraw = false;

    const data = buildUPlotData(p, inTrigMode);

    // setData internally triggers the setScale hook in uPlot (it reaffirms the
    // current scale even with auto:false).  Keep zoomGuard raised across the
    // entire setData + setScale block so the hook never calls onZoom and freezes
    // p.xRange unintentionally.  The guard is safe here: JS is single-threaded so
    // no genuine user drag-zoom event can fire during this synchronous block.
    zoomGuard = true;
    p.uplot.setData(data);

    // Re-apply the x-scale after setData so the viewport stays correct.
    if (trig.enabled && !inTrigMode) {
      // Armed / waiting for trigger: keep the current scale frozen.
    } else if (inTrigMode) {
      const preS  = trig.snapshot._preS  !== undefined ? trig.snapshot._preS  : trigPreSec();
      const postS = trig.snapshot._postS !== undefined ? trig.snapshot._postS : trigPostSec();
      p.uplot.setScale('x', { min: p.xRange ? p.xRange[0] : -preS,
                               max: p.xRange ? p.xRange[1] :  postS });
    } else if (p.xRange) {
      // Zoomed: re-apply so scale is correct after setData
      p.uplot.setScale('x', { min: p.xRange[0], max: p.xRange[1] });
    } else {
      // Rolling window: compute plotNow fresh each frame (same anchor as buildLiveData)
      // and set the scale immediately after setData for correct alignment.
      let plotNow = -Infinity;
      p.traces.forEach(key => {
        const buf = buffers[key];
        if (!buf || buf.size === 0) return;
        const t = buf.t[(buf.head - 1 + buf.cap) % buf.cap];
        if (t > plotNow) plotNow = t;
      });
      if (!isFinite(plotNow)) plotNow = Date.now() / 1000;
      p.uplot.setScale('x', { min: plotNow - windowSec, max: plotNow });
    }
    zoomGuard = false;
  });

  requestAnimationFrame(renderDirtyPlots);
}


/* ════════════════════════════════════════════════════════════════
   Global controls
   ════════════════════════════════════════════════════════════════ */
document.getElementById('btn-pause-global').addEventListener('click', () => {
  globalPause = !globalPause;
  const btn = document.getElementById('btn-pause-global');
  btn.textContent = globalPause ? '▶ Resume' : '⏸ Pause';
  btn.classList.toggle('active', globalPause);
  if (!globalPause) plots.forEach(p => { p.needsRedraw = true; });
  updateCursorBtnVisibility();
});

document.getElementById('window-select').addEventListener('change', e => {
  windowSec = parseFloat(e.target.value);
  // Don't trigger redraws while in trigger mode without a snapshot
  if (trig.enabled && !trig.snapshot) return;
  plots.forEach(p => { if (!p.xRange) p.needsRedraw = true; });
});

/* ════════════════════════════════════════════════════════════════
   Sidebar toggle
   ════════════════════════════════════════════════════════════════ */
let sidebarOpen = true;
function setSidebar(open) {
  sidebarOpen = open;
  document.getElementById('sidebar').classList.toggle('collapsed', !open);
  document.getElementById('btn-sidebar').classList.toggle('active', open);
  setTimeout(() => { plots.forEach(p => {
    if (p.uplot) p.uplot.setSize({ width: p.div.clientWidth, height: p.div.clientHeight });
  }); }, 200);
}
document.getElementById('btn-sidebar').addEventListener('click', () => setSidebar(!sidebarOpen));

/* ════════════════════════════════════════════════════════════════
   Utility
   ════════════════════════════════════════════════════════════════ */
function escHtml(s) {
  return String(s).replace(/&/g,'&amp;').replace(/</g,'&lt;').replace(/>/g,'&gt;').replace(/"/g,'&quot;');
}

/* ════════════════════════════════════════════════════════════════
   Init
   ════════════════════════════════════════════════════════════════ */
buildLayoutMenu();
applyLayout('l1x1');
document.getElementById('btn-csv-all').addEventListener('click', exportAllCSV);
connectWS();
requestAnimationFrame(renderDirtyPlots);
fetch('/version').then(r => r.text()).then(v => {
  document.getElementById('build-version').textContent = 'v' + v;
}).catch(() => {});