fix: client-side sparkline with local buffer, no server fetch on update

apps/web/src/views/home.ejs

@@ -75,9 +75,44 @@
       } catch {}
     }, 30000);
 
-    // SSE: on each ping, update text fields and fetch fresh sparkline
-    const _fetchingSparkline = new Set();
-    watchAccount(async (ping) => {
+    // Client-side sparkline — seed with SSR data, update locally on SSE
+    const _sparkData = {
+      <% it.monitors.forEach(function(m, i) {
+        const lats = (m.pings || []).filter(p => p.latency_ms != null).map(p => p.latency_ms);
+      %>'<%= m.id %>': [<%- lats.join(',') %>]<% if (i < it.monitors.length - 1) { %>,<% } %>
+      <% }) %>
+    };
+
+    function drawSparkline(values, el) {
+      const W = 120, H = 32;
+      if (!values.length) { el.innerHTML = ''; return; }
+      const max = Math.max(...values, 1);
+      const min = Math.min(...values, 0);
+      const range = max - min || 1;
+      const step = W / Math.max(values.length - 1, 1);
+      const pts = values.map((v, i) => {
+        const x = i * step;
+        const y = H - ((v - min) / range) * (H - 4) - 2;
+        return `${x},${y}`;
+      }).join(' ');
+      const svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
+      svg.setAttribute('viewBox', `0 0 ${W} ${H}`);
+      svg.setAttribute('width', W);
+      svg.setAttribute('height', H);
+      const pl = document.createElementNS('http://www.w3.org/2000/svg', 'polyline');
+      pl.setAttribute('points', pts);
+      pl.setAttribute('fill', 'none');
+      pl.setAttribute('stroke', '#60a5fa');
+      pl.setAttribute('stroke-width', '1.5');
+      pl.setAttribute('stroke-linecap', 'round');
+      pl.setAttribute('stroke-linejoin', 'round');
+      svg.appendChild(pl);
+      const old = el.querySelector('svg');
+      if (old) old.replaceWith(svg); else el.appendChild(svg);
+    }
+
+    // SSE: update cards in realtime
+    watchAccount((ping) => {
       const card = document.querySelector(`[data-monitor-id="${ping.monitor_id}"]`);
       if (!card) return;
 
@@ -89,22 +124,14 @@
       if (ping.latency_ms != null) card.querySelector('.stat-latency').textContent = ping.latency_ms + 'ms';
       card.querySelector('.stat-last').innerHTML = timeAgo(ping.checked_at);
 
-      // Sparkline
+      // Sparkline — update buffer and redraw locally
+      if (ping.latency_ms != null) {
+        const buf = _sparkData[ping.monitor_id] = _sparkData[ping.monitor_id] || [];
+        buf.push(ping.latency_ms);
+        if (buf.length > 20) buf.shift();
         const sparkEl = card.querySelector('.stat-sparkline');
-      if (!sparkEl || _fetchingSparkline.has(ping.monitor_id)) return;
-      _fetchingSparkline.add(ping.monitor_id);
-      try {
-        const res = await fetch(`/dashboard/monitors/${ping.monitor_id}/sparkline`, { credentials: 'same-origin' });
-        if (res.ok) {
-          const tmp = document.createElement('div');
-          tmp.innerHTML = await res.text();
-          const newSvg = tmp.firstElementChild;
-          const oldSvg = sparkEl.querySelector('svg');
-          if (newSvg && oldSvg) oldSvg.replaceWith(newSvg);
-          else if (newSvg) sparkEl.appendChild(newSvg);
+        if (sparkEl) drawSparkline(buf, sparkEl);
       }
-      } catch {}
-      _fetchingSparkline.delete(ping.monitor_id);
     });
   </script>