fix: evenly space chart runs at fixed width and trim initial data to match

apps/web/src/views/detail.ejs

@@ -179,12 +179,26 @@
       'us-west': '🇺🇸 US West', 'ap-southeast': '🇸🇬 AP Southeast'
     };
 
+    const MAX_RUNS = 50;
     let chartPings = <%~ JSON.stringify(chartPings.map(p => ({
       latency_ms: p.latency_ms, region: p.region || '__none__',
       checked_at: p.checked_at, up: p.up, run_id: p.run_id || null,
       status_code: p.status_code
     }))) %>;
 
+    // Trim initial data to MAX_RUNS
+    (function() {
+      const seen = []; const s = new Set();
+      for (const p of chartPings) {
+        const rid = p.run_id || p.checked_at;
+        if (!s.has(rid)) { s.add(rid); seen.push(rid); }
+      }
+      if (seen.length > MAX_RUNS) {
+        const stale = new Set(seen.slice(0, seen.length - MAX_RUNS));
+        chartPings = chartPings.filter(p => !stale.has(p.run_id || p.checked_at));
+      }
+    })();
+
     function renderChart() {
       const canvas = document.getElementById('chart-canvas');
       const container = canvas.parentElement;
@@ -208,18 +222,23 @@
         return;
       }
 
-      // Compute a shared x-position per run_id (avg checked_at of all pings in the run)
-      // so all regions in the same run align vertically on the chart
+      // Build ordered list of unique runs, sorted by avg checked_at
       const runTimes = {};
       for (const p of data) {
-        const rid = p.run_id || p.checked_at; // fallback for pings without run_id
+        const rid = p.run_id || p.checked_at;
         if (!runTimes[rid]) runTimes[rid] = [];
         runTimes[rid].push(new Date(p.checked_at).getTime());
       }
-      const runAvgTime = {};
-      for (const [rid, times] of Object.entries(runTimes)) {
-        runAvgTime[rid] = times.reduce((a, b) => a + b, 0) / times.length;
-      }
+      const runs = Object.keys(runTimes).sort((a, b) => {
+        const avgA = runTimes[a].reduce((x, y) => x + y, 0) / runTimes[a].length;
+        const avgB = runTimes[b].reduce((x, y) => x + y, 0) / runTimes[b].length;
+        return avgA - avgB;
+      });
+
+      // Evenly space runs across the chart width (fixed spacing like SSR)
+      const runIndex = {};
+      runs.forEach((rid, i) => { runIndex[rid] = i; });
+      const maxIdx = Math.max(runs.length - 1, 1);
 
       // Group by region
       const byRegion = {};
@@ -232,13 +251,12 @@
       const allLat = data.map(p => p.latency_ms);
       const yMin = Math.min(...allLat), yMax = Math.max(...allLat);
       const yRange = yMax - yMin || 1;
-      const avgTimes = Object.values(runAvgTime);
-      const tMin = Math.min(...avgTimes), tMax = Math.max(...avgTimes);
-      const tRange = tMax - tMin || 1;
 
-      function toX(t) { return pad.left + ((t - tMin) / tRange) * cW; }
       function toY(v) { return pad.top + cH - ((v - yMin) / yRange) * cH; }
-      function pingX(p) { return toX(runAvgTime[p.run_id || p.checked_at]); }
+      function pingX(p) {
+        const idx = runIndex[p.run_id || p.checked_at] || 0;
+        return pad.left + (idx / maxIdx) * cW;
+      }
 
       // Grid lines
       ctx.strokeStyle = 'rgba(75,85,99,0.3)'; ctx.lineWidth = 0.5;
@@ -310,9 +328,6 @@
 
       // Store for hover
       canvas._regionPoints = regionPoints;
-      canvas._toX = toX; canvas._toY = toY;
-      canvas._tMin = tMin; canvas._tRange = tRange;
-      canvas._W = W; canvas._H = H; canvas._pad = pad; canvas._cW = cW;
     }
 
     // Group pings by run_id for tooltip
@@ -472,7 +487,6 @@
         status_code: ping.status_code
       });
       // Count distinct runs and remove oldest runs as a group
-      const MAX_RUNS = 50;
       const seen = []; const runSet = new Set();
       for (const p of chartPings) {
         const rid = p.run_id || p.checked_at;