feat(stats): compare observers over a selected time period

src/api/client.ts

@@ -6,6 +6,7 @@ import type { ObserverSummary, Observer, AdvertObservation } from "../features/o
 import type { NodeSummary, Node, NodeObservation, NodeNeighbor } from "../features/nodes/types";
 import type {
   StatsOverview,
+  ObserverComparison,
   ObservationPoint,
   PayloadBreakdownItem,
   TopNode,
@@ -47,7 +48,7 @@ async function errorFrom(res: Response): Promise<ApiError> {
   return new ApiError(res.status, body.error?.code ?? "unknown", body.error?.message ?? res.statusText, retryAfterMs);
 }
 
-async function request<T>(path: string, params?: Record<string, string | number | undefined>): Promise<T> {
+async function request<T>(path: string, params?: Record<string, string | number | undefined>, signal?: AbortSignal): Promise<T> {
   const url = new URL(`${API_BASE}${path}`, window.location.origin);
   if (params) {
     for (const [key, value] of Object.entries(params)) {
@@ -57,7 +58,7 @@ async function request<T>(path: string, params?: Record<string, string | number
     }
   }
 
-  const res = await fetch(url.toString());
+  const res = await (signal ? fetch(url.toString(), { signal }) : fetch(url.toString()));
 
   if (!res.ok) throw await errorFrom(res);
   noteRequestOk();
@@ -67,6 +68,14 @@ async function request<T>(path: string, params?: Record<string, string | number
 
 // endpoint functions
 
+export function getObserverComparison(
+  iatas: string[] | undefined,
+  params: { observerA: string; observerB: string; since: number; until: number },
+  signal?: AbortSignal,
+): Promise<ObserverComparison> {
+  return request("/stats/observer-comparison", { ...params, iatas: iatasParam(iatas) }, signal);
+}
+
 // The region filter travels as the comma-separated `iatas` param; undefined/empty means all regions.
 function iatasParam(iatas?: string[]): string | undefined {
   return iatas && iatas.length > 0 ? iatas.join(",") : undefined;

src/features/stats/CompareObserversTab.tsx

@@ -0,0 +1,163 @@
+import { useEffect, useState, type FormEvent } from "react";
+import { useQuery } from "@tanstack/react-query";
+import { useSearchParams } from "react-router-dom";
+import { getObserver, getObserverComparison, getObserversPage } from "../../api/client";
+import { useRegion } from "../../hooks/useRegion";
+import { Card } from "./cards";
+
+type Selection = { observerA: string; observerB: string; since: number; until: number };
+const uuid = /^(?!00000000-0000-0000-0000-000000000000$)[\da-f]{8}-[\da-f]{4}-[\da-f]{4}-[\da-f]{4}-[\da-f]{12}$/i;
+const fieldClass = "min-w-0 w-full rounded border border-border bg-bg-base px-2.5 py-2 text-base text-text-normal";
+
+function validation(value: Selection): string | null {
+  if (!uuid.test(value.observerA) || !uuid.test(value.observerB) || value.observerA.toLowerCase() === value.observerB.toLowerCase()) {
+    return "Choose two different observers.";
+  }
+  if (!Number.isSafeInteger(value.since) || !Number.isSafeInteger(value.until) || value.since < 0 || value.until <= value.since || value.until > 253402300799999) {
+    return "Choose a valid start and a later end time.";
+  }
+  return null;
+}
+
+function localTime(ms: number) {
+  const date = new Date(ms);
+  return new Date(ms - date.getTimezoneOffset() * 60_000).toISOString().slice(0, 23);
+}
+
+function ObserverSelect({ label, value, onChange }: { label: string; value: string; onChange: (id: string) => void }) {
+  const { iatas, regionKey } = useRegion();
+  const [search, setSearch] = useState("");
+  const [name, setName] = useState("");
+  useEffect(() => {
+    const timer = setTimeout(() => setName(search.trim()), 250);
+    return () => clearTimeout(timer);
+  }, [search]);
+  const options = useQuery({
+    queryKey: ["comparison-observers", regionKey, name],
+    queryFn: () => getObserversPage(iatas, { name: name || undefined, limit: 50 }),
+    staleTime: 30_000,
+  });
+  const selected = useQuery({
+    queryKey: ["observer", value], queryFn: () => getObserver(value),
+    enabled: uuid.test(value), staleTime: 30_000, retry: false,
+  });
+  const rows = options.data?.items ?? [];
+  return (
+    <fieldset className="min-w-0 space-y-2">
+      <legend className="mb-2 text-sm text-text-muted">{label}</legend>
+      <input type="search" aria-label={`Search ${label}`} placeholder="Search all observers by name…"
+        value={search} onChange={(e) => setSearch(e.target.value)} className={fieldClass} />
+      <select aria-label={label} value={value} onChange={(e) => onChange(e.target.value)} className={fieldClass}>
+        <option value="">Choose an observer</option>
+        {value && !rows.some((o) => o.id === value) && <option value={value}>{selected.data?.displayName ?? value}</option>}
+        {rows.map((o) => <option key={o.id} value={o.id}>{o.displayName ?? o.id.slice(0, 8)} · {o.iata} · {o.id.slice(0, 8)}</option>)}
+      </select>
+      <p className="text-xs text-text-dim" role="status">
+        {options.isPending ? "Loading observers…" : options.isError ? "Observer search failed. Try again." : options.data?.hasMore ? "Showing 50 observers. Search to find others." : rows.length === 0 ? "No observers match this search." : "Search includes all matching observers in the selected region."}
+      </p>
+      {options.isError && <button type="button" onClick={() => void options.refetch()} className="text-sm text-primary">Retry observer search</button>}
+    </fieldset>
+  );
+}
+
+function ComparisonForm({ initial, onCompare }: { initial: Selection | null; onCompare: (value: Selection) => void }) {
+  const [a, setA] = useState(initial?.observerA ?? "");
+  const [b, setB] = useState(initial?.observerB ?? "");
+  const [since, setSince] = useState(() => localTime(initial?.since ?? Math.floor((Date.now() - 86_400_000) / 60_000) * 60_000));
+  const [until, setUntil] = useState(() => localTime(initial?.until ?? Math.floor(Date.now() / 60_000) * 60_000));
+  const [error, setError] = useState<string | null>(null);
+  function submit(e: FormEvent) {
+    e.preventDefault();
+    const value = { observerA: a.toLowerCase(), observerB: b.toLowerCase(), since: new Date(since).getTime(), until: new Date(until).getTime() };
+    const message = validation(value);
+    setError(message);
+    if (!message) onCompare(value);
+  }
+  return (
+    <form onSubmit={submit} className="space-y-4" noValidate>
+      <div className="grid gap-4 md:grid-cols-2">
+        <ObserverSelect label="Observer A" value={a} onChange={setA} />
+        <ObserverSelect label="Observer B" value={b} onChange={setB} />
+        <label className="min-w-0 space-y-2 text-sm text-text-muted"><span>Start (local time)</span>
+          <input type="datetime-local" step="0.001" value={since} onChange={(e) => setSince(e.target.value)} className={fieldClass} />
+        </label>
+        <label className="min-w-0 space-y-2 text-sm text-text-muted"><span>End (local time)</span>
+          <input type="datetime-local" step="0.001" value={until} onChange={(e) => setUntil(e.target.value)} className={fieldClass} />
+        </label>
+      </div>
+      {error && <p role="alert" className="text-sm text-danger">{error}</p>}
+      <button type="submit" className="rounded border border-primary-dim bg-primary/10 px-4 py-2 text-sm font-semibold text-primary">Compare</button>
+    </form>
+  );
+}
+
+export function CompareObserversTab() {
+  const { iatas, regionKey } = useRegion();
+  const [params, setParams] = useSearchParams();
+  const keys = ["compareA", "compareB", "compareSince", "compareUntil"];
+  const supplied = keys.some((key) => params.has(key));
+  const parsed: Selection = {
+    observerA: params.get("compareA") ?? "", observerB: params.get("compareB") ?? "",
+    since: Number(params.get("compareSince")), until: Number(params.get("compareUntil")),
+  };
+  const valid = keys.every((key) => params.getAll(key).length === 1 && params.get(key) !== "") && !validation(parsed);
+  const selection = valid ? parsed : null;
+  const result = useQuery({
+    queryKey: ["observer-comparison", regionKey, selection],
+    queryFn: ({ signal }) => getObserverComparison(iatas, selection!, signal),
+    enabled: selection !== null,
+    retry: false, staleTime: 30_000, refetchOnWindowFocus: false,
+  });
+  const observerA = useQuery({
+    queryKey: ["observer", selection?.observerA], queryFn: () => getObserver(selection!.observerA),
+    enabled: selection !== null, staleTime: 30_000, retry: false,
+  });
+  const observerB = useQuery({
+    queryKey: ["observer", selection?.observerB], queryFn: () => getObserver(selection!.observerB),
+    enabled: selection !== null, staleTime: 30_000, retry: false,
+  });
+  function compare(value: Selection) {
+    if (selection && Object.entries(value).every(([key, v]) => selection[key as keyof Selection] === v)) {
+      void result.refetch();
+      return;
+    }
+    setParams((old) => {
+      const next = new URLSearchParams(old);
+      next.set("compareA", value.observerA); next.set("compareB", value.observerB);
+      next.set("compareSince", String(value.since)); next.set("compareUntil", String(value.until));
+      return next;
+    });
+  }
+  const data = result.data;
+  const groups = data ? [
+    { name: "Only A", count: data.onlyA, color: "var(--color-primary)" },
+    { name: "Both", count: data.both, color: "var(--color-green)" },
+    { name: "Only B", count: data.onlyB, color: "var(--color-secondary)" },
+  ] : [];
+  return (
+    <div className="mx-auto flex w-full max-w-5xl flex-col gap-4 p-4">
+      <Card title="Compare observers">
+        <p className="mb-4 text-sm text-text-muted">Compare distinct flood packets reported by two observers over any retained time period.</p>
+        {supplied && !valid && <p role="alert" className="mb-3 text-sm text-danger">This comparison link has invalid or missing values. Choose observers and dates below.</p>}
+        <ComparisonForm key={keys.map((key) => params.get(key)).join("|")} initial={selection} onCompare={compare} />
+      </Card>
+      {selection && <Card title="Reported flood packets">
+        <p className="mb-2 break-words text-sm text-text-normal">A: {observerA.data?.displayName ?? selection.observerA} · B: {observerB.data?.displayName ?? selection.observerB}</p>
+        <p className="mb-3 break-words text-sm text-text-muted">{new Date(selection.since).toLocaleString()} to {new Date(selection.until).toLocaleString()} (local time; end excluded). Region: {iatas?.join(", ") || "All"}.</p>
+        {result.isFetching && <p role="status" className="text-sm text-text-muted">Comparing reported packets…</p>}
+        {result.isError && <div role="alert" className="text-sm text-danger"><p>{result.error.message}</p><button type="button" onClick={() => void result.refetch()} className="mt-2 text-primary">Retry comparison</button></div>}
+        {data && !result.isError && <>
+          <p className="mb-3 text-lg font-semibold text-text-bright">{data.totalPackets.toLocaleString()} distinct flood packets</p>
+          {data.totalPackets === 0 ? <p className="text-sm text-text-muted">No flood packets were reported by either observer in this period and region.</p> : <>
+            <div aria-hidden className="mb-4 flex h-5 overflow-hidden rounded">{groups.map((g) => <div key={g.name} style={{ width: `${g.count / data.totalPackets * 100}%`, background: g.color }} />)}</div>
+            <table className="w-full text-left text-sm tabular-nums" aria-label="Flood packet comparison">
+              <thead className="text-text-muted"><tr><th scope="col">Heard by</th><th scope="col" className="text-right">Packets</th><th scope="col" className="text-right">% of union</th></tr></thead>
+              <tbody>{groups.map((g) => <tr key={g.name} className="border-t border-border"><th scope="row" className="py-2 font-normal text-text-normal"><span aria-hidden className="mr-2 inline-block h-2 w-2 rounded-full" style={{ background: g.color }} />{g.name}</th><td className="text-right">{g.count.toLocaleString()}</td><td className="text-right">{(g.count / data.totalPackets * 100).toFixed(1)}%</td></tr>)}</tbody>
+            </table>
+          </>}
+          <p className="mt-4 text-xs text-text-dim">Percentages use the union of packets heard by either observer. Repeated receptions count once. These counts reflect retained reports, not radio packet loss; an offline observer, broker interruption or expired history can affect the result.</p>
+        </>}
+      </Card>}
+    </div>
+  );
+}

src/features/stats/StatsOverview.tsx

@@ -6,10 +6,11 @@ import { MeshTab } from "./MeshTab";
 import { TalkersTab } from "./TalkersTab";
 import { ClockDriftTab } from "./ClockDriftTab";
 import { ObserverTab } from "./ObserverTab";
+import { CompareObserversTab } from "./CompareObserversTab";
 import { NeighbourGraphTab } from "./NeighbourGraphTab";
 import type { StatsRange, StatsTab } from "./types";
 
-const TABS: StatsTab[] = ["mesh", "talkers", "clockdrift", "observer", "graph"];
+const TABS: StatsTab[] = ["mesh", "talkers", "clockdrift", "observer", "compare", "graph"];
 const RANGES: StatsRange[] = ["24h", "7d", "30d"];
 
 const asTab = (v: string | null): StatsTab => (TABS.includes(v as StatsTab) ? (v as StatsTab) : "mesh");
@@ -60,6 +61,7 @@ export function StatsOverview({ wsManager }: StatsOverviewProps) {
           <ObserverTab range={range} selectedObserverId={observerId} onSelectObserver={handleSelectObserver} wsManager={wsManager} />
         )}
         {tab === "graph" && <NeighbourGraphTab />}
+        {tab === "compare" && <CompareObserversTab />}
       </div>
     </div>
   );

src/features/stats/StatsSubHeader.tsx

@@ -59,6 +59,7 @@ const TAB_OPTIONS = [
   { value: "talkers", label: "Talkers", icon: <TalkersIcon /> },
   { value: "clockdrift", label: "Clock Drift", icon: <ClockDriftIcon /> },
   { value: "observer", label: "Observer", icon: <ObserverIcon /> },
+  { value: "compare", label: "Compare observers", icon: <ObserverIcon /> },
   { value: "graph", label: "Neighbour Graph", icon: <GraphIcon /> },
 ];
 
@@ -103,8 +104,8 @@ export function StatsSubHeader({ tab, onTabChange, range, onRangeChange }: Props
           />
         </div>
       )}
-      {/* graph is topology and clock-drift is each node's latest reading — neither is time-windowed */}
-      {tab !== "graph" && tab !== "clockdrift" && (
+      {/* Comparison has explicit dates; graph and clock drift have no rolling window. */}
+      {tab !== "graph" && tab !== "clockdrift" && tab !== "compare" && (
         <Segmented
           className="shrink-0"
           options={RANGE_OPTIONS}

src/features/stats/types.ts

@@ -3,6 +3,19 @@
 
 import type { NodeIATA } from "../nodes/types";
 
+// beacon-server /stats/observer-comparison: disjoint groups of distinct flood
+// packet hashes, selected by reception time in [since, until).
+export interface ObserverComparison {
+  observerA: string;
+  observerB: string;
+  since: number;
+  until: number;
+  totalPackets: number;
+  onlyA: number;
+  onlyB: number;
+  both: number;
+}
+
 export interface StatsOverview {
   totalPackets: number;
   totalObservations: number;
@@ -140,7 +153,7 @@ export interface ObserverActivity {
 }
 
 // Sub-tab + time-range identifiers shared across the Stats page.
-export type StatsTab = "mesh" | "talkers" | "clockdrift" | "observer" | "graph";
+export type StatsTab = "mesh" | "talkers" | "clockdrift" | "observer" | "compare" | "graph";
 export type StatsRange = "24h" | "7d" | "30d";
 
 export const RANGE_MS: Record<StatsRange, number> = {

tests/api/observer-comparison.test.ts

@@ -0,0 +1,17 @@
+import { afterEach, expect, it, vi } from "vitest";
+import { getObserverComparison } from "../../src/api/client";
+
+afterEach(() => vi.unstubAllGlobals());
+
+it("sends the complete comparison scope, including an epoch-zero start, and consumes cancellation", async () => {
+  const fetcher = vi.fn().mockResolvedValue({ ok: true, json: async () => ({ totalPackets: 0 }) });
+  vi.stubGlobal("fetch", fetcher);
+  const controller = new AbortController();
+  await getObserverComparison(["YVR", "YYJ"], { observerA: "a", observerB: "b", since: 0, until: 1000 }, controller.signal);
+  const [url, options] = fetcher.mock.calls[0];
+  expect(new URL(url).pathname).toContain("/stats/observer-comparison");
+  expect(Object.fromEntries(new URL(url).searchParams)).toEqual({ observerA: "a", observerB: "b", since: "0", until: "1000", iatas: "YVR,YYJ" });
+  expect(options.signal).toBe(controller.signal);
+  controller.abort();
+  expect(options.signal.aborted).toBe(true);
+});