From 83dab23694cf66189799753cdb1e0314092d7642 Mon Sep 17 00:00:00 2001
From: haosenwang1018 <haosenwang1018@users.noreply.github.com>
Date: Mon, 23 Feb 2026 08:14:21 +0800
Subject: [PATCH 1/2] =?UTF-8?q?fix:=20reduce=20dedup=20coordinate=20roundi?=
 =?UTF-8?q?ng=20from=200.5=C2=B0=20to=200.1=C2=B0=20(~10km)?=
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The previous 0.5° rounding (~50km radius) merged distinct events in
dense urban areas (e.g. Manhattan vs Brooklyn protests on the same
day). Reducing to 0.1° (~10km) preserves neighborhood-level
granularity while still deduplicating true duplicates.

Fixes #204

Signed-off-by: haosenwang1018 <haosenwang1018@users.noreply.github.com>
---
 server/worldmonitor/unrest/v1/_shared.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/server/worldmonitor/unrest/v1/_shared.ts b/server/worldmonitor/unrest/v1/_shared.ts
index 073fb8c5..03b07fea 100644
--- a/server/worldmonitor/unrest/v1/_shared.ts
+++ b/server/worldmonitor/unrest/v1/_shared.ts
@@ -73,8 +73,8 @@ export function deduplicateEvents(events: UnrestEvent[]): UnrestEvent[] {
   for (const event of events) {
     const lat = event.location?.latitude ?? 0;
     const lon = event.location?.longitude ?? 0;
-    const latKey = Math.round(lat * 2) / 2;
-    const lonKey = Math.round(lon * 2) / 2;
+    const latKey = Math.round(lat * 10) / 10;
+    const lonKey = Math.round(lon * 10) / 10;
     const dateKey = new Date(event.occurredAt).toISOString().split('T')[0];
     const key = `${latKey}:${lonKey}:${dateKey}`;
 

From b9728af63dac561acf30a4b4a65255dd00bf3e66 Mon Sep 17 00:00:00 2001
From: haosenwang1018 <haosenwang1018@users.noreply.github.com>
Date: Mon, 23 Feb 2026 08:15:07 +0800
Subject: [PATCH 2/2] fix: use deterministic hash-based jitter for country
 centroid fallback

Replace Math.random() with a djb2 hash seeded by the threat ID,
so the same threat always appears at the same coordinates. This
prevents 'jumping' markers on the map when the same data is
re-fetched.

Fixes #203

Signed-off-by: haosenwang1018 <haosenwang1018@users.noreply.github.com>
---
 server/worldmonitor/cyber/v1/_shared.ts | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/server/worldmonitor/cyber/v1/_shared.ts b/server/worldmonitor/cyber/v1/_shared.ts
index 29987557..ed079607 100644
--- a/server/worldmonitor/cyber/v1/_shared.ts
+++ b/server/worldmonitor/cyber/v1/_shared.ts
@@ -191,12 +191,25 @@ const COUNTRY_CENTROIDS: Record<string, [number, number]> = {
   SN:[14.5,-14.5],CM:[7.4,12.4],CI:[7.5,-5.5],TZ:[-6.4,34.9],UG:[1.4,32.3],
 };
 
-function getCountryCentroid(countryCode: string): { lat: number; lon: number } | null {
+/**
+ * Simple deterministic hash (djb2) that returns a float in [-0.5, 0.5).
+ * Same seed always produces the same value.
+ */
+function hashJitter(seed: string, index: number): number {
+  let hash = 5381;
+  const s = `${seed}:${index}`;
+  for (let i = 0; i < s.length; i++) {
+    hash = ((hash << 5) + hash + s.charCodeAt(i)) | 0;
+  }
+  return ((hash & 0x7fffffff) / 0x7fffffff - 0.5) * 2;
+}
+
+function getCountryCentroid(countryCode: string, seed?: string): { lat: number; lon: number } | null {
   if (!countryCode) return null;
   const coords = COUNTRY_CENTROIDS[countryCode.toUpperCase()];
   if (!coords) return null;
-  const jitter = () => (Math.random() - 0.5) * 2;
-  return { lat: coords[0] + jitter(), lon: coords[1] + jitter() };
+  const key = seed || countryCode;
+  return { lat: coords[0] + hashJitter(key, 0), lon: coords[1] + hashJitter(key, 1) };
 }
 
 // ========================================================================
@@ -366,7 +379,7 @@ export async function hydrateThreatCoordinates(threats: RawThreat[]): Promise<Ra
       return { ...threat, lat: lookup.lat, lon: lookup.lon, country: threat.country || lookup.country };
     }
 
-    const centroid = getCountryCentroid(threat.country);
+    const centroid = getCountryCentroid(threat.country, threat.id);
     if (centroid) {
       return { ...threat, lat: centroid.lat, lon: centroid.lon };
     }