feat(map): make 'Most Zapped' sort actually work + batched zap totals

SortDropdown offered 'Most Zapped' but MapPage's sort switch had no zaps case,
so picking it silently fell back to newest-first. Adds a batched useZapTotals
hook (ONE receipt query for every location) and implements the sort.

src/hooks/useZapTotals.ts

@@ -0,0 +1,105 @@
+import { useMemo } from 'react';
+import { useQuery } from '@tanstack/react-query';
+import { useNostr } from '@nostrify/react';
+import type { NostrEvent } from '@nostrify/nostrify';
+import { getSatoshisFromBolt11 } from '@/lib/bolt11';
+
+export interface ZapTotal {
+  count: number;
+  totalSats: number;
+}
+
+/**
+ * Stable lookup key for the zap receipts that belong to an event.
+ * Addressable events (30000–39999) are zapped via their `a` coordinate;
+ * everything else via its event id.
+ */
+export function zapTargetKey(event: NostrEvent): string {
+  if (event.kind >= 30000 && event.kind < 40000) {
+    const d = event.tags.find(([t]) => t === 'd')?.[1] ?? '';
+    return `${event.kind}:${event.pubkey}:${d}`;
+  }
+  return event.id;
+}
+
+/** Extract the sats from one kind-9735 zap receipt. Mirrors useZaps' logic. */
+function receiptSats(zap: NostrEvent): number {
+  const amountTag = zap.tags.find(([name]) => name === 'amount')?.[1];
+  if (amountTag) return Math.floor(parseInt(amountTag, 10) / 1000);
+
+  const bolt11 = zap.tags.find(([name]) => name === 'bolt11')?.[1];
+  if (bolt11) {
+    try {
+      return getSatoshisFromBolt11(bolt11);
+    } catch {
+      /* fall through */
+    }
+  }
+
+  const description = zap.tags.find(([name]) => name === 'description')?.[1];
+  if (description) {
+    try {
+      const request = JSON.parse(description);
+      const reqAmount = request.tags?.find(([name]: string[]) => name === 'amount')?.[1];
+      if (reqAmount) return Math.floor(parseInt(reqAmount, 10) / 1000);
+    } catch {
+      /* fall through */
+    }
+  }
+
+  return 0;
+}
+
+/**
+ * Batched zap totals for many events in ONE query per relay.
+ *
+ * Individual `<ZapButton>`s each issue their own receipt query; that's fine for
+ * a single detail page but ruinous for a list of 100 cards. This fetches all
+ * receipts for a set of targets at once and returns a `Map` keyed by
+ * {@link zapTargetKey} — use it for sorting/filtering lists by zaps.
+ */
+export function useZapTotals(events: NostrEvent[]) {
+  const { nostr } = useNostr();
+
+  const { ids, coords } = useMemo(() => {
+    const ids: string[] = [];
+    const coords: string[] = [];
+    for (const ev of events) {
+      if (ev.kind >= 30000 && ev.kind < 40000) coords.push(zapTargetKey(ev));
+      else ids.push(ev.id);
+    }
+    return { ids: [...new Set(ids)], coords: [...new Set(coords)] };
+  }, [events]);
+
+  return useQuery<Map<string, ZapTotal>>({
+    queryKey: ['zap-totals', ids.join(','), coords.join(',')],
+    enabled: ids.length > 0 || coords.length > 0,
+    staleTime: 60 * 1000,
+    queryFn: async (c) => {
+      const signal = AbortSignal.any([c.signal, AbortSignal.timeout(8000)]);
+
+      const filters: { kinds: number[]; '#e'?: string[]; '#a'?: string[] }[] = [];
+      if (ids.length > 0) filters.push({ kinds: [9735], '#e': ids });
+      if (coords.length > 0) filters.push({ kinds: [9735], '#a': coords });
+
+      const receipts = await nostr.query(filters, { signal });
+
+      const wanted = new Set<string>([...ids, ...coords]);
+      const totals = new Map<string, ZapTotal>();
+
+      for (const zap of receipts) {
+        const sats = receiptSats(zap);
+        // A receipt copies the tags it's paying; count each target it points at.
+        for (const [, value] of zap.tags) {
+          if (!wanted.has(value)) continue;
+          const cur = totals.get(value) ?? { count: 0, totalSats: 0 };
+          cur.count += 1;
+          cur.totalSats += sats;
+          totals.set(value, cur);
+        }
+      }
+
+      return totals;
+    },
+  });
+}

src/pages/MapPage.tsx

@@ -9,6 +9,7 @@ import { SpotCard, SpotCardSkeleton } from '@/components/SpotCard';
 import { WeatherToggle } from '@/components/WeatherToggle';
 import { TrustFilter, type TrustFilterLevel, filterByTrustLevel } from '@/components/TrustFilter';
 import { SortDropdown, type SortOption, calculateDistance } from '@/components/SortDropdown';
+import { useZapTotals, zapTargetKey } from '@/hooks/useZapTotals';
 import { Button } from '@/components/ui/button';
 import { Input } from '@/components/ui/input';
 import { Badge } from '@/components/ui/badge';
@@ -853,6 +854,12 @@ export default function MapPage() {
     return commentCounts?.get(eventId) ?? 0;
   };
 
+  // Batched zap totals for "Most Zapped" sorting (ONE query for every location).
+  const locationEvents = useMemo(() => allLocations.map((l) => l.event), [allLocations]);
+  const { data: zapTotals } = useZapTotals(locationEvents);
+  const getZapTotal = (event: (typeof locationEvents)[number]) =>
+    zapTotals?.get(zapTargetKey(event))?.totalSats ?? 0;
+
   // Get geohashes for weather fetching (only non-shop spots)
   const spotGeohashes = useMemo(() => {
     const geohashes = allLocations
@@ -959,6 +966,12 @@ export default function MapPage() {
           if (commentsB !== commentsA) return commentsB - commentsA; // Most comments first
           return b.event.created_at - a.event.created_at;
         }
+        case 'zaps': {
+          const zapsA = getZapTotal(a.event);
+          const zapsB = getZapTotal(b.event);
+          if (zapsB !== zapsA) return zapsB - zapsA; // Most zapped first
+          return b.event.created_at - a.event.created_at;
+        }
         case 'recent':
         default:
           return b.event.created_at - a.event.created_at; // Newest first
@@ -966,7 +979,7 @@ export default function MapPage() {
     });
 
     return filtered;
-  }, [allLocations, searchQuery, selectedCategories, weatherEnabled, weatherData, weatherFilter, showSpots, showShops, trustFilter, trustScores, sortBy, userLocation, commentCounts]);
+  }, [allLocations, searchQuery, selectedCategories, weatherEnabled, weatherData, weatherFilter, showSpots, showShops, trustFilter, trustScores, sortBy, userLocation, commentCounts, zapTotals]);
 
   // Spots shown as MAP MARKERS. Hide spots the community has confirmed as
   // "gone" (demolished) so they don't clutter the map — they still appear