refactor(live-chat): lift NIP-53 live-stream state into commons

Address the architectural critique from self-review. The leaderboard
math and the shared system card are now platform-neutral primitives in
commons, the on-UI-thread aggregation is gone, and two latent
correctness bugs around subscription lifecycle and zap routing are
fixed.

- Introduce a pure LiveActivityTopZappersAggregator in commons that
  takes plain ZapContribution values and returns a sorted, deduped,
  anon-bucketed top-N list. Covered by a unit-test suite that is
  Compose/Android-independent.
- Introduce LiveStreamTopZappersViewModel in commons/commonMain. It
  owns two partitioned contribution maps (stream-scoped and
  goal-scoped), mutates them under a Mutex on the IO dispatcher in
  response to channel.changesFlow and Note.zaps.stateFlow emissions,
  and publishes the aggregator result via a StateFlow<List<TopZapperEntry>>.
  UI is now a dumb consumer with no aggregation logic left in the
  composable.
- Move StreamSystemCard to commons/commonMain/compose/ so Desktop can
  consume it alongside Android.
- Fix attachZapToLiveActivityChannel to run even when a zap receipt was
  already consumed by another subscription. Previously a zap first seen
  by notifications/profile would never reach the stream's channel
  cache; addNote is already idempotent so this is a safe retro-route.
- Fix ChannelFilterAssemblerSubscription to re-invalidate filters when
  a live-activity channel's metadata arrives. The 30311 stream event
  usually lands after the initial assembler run, so the goal-tag-driven
  subscription never fired. Now it re-runs as metadata resolves and the
  goal id is discovered.

https://claude.ai/code/session_01WJA5PvDABegBYUu6h42YZi

amethyst/src/main/java/com/vitorpamplona/amethyst/model/LocalCache.kt

@@ -1555,8 +1555,14 @@ object LocalCache : ILocalCache, ICacheProvider {
         wasVerified: Boolean,
     ): Boolean {
         val note = getOrCreateNote(event.id)
-        // Already processed this event.
-        if (note.event != null) return false
+
+        // Already processed this event — still ensure it's routed into any live-activity
+        // channel(s) it references. A zap that was first consumed by, e.g., the notifications
+        // subscription must still appear in the stream's chat when the user opens the stream.
+        if (note.event != null) {
+            attachZapToLiveActivityChannel(event, note, relay)
+            return false
+        }
 
         if (wasVerified || justVerify(event)) {
             val existingZapRequest = event.zapRequest?.id?.let { getNoteIfExists(it) }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/feed/types/RenderChatClip.kt

@@ -36,6 +36,7 @@ import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.compose.nip53LiveActivities.StreamSystemCard
 import com.vitorpamplona.amethyst.model.Note
 import com.vitorpamplona.amethyst.service.playback.composable.VideoView
 import com.vitorpamplona.amethyst.ui.navigation.navs.INav

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/feed/types/RenderChatRaid.kt

@@ -39,6 +39,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.compose.nip53LiveActivities.StreamSystemCard
 import com.vitorpamplona.amethyst.model.Note
 import com.vitorpamplona.amethyst.ui.navigation.navs.INav
 import com.vitorpamplona.amethyst.ui.navigation.routes.Route

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/feed/types/RenderChatZap.kt

@@ -36,6 +36,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.compose.nip53LiveActivities.StreamSystemCard
 import com.vitorpamplona.amethyst.model.Note
 import com.vitorpamplona.amethyst.ui.navigation.navs.INav
 import com.vitorpamplona.amethyst.ui.note.CrossfadeToDisplayComment

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/feed/types/StreamSystemCard.kt

@@ -1,65 +0,0 @@
-/*
- * Copyright (c) 2025 Vitor Pamplona
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy of
- * this software and associated documentation files (the "Software"), to deal in
- * the Software without restriction, including without limitation the rights to use,
- * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
- * Software, and to permit persons to whom the Software is furnished to do so,
- * subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
- * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
- * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
- * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
- * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
- */
-package com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.feed.types
-
-import androidx.compose.foundation.background
-import androidx.compose.foundation.clickable
-import androidx.compose.foundation.layout.Box
-import androidx.compose.foundation.layout.BoxScope
-import androidx.compose.foundation.layout.fillMaxWidth
-import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.shape.RoundedCornerShape
-import androidx.compose.material3.MaterialTheme
-import androidx.compose.runtime.Composable
-import androidx.compose.ui.Modifier
-import androidx.compose.ui.draw.clip
-import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.unit.dp
-
-/**
- * Shared rounded, accent-tinted container used by the centered "system-style"
- * cards rendered inside the live stream chat feed (zaps, raids, clips).
- *
- * Keeps the three renderers visually consistent so they clearly stand apart
- * from regular chat bubbles. The content slot uses a BoxScope so callers can
- * pick their own internal layout (Row / Column / whatever).
- */
-@Composable
-fun StreamSystemCard(
-    accent: Color = MaterialTheme.colorScheme.primary,
-    accentAlpha: Float = 0.12f,
-    onClick: (() -> Unit)? = null,
-    content: @Composable BoxScope.() -> Unit,
-) {
-    val base =
-        Modifier
-            .fillMaxWidth()
-            .padding(horizontal = 8.dp, vertical = 2.dp)
-            .clip(RoundedCornerShape(8.dp))
-            .background(accent.copy(alpha = accentAlpha))
-
-    val clickable = if (onClick != null) base.clickable(onClick = onClick) else base
-
-    Box(
-        modifier = clickable.padding(horizontal = 10.dp, vertical = 8.dp),
-        content = content,
-    )
-}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/datasource/ChannelFilterAssemblerSubscription.kt

@@ -21,8 +21,12 @@
 package com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.publicChannels.datasource
 
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
 import androidx.compose.runtime.remember
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.vitorpamplona.amethyst.commons.model.Channel
+import com.vitorpamplona.amethyst.commons.model.nip53LiveActivities.LiveActivitiesChannel
 import com.vitorpamplona.amethyst.commons.relayClient.subscriptions.KeyDataSourceSubscription
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
 
@@ -40,4 +44,18 @@ fun ChannelFilterAssemblerSubscription(
         }
 
     KeyDataSourceSubscription(state, dataSource)
+
+    // Live streams need the 30311 event to populate `channel.info` before we can read its
+    // `goal` tag and add the goal+zap subscriptions. Re-invalidate when metadata changes so
+    // the goal filter fires as soon as the stream event arrives.
+    if (channel is LiveActivitiesChannel) {
+        val metadataState by channel
+            .flow()
+            .metadata.stateFlow
+            .collectAsStateWithLifecycle()
+        val goalId = channel.info?.goalEventId()
+        LaunchedEffect(goalId, metadataState) {
+            dataSource.invalidateFilters()
+        }
+    }
 }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/nip53LiveActivities/header/LiveStreamTopZappers.kt

@@ -43,11 +43,14 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.dp
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import androidx.lifecycle.viewmodel.compose.viewModel
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.commons.model.nip53LiveActivities.LiveActivitiesChannel
-import com.vitorpamplona.amethyst.model.Note
-import com.vitorpamplona.amethyst.service.relayClient.reqCommand.event.observeNoteZaps
+import com.vitorpamplona.amethyst.commons.nip53LiveActivities.TopZapperEntry
+import com.vitorpamplona.amethyst.commons.viewmodels.LiveStreamTopZappersViewModel
 import com.vitorpamplona.amethyst.ui.navigation.navs.INav
 import com.vitorpamplona.amethyst.ui.navigation.routes.Route
 import com.vitorpamplona.amethyst.ui.note.UserPicture
@@ -58,27 +61,14 @@ import com.vitorpamplona.amethyst.ui.stringRes
 import com.vitorpamplona.amethyst.ui.theme.BitcoinOrange
 import com.vitorpamplona.amethyst.ui.theme.Size16Modifier
 import com.vitorpamplona.amethyst.ui.theme.Size24dp
-import com.vitorpamplona.quartz.nip01Core.core.HexKey
-import com.vitorpamplona.quartz.nip57Zaps.LnZapEvent
-import com.vitorpamplona.quartz.nip57Zaps.LnZapRequestEvent
 import java.math.BigDecimal
 
-private const val TOP_ZAPPERS_LIMIT = 10
-
-/** Sentinel key used to bucket every anonymous/private zap into a single leaderboard entry. */
-private const val ANON_KEY = "anon"
-
-private data class TopZapperEntry(
-    val zapperPubKey: HexKey,
-    val totalSats: BigDecimal,
-    val isAnonymous: Boolean,
-)
-
 /**
- * Horizontally-scrollable leaderboard of the top zappers on a live stream.
- * Aggregates zaps from both the stream's #a subscription and the attached
- * NIP-75 zap goal (if any), de-duplicating by zap-receipt id. Matches
- * zap.stream's TopZappers UX: pill chips with avatar + lightning + sats.
+ * Horizontally-scrollable leaderboard of the top zappers on a live stream. Matches
+ * zap.stream's TopZappers look: pill chips with avatar + lightning + sats.
+ *
+ * State is owned by [LiveStreamTopZappersViewModel], which maintains the aggregation
+ * incrementally off the UI thread and publishes a stable `List<TopZapperEntry>`.
  */
 @Composable
 fun LiveStreamTopZappers(
@@ -86,43 +76,33 @@ fun LiveStreamTopZappers(
     accountViewModel: AccountViewModel,
     nav: INav,
 ) {
+    val topZappersVm: LiveStreamTopZappersViewModel =
+        viewModel(
+            key = "TopZappers-${channel.address.toValue()}",
+            factory =
+                object : ViewModelProvider.Factory {
+                    @Suppress("UNCHECKED_CAST")
+                    override fun <T : ViewModel> create(modelClass: Class<T>): T = LiveStreamTopZappersViewModel(channel) as T
+                },
+        )
+
+    // Track the goal note lifecycle — pass it to the VM as it resolves, clear on channel change.
     val goalId = channel.info?.goalEventId()
-
     if (goalId != null) {
-        var goalNote by remember(goalId) { mutableStateOf(accountViewModel.getNoteIfExists(goalId)) }
-        if (goalNote == null) {
-            LaunchedEffect(goalId) {
-                goalNote = accountViewModel.checkGetOrCreateNote(goalId)
+        var goalNoteHolder by remember(goalId) {
+            mutableStateOf(accountViewModel.getNoteIfExists(goalId))
+        }
+        LaunchedEffect(goalId) {
+            if (goalNoteHolder == null) {
+                goalNoteHolder = accountViewModel.checkGetOrCreateNote(goalId)
             }
+            topZappersVm.setGoalNote(goalNoteHolder)
         }
-        TopZappersStrip(channel, goalNote, accountViewModel, nav)
     } else {
-        TopZappersStrip(channel, null, accountViewModel, nav)
+        LaunchedEffect(channel) { topZappersVm.setGoalNote(null) }
     }
-}
 
-@Composable
-private fun TopZappersStrip(
-    channel: LiveActivitiesChannel,
-    goalNote: Note?,
-    accountViewModel: AccountViewModel,
-    nav: INav,
-) {
-    // Trigger recomposition whenever a new zap lands in the channel cache.
-    val channelTick by channel.changesFlow().collectAsStateWithLifecycle(initialValue = null)
-
-    // Trigger recomposition when zaps arrive for the goal note.
-    val goalZapsState =
-        if (goalNote != null) {
-            observeNoteZaps(goalNote, accountViewModel).value
-        } else {
-            null
-        }
-
-    val entries =
-        remember(channel, channelTick, goalNote, goalZapsState) {
-            aggregateTopZappers(channel, goalNote)
-        }
+    val entries by topZappersVm.topZappers.collectAsStateWithLifecycle()
 
     if (entries.isEmpty()) return
 
@@ -131,7 +111,7 @@ private fun TopZappersStrip(
         horizontalArrangement = Arrangement.spacedBy(6.dp),
         contentPadding = PaddingValues(horizontal = 4.dp),
     ) {
-        items(entries, key = { it.zapperPubKey }) { entry ->
+        items(entries, key = { it.bucketKey }) { entry ->
             ZapperPill(entry, accountViewModel, nav)
         }
     }
@@ -147,7 +127,7 @@ private fun ZapperPill(
         if (entry.isAnonymous) {
             Modifier
         } else {
-            Modifier.clickable { nav.nav(Route.Profile(entry.zapperPubKey)) }
+            Modifier.clickable { nav.nav(Route.Profile(entry.bucketKey)) }
         }
 
     Surface(
@@ -168,7 +148,7 @@ private fun ZapperPill(
                 )
             } else {
                 UserPicture(
-                    userHex = entry.zapperPubKey,
+                    userHex = entry.bucketKey,
                     size = Size24dp,
                     accountViewModel = accountViewModel,
                     nav = nav,
@@ -176,53 +156,10 @@ private fun ZapperPill(
             }
             ZapIcon(Size16Modifier, BitcoinOrange)
             Text(
-                text = showAmountInteger(entry.totalSats),
+                text = showAmountInteger(BigDecimal.valueOf(entry.totalSats)),
                 style = MaterialTheme.typography.labelMedium,
             )
             Spacer(Modifier.padding(start = 2.dp))
         }
     }
 }
-
-private fun aggregateTopZappers(
-    channel: LiveActivitiesChannel,
-    goalNote: Note?,
-): List<TopZapperEntry> {
-    // receiptId -> (zapperBucketKey, sats) — dedupes a zap that appears via both #a and #e.
-    val byReceipt = HashMap<HexKey, Pair<HexKey, BigDecimal>>()
-
-    // Stream-level zaps routed to the channel cache.
-    channel.notes.forEach { _, note ->
-        val ev = note.event
-        if (ev is LnZapEvent) {
-            val request = ev.zapRequest ?: return@forEach
-            val sats = ev.amount() ?: return@forEach
-            byReceipt[note.idHex] = bucketKeyFor(request) to sats
-        }
-    }
-
-    // Goal-scoped zaps attached to the goal note via #e.
-    goalNote?.zaps?.forEach { (zapRequestNote, receiptNote) ->
-        val receiptEv = receiptNote?.event as? LnZapEvent ?: return@forEach
-        val request = zapRequestNote.event as? LnZapRequestEvent ?: return@forEach
-        val sats = receiptEv.amount() ?: return@forEach
-        byReceipt[receiptNote.idHex] = bucketKeyFor(request) to sats
-    }
-
-    if (byReceipt.isEmpty()) return emptyList()
-
-    val totals = HashMap<HexKey, BigDecimal>(byReceipt.size)
-    byReceipt.values.forEach { (pk, sats) ->
-        totals[pk] = (totals[pk] ?: BigDecimal.ZERO) + sats
-    }
-
-    return totals.entries
-        .asSequence()
-        .sortedByDescending { it.value }
-        .take(TOP_ZAPPERS_LIMIT)
-        .map { TopZapperEntry(it.key, it.value, isAnonymous = it.key == ANON_KEY) }
-        .toList()
-}
-
-/** Returns the aggregation key for a zap request: real pubkey, or the anon sentinel for any `anon`-tagged zap. */
-private fun bucketKeyFor(request: LnZapRequestEvent): HexKey = if (request.tags.any { it.isNotEmpty() && it[0] == "anon" }) ANON_KEY else request.pubKey