finish ThreadScreen

commons/src/jvmAndroid/kotlin/com/vitorpamplona/amethyst/commons/subscriptions/FeedSubscription.kt

@@ -86,3 +86,48 @@ fun createContactListSubscription(
         onEvent = onEvent,
         onEose = onEose,
     )
+
+/**
+ * Creates a subscription config for fetching a specific note by ID.
+ */
+fun createNoteSubscription(
+    relays: Set<NormalizedRelayUrl>,
+    noteId: String,
+    onEvent: (Event, Boolean, NormalizedRelayUrl, List<Filter>?) -> Unit,
+    onEose: (NormalizedRelayUrl, List<Filter>?) -> Unit = { _, _ -> },
+): SubscriptionConfig =
+    SubscriptionConfig(
+        subId = generateSubId("note-${noteId.take(8)}"),
+        filters = listOf(FilterBuilders.byIds(listOf(noteId))),
+        relays = relays,
+        onEvent = onEvent,
+        onEose = onEose,
+    )
+
+/**
+ * Creates a subscription config for fetching all replies to a note (thread).
+ *
+ * @param noteId The root note ID to fetch replies for
+ * @param limit Maximum number of reply events to request
+ */
+fun createThreadRepliesSubscription(
+    relays: Set<NormalizedRelayUrl>,
+    noteId: String,
+    limit: Int = 200,
+    onEvent: (Event, Boolean, NormalizedRelayUrl, List<Filter>?) -> Unit,
+    onEose: (NormalizedRelayUrl, List<Filter>?) -> Unit = { _, _ -> },
+): SubscriptionConfig =
+    SubscriptionConfig(
+        subId = generateSubId("thread-${noteId.take(8)}"),
+        filters =
+            listOf(
+                FilterBuilders.byETags(
+                    eventIds = listOf(noteId),
+                    kinds = listOf(1), // TextNoteEvent
+                    limit = limit,
+                ),
+            ),
+        relays = relays,
+        onEvent = onEvent,
+        onEose = onEose,
+    )

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/Main.kt

@@ -84,6 +84,7 @@ import com.vitorpamplona.amethyst.desktop.ui.ComposeNoteDialog
 import com.vitorpamplona.amethyst.desktop.ui.FeedScreen
 import com.vitorpamplona.amethyst.desktop.ui.LoginScreen
 import com.vitorpamplona.amethyst.desktop.ui.NotificationsScreen
+import com.vitorpamplona.amethyst.desktop.ui.ThreadScreen
 import com.vitorpamplona.amethyst.desktop.ui.UserProfileScreen
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
@@ -110,6 +111,10 @@ sealed class DesktopScreen {
         val pubKeyHex: String,
     ) : DesktopScreen()
 
+    data class Thread(
+        val noteId: String,
+    ) : DesktopScreen()
+
     object Settings : DesktopScreen()
 }
 
@@ -351,6 +356,9 @@ fun MainContent(
                         onNavigateToProfile = { pubKeyHex ->
                             onScreenChange(DesktopScreen.UserProfile(pubKeyHex))
                         },
+                        onNavigateToThread = { noteId ->
+                            onScreenChange(DesktopScreen.Thread(noteId))
+                        },
                     )
                 DesktopScreen.Search -> SearchPlaceholder()
                 DesktopScreen.Messages -> MessagesPlaceholder()
@@ -377,6 +385,19 @@ fun MainContent(
                             onScreenChange(DesktopScreen.UserProfile(pubKeyHex))
                         },
                     )
+                is DesktopScreen.Thread ->
+                    ThreadScreen(
+                        noteId = currentScreen.noteId,
+                        relayManager = relayManager,
+                        account = account,
+                        onBack = { onScreenChange(DesktopScreen.Feed) },
+                        onNavigateToProfile = { pubKeyHex ->
+                            onScreenChange(DesktopScreen.UserProfile(pubKeyHex))
+                        },
+                        onNavigateToThread = { noteId ->
+                            onScreenChange(DesktopScreen.Thread(noteId))
+                        },
+                    )
                 DesktopScreen.Settings -> RelaySettingsScreen(relayManager, account)
             }
         }

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/FeedScreen.kt

@@ -20,6 +20,7 @@
  */
 package com.vitorpamplona.amethyst.desktop.ui
 
+import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
@@ -75,8 +76,14 @@ fun FeedNoteCard(
     account: AccountState.LoggedIn?,
     onReply: () -> Unit,
     onNavigateToProfile: (String) -> Unit = {},
+    onNavigateToThread: (String) -> Unit = {},
 ) {
-    Column {
+    Column(
+        modifier =
+            Modifier.clickable {
+                onNavigateToThread(event.id)
+            },
+    ) {
         NoteCard(
             note = event.toNoteDisplayData(),
             onAuthorClick = onNavigateToProfile,
@@ -101,6 +108,7 @@ fun FeedScreen(
     account: AccountState.LoggedIn? = null,
     onCompose: () -> Unit = {},
     onNavigateToProfile: (String) -> Unit = {},
+    onNavigateToThread: (String) -> Unit = {},
 ) {
     val connectedRelays by relayManager.connectedRelays.collectAsState()
     val relayStatuses by relayManager.relayStatuses.collectAsState()
@@ -274,6 +282,7 @@ fun FeedScreen(
                         account = account,
                         onReply = { replyToEvent = event },
                         onNavigateToProfile = onNavigateToProfile,
+                        onNavigateToThread = onNavigateToThread,
                     )
                 }
             }

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/ThreadScreen.kt

@@ -0,0 +1,277 @@
+/**
+ * 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.desktop.ui
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.commons.account.AccountState
+import com.vitorpamplona.amethyst.commons.state.EventCollectionState
+import com.vitorpamplona.amethyst.commons.subscriptions.createNoteSubscription
+import com.vitorpamplona.amethyst.commons.subscriptions.createThreadRepliesSubscription
+import com.vitorpamplona.amethyst.commons.subscriptions.rememberSubscription
+import com.vitorpamplona.amethyst.commons.ui.components.LoadingState
+import com.vitorpamplona.amethyst.commons.ui.note.NoteCard
+import com.vitorpamplona.amethyst.commons.ui.thread.drawReplyLevel
+import com.vitorpamplona.amethyst.commons.util.toNoteDisplayData
+import com.vitorpamplona.amethyst.desktop.network.DesktopRelayConnectionManager
+import com.vitorpamplona.quartz.nip01Core.core.Event
+
+/**
+ * Desktop Thread Screen - displays a note and all its replies in a thread view.
+ *
+ * Uses the shared drawReplyLevel modifier from commons to display reply nesting.
+ */
+@Composable
+fun ThreadScreen(
+    noteId: String,
+    relayManager: DesktopRelayConnectionManager,
+    account: AccountState.LoggedIn?,
+    onBack: () -> Unit,
+    onNavigateToProfile: (String) -> Unit = {},
+    onNavigateToThread: (String) -> Unit = {},
+) {
+    val connectedRelays by relayManager.connectedRelays.collectAsState()
+    val relayStatuses by relayManager.relayStatuses.collectAsState()
+    val scope = rememberCoroutineScope()
+
+    // State for the root note
+    var rootNote by remember { mutableStateOf<Event?>(null) }
+
+    // State for reply events
+    val replyEventState =
+        remember(noteId) {
+            EventCollectionState<Event>(
+                getId = { it.id },
+                sortComparator = compareBy { it.createdAt },
+                maxSize = 500,
+                scope = scope,
+            )
+        }
+    val replyEvents by replyEventState.items.collectAsState()
+
+    // Cache for calculating reply levels
+    val levelCache = remember(noteId) { mutableMapOf<String, Int>() }
+
+    // Subscribe to the root note
+    rememberSubscription(relayStatuses, noteId, relayManager = relayManager) {
+        val configuredRelays = relayStatuses.keys
+        if (configuredRelays.isNotEmpty()) {
+            createNoteSubscription(
+                relays = configuredRelays,
+                noteId = noteId,
+                onEvent = { event, _, _, _ ->
+                    if (event.id == noteId) {
+                        rootNote = event
+                        levelCache[event.id] = 0
+                    }
+                },
+            )
+        } else {
+            null
+        }
+    }
+
+    // Subscribe to replies
+    rememberSubscription(relayStatuses, noteId, relayManager = relayManager) {
+        val configuredRelays = relayStatuses.keys
+        if (configuredRelays.isNotEmpty()) {
+            createThreadRepliesSubscription(
+                relays = configuredRelays,
+                noteId = noteId,
+                onEvent = { event, _, _, _ ->
+                    replyEventState.addItem(event)
+                },
+            )
+        } else {
+            null
+        }
+    }
+
+    // Calculate reply level for an event based on e-tags
+    fun calculateLevel(event: Event): Int {
+        levelCache[event.id]?.let { return it }
+
+        // Find the event this is replying to (last e-tag or marked reply/root)
+        val replyToId = findReplyToId(event)
+        val level =
+            if (replyToId == null || replyToId == noteId) {
+                1 // Direct reply to root
+            } else {
+                (levelCache[replyToId] ?: 0) + 1
+            }
+        levelCache[event.id] = level
+        return level
+    }
+
+    Column(modifier = Modifier.fillMaxSize()) {
+        // Header with back button
+        Row(
+            modifier = Modifier.fillMaxWidth().padding(bottom = 16.dp),
+            verticalAlignment = Alignment.CenterVertically,
+        ) {
+            IconButton(onClick = onBack) {
+                Icon(
+                    Icons.AutoMirrored.Filled.ArrowBack,
+                    contentDescription = "Back",
+                    modifier = Modifier.size(24.dp),
+                )
+            }
+            Spacer(Modifier.width(8.dp))
+            Text(
+                "Thread",
+                style = MaterialTheme.typography.headlineMedium,
+                color = MaterialTheme.colorScheme.onBackground,
+            )
+        }
+
+        if (connectedRelays.isEmpty()) {
+            LoadingState("Connecting to relays...")
+        } else if (rootNote == null) {
+            LoadingState("Loading thread...")
+        } else {
+            LazyColumn(
+                verticalArrangement = Arrangement.spacedBy(0.dp),
+            ) {
+                // Root note (no reply level indicator)
+                item(key = noteId) {
+                    Column(
+                        modifier =
+                            Modifier.clickable {
+                                // Already viewing this thread, no-op
+                            },
+                    ) {
+                        NoteCard(
+                            note = rootNote!!.toNoteDisplayData(),
+                            onAuthorClick = onNavigateToProfile,
+                        )
+                        if (account != null) {
+                            NoteActionsRow(
+                                event = rootNote!!,
+                                relayManager = relayManager,
+                                account = account,
+                                onReplyClick = { /* TODO: Open reply dialog */ },
+                                modifier = Modifier.padding(horizontal = 12.dp, vertical = 4.dp),
+                            )
+                        }
+                    }
+                    HorizontalDivider(thickness = 1.dp)
+                }
+
+                // Reply notes with level indicators
+                items(replyEvents, key = { it.id }) { event ->
+                    val level = calculateLevel(event)
+
+                    Column(
+                        modifier =
+                            Modifier
+                                .drawReplyLevel(
+                                    level = level,
+                                    color = MaterialTheme.colorScheme.outlineVariant,
+                                    selected =
+                                        if (event.id == noteId) {
+                                            MaterialTheme.colorScheme.primary
+                                        } else {
+                                            MaterialTheme.colorScheme.outlineVariant
+                                        },
+                                ).clickable {
+                                    onNavigateToThread(event.id)
+                                },
+                    ) {
+                        NoteCard(
+                            note = event.toNoteDisplayData(),
+                            onAuthorClick = onNavigateToProfile,
+                        )
+                        if (account != null) {
+                            NoteActionsRow(
+                                event = event,
+                                relayManager = relayManager,
+                                account = account,
+                                onReplyClick = { /* TODO: Open reply dialog */ },
+                                modifier = Modifier.padding(horizontal = 12.dp, vertical = 4.dp),
+                            )
+                        }
+                    }
+                    HorizontalDivider(thickness = 1.dp)
+                }
+
+                // Empty state for no replies
+                if (replyEvents.isEmpty()) {
+                    item {
+                        Spacer(Modifier.height(32.dp))
+                        Text(
+                            "No replies yet",
+                            style = MaterialTheme.typography.bodyMedium,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant,
+                            modifier = Modifier.padding(16.dp),
+                        )
+                    }
+                }
+            }
+        }
+    }
+}
+
+/**
+ * Finds the event ID this event is replying to.
+ * Uses NIP-10 markers (reply/root) or falls back to last e-tag.
+ */
+private fun findReplyToId(event: Event): String? {
+    val eTags = event.tags.filter { it.size >= 2 && it[0] == "e" }
+    if (eTags.isEmpty()) return null
+
+    // Check for NIP-10 marked tags first
+    val replyTag = eTags.find { it.size >= 4 && it[3] == "reply" }
+    if (replyTag != null) return replyTag[1]
+
+    val rootTag = eTags.find { it.size >= 4 && it[3] == "root" }
+    if (rootTag != null && eTags.size == 1) return rootTag[1]
+
+    // Fall back to positional (last e-tag is the reply-to)
+    return eTags.lastOrNull()?.get(1)
+}