feat(nip29): shareable group naddr + invite-code join flow

Nostr-native invites/deep-links for relay groups (no proprietary URL scheme):

- RelayGroupChannel.toNAddr(): a NIP-19 `naddr` for the group's kind-39000
  metadata (authored by the relay key, host relay as hint) — a cross-client
  coordinate that opens the group.
- ClickableRoute: a clicked/rendered `naddr` for kind 39000 routes straight into
  the group chat (Route.RelayGroup with the relay hint) instead of the generic
  addressable-note view.
- InviteRelayGroupDialog now shares the group `nostr:naddr…` (for discovery) plus
  the one-time code for closed groups; copy grabs both.
- JoinRelayGroupDialog: closed groups prompt for the invite code, which the join
  request (9021) carries; open groups still join in one tap.

Follow-up: cold-start `nostr:naddr` deep links (from outside the app) still route
to the generic note view; only the in-app clicked/rendered path is wired here.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B5MLY4hq5LXJ2D5WeLRyXj

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/components/ClickableRoute.kt

@@ -77,6 +77,7 @@ import com.vitorpamplona.quartz.nip19Bech32.entities.NPub
 import com.vitorpamplona.quartz.nip19Bech32.entities.NRelay
 import com.vitorpamplona.quartz.nip19Bech32.entities.NSec
 import com.vitorpamplona.quartz.nip19Bech32.toNIP19
+import com.vitorpamplona.quartz.nip29RelayGroups.metadata.GroupMetadataEvent
 import com.vitorpamplona.quartz.nip30CustomEmoji.CustomEmoji
 import kotlinx.collections.immutable.ImmutableList
 import kotlinx.collections.immutable.ImmutableMap
@@ -201,6 +202,21 @@ private fun DisplayAddress(
     accountViewModel: AccountViewModel,
     nav: INav,
 ) {
+    // A NIP-29 group is addressed by its relay-signed kind-39000 metadata. Route
+    // straight into the group chat rather than the generic addressable-note view.
+    // The relay is only carried in the naddr's relay hint (the group id is unique
+    // only per relay), so we need that hint to open it.
+    val groupRelay = if (nip19.kind == GroupMetadataEvent.KIND) nip19.relay.firstOrNull() else null
+    if (groupRelay != null) {
+        CreateClickableText(
+            clickablePart = "#${nip19.dTag}",
+            suffix = additionalChars,
+            route = Route.RelayGroup(nip19.dTag, groupRelay.url),
+            nav = nav,
+        )
+        return
+    }
+
     var noteBase by remember(nip19) { mutableStateOf(accountViewModel.getNoteIfExists(nip19.aTag())) }
 
     if (noteBase == null) {

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/relayGroup/InviteRelayGroupDialog.kt

@@ -59,23 +59,46 @@ fun InviteRelayGroupDialog(
         accountViewModel.createRelayGroupInvite(channel, code)
     }
 
+    // A shareable, cross-client coordinate for the group (opens the chat in any
+    // NIP-29 client). Null until the relay-signed metadata has loaded.
+    val nAddr = channel.toNAddr()?.let { "nostr:$it" }
+    val isClosed = channel.isClosed()
+
     AlertDialog(
         onDismissRequest = onDismiss,
         title = { Text(stringRes(R.string.relay_group_invite_title)) },
         text = {
             Column {
                 Text(stringRes(R.string.relay_group_invite_description))
-                Text(
-                    text = code,
-                    fontFamily = FontFamily.Monospace,
-                    style = MaterialTheme.typography.titleLarge,
-                    color = MaterialTheme.colorScheme.primary,
-                )
+
+                nAddr?.let {
+                    Text(
+                        text = it,
+                        fontFamily = FontFamily.Monospace,
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.primary,
+                        maxLines = 2,
+                    )
+                }
+
+                // Closed groups additionally need a one-time code to join.
+                if (isClosed) {
+                    Text(stringRes(R.string.relay_group_invite_code_label))
+                    Text(
+                        text = code,
+                        fontFamily = FontFamily.Monospace,
+                        style = MaterialTheme.typography.titleLarge,
+                        color = MaterialTheme.colorScheme.primary,
+                    )
+                }
             }
         },
         confirmButton = {
             TextButton(onClick = {
-                clipboard.setText(AnnotatedString(code))
+                // Copy the most useful thing: the group link, plus the code when
+                // the group is closed (so a recipient has both to join).
+                val toCopy = listOfNotNull(nAddr, if (isClosed) code else null).joinToString("\n")
+                clipboard.setText(AnnotatedString(toCopy.ifBlank { code }))
                 onDismiss()
             }) {
                 Text(stringRes(R.string.copy))

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/relayGroup/JoinRelayGroupDialog.kt

@@ -0,0 +1,87 @@
+/*
+ * 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.publicChannels.relayGroup
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.model.nip29RelayGroups.RelayGroupChannel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+
+/**
+ * Ask for an invite code before joining a closed (invite-only) NIP-29 group, then
+ * send the join request (kind 9021) carrying the code. Open groups don't need this
+ * — they join directly.
+ */
+@Composable
+fun JoinRelayGroupDialog(
+    channel: RelayGroupChannel,
+    accountViewModel: AccountViewModel,
+    onJoined: () -> Unit,
+    onDismiss: () -> Unit,
+) {
+    var code by remember { mutableStateOf("") }
+
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text(stringRes(R.string.relay_group_join_title)) },
+        text = {
+            Column {
+                Text(stringRes(R.string.relay_group_join_code_hint))
+                OutlinedTextField(
+                    value = code,
+                    onValueChange = { code = it },
+                    singleLine = true,
+                    label = { Text(stringRes(R.string.relay_group_join_code_label)) },
+                    modifier = Modifier.fillMaxWidth().padding(top = 8.dp),
+                )
+            }
+        },
+        confirmButton = {
+            TextButton(
+                enabled = code.isNotBlank(),
+                onClick = {
+                    accountViewModel.joinRelayGroup(channel, code.trim())
+                    onJoined()
+                    onDismiss()
+                },
+            ) {
+                Text(stringRes(R.string.relay_group_join_confirm))
+            }
+        },
+        dismissButton = {
+            TextButton(onClick = onDismiss) { Text(stringRes(R.string.cancel)) }
+        },
+    )
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/relayGroup/RelayGroupTopBar.kt

@@ -70,6 +70,7 @@ fun RelayGroupTopBar(
 
     var menuOpen by remember { mutableStateOf(false) }
     var showInvite by remember { mutableStateOf(false) }
+    var showJoinCode by remember { mutableStateOf(false) }
 
     TopBarExtensibleWithBackButton(
         title = {
@@ -101,8 +102,13 @@ fun RelayGroupTopBar(
 
                 !displayMembership.isMember() -> {
                     FilledTonalButton(onClick = {
-                        requested = true
-                        accountViewModel.joinRelayGroup(channel)
+                        // Closed groups need an invite code; open groups join directly.
+                        if (channel.isClosed()) {
+                            showJoinCode = true
+                        } else {
+                            requested = true
+                            accountViewModel.joinRelayGroup(channel)
+                        }
                     }) {
                         Text(stringRes(R.string.join))
                     }
@@ -139,6 +145,15 @@ fun RelayGroupTopBar(
     if (showInvite) {
         InviteRelayGroupDialog(channel, accountViewModel) { showInvite = false }
     }
+
+    if (showJoinCode) {
+        JoinRelayGroupDialog(
+            channel = channel,
+            accountViewModel = accountViewModel,
+            onJoined = { requested = true },
+            onDismiss = { showJoinCode = false },
+        )
+    }
 }
 
 @Composable

amethyst/src/main/res/values/strings.xml

@@ -1941,6 +1941,11 @@
     <string name="relay_group_invite_description">Share this code so people can join this channel.</string>
     <string name="relay_group_invite_generating">Creating an invite…</string>
     <string name="relay_group_invite_copied">Invite code copied</string>
+    <string name="relay_group_invite_code_label">Invite code (for this invite-only channel):</string>
+    <string name="relay_group_join_title">Join channel</string>
+    <string name="relay_group_join_code_label">Invite code</string>
+    <string name="relay_group_join_code_hint">This channel is invite-only. Enter the code you were given.</string>
+    <string name="relay_group_join_confirm">Join</string>
     <string name="relay_group_pending">Requested</string>
     <string name="relay_group_role_admin">Admin</string>
     <string name="relay_group_role_moderator">Moderator</string>

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/nip29RelayGroups/RelayGroupChannel.kt

@@ -24,6 +24,7 @@ import androidx.compose.runtime.Stable
 import com.vitorpamplona.amethyst.commons.model.Channel
 import com.vitorpamplona.amethyst.commons.model.Note
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip19Bech32.entities.NAddress
 import com.vitorpamplona.quartz.nip29RelayGroups.GroupId
 import com.vitorpamplona.quartz.nip29RelayGroups.metadata.GroupAdminsEvent
 import com.vitorpamplona.quartz.nip29RelayGroups.metadata.GroupMembersEvent
@@ -108,6 +109,16 @@ class RelayGroupChannel(
         updateChannelInfo()
     }
 
+    /**
+     * The shareable NIP-19 `naddr` coordinate for this group's metadata (kind
+     * 39000, authored by the relay's own key, with the host relay as a hint), or
+     * null until the relay-signed metadata has loaded (we need its author key).
+     */
+    fun toNAddr(): String? {
+        val relaySelf = event?.pubKey ?: return null
+        return NAddress.create(GroupMetadataEvent.KIND, relaySelf, groupId.id, groupId.relayUrl)
+    }
+
     /** Number of known members (admins are members too). */
     fun memberCount(): Int = (members + admins.map { it.pubKey }).size