feat(concord): create, mint-invite, and deep-link join flows

Account gains createConcordCommunity (mint genesis, publish, join),
mintConcordInvite (publish kind-33301 bundle, return the shareable link), and
joinConcordViaInvite (parse link, fetch+unlock bundle, add to the 13302 list).

ConcordInviteScreen auto-redeems an invite deep link (Route.ConcordInvite) and
forwards to the joined community's channel list, with a retry on relay miss.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CzJ2Cwo8tg4oZq43oRa3ig

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

@@ -160,6 +160,7 @@ import com.vitorpamplona.quartz.nip01Core.core.AddressableEvent
 import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.core.hexToByteArray
+import com.vitorpamplona.quartz.nip01Core.core.toHexKey
 import com.vitorpamplona.quartz.nip01Core.crypto.KeyPair
 import com.vitorpamplona.quartz.nip01Core.hints.AddressHintProvider
 import com.vitorpamplona.quartz.nip01Core.hints.EventHintBundle
@@ -167,6 +168,7 @@ import com.vitorpamplona.quartz.nip01Core.hints.EventHintProvider
 import com.vitorpamplona.quartz.nip01Core.hints.PubKeyHintProvider
 import com.vitorpamplona.quartz.nip01Core.metadata.MetadataEvent
 import com.vitorpamplona.quartz.nip01Core.relay.client.INostrClient
+import com.vitorpamplona.quartz.nip01Core.relay.client.accessories.fetchAll
 import com.vitorpamplona.quartz.nip01Core.relay.client.accessories.fetchFirst
 import com.vitorpamplona.quartz.nip01Core.relay.filters.Filter
 import com.vitorpamplona.quartz.nip01Core.relay.normalizer.NormalizedRelayUrl
@@ -1488,9 +1490,102 @@ class Account(
     /** Add a joined Concord community (secret-bearing entry) to the private kind-13302 list. */
     suspend fun joinConcordCommunity(entry: ConcordCommunityListEntry) = sendMyPublicAndPrivateOutbox(concordChannelList.follow(entry))
 
+    /**
+     * Create a new Concord community: mint its genesis (metadata + #general),
+     * publish the owner-signed genesis wraps to [relays] (or our outbox), and add
+     * the secret-bearing entry to the kind-13302 joined list. Returns the new
+     * community id, or null if not writeable.
+     */
+    suspend fun createConcordCommunity(
+        name: String,
+        description: String? = null,
+        relays: List<String> = emptyList(),
+    ): String? {
+        if (!isWriteable()) return null
+        val relayUrls = relays.ifEmpty { outboxRelays.flow.value.map { it.url } }
+        val community = ConcordActions.createCommunity(signer, name, TimeUtils.now(), description, relayUrls)
+
+        val publishTo = relayUrls.mapNotNullTo(mutableSetOf()) { RelayUrlNormalizer.normalizeOrNull(it) }.ifEmpty { outboxRelays.flow.value }
+        community.genesisWraps.forEach { client.publish(it, publishTo) }
+
+        joinConcordCommunity(
+            ConcordCommunityListEntry(
+                id = community.communityIdHex,
+                owner = community.ownerPubKey,
+                ownerSalt = community.ownerSalt.toHexKey(),
+                root = community.communityRoot.toHexKey(),
+                rootEpoch = community.rootEpoch,
+                relays = relayUrls,
+                name = name,
+            ),
+        )
+        return community.communityIdHex
+    }
+
+    /**
+     * Mint a shareable invite link for a joined community and publish its
+     * kind-33301 public bundle to the community relays. Returns the `…/invite/…`
+     * URL, or null if the community isn't joined or isn't writeable.
+     */
+    suspend fun mintConcordInvite(
+        communityId: String,
+        base: String = "https://amethyst.social",
+    ): String? {
+        if (!isWriteable()) return null
+        val entry = concordChannelList.liveCommunities.value.firstOrNull { it.id == communityId } ?: return null
+        val invite =
+            ConcordActions.inviteFor(
+                communityIdHex = entry.id,
+                ownerPubKey = entry.owner,
+                ownerSaltHex = entry.ownerSalt,
+                communityRootHex = entry.root,
+                rootEpoch = entry.rootEpoch,
+                name = entry.name,
+                relays = entry.relays,
+            )
+        val minted = ConcordActions.mintInviteLink(base, invite, TimeUtils.now(), entry.relays)
+
+        val publishTo = entry.relays.mapNotNullTo(mutableSetOf()) { RelayUrlNormalizer.normalizeOrNull(it) }.ifEmpty { outboxRelays.flow.value }
+        if (publishTo.isNotEmpty()) client.publish(minted.bundleEvent, publishTo)
+        return minted.url
+    }
+
     /** Drop a joined Concord community from the private kind-13302 list by its id. */
     suspend fun leaveConcordCommunity(communityId: String) = sendMyPublicAndPrivateOutbox(concordChannelList.unfollow(communityId))
 
+    /**
+     * Redeem a Concord invite link (`…/invite/<naddr>#<fragment>`): parse it, fetch
+     * the kind-33301 public bundle from the link's relays (+ our outbox), unlock it
+     * with the fragment token, and add the resulting secret-bearing entry to the
+     * kind-13302 joined list. Returns the joined community id, or null if the link
+     * is invalid, unreadable, or no valid bundle is found.
+     */
+    suspend fun joinConcordViaInvite(url: String): String? {
+        if (!isWriteable()) return null
+        val parsed = ConcordActions.parseInviteLink(url) ?: return null
+
+        val relays =
+            (parsed.fragment.relays.mapNotNull { RelayUrlNormalizer.normalizeOrNull(it) } + outboxRelays.flow.value).toSet()
+        if (relays.isEmpty()) return null
+
+        val filters = relays.associateWith { listOf(ConcordActions.bundleFilter(parsed.linkSignerPubKey)) }
+        val wraps = client.fetchAll(filters = filters)
+        val bundle = wraps.firstNotNullOfOrNull { ConcordActions.openBundle(it, parsed.fragment.token) } ?: return null
+
+        val entry =
+            ConcordCommunityListEntry(
+                id = bundle.communityId,
+                owner = bundle.owner,
+                ownerSalt = bundle.ownerSalt,
+                root = bundle.communityRoot,
+                rootEpoch = bundle.rootEpoch,
+                relays = bundle.relays,
+                name = bundle.name,
+            )
+        joinConcordCommunity(entry)
+        return bundle.communityId
+    }
+
     /**
      * Post [text] to a Concord channel: derive the channel plane key, build an
      * encrypted-seal kind-1059 wrap authored by that plane key (not our identity),

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/AppNavigation.kt

@@ -102,6 +102,7 @@ import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.privateDM.ChatroomScr
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.privateDM.send.NewGroupDMScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.publicChannels.concord.ConcordChannelListScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.publicChannels.concord.ConcordChannelScreen
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.publicChannels.concord.ConcordInviteScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.publicChannels.ephemChat.EphemeralChatScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.publicChannels.ephemChat.metadata.NewEphemeralChatScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.publicChannels.nip28PublicChat.PublicChatChannelScreen
@@ -605,6 +606,14 @@ fun BuildNavigation(
             )
         }
 
+        composableFromEndArgs<Route.ConcordInvite> {
+            ConcordInviteScreen(
+                link = it.link,
+                accountViewModel = accountViewModel,
+                nav = nav,
+            )
+        }
+
         composableFromEndArgs<Route.RelayGroupMembers> {
             RelayGroupMembersScreen(
                 id = it.id,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/concord/ConcordInviteScreen.kt

@@ -0,0 +1,115 @@
+/*
+ * 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.concord
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.Button
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.stringRes
+
+private sealed interface RedeemState {
+    data object Working : RedeemState
+
+    data class Done(
+        val communityId: String,
+    ) : RedeemState
+
+    data object Failed : RedeemState
+}
+
+/**
+ * Auto-redeems a Concord invite link (deep-link target for [Route.ConcordInvite]).
+ * On open it fetches + unlocks the bundle, joins the community, and forwards to its
+ * channel list. On failure it offers a retry, so a transient relay miss doesn't
+ * strand the user.
+ */
+@Composable
+fun ConcordInviteScreen(
+    link: String,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    var state by remember(link) { mutableStateOf<RedeemState>(RedeemState.Working) }
+
+    LaunchedEffect(link, state) {
+        if (state is RedeemState.Working) {
+            val communityId = accountViewModel.account.joinConcordViaInvite(link)
+            state = if (communityId != null) RedeemState.Done(communityId) else RedeemState.Failed
+        }
+    }
+
+    LaunchedEffect(state) {
+        (state as? RedeemState.Done)?.let { done ->
+            nav.newStack(Route.ConcordServer(done.communityId))
+        }
+    }
+
+    Column(
+        modifier = Modifier.fillMaxSize().padding(24.dp),
+        verticalArrangement = Arrangement.Center,
+        horizontalAlignment = Alignment.CenterHorizontally,
+    ) {
+        when (state) {
+            is RedeemState.Working -> {
+                CircularProgressIndicator()
+                Text(
+                    stringRes(com.vitorpamplona.amethyst.R.string.concord_redeeming_invite),
+                    modifier = Modifier.padding(top = 16.dp),
+                    textAlign = TextAlign.Center,
+                )
+            }
+
+            is RedeemState.Failed -> {
+                Text(
+                    stringRes(com.vitorpamplona.amethyst.R.string.concord_invite_failed),
+                    style = MaterialTheme.typography.bodyLarge,
+                    textAlign = TextAlign.Center,
+                )
+                Button(
+                    onClick = { state = RedeemState.Working },
+                    modifier = Modifier.padding(top = 16.dp),
+                ) {
+                    Text(stringRes(com.vitorpamplona.amethyst.R.string.retry))
+                }
+            }
+
+            is RedeemState.Done -> Unit
+        }
+    }
+}

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

@@ -305,6 +305,8 @@
     <string name="already_have_an_account">Already have a Nostr account?</string>
     <string name="loading_feed">Loading feed</string>
     <string name="loading_account">Loading account</string>
+    <string name="concord_redeeming_invite">Redeeming invite…</string>
+    <string name="concord_invite_failed">Could not fetch this invite. The link may be expired or its relays unreachable.</string>
     <string name="chats_history_proto_nip17">encrypted</string>
     <string name="chats_history_proto_nip04">legacy</string>
     <string name="chats_reply_searching_history">Looking for the original message…</string>