move ThreadFilter to commons

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/IAccount.kt

@@ -81,4 +81,7 @@ interface IAccount {
     val hiddenWordsCase: List<DualCase>
     val hiddenUsersHashCodes: Set<Int>
     val spammersHashCodes: Set<Int>
+
+    /** Set of followed user pubkeys (for feed ordering/highlighting) */
+    fun followingKeySet(): Set<String>
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/viewmodels/thread/ThreadFeedFilter.kt

@@ -0,0 +1,83 @@
+/**
+ * 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.commons.viewmodels.thread
+
+import androidx.compose.runtime.Immutable
+import com.vitorpamplona.amethyst.commons.model.IAccount
+import com.vitorpamplona.amethyst.commons.model.LevelSignature
+import com.vitorpamplona.amethyst.commons.model.Note
+import com.vitorpamplona.amethyst.commons.model.ThreadAssembler
+import com.vitorpamplona.amethyst.commons.model.ThreadLevelCalculator
+import com.vitorpamplona.amethyst.commons.model.cache.ICacheProvider
+import com.vitorpamplona.amethyst.commons.ui.feeds.FeedFilter
+import com.vitorpamplona.quartz.utils.TimeUtils
+import kotlinx.collections.immutable.toImmutableSet
+
+/**
+ * Filter for assembling and sorting thread feeds.
+ *
+ * This filter uses ThreadAssembler to find all notes in a thread and
+ * ThreadLevelCalculator to sort them by reply level and relevance.
+ *
+ * @param account The current user's account (provides user profile and following set)
+ * @param noteId The root note ID of the thread to display
+ * @param cacheProvider The cache provider for accessing notes
+ */
+@Immutable
+class ThreadFeedFilter(
+    val account: IAccount,
+    private val noteId: String,
+    private val cacheProvider: ICacheProvider,
+) : FeedFilter<Note>() {
+    override fun feedKey(): String = noteId
+
+    override fun feed(): List<Note> {
+        val cachedSignatures: MutableMap<Note, LevelSignature> = mutableMapOf()
+        val followingKeySet = account.followingKeySet()
+        val eventsToWatch = ThreadAssembler(cacheProvider).findThreadFor(noteId) ?: return emptyList()
+
+        // Filter out drafts made by other accounts on device
+        val filteredEvents =
+            eventsToWatch.allNotes
+                .filter { !it.isDraft() || (it.author?.pubkeyHex == account.pubKey) }
+                .toImmutableSet()
+        val filteredThreadInfo = ThreadAssembler.ThreadInfo(eventsToWatch.root, filteredEvents)
+
+        val eventsInHex = filteredThreadInfo.allNotes.map { it.idHex }.toSet()
+        val now = TimeUtils.now()
+
+        // Currently orders by date of each event, descending, at each level of the reply stack
+        val order =
+            compareByDescending<Note> {
+                ThreadLevelCalculator
+                    .replyLevelSignature(
+                        it,
+                        eventsInHex,
+                        cachedSignatures,
+                        account.userProfile(),
+                        followingKeySet,
+                        now,
+                    ).signature
+            }
+
+        return filteredThreadInfo.allNotes.sortedWith(order)
+    }
+}