Deduplicate posts in the feed

app/build.gradle.kts

@@ -189,7 +189,7 @@ dependencies {
     implementation("androidx.profileinstaller:profileinstaller")
     baselineProfile(project(":benchmarks"))
 
-    implementation("it.vercruysse.lemmyapi:lemmy-api:0.3.3-SNAPSHOT")
+    implementation("it.vercruysse.lemmyapi:lemmy-api:0.3.4-SNAPSHOT")
     implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.7.1")
 
     // For custom logging plugin

app/src/main/java/com/jerboa/feed/FeedController.kt

@@ -8,7 +8,7 @@ open class FeedController<T> {
 
     val feed: List<T> = items
 
-    fun updateAll(
+    open fun updateAll(
         selector: (List<T>) -> List<Int>,
         transformer: (T) -> T,
     ) {
@@ -17,7 +17,7 @@ open class FeedController<T> {
         }
     }
 
-    fun safeUpdate(
+    open fun safeUpdate(
         index: Int,
         transformer: (T) -> T,
     ) {
@@ -29,7 +29,7 @@ open class FeedController<T> {
         safeUpdate(index, transformer(items[index]))
     }
 
-    fun safeUpdate(
+    open fun safeUpdate(
         selector: (List<T>) -> Int,
         transformer: (T) -> T,
     ) {
@@ -44,7 +44,7 @@ open class FeedController<T> {
      * Example: a network request to update an item succeeded after the list has changed.
      * So, we ignore it
      */
-    fun safeUpdate(
+    open fun safeUpdate(
         index: Int,
         new: T,
     ) {
@@ -55,26 +55,28 @@ open class FeedController<T> {
         }
     }
 
-    fun init(newItems: List<T>) {
-        items.clear()
-        items.addAll(newItems)
+    open fun init(newItems: List<T>) {
+        clear()
+        addAll(newItems)
     }
 
-    fun get(index: Int): T? = items.getOrNull(index)
+    open fun get(index: Int): T? = items.getOrNull(index)
 
-    fun add(item: T) = items.add(item)
+    open fun add(item: T) = items.add(item)
 
-    fun remove(item: T) = items.remove(item)
+    open fun remove(item: T) = items.remove(item)
 
-    fun removeAt(index: Int) {
+    open fun removeAt(index: Int) {
         if (isValidIndex(index)) {
             items.removeAt(index)
         }
     }
 
-    fun clear() = items.clear()
+    open fun clear() = items.clear()
 
-    fun addAll(newItems: List<T>) = items.addAll(newItems)
+    open fun addAll(newItems: List<T>) {
+        items.addAll(newItems)
+    }
 
     protected inline fun <E> Iterable<E>.indexesOf(predicate: (E) -> Boolean) =
         mapIndexedNotNull { index, elem ->

app/src/main/java/com/jerboa/feed/PostController.kt

@@ -5,7 +5,7 @@ import it.vercruysse.lemmyapi.datatypes.HidePost
 import it.vercruysse.lemmyapi.datatypes.Person
 import it.vercruysse.lemmyapi.datatypes.PostView
 
-open class PostController : FeedController<PostView>() {
+open class PostController : UniqueFeedController<PostView>() {
     fun findAndUpdatePost(updatedPostView: PostView) {
         safeUpdate({ posts ->
             posts.indexOfFirst {

app/src/main/java/com/jerboa/feed/UniqueFeedController.kt

@@ -0,0 +1,33 @@
+package com.jerboa.feed
+
+import it.vercruysse.lemmyapi.Identity
+
+open class UniqueFeedController<T : Identity> : FeedController<T>() {
+    private val ids = mutableSetOf<Long>()
+
+    override fun add(item: T): Boolean {
+        if (ids.add(item.id)) {
+            items.add(item)
+            return true
+        }
+        return false
+    }
+
+    override fun addAll(newItems: List<T>) {
+        newItems.forEach {
+            if (ids.add(it.id)) {
+                items.add(it)
+            }
+        }
+    }
+
+    override fun clear() {
+        super.clear()
+        ids.clear()
+    }
+
+    override fun remove(item: T): Boolean {
+        ids.remove(item.id)
+        return super.remove(item)
+    }
+}

app/src/test/java/com/jerboa/feed/UniqueFeedControllerTest.kt

@@ -0,0 +1,82 @@
+package com.jerboa.feed
+
+import it.vercruysse.lemmyapi.Identity
+import org.junit.Assert.*
+import org.junit.Test
+
+class UniqueFeedControllerTest {
+    private data class PostView(
+        override val id: Long,
+    ) : Identity
+
+    @Test
+    fun `Should not add duplicate posts`() {
+        val controller = UniqueFeedController<PostView>()
+        controller.add(PostView(1))
+        assertEquals(1, controller.feed.size)
+        controller.add(PostView(1))
+        assertEquals(1, controller.feed.size)
+        controller.add(PostView(2))
+        assertEquals(2, controller.feed.size)
+    }
+
+    @Test
+    fun `Should remove post`() {
+        val controller = UniqueFeedController<PostView>()
+        controller.add(PostView(1))
+        assertEquals(1, controller.feed.size)
+        controller.remove(PostView(1))
+        assertEquals(0, controller.feed.size)
+    }
+
+    @Test
+    fun `Post removal should clear id`() {
+        val controller = UniqueFeedController<PostView>()
+        controller.add(PostView(1))
+        assertEquals(1, controller.feed.size)
+        controller.remove(PostView(1))
+        assertTrue(controller.feed.isEmpty())
+        controller.add(PostView(1))
+        assertEquals(1, controller.feed.size)
+    }
+
+    @Test
+    fun `Should clear all posts`() {
+        val controller = UniqueFeedController<PostView>()
+        controller.add(PostView(1))
+        controller.add(PostView(2))
+        assertEquals(2, controller.feed.size)
+        controller.clear()
+        assertTrue(controller.feed.isEmpty())
+    }
+
+    @Test
+    fun `Clear should clear ids`() {
+        val controller = UniqueFeedController<PostView>()
+        controller.add(PostView(1))
+        controller.add(PostView(2))
+        assertEquals(2, controller.feed.size)
+        controller.clear()
+        assertTrue(controller.feed.isEmpty())
+        controller.add(PostView(1))
+        controller.add(PostView(2))
+        assertEquals(2, controller.feed.size)
+    }
+
+    @Test
+    fun `Add all should not add duplicates`() {
+        val controller = UniqueFeedController<PostView>()
+        controller.addAll(listOf(PostView(1), PostView(2), PostView(1)))
+        assertEquals(2, controller.feed.size)
+    }
+
+    @Test
+    fun `Init should clear ids`() {
+        val controller = UniqueFeedController<PostView>()
+        controller.add(PostView(1))
+        controller.add(PostView(2))
+        assertEquals(2, controller.feed.size)
+        controller.init(listOf(PostView(1), PostView(2)))
+        assertEquals(2, controller.feed.size)
+    }
+}