From c4cc2ca6ac7fb555ed028b2ddac13a342775fc61 Mon Sep 17 00:00:00 2001
From: Bnyro <bnyro@tutanota.com>
Date: Mon, 31 Jul 2023 15:13:49 +0200
Subject: [PATCH] fix: preserve the video order of imported playlists

---
 .../github/libretube/api/PlaylistsHelper.kt   | 21 ++++++++-----------
 .../libretube/extensions/ParallelMap.kt       | 10 +++++++++
 2 files changed, 19 insertions(+), 12 deletions(-)
 create mode 100644 app/src/main/java/com/github/libretube/extensions/ParallelMap.kt

diff --git a/app/src/main/java/com/github/libretube/api/PlaylistsHelper.kt b/app/src/main/java/com/github/libretube/api/PlaylistsHelper.kt
index afbc3f422..a8e7cbdb9 100644
--- a/app/src/main/java/com/github/libretube/api/PlaylistsHelper.kt
+++ b/app/src/main/java/com/github/libretube/api/PlaylistsHelper.kt
@@ -11,6 +11,7 @@ import com.github.libretube.constants.YOUTUBE_FRONTEND_URL
 import com.github.libretube.db.DatabaseHolder
 import com.github.libretube.db.obj.LocalPlaylist
 import com.github.libretube.enums.PlaylistType
+import com.github.libretube.extensions.parallelMap
 import com.github.libretube.extensions.toID
 import com.github.libretube.helpers.PreferenceHelper
 import com.github.libretube.helpers.ProxyHelper
@@ -188,20 +189,16 @@ object PlaylistsHelper {
                     } else {
                         // if not logged in, all video information needs to become fetched manually
                         // Only do so with 20 videos at once to prevent performance issues
-                        playlist.videos.mapIndexed { index, id -> id to index }
-                            .groupBy { it.second % 20 }.forEach { (_, videos) ->
-                                videos.map {
-                                    async {
-                                        runCatching {
-                                            val stream = RetrofitInstance.api.getStreams(it.first)
-                                                .toStreamItem(
-                                                    it.first
-                                                )
-                                            addToPlaylist(playlistId, stream)
-                                        }
+                        val streams = playlist.videos.mapIndexed { index, id -> id to index }
+                            .groupBy { it.second % 20 }.map { (_, videos) ->
+                                videos.parallelMap {
+                                    runCatching {
+                                        RetrofitInstance.api.getStreams(it.first)
+                                            .toStreamItem(it.first)
                                     }
-                                }.awaitAll()
+                                }.mapNotNull { it.getOrNull() }
                             }
+                        addToPlaylist(playlistId, *streams.flatten().toTypedArray())
                     }
                 }
             }.awaitAll()
diff --git a/app/src/main/java/com/github/libretube/extensions/ParallelMap.kt b/app/src/main/java/com/github/libretube/extensions/ParallelMap.kt
new file mode 100644
index 000000000..401f90151
--- /dev/null
+++ b/app/src/main/java/com/github/libretube/extensions/ParallelMap.kt
@@ -0,0 +1,10 @@
+package com.github.libretube.extensions
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.async
+import kotlinx.coroutines.awaitAll
+import kotlinx.coroutines.coroutineScope
+
+suspend fun <A, B> List<A>.parallelMap(f: suspend (A) -> B): List<B> = coroutineScope {
+    map { async(Dispatchers.IO) { f(it) } }.awaitAll()
+}