From 61d4ca16debdb1b654ba32cb0c0307088d133ada Mon Sep 17 00:00:00 2001
From: Geert Rademakes <g26107@eon.com>
Date: Fri, 8 Aug 2025 14:25:50 +0200
Subject: [PATCH] feat(playlists): track custom order in separate 'order'
 array; reading API honors 'order' while preserving 'tracks'

---
 packages/backend/src/models/Playlist.ts  |  2 ++
 packages/backend/src/routes/playlists.ts | 10 +++-------
 packages/backend/src/routes/songs.ts     | 10 ++++++++--
 3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/packages/backend/src/models/Playlist.ts b/packages/backend/src/models/Playlist.ts
index d9661d7..b88f11b 100644
--- a/packages/backend/src/models/Playlist.ts
+++ b/packages/backend/src/models/Playlist.ts
@@ -9,6 +9,8 @@ const playlistSchema = new mongoose.Schema({
     required: true
   },
   tracks: [String],
+  // Optional custom order of track IDs (display-only, not exported)
+  order: [String],
   children: [{
     type: mongoose.Schema.Types.Mixed
   }]
diff --git a/packages/backend/src/routes/playlists.ts b/packages/backend/src/routes/playlists.ts
index 5450c1a..bb454d5 100644
--- a/packages/backend/src/routes/playlists.ts
+++ b/packages/backend/src/routes/playlists.ts
@@ -80,7 +80,7 @@ router.post('/batch', async (req, res) => {
   }
 });
 
-// Reorder tracks inside a playlist (by name)
+// Reorder tracks inside a playlist (by name). Stores order separately in `order` to avoid interfering with original `tracks`.
 router.post('/reorder', async (req: Request, res: Response) => {
   try {
     const { playlistName, orderedIds } = req.body as { playlistName: string; orderedIds: string[] };
@@ -94,13 +94,9 @@ router.post('/reorder', async (req: Request, res: Response) => {
     const reorderNode = (node: any): any => {
       if (!node) return node;
       if (node.type === 'playlist' && node.name === playlistName) {
-        // Ensure unique order and only include known IDs
+        // Store order separately; do not mutate tracks
         const unique = Array.from(new Set(orderedIds));
-        // If tracks exist, keep only ids present in unique, and append any tracks not included to preserve membership
-        const current: string[] = Array.isArray(node.tracks) ? node.tracks : [];
-        const orderedKnown = unique.filter(id => current.includes(id));
-        const missing = current.filter(id => !unique.includes(id));
-        node.tracks = [...orderedKnown, ...missing];
+        node.order = unique;
         updated = true;
         return node;
       }
diff --git a/packages/backend/src/routes/songs.ts b/packages/backend/src/routes/songs.ts
index 88f7100..6b5b10a 100644
--- a/packages/backend/src/routes/songs.ts
+++ b/packages/backend/src/routes/songs.ts
@@ -110,8 +110,14 @@ router.get('/playlist/*', async (req: Request, res: Response) => {
 
     // Get all track IDs from the playlist (including nested playlists)
     const getAllTrackIds = (node: any): string[] => {
-      if (node.type === 'playlist' && node.tracks) {
-        return node.tracks;
+      if (node.type === 'playlist') {
+        const base = Array.isArray(node.tracks) ? node.tracks : [];
+        const order = Array.isArray(node.order) ? node.order : [];
+        if (order.length === 0) return base;
+        const setBase = new Set(base);
+        const orderedKnown = order.filter((id: string) => setBase.has(id));
+        const missing = base.filter((id: string) => !order.includes(id));
+        return [...orderedKnown, ...missing];
       }
       if (node.type === 'folder' && node.children) {
         return node.children.flatMap((child: any) => getAllTrackIds(child));