From 8ec85d39c55769c564298782a51c6ec25dd6ba9f Mon Sep 17 00:00:00 2001
From: salmon <salmonik@tuta.io>
Date: Wed, 12 Aug 2026 02:56:18 +0200
Subject: fix a bug where adding track using `now` when shuffle is on does not
 work as expected

---
 tests/queue.rs | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)

(limited to 'tests/queue.rs')

diff --git a/tests/queue.rs b/tests/queue.rs
index d338f2a..67cbabf 100644
--- a/tests/queue.rs
+++ b/tests/queue.rs
@@ -567,6 +567,83 @@ fn test_shuffle_off_keeps_unplayed_duplicate_entries() {
     assert_eq!(q.position(), 1);
 }
 
+#[test]
+fn test_shuffle_play_now_current_is_inserted_track() {
+    // BUG: under shuffle, `insert_after_current` re-shuffles the tail
+    // (`update_shuffle_indices`), so the inserted track's play-order slot is a
+    // random draw instead of `position + 1`. The daemon's "now" flow (insert →
+    // `set_position(pos+1)` → play `track_at(position)`, src/daemon.rs) then
+    // starts the right file while `current()`/`next()`/the queue display
+    // follow a *different* track, and auto-advance can replay or skip the
+    // inserted track entirely.
+    //
+    // Contract: after the "now" sequence, `current()` must be the inserted
+    // track. The seed sweep keeps the test deterministic — for a fixed seed the
+    // outcome never varies between runs, and pre-fix a given seed satisfies the
+    // invariant with probability 1/(tail size) = 1/3, so the chance all 40
+    // seeds accidentally pass is ~3e-19. The fix makes the invariant hold
+    // structurally (insert into the play order at `position+1`), independent
+    // of the seed.
+    let inserted = PathBuf::from("/music/new.mp3");
+    for seed in 1..=40u64 {
+        let mut q = Queue::with_seed(seed);
+        add_track(&mut q, "/music/a.mp3");
+        add_track(&mut q, "/music/b.mp3");
+        add_track(&mut q, "/music/c.mp3");
+        q.set_shuffle(ShuffleMode::All);
+
+        // `rsp play --now new.mp3` with a non-empty queue: insert after the
+        // current track and move the cursor onto it.
+        q.insert_after_current(inserted.clone());
+        let new_pos = q.position() + 1;
+        q.set_position(new_pos);
+
+        assert_eq!(q.position(), 1);
+        let cur = q.current().expect("queue is not empty");
+        assert_eq!(
+            cur.path, inserted,
+            "seed {}: current() after play-now is {:?}, expected {:?}; shuffled_indices={:?}",
+            seed,
+            cur.path,
+            inserted,
+            q.shuffled_indices()
+        );
+    }
+}
+
+// ---------- Seedable RNG ----------
+// The queue uses a seeded PRNG (rand::rngs::StdRng) instead of the OS-seeded
+// thread RNG, so shuffle order is reproducible via Queue::with_seed. Shuffle
+// is not a security domain — a PRNG suffices, and deterministic tests need a
+// fixed seed.
+
+#[test]
+fn test_same_seed_produces_same_shuffle_order() {
+    let mut q1 = Queue::with_seed(0x5EED);
+    let mut q2 = Queue::with_seed(0x5EED);
+    for i in 0..10 {
+        add_track(&mut q1, &format!("/music/t{}.mp3", i));
+        add_track(&mut q2, &format!("/music/t{}.mp3", i));
+    }
+    q1.set_shuffle(ShuffleMode::All);
+    q2.set_shuffle(ShuffleMode::All);
+    assert_eq!(q1.shuffled_indices(), q2.shuffled_indices());
+}
+
+#[test]
+fn test_different_seed_produces_different_shuffle_order() {
+    let mut q1 = Queue::with_seed(1);
+    let mut q2 = Queue::with_seed(2);
+    for i in 0..20 {
+        add_track(&mut q1, &format!("/music/t{}.mp3", i));
+        add_track(&mut q2, &format!("/music/t{}.mp3", i));
+    }
+    q1.set_shuffle(ShuffleMode::All);
+    q2.set_shuffle(ShuffleMode::All);
+    // 20! permutations — identical order for two seeds is practically impossible.
+    assert_ne!(q1.shuffled_indices(), q2.shuffled_indices());
+}
+
 // ---------- Track struct ----------
 
 #[test]
-- 
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