fix: Make "Play Next" actually play next under shuffle (#329)

[eddyizm]

Summary

Applied the "Play Next under shuffle" fix (from @herrerad85 commit #c55440e3d9d55988995cdce759470d45962ac6e7 ) across 4 files, adapted to the current repo (which was in the patch's exact "before" state) resolves #329 :

• Constants.kt — added CUSTOM_COMMAND_PLAY_NEXT + PLAY_NEXT_INSERT_POS / PLAY_NEXT_COUNT / PLAY_NEXT_TARGET_COUNT.
• BaseSessionCallback.kt — registered the custom command in onConnect and handled it in onCustomCommand (calls service.requestPlayNextFixup(...)).
• MediaManager.java — added 4 imports; both enqueue overloads now insert at current + 1 on the timeline and call the new insertPlayNext() helper, which sends the fixup command to the service and does the timeline addMediaItems.
• BaseMediaService.kt — added requestPlayNextFixup/tryApplyPlayNextFixup (rebuilds DefaultShuffleOrder so the inserted items play immediately after the current track; safe no-op when shuffle off or counts mismatch) and a tryApplyPlayNextFixup() call in onTimelineChanged.
  Root cause it fixes: under shuffle, getNextMediaItemIndex() is shuffle-order-dependent and ExoPlayer randomizes a newly-inserted item's shuffle position — so "play next" landed at a random spot. Now the item is deterministically inserted at current+1 on the timeline and re-spliced into shuffle position current+1.

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📝 Walkthrough

Walkthrough

Changes

Play-next shuffle workflow

Layer / File(s)	Summary
Play-next insertion protocol app/src/main/java/com/cappielloantonio/tempo/util/Constants.kt, app/src/main/java/com/cappielloantonio/tempo/service/MediaManager.java	Defines command parameters and routes single- and multi-item “play next” enqueue operations through timeline insertion with metadata.
Session command forwarding app/src/main/java/com/cappielloantonio/tempo/service/BaseSessionCallback.kt	Advertises the play-next command to applicable controllers and forwards its arguments to the media service.
Deferred shuffle-order correction app/src/main/java/com/cappielloantonio/tempo/service/BaseMediaService.kt	Stores pending fixup data, waits for timeline visibility, and rebuilds shuffle order by placing inserted items after the current track when state is valid.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Possibly related PRs

• eddyizm/tempus#866: Modifies BaseMediaService.onTimelineChanged for another timeline-driven queue operation.

Suggested reviewers: mafo-28, herrerad85

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: fixing Play Next behavior when shuffle is enabled.

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• Commit unit tests in branch bug/play-next-inconsistent

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Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
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Inline comments:
In `@app/src/main/java/com/cappielloantonio/tempo/service/BaseMediaService.kt`:
- Around line 179-223: Replace the single pending-request fields used by
requestPlayNextFixup and tryApplyPlayNextFixup with a FIFO queue of (insertPos,
count, target) requests. Enqueue every valid request, then have
tryApplyPlayNextFixup inspect the queue head and retain it until its target item
count is visible and the fixup is successfully handled; remove only the
processed or explicitly invalidated request, then continue applying any newly
eligible queued requests so overlapping Play Next operations are preserved.

In `@app/src/main/java/com/cappielloantonio/tempo/service/MediaManager.java`:
- Around line 357-380: Update insertPlayNext to retain the ListenableFuture
returned by browser.sendCustomCommand and attach failure handling that logs
rejected or failed fixup commands, including the throwable details. Keep the
existing timeline insertion and successful-command behavior unchanged, and use
the class’s established logging mechanism.

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📥 Commits

Reviewing files that changed from the base of the PR and between 6dcd52e and 8a8a32c.

📒 Files selected for processing (4)

• app/src/main/java/com/cappielloantonio/tempo/service/BaseMediaService.kt
• app/src/main/java/com/cappielloantonio/tempo/service/BaseSessionCallback.kt
• app/src/main/java/com/cappielloantonio/tempo/service/MediaManager.java
• app/src/main/java/com/cappielloantonio/tempo/util/Constants.kt