fix(stats): credit the play in progress when the app quits

[InstaZDLL]

Problem

A play is credited when it ends, and quitting ends it: the decoder answers Shutdown like a skip (15 s or more of listening → TrackListened → play_event + scrobble queue). But:

• RunEvent::Exit only wrote the resume point, and the process exited with the credit still in the analytics channel;
• the tray's Quit (AppHandle::exit) never sent Shutdown at all; only the window close did.

So the last track listened to before quitting never reached the history, the stats or Last.fm.

Fix

• AudioEngine::shut_down_and_flush(budget): sends Shutdown, waits for the decoder thread to finish, then queues AnalyticsMsg::Flush(Arc<Notify>) behind the credit and waits for its answer. The channel is FIFO and the task handles one message at a time, so the answer means the row is written. The whole wait is bounded (2 s), so a decoder stuck in a slow read cannot hold the process open.
• The five Shutdown returns in play_track / play_dop_track go through shutdown_outcome, which re-queues Shutdown in pending_cmd: the decoder loop now ends once the credit is sent, instead of going back to wait for a command, which is what makes "thread finished" mean "credit sent".
• RunEvent::Exit silences the output (as the close path already does), writes the resume point, then calls it.

Only the decoder credits, so a window close that already sent Shutdown is not counted twice.

Docs: playback.md, "The last play at exit".

Summary by CodeRabbit

• Améliorations
  • À la fermeture de l’application, le point de reprise est enregistré et la lecture audio est arrêtée. Les données analytiques en attente sont ensuite traitées, dans la limite de deux secondes.
  • Une lecture déjà interrompue par la fermeture de la fenêtre n’est pas comptabilisée deux fois.
• Documentation
  • La documentation précise le comportement de la lecture à la fermeture, notamment le délai d’attente et le risque qu’une lecture lente ne soit pas comptabilisée.

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🧰 Additional context used

📚 Code guidelines (2)

AGENTS.md — auto-discovered
CLAUDE.md — auto-discovered

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📥 Commits

Reviewing files that changed from the base of the PR and between 21de015 and de98561.

📒 Files selected for processing (4)

• docs/features/playback.md
• src-tauri/crates/app/src/audio/analytics.rs
• src-tauri/crates/app/src/audio/engine.rs
• src-tauri/crates/app/src/lib.rs

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📝 Walkthrough

Walkthrough

À la fermeture, l’application met en pause la sortie audio et enregistre le point de reprise. Elle arrête ensuite le moteur audio et attend le traitement des analyses, dans une limite de deux secondes.

Changes

Arrêt audio et vidage des analyses

Layer / File(s)	Summary
Traitement de l’interruption du décodeur src-tauri/crates/app/src/audio/decoder.rs	Les chemins DoP et PCM utilisent shutdown_outcome pour interrompre la lecture, mettre le lecteur à l’état Idle et conserver la commande Shutdown en attente.
Barrière de vidage des analyses src-tauri/crates/app/src/audio/analytics.rs, src-tauri/crates/app/src/audio/engine.rs	AnalyticsMsg::Flush confirme le traitement des messages précédents. AudioEngine::shut_down_and_flush arrête le décodeur, puis attend cette confirmation dans la limite de temps prévue.
Intégration à la fermeture src-tauri/crates/app/src/lib.rs, docs/features/playback.md	RunEvent::Exit met en pause la sortie audio, enregistre le point de reprise, puis demande l’arrêt et le vidage des analyses avec un délai de deux secondes. La documentation décrit ce traitement.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant ExitEvent
  participant AudioEngine
  participant Decoder
  participant AnalyticsQueue
  ExitEvent->>AudioEngine: request shutdown and flush within two seconds
  AudioEngine->>Decoder: send Shutdown
  Decoder->>AnalyticsQueue: send interrupted playback data
  AudioEngine->>AnalyticsQueue: send Flush
  AnalyticsQueue-->>AudioEngine: confirm earlier messages were processed

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Merge Risk: ⚪ Minimal · up to de985

Exit now silences playback, preserves the resume point, and best-effort processes the final play within the shutdown budget.

Security Architecture Review

Security architecture risk: 🔵 Low · up to de985

The change stays within the application's existing permissions and account checks. Shutdown remains best-effort, with limits around failed writes, interruption and repeated calls.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The demonstrated change affects in-process shutdown coordination, active-profile play history and eligible scrobble queue entries. The new path carries no credentials or selectable remote destination and has no demonstrated expansion to other services, environments or privilege levels.

Trust Boundaries and Controls

• observed — The only established caller supplies a fixed budget from the internal exit handler. Flush bypasses profile-pool acquisition only to signal completion; it performs no data access. Interruption credit still requires a positive library-track identifier, at least fifteen seconds of listening, and the existing profile-pool path.

Resilience and Maintainability Implications

• inferred — The completion guarantee depends on a single invocation retaining the decoder handle. Taking that handle before awaiting means a concurrent call, or a retry after cancellation or timeout, could enqueue Flush before decoder completion. Only one production caller was established, so this remains a reuse limitation rather than a demonstrated attack path.

Hardening Proposals

• proposed — If shutdown becomes reusable or callable concurrently, preserve a shared completion state across cancellation and retries so every invocation observes decoder termination before acknowledging analytics handling.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 77.78% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 4 files. (1 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	Le titre suit le format Conventional Commits et décrit clairement le crédit de la lecture en cours à la fermeture de l’application.
Description check	✅ Passed	La description explique le problème et la solution. Elle ne contient pas de section « How I tested », de checklist ni de référence à un ticket, mais elle reste suffisamment complète pour comprendre le…
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.

Full details: Docstring Coverage

Explanation

Docstring coverage is 77.78% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 4 files. (1 skipped: 1 unsupported.)

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Actionable comments posted: 2

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• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @src-tauri/crates/app/src/audio/analytics.rs:
- Around line 122-124: Update analytics_task so the Flush barrier reports
failures from require_profile_pool and insert_play_event instead of notifying
completion as if writes succeeded. Propagate or retain write errors until Flush,
and only signal a successful flush after preceding play_event writes have
completed successfully.

Review comments at @src-tauri/crates/app/src/lib.rs:
- Line 1303: Update the shutdown flow around write_resume_point to capture the
playback position and set paused_output to true before awaiting the resume-point
write, so output is muted immediately when Quit is selected.

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📥 Commits

Reviewing files that changed from the base of the PR and between 054d472 and 21de015.

📒 Files selected for processing (5)

• docs/features/playback.md
• src-tauri/crates/app/src/audio/analytics.rs
• src-tauri/crates/app/src/audio/decoder.rs
• src-tauri/crates/app/src/audio/engine.rs
• src-tauri/crates/app/src/lib.rs

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