fix: room expiry edge cases

[madawei2699]

Summary

Oracle analysis of the room expiry flow identified several bugs and edge cases.

Fixes

🔴 Bugs

Double leaveRoom() (#6)
Both the setInterval countdown-to-zero path and expiryFinalRef setTimeout called leaveRoom() + redirect, causing the second call to throw on an already-destroyed meeting object. Added hasLeftRef guard so the leave executes exactly once regardless of which path fires first.

Cron disconnect shows "Reconnecting" instead of expiry message (#5)
When the cron job deletes participants, RTK fires a disconnect event and onRoomLeft was unconditionally setting connectionStatus = "reconnecting", leaving users staring at a spinner with no explanation. Now checks Date.now() >= expiresAtRef.current in onRoomLeft — if the room has expired, calls doExpireLeave() and redirects home instead.

🟡 Improvements

Warning timer drift (#7A)
expiryTimerRef was hardcoded to 6600 * 1000ms. If the device sleeps and resumes, the setTimeout fires late. Changed to expiresAt - now - 10min so the delay is always calibrated to the absolute expiry time.

Backgrounded tab throttling (#7B)
Browsers throttle setInterval in backgrounded tabs to ≥1 minute, causing the countdown to desync. Added a visibilitychange listener that recalibrates timeLeft from expiresAt immediately when the tab becomes visible again. If the room has already expired, calls doExpireLeave() directly.

KV TTL reduced from 30 days to 4 hours (#4)
Rooms live for 2 hours. Keeping KV records for 30 days was wasteful and caused the cron's kv.list() to scan through large amounts of dead records. Changed to 4 hours (2h room lifetime + 2h buffer) so KV auto-purges stale records. Cron is kept as defense-in-depth but is no longer the primary cleanup mechanism.

[gemini-code-assist]

Code Review

This pull request enhances the chat room expiration logic by introducing a hasLeftRef to track leave status, adding a visibility change listener to detect expiration upon tab focus, and refactoring timers to use dynamic expiration values. Additionally, the KV storage TTL for rooms has been reduced to 4 hours. Feedback suggests resetting the hasLeftRef in the cleanup function to ensure the hook remains robust if reused without a full page reload.

[gemini-code-assist]

The hasLeftRef should be reset to false in the cleanup function, similar to how hasJoinedRef is reset. While the current implementation uses a hard redirect (window.location.href = "/") which re-initializes the hook state, resetting the ref explicitly ensures that the expiration logic remains correct if the hook is reused across different room sessions without a full page reload (e.g., if the redirect logic is changed in the future or if the hook is used in a context where navigation doesn't trigger a reload).

      hasJoinedRef.current = false
      hasLeftRef.current = false

[Copilot]

Pull request overview

Fixes several edge cases in the room expiry flow: prevents double leaveRoom() calls, properly handles cron-initiated disconnects as expiry rather than reconnection attempts, recalibrates timers against the absolute expiry timestamp to handle device sleep and background-tab throttling, and reduces the KV TTL from 30 days to 4 hours to align with the 2-hour room lifetime.

Changes:

• Introduces hasLeftRef guard plus a shared doExpireLeave() helper so leave/redirect runs exactly once regardless of trigger (interval, final setTimeout, or roomLeft event).
• Recalibrates the warning and final-expiry timers against expiresAtRef and adds a visibilitychange handler so backgrounded/asleep tabs resync timeLeft and expire correctly.
• Reduces ROOM_KV_TTL_S to 4 hours so KV auto-purges dead room records and the cron's kv.list() stays small.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
app/src/pages/api/token.ts	Extracts ROOM_KV_TTL_S = 4h and uses it for both KV writes in place of the previous 30-day TTL.
app/src/hooks/useChatRoom.ts	Adds hasLeftRef + doExpireLeave(), expiry-aware onRoomLeft, visibility-change recalibration, and absolute-time-based warning/final timers.

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