An on-demand channel (`PlayoutMode.OnDemand`) already is the "resume where I
left off" feature: `Playout.OnDemandCheckpoint` persists the viewer's position
and `PlayoutTimeShifter.TimeShift` slides the materialized timeline forward on
tune-in so the paused item is active again. Because it rewrites `GuideStart`/
`GuideFinish` alongside `Start`/`Finish`, guide and playback freeze together —
structurally avoiding the free-running-wall-clock desync #68 was filed about.
The one gap: `TimeShift` rewrote the stored `PlayoutItem` rows but the XMLTV
guide is served from a cached fragment that only `RefreshChannelData` rebuilds,
and the tune-in path never enqueued it. So an external EPG client polling after
a thaw could see a stale timeline until the next incidental rebuild.
Fix: `IPlayoutTimeShifter.TimeShift` now returns the channel numbers whose cached
guide is stale — the shifted channel plus any channels that mirror it (the same
fan-out `BuildPlayoutHandler` already does) — and `TimeShiftOnDemandPlayoutHandler`
enqueues a `RefreshChannelData` for each on `CancellationToken.None` (post-commit
side effect must not be abandoned if the session token cancels).
Tests: handler enqueues a rebuild per stale channel (+ mirror + no-shift cases);
`PlayoutTimeShifter` reports source+mirrors on a shift, empty on Continuous /
zero-offset / active-unforced, and correctly seeds+shifts a never-watched playout.
Non-vacuity of the enqueue proven by a compiling negative control.
Docs: channels.md (On-demand resume section), domain-model.md, decisions.md
(scheduling.ondemand-guide-refresh-on-thaw). Per-viewer resume is out of scope
(single per-channel checkpoint; #68 says per-channel suffices).
fixes#68
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
timothyandClaude Opus 4.8