docs(spec): auto-pause on empty channel design (#79 item 3)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/superpowers/specs/2026-05-30-autopause-empty-channel-design.md

@@ -0,0 +1,101 @@
+# Auto-pause on empty channel — design
+
+**Issue:** [#79](https://github.com/ZHANGTIANYAO1/teamspeak-music-bot/issues/79) item 3
+**Date:** 2026-05-30
+**Status:** Approved (brainstorm), pending implementation plan
+
+## Problem
+
+When everyone leaves the bot's voice channel, music keeps playing to an empty room.
+The maintainer wants an option to **auto-pause when the channel is empty** (no disconnect)
+and resume when someone returns.
+
+## Decisions (from brainstorm)
+
+- **Global toggle**, reusing the **already-declared but currently dead** `config.autoPauseOnEmpty`
+  (`src/data/config.ts`, default `true`). No per-bot granularity (YAGNI).
+- **Event-driven, near-instant** reaction (not the 30s poll alone) — subscribe to TS client
+  enter/leave/move events; keep the existing 30s idle poll as a fallback.
+- **Auto-resume only what we auto-paused** — a user-paused track is never auto-resumed.
+- Independent of the existing **idle-disconnect** (`idleTimeoutMinutes`): both share the same
+  emptiness signal but act independently (pause immediately; disconnect after N minutes).
+
+## Current state (verified)
+
+- `client.ts` `getClientsInChannel()` returns all clients in the bot's channel *including the
+  bot*; callers compute "others" as `length - 1`. No persistent roster.
+- The library emits `clientEnter` / `clientLeave` / `clientMoved`; `client.ts` currently only
+  *logs* `clientEnter` and does not re-emit leave/moved.
+- The idle poller in `instance.ts` (`_startIdlePoller`, every 30s) already computes
+  `userCount = getClientsInChannel().length - 1` and, when `<= 0`, schedules an
+  idle-disconnect after `idleTimeoutMinutes`.
+- `player.pause()` / `player.resume()` already pause/resume **without disconnecting** (ffmpeg
+  stays alive, no voice sent). The player only knows `idle|playing|paused` — there is **no**
+  auto-vs-user-pause distinction today.
+- `BotConfig.autoPauseOnEmpty` exists (default true) but is **read nowhere**.
+
+## Design
+
+### Occupancy signal (shared)
+Extract the idle poller's count into one method on `BotInstance`:
+`checkChannelOccupancy()` → queries `getClientsInChannel()`, computes `userCount = length - 1`,
+and drives **both** the existing idle-disconnect timer (unchanged behavior) **and** the new
+auto-pause logic below. It is called by:
+1. the existing 30s poll (fallback), and
+2. new TS event handlers.
+
+### Event subscription
+`client.ts`: subscribe to and **re-emit** `clientEnter`, `clientLeave`, `clientMoved` up to
+`BotInstance`. `BotInstance.setupTsEvents()` calls `checkChannelOccupancy()` on each (a re-query
+is simplest, since `clientLeave` carries no channel id). This gives near-instant pause/resume;
+the poll remains as a safety net.
+
+### Auto-pause logic (inside `checkChannelOccupancy`)
+Add a private `autoPaused = false` flag to `BotInstance`.
+- **Empty** (`userCount <= 0`): if `config.autoPauseOnEmpty` **and** `player.getState() === "playing"`
+  → `player.pause()`, `autoPaused = true`, emit `stateChange`. (Idle-disconnect timer still
+  scheduled as today.)
+- **Re-populated** (`userCount > 0`): if `autoPaused` **and** `player.getState() === "paused"`
+  → `player.resume()`, `autoPaused = false`, emit `stateChange`. (Idle timer cancelled as today.)
+
+### `autoPaused` bookkeeping (so user pauses are respected)
+Clear `autoPaused = false` in `cmdPause`, `cmdResume`, `cmdStop`, `cmdPlay`, and on
+connect/disconnect (the `disconnected` handler calls `player.stop()` → idle). Net effect: only a
+track *we* auto-paused gets auto-resumed; a user-paused track stays paused when someone returns.
+
+### Config wiring
+- `GET /api/bot/settings`: include `autoPauseOnEmpty` in the payload (alongside `idleTimeoutMinutes`).
+- `POST /api/bot/settings`: accept + validate a boolean `autoPauseOnEmpty`, `saveConfig`, and
+  propagate to live bots via a new `BotInstance.updateAutoPause(enabled)` (mirrors
+  `updateIdleTimeout`). Since the instance reads `this.config.autoPauseOnEmpty` live, propagation
+  can be as simple as updating the stored config reference / a field the check reads.
+- Frontend `Settings.vue` → the **行为设置** section (already `bot.manage`-gated): add a toggle
+  for `autoPauseOnEmpty` next to the idle-timeout control; load it in the settings fetch and send
+  it on save.
+
+## Components / files
+
+- `src/ts-protocol/client.ts` — subscribe + re-emit `clientEnter`/`clientLeave`/`clientMoved`.
+- `src/bot/instance.ts` — `autoPaused` field; `checkChannelOccupancy()` (refactored from the
+  idle poller, drives idle + auto-pause); event handlers; clear `autoPaused` in user commands +
+  connect/disconnect; `updateAutoPause(enabled)`.
+- `src/web/api/bot.ts` — `GET`/`POST /settings` handle `autoPauseOnEmpty`.
+- `web/src/views/Settings.vue` (+ player store settings load/save) — the toggle.
+- `src/data/config.ts` — field already exists (no change beyond confirming default).
+
+## Testing
+
+- **Decision unit test (TDD):** extract the pause/resume decision into a testable method, e.g.
+  `applyOccupancy(userCount)` operating on an injected fake player (`getState`/`pause`/`resume`)
+  + the `autoPaused` flag + the config flag. Cases: empty+playing+enabled → pause + `autoPaused`;
+  re-populated+`autoPaused`+paused → resume + clear; re-populated when NOT `autoPaused` (user
+  pause) → no resume; flag disabled → no pause; empty while idle (not playing) → no-op.
+- **API test:** `GET`/`POST /api/bot/settings` round-trips `autoPauseOnEmpty` (validates boolean,
+  persists, propagates).
+- Live TS event wiring is verified by code review + a manual run (can't unit-test a real server).
+
+## Non-goals
+
+- No per-bot toggle (global only). No change to idle-disconnect behavior. No new dependency.
+- Reaction relies on events the bot can already see (same-channel members are always in view);
+  no extra channel subscription needed.