# Production Readiness — Streaming Pipeline Gaps

> **For Hermes:** Use subagent-driven-development skill to implement this plan task-by-task.

**Goal:** Close all HIGH/MEDIUM streaming pipeline gaps from STREAMING.md contract to reach production-readiness for linearvoid.tv.

**Architecture:** Modify `backend/playout/src/playlist.go` (Go playout engine) for R2 sync, segment naming, and health endpoint. Modify `frontend/src/main.ts` (TypeScript SPA) for player error recovery. Infrastructure-only (CORS on R2) is documented but needs manual Cloudflare action.

**Tech Stack:** Go (playout), TypeScript (frontend SPA), FFmpeg, AWS SDK for R2, hls.js

---

## Priority 1: Continuous R2 Sync + Unique Segment Naming 🔴

These are tightly coupled — unique naming enables safe per-segment upload.

### Task 1: Add run/session ID and monotonic media sequence

**Objective:** Generate a unique run ID on playout start and a monotonically increasing segment counter used in segment filenames.

**Files:**
- Modify: `backend/playout/src/playlist.go` (global vars, FFmpeg args, syncLatestToR2)
- Modify: `backend/playout/src/playlist_test.go` (update tests for new naming)

**Step 1: Add run ID and sequence to global state**
```go
var (
    runID       string // e.g. "r-20260810T170412Z"
    segSequence uint64 // monotonically increasing segment counter
)

func initRunID() {
    runID = "r-" + time.Now().UTC().Format("20060102T150405Z")
}
```

**Step 2: Update FFmpeg segment filename pattern**
Replace strftime pattern with run ID + sequence:
```go
// Current (bad):
"-hls_segment_filename", "/app/hls/segment_%Y%m%d_%H%M%S.m4s",
// New (unique):
"-hls_segment_filename", fmt.Sprintf("/app/hls/%s/seg-%%06d.m4s", runID),
```

**Step 3: Update syncLatestToR2 for new naming**
```go
func syncLatestToR2(hlsDir string) error {
    runDir := filepath.Join(hlsDir, runID)
    files, err := filepath.Glob(filepath.Join(runDir, "seg-*.m4s"))
    // Upload to R2: live/{runID}/seg-{seq}.m4s
}
```

**Verification:**
- Run: `cd backend/playout && go test -v -run TestLoadPlaylist`
- Expected: Playlist tests still pass with new naming
- Manual check: inspect hls directory for `r-*` subdirectory structure

---

### Task 2: Add filesystem watch for per-segment R2 upload

**Objective:** Upload each segment to R2 as FFmpeg completes it, instead of waiting for FFmpeg to exit. Use a filesystem watcher (fsnotify) triggered by new `.m4s` files.

**Files:**
- Modify: `backend/playout/src/playlist.go` (add watcher goroutine)
- Modify: `backend/playout/go.mod` (add fsnotify dependency)

**Step 1: Add fsnotify dependency**
```bash
cd backend/playout && go get github.com/fsnotify/fsnotify
```

**Step 2: Implement segment publish goroutine**
```go
func watchAndPublishSegments(ctx context.Context, hlsDir string) {
    watcher, _ := fsnotify.NewWatcher()
    defer watcher.Close()
    watcher.Add(hlsDir)
    
    for {
        select {
        case event := <-watcher.Events:
            if event.Op&fsnotify.Create != 0 && strings.HasSuffix(event.Name, ".m4s") {
                // Wait for file to be fully written
                time.Sleep(500 * time.Millisecond)
                uploadSegment(event.Name)
            }
        case <-ctx.Done():
            return
        }
    }
}
```

**Step 3: Wire watcher into main() loop**
Start the watcher goroutine before FFmpeg command, cancel context on exit.

**Verification:**
- Run: `go test -v ./...` in playout directory
- Manual: start playout, check R2 bucket for segments appearing in real-time
- Expected: new segments appear in R2 within ~7s of creation

---

### Task 3: Atomic manifest publication

**Objective:** Upload manifest to temp key (`live/playlist.m3u8.tmp`), then atomically copy/replace to `live/playlist.m3u8`.

**Files:**
- Modify: `backend/playout/src/playlist.go` (syncLatestToR2 / publishManifest)

**Step 1: Write publishManifest function**
```go
func publishManifest(localPath string) error {
    // 1. Upload to temp key
    if err := SyncToR2(localPath, "live/playlist.m3u8.tmp"); err != nil {
        return err
    }
    // 2. Atomic copy to final key (R2 supports CopyObject)
    _, err := r2Client.CopyObject(context.TODO(), &s3.CopyObjectInput{
        Bucket:     aws.String(bucket),
        CopySource: aws.String(bucket + "/live/playlist.m3u8.tmp"),
        Key:        aws.String("live/playlist.m3u8"),
    })
    return err
}
```

**Verification:**
- Run: `go test -v -run TestSyncToR2_ManifestCacheHeaders`
- Expected: manifest appears atomically in R2
- Manual: curl `media.linearvoid.tv/hls/playlist.m3u8` — should never 404

---

### Task 4: Fix manifest Cache-Control contract

**Objective:** Align manifest cache headers with STREAMING.md contract.

**Files:**
- Modify: `backend/playout/src/playlist.go` (constants)

**Step 1: Update constant**
```go
// Current (wrong):
manifestCacheControl = "public, max-age=2"
// New (per contract):
manifestCacheControl = "public, max-age=1, s-maxage=2, must-revalidate"
```

**Verification:**
- Run: `go test -v -run TestSyncToR2_ManifestCacheHeaders`
- Expected: test still passes with new header values

---

## Priority 2: Player Error Recovery 🟡

### Task 5: Add hls.js error handler with retry logic

**Objective:** Handle hls.js errors with bounded retries, exponential backoff, and a visible reconnecting state.

**Files:**
- Modify: `frontend/src/main.ts` (initPlayerAndChat, add error handler)
- Modify: `frontend/src/style.css` (reconnecting overlay style)
- Modify: `frontend/index.html` (add reconnecting indicator element)

**Step 1: Add reconnecting overlay HTML**
```html
<div id="reconnecting-overlay" class="reconnecting-overlay hidden">
  <div class="reconnecting-spinner"></div>
  <span>Reconnecting...</span>
</div>
```

**Step 2: Implement error handler in main.ts**
```typescript
let errorCount = 0;
const MAX_RETRIES = 5;
const BASE_DELAY_MS = 2000;

hls.on(Hls.Events.ERROR, (_event, data) => {
    if (data.fatal) {
        switch (data.type) {
            case Hls.ErrorTypes.NETWORK_ERROR:
                errorCount++;
                if (errorCount <= MAX_RETRIES) {
                    const delay = BASE_DELAY_MS * Math.pow(2, errorCount - 1);
                    showReconnecting();
                    setTimeout(() => hls?.startLoad(), delay);
                } else {
                    showReconnecting('Stream unavailable');
                }
                break;
            case Hls.ErrorTypes.MEDIA_ERROR:
                errorCount++;
                if (errorCount <= 1) {
                    hls?.recoverMediaError();
                } else {
                    hls?.destroy();
                    showReconnecting('Stream unavailable');
                }
                break;
            default:
                hls?.destroy();
                showReconnecting('Stream unavailable');
                break;
        }
    }
});

// Add drift detection
hls.on(Hls.Events.LEVEL_UPDATED, () => {
    const latency = hls.latency;
    if (latency > 35) {
        hls.currentLevel = -1; // seek to live edge
    }
});
```

**Step 3: Write test for error recovery**
Add to `frontend/src/main.test.ts`:
```typescript
it("retries on network error with exponential backoff", async () => {
    // Mock hls.js error event, verify retry with backoff
});
```

**Verification:**
- Run: `cd frontend && npx vitest run`
- Expected: 31 existing tests pass + new error recovery test
- Manual: kill playout process, verify player shows "Reconnecting..." and recovers when playout restarts

---

## Priority 3: Health Endpoint Detail 🟢

### Task 6: Enrich /health endpoint

**Objective:** Add active item, playlist revision, run ID, last segment info, last R2 pub timestamp, consecutive failures to `/health`.

**Files:**
- Modify: `backend/playout/src/playlist.go` (HealthHandler, global state)

**Step 1: Add tracking state**
```go
var (
    activeItem       string
    playlistRevision string
    lastSegmentSeq   uint64
    lastR2PubTime    time.Time
    consecutiveFails int
)
```

**Step 2: Update HealthHandler**
```go
func HealthHandler(w http.ResponseWriter, r *http.Request) {
    resp := map[string]any{
        "status":              status,
        "service":             "playout",
        "mode":                playoutMode,
        "restarts":            restartCount,
        "run_id":              runID,
        "active_item":         activeItem,
        "playlist_revision":   playlistRevision,
        "last_segment_seq":    lastSegmentSeq,
        "last_r2_pub":         lastR2PubTime.UTC().Format(time.RFC3339),
        "consecutive_failures": consecutiveFails,
        "timestamp":           time.Now().UTC().Format(time.RFC3339),
    }
    json.NewEncoder(w).Encode(resp)
}
```

**Verification:**
- Run: `go test -v -run TestHealthHandler`
- Manual: `curl localhost:8081/health | jq`
- Expected: all new fields present and populated

---

## Execution Order

1. Task 1 → Task 2 → Task 3 (coupled: naming enables sync, sync enables atomic publish)
2. Task 4 (quick constant change, can be batched with Task 3)
3. Task 5 (independent frontend work)
4. Task 6 (quick, can be batched with Task 1-3)

**Total estimated changes:** ~200 lines Go, ~60 lines TypeScript, ~20 lines HTML, ~10 lines CSS

## Files Changed

| File | Purpose |
|------|---------|
| `backend/playout/src/playlist.go` | Core changes: run ID, unique naming, filesystem watcher, atomic publish, health |
| `backend/playout/src/playlist_test.go` | Update for new naming + add watcher tests |
| `backend/playout/go.mod` | Add fsnotify |
| `frontend/src/main.ts` | Player error recovery |
| `frontend/src/style.css` | Reconnecting overlay styles |
| `frontend/index.html` | Reconnecting overlay element |
| `frontend/src/main.test.ts` | Error recovery tests |