Announce finished and failed downloads in the background (M10)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/ui/watch.go

@@ -0,0 +1,86 @@
+package ui
+
+import (
+	"context"
+	"time"
+
+	"git.stinnesbeck.com/nils/arr-tui/internal/sabnzbd"
+	"github.com/rivo/tview"
+)
+
+// watchInterval is how often SABnzbd's history is checked for finished
+// downloads in the background, whatever view is showing.
+const watchInterval = 15 * time.Second
+
+// downloadEvent is a download that just finished or failed.
+type downloadEvent struct {
+	name    string
+	failed  bool
+	message string // failure reason, if any
+}
+
+// diffHistory compares SABnzbd's history with what was seen before and
+// returns the downloads that reached a final state since. seen maps job id to
+// the last known status and is updated. With baseline set (the first poll) the
+// current state is only recorded, so downloads that finished before arr-tui
+// started do not produce notifications.
+func diffHistory(seen map[string]string, slots []sabnzbd.HistorySlot, baseline bool) []downloadEvent {
+	var events []downloadEvent
+	for _, s := range slots {
+		prev, known := seen[s.ID]
+		seen[s.ID] = s.Status
+		final := s.Status == "Completed" || s.Failed()
+		if baseline || !final || (known && prev == s.Status) {
+			continue
+		}
+		events = append(events, downloadEvent{name: s.Name, failed: s.Failed(), message: s.FailMessage})
+	}
+	return events
+}
+
+// watchDownloads polls SABnzbd's history until ctx ends and reports finished
+// and failed downloads as popups (and a bell, if enabled). Errors are not
+// reported here: the connection indicator and the log already do that.
+func (a *App) watchDownloads(ctx context.Context, sab *sabnzbd.Client, bell bool) {
+	seen := map[string]string{}
+	baseline := true
+	t := time.NewTicker(watchInterval)
+	defer t.Stop()
+	for {
+		hctx, cancel := context.WithTimeout(ctx, 10*time.Second)
+		slots, err := sab.History(hctx, 30)
+		cancel()
+		if err == nil {
+			events := diffHistory(seen, slots, baseline)
+			baseline = false
+			if len(events) > 0 {
+				a.post(func() { a.announce(events, bell) })
+			}
+		}
+		select {
+		case <-ctx.Done():
+			return
+		case <-t.C:
+		}
+	}
+}
+
+// announce shows a popup for each event; UI goroutine only.
+func (a *App) announce(events []downloadEvent, bell bool) {
+	for _, e := range events {
+		if e.failed {
+			text := "Download failed: " + tview.Escape(e.name)
+			if e.message != "" {
+				text += " (" + tview.Escape(truncate(e.message, 60)) + ")"
+			}
+			a.SetMessage("[red]" + text)
+		} else {
+			a.SetMessage("[green]Download finished: " + tview.Escape(e.name))
+		}
+	}
+	if bell {
+		if a.screen != nil {
+			a.screen.Beep()
+		}
+	}
+}