minstrel/internal/library/notify.go

package library

import (
	"context"
	"sync"

	"github.com/jackc/pgx/v5/pgtype"

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
	"git.fabledsword.com/bvandeusen/minstrel/internal/notifications"
)

// Package-level notifier for library-health notices to admins: a
// scan that failed, tracks gone missing, new duplicates. Set once at startup
// beside SetEventBus, for the same reason the bus is package-level. Nil, as in
// tests that never set it, means nobody is told.
var (
	notifierMu sync.RWMutex
	notifier   *notifications.Notifier
)

// SetNotifier wires the notifications inbox into the library package.
func SetNotifier(n *notifications.Notifier) {
	notifierMu.Lock()
	defer notifierMu.Unlock()
	notifier = n
}

// notifyAdmins tells every admin about a library-health event. These kinds
// coalesce, so a burst is one unread notice with a running count.
func notifyAdmins(ctx context.Context, kind notifications.Kind, p notifications.Payload) {
	notifierMu.RLock()
	n := notifier
	notifierMu.RUnlock()
	n.NotifyLogged(ctx, kind, notifications.ToAdmins(pgtype.UUID{}), p.Map())
}

// notifyItems is how many names a notice carries; the notifications package
// keeps the newest ten across a coalesced burst.
const notifyItems = 10

// TrackLabel names a track as a notice does: "Artist – Title", or the title
// alone when the artist is unknown.
func TrackLabel(artist, title string) string {
	if artist == "" {
		return title
	}
	return artist + " – " + title
}

// notifyStillMissing tells admins which of the tracks a scan marked missing
// are still gone after it adopted moves and folded replacements. A marked
// track the scan healed is not news: reporting it would make a quality
// upgrade read as lost music.
func (s *Scanner) notifyStillMissing(ctx context.Context, marked []pgtype.UUID) {
	if len(marked) == 0 || ctx.Err() != nil {
		return
	}
	rows, err := dbq.New(s.pool).ListStillMissingTrackLabels(ctx, marked)
	if err != nil {
		s.logger.Warn("library scan: listing missing tracks for the notice failed", "err", err)
		return
	}
	if len(rows) == 0 {
		return
	}
	items := make([]string, 0, min(len(rows), notifyItems))
	for _, r := range rows[:min(len(rows), notifyItems)] {
		items = append(items, TrackLabel(r.ArtistName, r.Title))
	}
	notifyAdmins(ctx, notifications.KindTracksMissing, notifications.Payload{Count: int64(len(rows)), Items: items})
}

// notifyScanFinished tells admins a scan run ended in error. A scan cut short
// by shutdown is not a failure anyone needs telling about.
func notifyScanFinished(ctx context.Context, errMsg string) {
	if errMsg == "" || ctx.Err() != nil {
		return
	}
	notifyAdmins(ctx, notifications.KindScanFailed, notifications.Payload{Count: 1, Detail: errMsg})
}