Notifications, and automatic cleanup of empty folders

Settings → Notifications sends a message to Discord, Pushover, ntfy,
Gotify or a JSON webhook when a scan finds songs that newly need
review, when auto-link replaced identical files, and when an automatic
cleanup ran. Each event can be turned off and each service tested; an
optional Playlink address adds a link back to the right page.

A new per-pair option removes empty slave folders after each scan. Only
folders with no file at all inside are removed (into the quarantine,
recorded in History); folders holding any file wait in Cleanup, folders
changed within the settle time are skipped, and dry run removes nothing.

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

internal/engine/autocleanup_test.go

@@ -0,0 +1,137 @@
+package engine
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"testing"
+
+	"github.com/cdnutter/playlink/internal/notify"
+	"github.com/cdnutter/playlink/internal/store"
+)
+
+// events records what the engine would notify about.
+type events struct {
+	mu  sync.Mutex
+	got []notify.Event
+}
+
+func (ev *env) captureEvents() *events {
+	r := &events{}
+	ev.e.SetNotify(func(_ context.Context, e notify.Event) {
+		r.mu.Lock()
+		r.got = append(r.got, e)
+		r.mu.Unlock()
+	})
+	return r
+}
+
+func (r *events) take() []notify.Event {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	out := r.got
+	r.got = nil
+	return out
+}
+
+func kinds(es []notify.Event) string {
+	var k []string
+	for _, e := range es {
+		k = append(k, e.Kind)
+	}
+	return strings.Join(k, ",")
+}
+
+func (ev *env) automate(t *testing.T, settle int) {
+	t.Helper()
+	ev.pair.AutoLinkIdentical, ev.pair.AutoCleanupEmpty, ev.pair.SettleMinutes = true, true, settle
+	if err := ev.st.SavePair(ctx, &ev.pair); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestAutoCleanupRemovesOnlyEmptyFolders(t *testing.T) {
+	ev := setup(t, false)
+	ev.automate(t, 0)
+	rec := ev.captureEvents()
+	ev.write(ev.master, "A/Same/1 Song.flac", "same")
+	ev.write(ev.slave, "A/Same/1 Song.flac", "same")
+	ev.write(ev.master, "A/Diff/1 Song.flac", "master")
+	ev.write(ev.slave, "A/Diff/1 Song.flac", "slave!")
+	os.MkdirAll(filepath.Join(ev.slave, "B/Empty/Disc 1"), 0o755)
+	ev.write(ev.slave, "C/Art/cover.jpg", "art")
+	ev.write(ev.slave, "D/.DS_Store", "x") // any file at all keeps the folder
+
+	ev.scan()
+	if exists(filepath.Join(ev.slave, "B")) {
+		t.Fatal("empty folder B should have been removed")
+	}
+	for _, keep := range []string{"C/Art/cover.jpg", "D/.DS_Store", "A/Same/1 Song.flac"} {
+		if !exists(filepath.Join(ev.slave, keep)) {
+			t.Fatalf("%s should be kept", keep)
+		}
+	}
+	es := rec.take()
+	if kinds(es) != "review,linked,cleanup" {
+		t.Fatalf("events = %s", kinds(es))
+	}
+	if es[0].Message != "1 song needs review." || es[0].PairID != ev.pair.ID {
+		t.Fatalf("review event: %+v", es[0])
+	}
+	if !strings.Contains(es[1].Message, "1 identical file") {
+		t.Fatalf("linked event: %+v", es[1])
+	}
+	if !strings.Contains(es[2].Message, "1 empty folder") || !strings.Contains(es[2].Message, "2 folders without music still hold files") {
+		t.Fatalf("cleanup event: %+v", es[2])
+	}
+	// Removed folders are quarantined and listed in History like manual ones.
+	ops, _, err := ev.st.Ops(ctx, store.OpFilter{PairID: ev.pair.ID, Limit: 100})
+	if err != nil {
+		t.Fatal(err)
+	}
+	var found bool
+	for _, o := range ops {
+		if o.Action == "remove-folder" && o.RelSlave == "B" && strings.HasPrefix(o.Trigger, "auto:") && exists(o.QuarantinePath) {
+			found = true
+		}
+	}
+	if !found {
+		t.Fatalf("no quarantined auto removal of B in %+v", ops)
+	}
+
+	// Nothing new: a second scan stays quiet.
+	ev.scan()
+	if es := rec.take(); len(es) != 0 {
+		t.Fatalf("second scan notified: %s", kinds(es))
+	}
+}
+
+func TestAutoCleanupWaitsForSettleAndDryRun(t *testing.T) {
+	ev := setup(t, false)
+	ev.automate(t, 10)
+	rec := ev.captureEvents()
+	os.MkdirAll(filepath.Join(ev.slave, "Fresh"), 0o755)
+	ev.write(ev.slave, "A/1 Song.flac", "x")
+	ev.scan()
+	if !exists(filepath.Join(ev.slave, "Fresh")) {
+		t.Fatal("a folder changed within the settle time must be left alone")
+	}
+	if es := rec.take(); len(es) != 0 {
+		t.Fatalf("events = %s", kinds(es))
+	}
+
+	dry := setup(t, true)
+	dry.automate(t, 0)
+	rec = dry.captureEvents()
+	os.MkdirAll(filepath.Join(dry.slave, "Empty"), 0o755)
+	dry.write(dry.slave, "A/1 Song.flac", "x")
+	dry.scan()
+	if !exists(filepath.Join(dry.slave, "Empty")) {
+		t.Fatal("dry run removed a folder")
+	}
+	if es := rec.take(); len(es) != 0 {
+		t.Fatalf("dry run notified: %s", kinds(es))
+	}
+}