feat(notifications): the inbox store, one writer, coalescing and retention (#5338)

M489 step 1. The event bus is fire-and-forget, so a client that isn't
connected never hears that a request completed or that tracks went missing.
user_notifications is the durable record; the bus only nudges.

- Migration 0073: user_notifications (kind CHECK-gated, payload jsonb,
  read_at, coalesce_key, emailed_at) and user_notification_prefs (per user,
  per kind: inbox, phone, email). A missing pref row means the kind's
  defaults, so nothing is seeded.
- internal/notifications.Notifier is the only writer. It resolves recipients
  (admin kinds reach admins only, and never the excepted user), honours the
  inbox pref (phone and email ride on it), writes, and publishes a
  contentless notification.created nudge per recipient.
- Burst-prone admin kinds coalesce into one unread row: tracks_missing and
  scan_failed add up their counts, duplicates_found and playback_errors take
  the latest total. Once read, the next event is a new row.
- Retention: read rows go after 90 days, anything after a year, on the
  library_changes compactor's daily shape.

Tests: unit (channel rules, kind table) and integration (recipients, nudge,
coalescing both ways, prefs, owner-scoped idempotent mark-read, every kind
against both schema CHECKs, retention cut-offs).

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

internal/notifications/kinds.go

@@ -0,0 +1,130 @@
+// Package notifications is the one writer of the per-user notifications inbox
+// (M489, #726). Producers across the server call Notifier.Notify; nothing else
+// inserts into user_notifications.
+//
+// The event bus alone was fire-and-forget: a client that was not connected
+// when a request completed, or when tracks went missing, never heard of it. A
+// row here is the durable record. The bus only nudges open clients to come
+// and read it.
+package notifications
+
+// Kind names one sort of notification. The set is CHECK-gated in migration
+// 0073 (rule 36): a new kind adds its value there, in the same change, and
+// TestKindsMatchMigrationCheck fails until it does.
+type Kind string
+
+const (
+	KindRequestApproved   Kind = "request_approved"
+	KindRequestRejected   Kind = "request_rejected"
+	KindRequestCompleted  Kind = "request_completed"
+	KindRequestPending    Kind = "request_pending"
+	KindQuarantineFlagged Kind = "quarantine_flagged"
+	KindScanFailed        Kind = "scan_failed"
+	KindTracksMissing     Kind = "tracks_missing"
+	KindDuplicatesFound   Kind = "duplicates_found"
+	KindPlaybackErrors    Kind = "playback_errors"
+)
+
+// Audience is who a kind can reach. Admin kinds are never offered to, or
+// stored for, a non-admin.
+type Audience int
+
+const (
+	AudienceRequester Audience = iota
+	AudienceAdmin
+)
+
+// EmailGroup is how a kind's emails are grouped. Nothing is emailed per event.
+type EmailGroup int
+
+const (
+	// EmailBatch: one email per batch window, holding everything that
+	// accumulated since the first un-emailed item.
+	EmailBatch EmailGroup = iota
+	// EmailSummary: at most one summary a day, at a set local hour. For new
+	// music arriving, which comes in bursts and is not urgent.
+	EmailSummary
+)
+
+// Channels are where a kind reaches a user. Inbox is the master switch: with
+// it off nothing is stored, so there is nothing for the phone or email to
+// deliver. Effective applies that.
+type Channels struct {
+	Inbox bool
+	Phone bool
+	Email bool
+}
+
+// Effective is what will actually be delivered: phone and email ride on the
+// inbox row, so they cannot be on without it.
+func (c Channels) Effective() Channels {
+	return Channels{Inbox: c.Inbox, Phone: c.Inbox && c.Phone, Email: c.Inbox && c.Email}
+}
+
+type spec struct {
+	audience Audience
+	// coalesce: while one of these is unread, a new event updates it in place
+	// rather than adding a row. For the burst-prone admin kinds.
+	coalesce bool
+	// sumCount: a coalesced update adds the payload's `count` to the unread
+	// row's, because each event is "N more". Without it the newer payload
+	// replaces the older, because each event states the whole current total.
+	sumCount bool
+	group    EmailGroup
+	defaults Channels
+}
+
+var (
+	allOn       = Channels{Inbox: true, Phone: true, Email: true}
+	healthAlert = Channels{Inbox: true, Phone: true, Email: false}
+)
+
+var specs = map[Kind]spec{
+	KindRequestApproved:   {audience: AudienceRequester, group: EmailBatch, defaults: allOn},
+	KindRequestRejected:   {audience: AudienceRequester, group: EmailBatch, defaults: allOn},
+	KindRequestCompleted:  {audience: AudienceRequester, group: EmailSummary, defaults: allOn},
+	KindRequestPending:    {audience: AudienceAdmin, group: EmailBatch, defaults: allOn},
+	KindQuarantineFlagged: {audience: AudienceAdmin, group: EmailBatch, defaults: allOn},
+	KindScanFailed:        {audience: AudienceAdmin, coalesce: true, sumCount: true, group: EmailBatch, defaults: healthAlert},
+	KindTracksMissing:     {audience: AudienceAdmin, coalesce: true, sumCount: true, group: EmailBatch, defaults: healthAlert},
+	KindDuplicatesFound:   {audience: AudienceAdmin, coalesce: true, group: EmailBatch, defaults: healthAlert},
+	KindPlaybackErrors:    {audience: AudienceAdmin, coalesce: true, group: EmailBatch, defaults: healthAlert},
+}
+
+// order is the display order for settings screens: the requester's own kinds
+// first, then the admin ones.
+var order = []Kind{
+	KindRequestApproved,
+	KindRequestRejected,
+	KindRequestCompleted,
+	KindRequestPending,
+	KindQuarantineFlagged,
+	KindScanFailed,
+	KindTracksMissing,
+	KindDuplicatesFound,
+	KindPlaybackErrors,
+}
+
+// Kinds returns every kind in display order.
+func Kinds() []Kind { return append([]Kind(nil), order...) }
+
+// Valid reports whether k is a known kind.
+func (k Kind) Valid() bool { _, ok := specs[k]; return ok }
+
+// AdminOnly reports whether k reaches only admins.
+func (k Kind) AdminOnly() bool { return specs[k].audience == AudienceAdmin }
+
+// Defaults are the channels a user has for k until they change them.
+func (k Kind) Defaults() Channels { return specs[k].defaults }
+
+// EmailGroup is how k's emails are grouped.
+func (k Kind) EmailGroup() EmailGroup { return specs[k].group }
+
+// coalesceKey is the key k's rows coalesce on, or "" when k never coalesces.
+// One key per kind: two unread "tracks missing" rows would only split a count.
+func (k Kind) coalesceKey() string {
+	if specs[k].coalesce {
+		return string(k)
+	}
+	return ""
+}

internal/notifications/kinds_test.go

@@ -0,0 +1,61 @@
+package notifications
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestEffective_PhoneAndEmailRideOnInbox(t *testing.T) {
+	cases := []struct {
+		in, want Channels
+	}{
+		{Channels{true, true, true}, Channels{true, true, true}},
+		{Channels{true, false, true}, Channels{true, false, true}},
+		{Channels{false, true, true}, Channels{false, false, false}},
+		{Channels{false, false, false}, Channels{false, false, false}},
+	}
+	for _, c := range cases {
+		require.Equal(t, c.want, c.in.Effective(), "in=%+v", c.in)
+	}
+}
+
+// The display order and the spec table must name the same kinds, or a kind
+// is either unreachable from settings or has no behaviour.
+func TestKinds_OrderAndSpecsAgree(t *testing.T) {
+	require.Len(t, order, len(specs))
+	seen := map[Kind]bool{}
+	for _, k := range Kinds() {
+		require.True(t, k.Valid(), "%s in order but not in specs", k)
+		require.False(t, seen[k], "%s listed twice", k)
+		seen[k] = true
+	}
+}
+
+func TestKinds_AdminKindsDefaultEmailOffExceptRequestQueue(t *testing.T) {
+	// The burst-prone health kinds stay out of email unless an admin opts
+	// in; the request queue and quarantine flags are things an admin acts on.
+	for _, k := range []Kind{KindScanFailed, KindTracksMissing, KindDuplicatesFound, KindPlaybackErrors} {
+		require.True(t, k.AdminOnly(), k)
+		require.False(t, k.Defaults().Email, k)
+		require.NotEmpty(t, k.coalesceKey(), "%s should coalesce", k)
+	}
+	for _, k := range []Kind{KindRequestApproved, KindRequestRejected, KindRequestCompleted} {
+		require.False(t, k.AdminOnly(), k)
+		require.Equal(t, Channels{true, true, true}, k.Defaults(), k)
+		require.Empty(t, k.coalesceKey(), "%s must never coalesce: each request is its own news", k)
+	}
+	require.Equal(t, EmailSummary, KindRequestCompleted.EmailGroup())
+	require.Equal(t, EmailBatch, KindRequestApproved.EmailGroup())
+}
+
+func TestNotify_NilNotifierIsANoOp(t *testing.T) {
+	var n *Notifier
+	require.NoError(t, n.Notify(context.Background(), KindRequestApproved, Recipients{}, nil))
+}
+
+func TestNotify_UnknownKindIsRefusedBeforeTouchingTheDB(t *testing.T) {
+	n := New(nil, nil, nil)
+	require.Error(t, n.Notify(context.Background(), Kind("bogus"), Recipients{}, nil))
+}

internal/notifications/notifier.go

@@ -0,0 +1,198 @@
+package notifications
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5/pgtype"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/eventbus"
+)
+
+// EventCreated is the bus event a recipient's open clients receive when a
+// row lands for them. It is a nudge with no content: the client fetches the
+// inbox. A frame that carried the notification could not be told apart from
+// a repeat after a reconnect, and a frame nobody received is then one nobody
+// needed, because the client pulls on reconnect anyway (Roundtable #2535).
+const EventCreated = "notification.created"
+
+// Recipients names who an event is for.
+type Recipients struct {
+	Users []pgtype.UUID
+	// Admins adds every admin.
+	Admins bool
+	// Except is never notified, even when it is in Users or is an admin. The
+	// admin who filed a request needs no notice that it is pending.
+	Except pgtype.UUID
+}
+
+// ToUser addresses one user.
+func ToUser(id pgtype.UUID) Recipients { return Recipients{Users: []pgtype.UUID{id}} }
+
+// ToAdmins addresses every admin except one (pass the zero UUID for none).
+func ToAdmins(except pgtype.UUID) Recipients { return Recipients{Admins: true, Except: except} }
+
+// Notifier writes notifications and nudges recipients' clients. A nil
+// *Notifier is valid and does nothing, so producers built without one (most
+// tests) need no special case.
+type Notifier struct {
+	db     dbq.DBTX
+	bus    *eventbus.Bus
+	logger *slog.Logger
+}
+
+// New returns a Notifier writing through db. bus may be nil.
+func New(db dbq.DBTX, bus *eventbus.Bus, logger *slog.Logger) *Notifier {
+	if logger == nil {
+		logger = slog.Default()
+	}
+	return &Notifier{db: db, bus: bus, logger: logger}
+}
+
+// Notify records kind for each recipient whose inbox preference allows it,
+// then nudges their open clients.
+//
+// For a coalescing kind, an unread row of that kind is updated in place
+// rather than a new one added. payload["count"] then adds to the unread
+// row's count for kinds whose events each mean "N more".
+//
+// The error is for logging. A notification must never fail the action that
+// caused it, so producers log and carry on; NotifyLogged does exactly that.
+func (n *Notifier) Notify(ctx context.Context, kind Kind, to Recipients, payload map[string]any) error {
+	if n == nil {
+		return nil
+	}
+	if !kind.Valid() {
+		return fmt.Errorf("notifications: unknown kind %q", kind)
+	}
+	q := dbq.New(n.db)
+
+	ids, err := n.resolve(ctx, q, kind, to)
+	if err != nil || len(ids) == 0 {
+		return err
+	}
+	channels, err := channelsFor(ctx, q, kind, ids)
+	if err != nil {
+		return err
+	}
+	if payload == nil {
+		payload = map[string]any{}
+	}
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return fmt.Errorf("notifications: encode %s payload: %w", kind, err)
+	}
+
+	var delivered []pgtype.UUID
+	for _, id := range ids {
+		if !channels[id].Inbox {
+			continue
+		}
+		if err := write(ctx, q, kind, id, body); err != nil {
+			return fmt.Errorf("notifications: write %s: %w", kind, err)
+		}
+		delivered = append(delivered, id)
+	}
+	n.nudge(delivered)
+	return nil
+}
+
+// NotifyLogged is Notify for producers: a failure is logged at WARN and
+// otherwise ignored.
+func (n *Notifier) NotifyLogged(ctx context.Context, kind Kind, to Recipients, payload map[string]any) {
+	if err := n.Notify(ctx, kind, to, payload); err != nil {
+		n.logger.Warn("notifications: notify failed", "kind", string(kind), "err", err)
+	}
+}
+
+// resolve turns Recipients into a deduplicated list of user ids. Admin kinds
+// are delivered only to admins, whatever Users says, so a producer that
+// addresses a non-admin by mistake stores nothing for them.
+func (n *Notifier) resolve(ctx context.Context, q *dbq.Queries, kind Kind, to Recipients) ([]pgtype.UUID, error) {
+	var admins []pgtype.UUID
+	if to.Admins || kind.AdminOnly() {
+		var err error
+		if admins, err = q.ListAdminUserIDs(ctx); err != nil {
+			return nil, fmt.Errorf("notifications: list admins: %w", err)
+		}
+	}
+	isAdmin := make(map[pgtype.UUID]bool, len(admins))
+	for _, a := range admins {
+		isAdmin[a] = true
+	}
+
+	var candidates []pgtype.UUID
+	candidates = append(candidates, to.Users...)
+	if to.Admins {
+		candidates = append(candidates, admins...)
+	}
+
+	seen := make(map[pgtype.UUID]bool, len(candidates))
+	out := make([]pgtype.UUID, 0, len(candidates))
+	for _, id := range candidates {
+		if !id.Valid || seen[id] || (to.Except.Valid && id == to.Except) {
+			continue
+		}
+		if kind.AdminOnly() && !isAdmin[id] {
+			continue
+		}
+		seen[id] = true
+		out = append(out, id)
+	}
+	return out, nil
+}
+
+// channelsFor returns each recipient's effective channels for kind: their
+// stored preference, or the kind's defaults when they have none.
+func channelsFor(ctx context.Context, q *dbq.Queries, kind Kind, ids []pgtype.UUID) (map[pgtype.UUID]Channels, error) {
+	rows, err := q.ListNotificationPrefsForKind(ctx, dbq.ListNotificationPrefsForKindParams{
+		Kind:    string(kind),
+		UserIds: ids,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("notifications: read prefs: %w", err)
+	}
+	out := make(map[pgtype.UUID]Channels, len(ids))
+	for _, id := range ids {
+		out[id] = kind.Defaults().Effective()
+	}
+	for _, r := range rows {
+		out[r.UserID] = Channels{Inbox: r.Inbox, Phone: r.Phone, Email: r.Email}.Effective()
+	}
+	return out, nil
+}
+
+func write(ctx context.Context, q *dbq.Queries, kind Kind, userID pgtype.UUID, body []byte) error {
+	key := kind.coalesceKey()
+	if key == "" {
+		_, err := q.InsertNotification(ctx, dbq.InsertNotificationParams{
+			UserID: userID, Kind: string(kind), Payload: body,
+		})
+		return err
+	}
+	_, err := q.UpsertCoalescedNotification(ctx, dbq.UpsertCoalescedNotificationParams{
+		UserID:      userID,
+		Kind:        string(kind),
+		Payload:     body,
+		CoalesceKey: &key,
+		SumCount:    specs[kind].sumCount,
+	})
+	return err
+}
+
+func (n *Notifier) nudge(ids []pgtype.UUID) {
+	if n.bus == nil {
+		return
+	}
+	for _, id := range ids {
+		n.bus.Publish(eventbus.Event{
+			Kind:   EventCreated,
+			UserID: uuid.UUID(id.Bytes).String(),
+			Data:   map[string]any{},
+		})
+	}
+}

internal/notifications/notifier_db_test.go

@@ -0,0 +1,267 @@
+package notifications_test
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"log/slog"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5/pgtype"
+	"github.com/jackc/pgx/v5/pgxpool"
+	"github.com/stretchr/testify/require"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/dbtest"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/eventbus"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/notifications"
+)
+
+func testPool(t *testing.T) *pgxpool.Pool {
+	t.Helper()
+	if testing.Short() {
+		t.Skip("skipping integration test in -short mode")
+	}
+	dsn := os.Getenv("MINSTREL_TEST_DATABASE_URL")
+	if dsn == "" {
+		t.Skip("MINSTREL_TEST_DATABASE_URL not set")
+	}
+	if err := db.Migrate(dsn, slog.New(slog.NewTextHandler(io.Discard, nil))); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+	pool, err := pgxpool.New(context.Background(), dsn)
+	if err != nil {
+		t.Fatalf("pool: %v", err)
+	}
+	t.Cleanup(pool.Close)
+	dbtest.ResetDB(t, pool)
+	return pool
+}
+
+func mkUser(t *testing.T, q *dbq.Queries, name string, admin bool) pgtype.UUID {
+	t.Helper()
+	u, err := q.CreateUser(context.Background(), dbq.CreateUserParams{
+		Username:     dbtest.TestUserPrefix + name,
+		PasswordHash: "x",
+		ApiTokenHash: "tok-" + name, // unique per user
+		IsAdmin:      admin,
+	})
+	require.NoError(t, err)
+	return u.ID
+}
+
+func rowsFor(t *testing.T, q *dbq.Queries, user pgtype.UUID) []dbq.ListNotificationsRow {
+	t.Helper()
+	rows, err := q.ListNotifications(context.Background(), dbq.ListNotificationsParams{UserID: user, PageLimit: 100})
+	require.NoError(t, err)
+	return rows
+}
+
+func count(t *testing.T, payload []byte) int64 {
+	t.Helper()
+	var p struct {
+		Count int64 `json:"count"`
+	}
+	require.NoError(t, json.Unmarshal(payload, &p))
+	return p.Count
+}
+
+func TestNotify_WritesARowAndNudgesOnlyThatUser(t *testing.T) {
+	pool := testPool(t)
+	q := dbq.New(pool)
+	ctx := context.Background()
+	alice := mkUser(t, q, "alice", false)
+	bob := mkUser(t, q, "bob", false)
+
+	bus := eventbus.New()
+	events, unsub := bus.Subscribe(8)
+	defer unsub()
+
+	n := notifications.New(pool, bus, nil)
+	require.NoError(t, n.Notify(ctx, notifications.KindRequestApproved,
+		notifications.ToUser(alice), map[string]any{"request_id": "r1", "title": "WWW"}))
+
+	rows := rowsFor(t, q, alice)
+	require.Len(t, rows, 1)
+	require.Equal(t, "request_approved", rows[0].Kind)
+	require.False(t, rows[0].ReadAt.Valid)
+	require.JSONEq(t, `{"request_id":"r1","title":"WWW"}`, string(rows[0].Payload))
+	require.Empty(t, rowsFor(t, q, bob))
+
+	select {
+	case e := <-events:
+		require.Equal(t, notifications.EventCreated, e.Kind)
+		require.Equal(t, uuid.UUID(alice.Bytes).String(), e.UserID)
+		require.Empty(t, e.Data, "the nudge carries no content; the client fetches")
+	case <-time.After(time.Second):
+		t.Fatal("no nudge published")
+	}
+}
+
+func TestNotify_AdminKindReachesAdminsOnly_AndNeverTheExcepted(t *testing.T) {
+	pool := testPool(t)
+	q := dbq.New(pool)
+	ctx := context.Background()
+	requester := mkUser(t, q, "admin-requester", true)
+	other := mkUser(t, q, "admin-other", true)
+	plain := mkUser(t, q, "plain", false)
+
+	n := notifications.New(pool, nil, nil)
+	// A plain user named directly must still get nothing: the kind is admin-only.
+	to := notifications.ToAdmins(requester)
+	to.Users = []pgtype.UUID{plain}
+	require.NoError(t, n.Notify(ctx, notifications.KindRequestPending, to, nil))
+
+	require.Empty(t, rowsFor(t, q, requester), "the admin who filed it needs no notice")
+	require.Len(t, rowsFor(t, q, other), 1)
+	require.Empty(t, rowsFor(t, q, plain))
+}
+
+func TestNotify_CoalescedCountAddsUpWhileUnread_AndStartsAfreshOnceRead(t *testing.T) {
+	pool := testPool(t)
+	q := dbq.New(pool)
+	ctx := context.Background()
+	admin := mkUser(t, q, "admin", true)
+	n := notifications.New(pool, nil, nil)
+	to := notifications.ToUser(admin)
+
+	require.NoError(t, n.Notify(ctx, notifications.KindTracksMissing, to, map[string]any{"count": 3}))
+	require.NoError(t, n.Notify(ctx, notifications.KindTracksMissing, to, map[string]any{"count": 4}))
+	rows := rowsFor(t, q, admin)
+	require.Len(t, rows, 1, "a burst is one notification")
+	require.Equal(t, int64(7), count(t, rows[0].Payload))
+
+	_, err := q.MarkNotificationRead(ctx, dbq.MarkNotificationReadParams{ID: rows[0].ID, UserID: admin})
+	require.NoError(t, err)
+	require.NoError(t, n.Notify(ctx, notifications.KindTracksMissing, to, map[string]any{"count": 2}))
+
+	rows = rowsFor(t, q, admin)
+	require.Len(t, rows, 2, "after it is read, the next event is new news")
+	require.Equal(t, int64(2), count(t, rows[0].Payload))
+	require.False(t, rows[0].ReadAt.Valid)
+	require.True(t, rows[1].ReadAt.Valid)
+}
+
+func TestNotify_CoalescedTotalReplacesWhenEventsStateTheWhole(t *testing.T) {
+	pool := testPool(t)
+	q := dbq.New(pool)
+	ctx := context.Background()
+	admin := mkUser(t, q, "admin", true)
+	n := notifications.New(pool, nil, nil)
+
+	// duplicates_found states the pending total each time; it must not sum.
+	require.NoError(t, n.Notify(ctx, notifications.KindDuplicatesFound, notifications.ToUser(admin), map[string]any{"count": 5}))
+	require.NoError(t, n.Notify(ctx, notifications.KindDuplicatesFound, notifications.ToUser(admin), map[string]any{"count": 3}))
+	rows := rowsFor(t, q, admin)
+	require.Len(t, rows, 1)
+	require.Equal(t, int64(3), count(t, rows[0].Payload))
+}
+
+func TestNotify_RequestKindsNeverCoalesce(t *testing.T) {
+	pool := testPool(t)
+	q := dbq.New(pool)
+	ctx := context.Background()
+	alice := mkUser(t, q, "alice", false)
+	n := notifications.New(pool, nil, nil)
+	for _, id := range []string{"r1", "r2"} {
+		require.NoError(t, n.Notify(ctx, notifications.KindRequestCompleted, notifications.ToUser(alice), map[string]any{"request_id": id}))
+	}
+	require.Len(t, rowsFor(t, q, alice), 2)
+}
+
+func TestNotify_InboxOffStoresNothing_AndDefaultsApplyWithoutAPref(t *testing.T) {
+	pool := testPool(t)
+	q := dbq.New(pool)
+	ctx := context.Background()
+	muted := mkUser(t, q, "muted", false)
+	fresh := mkUser(t, q, "fresh", false)
+	require.NoError(t, q.UpsertNotificationPref(ctx, dbq.UpsertNotificationPrefParams{
+		UserID: muted, Kind: "request_rejected", Inbox: false, Phone: true, Email: true,
+	}))
+
+	n := notifications.New(pool, nil, nil)
+	to := notifications.Recipients{Users: []pgtype.UUID{muted, fresh}}
+	require.NoError(t, n.Notify(ctx, notifications.KindRequestRejected, to, nil))
+
+	require.Empty(t, rowsFor(t, q, muted), "inbox off is off, whatever phone and email say")
+	require.Len(t, rowsFor(t, q, fresh), 1)
+}
+
+func TestMarkRead_ScopedToTheOwner_AndIdempotent(t *testing.T) {
+	pool := testPool(t)
+	q := dbq.New(pool)
+	ctx := context.Background()
+	alice := mkUser(t, q, "alice", false)
+	mallory := mkUser(t, q, "mallory", false)
+	n := notifications.New(pool, nil, nil)
+	require.NoError(t, n.Notify(ctx, notifications.KindRequestApproved, notifications.ToUser(alice), nil))
+	id := rowsFor(t, q, alice)[0].ID
+
+	got, err := q.MarkNotificationRead(ctx, dbq.MarkNotificationReadParams{ID: id, UserID: mallory})
+	require.NoError(t, err)
+	require.Zero(t, got, "another user's id matches nothing")
+	require.False(t, rowsFor(t, q, alice)[0].ReadAt.Valid)
+
+	for i := 0; i < 2; i++ {
+		got, err = q.MarkNotificationRead(ctx, dbq.MarkNotificationReadParams{ID: id, UserID: alice})
+		require.NoError(t, err)
+		require.Equal(t, int64(1), got, "a repeat still matches, so it is not mistaken for 'not yours'")
+	}
+	unread, err := q.CountUnreadNotifications(ctx, alice)
+	require.NoError(t, err)
+	require.Zero(t, unread)
+}
+
+// Every kind the code knows must pass both CHECKs in the real schema. This is
+// rule 36's guard: a kind added in Go without the migration fails here, not in
+// production at INSERT time.
+func TestEveryKindPassesTheSchemaChecks(t *testing.T) {
+	pool := testPool(t)
+	q := dbq.New(pool)
+	ctx := context.Background()
+	user := mkUser(t, q, "kinds", true)
+	for _, k := range notifications.Kinds() {
+		_, err := q.InsertNotification(ctx, dbq.InsertNotificationParams{UserID: user, Kind: string(k), Payload: []byte(`{}`)})
+		require.NoError(t, err, "user_notifications rejects %s", k)
+		require.NoError(t, q.UpsertNotificationPref(ctx, dbq.UpsertNotificationPrefParams{
+			UserID: user, Kind: string(k), Inbox: true, Phone: true, Email: true,
+		}), "user_notification_prefs rejects %s", k)
+	}
+	// And the check is real: an unknown kind is refused.
+	_, err := q.InsertNotification(ctx, dbq.InsertNotificationParams{UserID: user, Kind: "bogus", Payload: []byte(`{}`)})
+	require.Error(t, err)
+}
+
+func TestRetention_TrimsOldReadRowsAndAncientUnreadOnes(t *testing.T) {
+	pool := testPool(t)
+	q := dbq.New(pool)
+	ctx := context.Background()
+	user := mkUser(t, q, "retention", false)
+
+	now := time.Now()
+	insert := func(created time.Time, read *time.Time) {
+		var readAt any
+		if read != nil {
+			readAt = *read
+		}
+		_, err := pool.Exec(ctx,
+			`INSERT INTO user_notifications (user_id, kind, created_at, read_at) VALUES ($1, 'request_approved', $2, $3)`,
+			user, created, readAt)
+		require.NoError(t, err)
+	}
+	day := 24 * time.Hour
+	oldRead := now.Add(-100 * day)
+	recentRead := now.Add(-10 * day)
+	insert(now.Add(-120*day), &oldRead)   // read 100 days ago: goes
+	insert(now.Add(-20*day), &recentRead) // read 10 days ago: stays
+	insert(now.Add(-400*day), nil)        // unread but over a year old: goes
+	insert(now.Add(-200*day), nil)        // unread, 200 days: stays
+
+	r := notifications.NewRetention(pool, slog.New(slog.NewTextHandler(io.Discard, nil)))
+	require.Equal(t, int64(2), r.TrimOnce(ctx, now))
+	require.Len(t, rowsFor(t, q, user), 2)
+}

internal/notifications/retention.go

@@ -0,0 +1,66 @@
+package notifications
+
+import (
+	"context"
+	"log/slog"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgtype"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+)
+
+const (
+	// ReadRetention is how long a read notification is kept. An inbox is a
+	// record of what happened lately, not an archive.
+	ReadRetention = 90 * 24 * time.Hour
+	// AnyRetention bounds an inbox nobody opens: past it, even unread rows go.
+	AnyRetention = 365 * 24 * time.Hour
+	// retentionInterval matches the library_changes compactor's daily tick.
+	retentionInterval = 24 * time.Hour
+)
+
+// Retention trims old notifications on a daily tick, in the shape of the
+// library_changes compactor (internal/sync/compactor.go).
+type Retention struct {
+	db     dbq.DBTX
+	logger *slog.Logger
+}
+
+// NewRetention returns a Retention trimming through db.
+func NewRetention(db dbq.DBTX, logger *slog.Logger) *Retention {
+	return &Retention{db: db, logger: logger}
+}
+
+// Run blocks until ctx is cancelled. It trims once at startup, so a process
+// that has been down a while catches up, then daily.
+func (r *Retention) Run(ctx context.Context) {
+	r.TrimOnce(ctx, time.Now())
+	t := time.NewTicker(retentionInterval)
+	defer t.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case now := <-t.C:
+			r.TrimOnce(ctx, now)
+		}
+	}
+}
+
+// TrimOnce deletes what has outlived its retention as of now. Errors are
+// logged, never fatal: the next tick tries again.
+func (r *Retention) TrimOnce(ctx context.Context, now time.Time) int64 {
+	n, err := dbq.New(r.db).TrimNotifications(ctx, dbq.TrimNotificationsParams{
+		ReadCutoff: pgtype.Timestamptz{Time: now.Add(-ReadRetention), Valid: true},
+		AnyCutoff:  pgtype.Timestamptz{Time: now.Add(-AnyRetention), Valid: true},
+	})
+	if err != nil {
+		r.logger.Warn("notifications retention: trim failed", "err", err)
+		return 0
+	}
+	if n > 0 {
+		r.logger.Info("notifications retention: trimmed rows", "count", n)
+	}
+	return n
+}