Allow retention_days of 0 to mean retain forever (closes #79)

RetentionDays carried gorm:"default:30", so GORM substituted 30 for a
zero value while building the insert. A webhook could therefore never
be configured to keep its events indefinitely: the reaper's
retain-forever branch existed but was unreachable from the normal
create and edit flows.

Introduce database.RetentionForeverDays = 365 * 1000 as the sentinel
for "retain forever" and a Webhook.BeforeSave hook that rewrites any
non-positive RetentionDays to it. The rewrite has to live in the hook
rather than at the call sites: GORM applies the column default while
converting the model to insert values, which happens after BeforeSave,
so anything later loses that race. Putting it on the model also means
a future call site, such as the planned REST API, cannot bypass it.

The reaper now skips a webhook when Webhook.RetainsForever reports
true, which recognises the sentinel and keeps honouring the old <= 0
values for rows written before it existed. Without this the sentinel,
being positive, would have produced a cutoff a thousand years in the
past and a DELETE matching nothing on every sweep.

Form handling is shared by create and edit through parseRetentionDays
so the two cannot drift: an empty field keeps the previous behaviour
(default on create, unchanged on edit), 0 is honoured, and an
unparseable or negative value is a 400 that re-renders the form rather
than a silently substituted default.

The retention inputs drop max="365". That cap was not cosmetic: the
edit form pre-fills the stored value, so a retain-forever webhook
rendered 365000 into an input capped at 365 and browser validation
would have blocked saving any edit to it. min becomes 0 with a hint
explaining what 0 does, and the list and detail views render a
RetentionLabel of "forever" instead of a raw day count.

The 30-day default is consolidated into database.DefaultRetentionDays,
referenced from the handler and from the create form's pre-filled
value, with a test asserting it agrees with the struct tag that cannot
reference it.

internal/database/database_test.go

@@ -18,6 +18,11 @@ const (
 	testVersion = "test"
 	// testContentType is the event content type used in tests.
 	testContentType = "application/json"
+	// testWebhookName is the Webhook.Name used in tests.
+	testWebhookName = "test-webhook"
+	// testForeverLabel is Webhook.RetentionLabel for a retain-forever
+	// webhook.
+	testForeverLabel = "forever"
 )
 
 func setupTestDB(

internal/database/model_webhook.go

@@ -1,6 +1,39 @@
 package database
 
+import (
+	"strconv"
+
+	"gorm.io/gorm"
+)
+
+const (
+	// DefaultRetentionDays is the event retention period applied to a
+	// webhook created without an explicit retention value. It is the
+	// single source of truth for that policy and must stay in sync
+	// with the `gorm:"default:30"` column default on
+	// Webhook.RetentionDays below; a struct tag cannot reference a
+	// constant, so a test asserts the two agree.
+	DefaultRetentionDays = 30
+
+	// RetentionForeverDays is the sentinel RetentionDays value meaning
+	// "retain events forever". Users express that intent as 0, which
+	// Webhook.BeforeSave rewrites to this value: the column default
+	// substitutes DefaultRetentionDays for a zero value at insert
+	// time, so a zero can never survive a round trip to the database.
+	// Nothing outside this file may hardcode the number.
+	RetentionForeverDays = 365 * 1000
+)
+
 // Webhook represents a webhook processing unit that groups entrypoints and targets
+//
+// The receiver kinds below are deliberately mixed. BeforeSave has to
+// take a pointer because it mutates the record, and GORM only invokes
+// hooks declared that way. RetainsForever and RetentionLabel have to
+// take values because html/template calls them on webhooks held in a
+// template data map, which reflection cannot address; a pointer
+// receiver there fails at render time rather than at compile time.
+//
+//nolint:recvcheck // GORM needs a pointer hook; templates need values.
 type Webhook struct {
 	BaseModel
 
@@ -8,7 +41,9 @@ type Webhook struct {
 	Name        string `gorm:"not null"           json:"name"`
 	Description string `json:"description"`
 
-	// RetentionDays is the number of days to retain events.
+	// RetentionDays is the number of days to retain events. A value of
+	// RetentionForeverDays means retain forever. The column default
+	// must equal DefaultRetentionDays.
 	RetentionDays int `gorm:"default:30" json:"retentionDays"`
 
 	// Relations
@@ -16,3 +51,44 @@ type Webhook struct {
 	Entrypoints []Entrypoint `json:"entrypoints,omitempty"`
 	Targets     []Target     `json:"targets,omitempty"`
 }
+
+// BeforeSave normalises RetentionDays on every insert and update. A
+// non-positive value is the user's way of asking for "retain forever",
+// which is stored as the RetentionForeverDays sentinel.
+//
+// This has to happen in a hook rather than at the call sites. GORM
+// substitutes the column default (DefaultRetentionDays) for a zero
+// value while building the insert statement, which runs after
+// BeforeSave; rewriting any later than this loses that race and the
+// row lands at 30 days. Living on the model also means a future call
+// site — a REST API, a fixture, a migration — cannot bypass it.
+func (w *Webhook) BeforeSave(_ *gorm.DB) error {
+	if w.RetentionDays <= 0 {
+		w.RetentionDays = RetentionForeverDays
+	}
+
+	return nil
+}
+
+// RetainsForever reports whether this webhook's events are kept
+// indefinitely. It accepts the RetentionForeverDays sentinel written by
+// BeforeSave and, defensively, the non-positive values that rows
+// written before the sentinel existed may still carry.
+func (w Webhook) RetainsForever() bool {
+	return w.RetentionDays <= 0 ||
+		w.RetentionDays >= RetentionForeverDays
+}
+
+// RetentionLabel returns the webhook's retention policy as display
+// text, so that no template has to know about the sentinel value.
+func (w Webhook) RetentionLabel() string {
+	if w.RetainsForever() {
+		return "forever"
+	}
+
+	if w.RetentionDays == 1 {
+		return "1 day"
+	}
+
+	return strconv.Itoa(w.RetentionDays) + " days"
+}

internal/database/model_webhook_test.go

@@ -0,0 +1,184 @@
+package database_test
+
+import (
+	"context"
+	"reflect"
+	"strconv"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// startedTestDB returns a started main database for model-level tests.
+func startedTestDB(t *testing.T) *gorm.DB {
+	t.Helper()
+
+	db, lc := setupTestDB(t)
+
+	ctx := context.Background()
+	require.NoError(t, lc.Start(ctx))
+	t.Cleanup(func() { require.NoError(t, lc.Stop(ctx)) })
+
+	return db.DB()
+}
+
+// storedRetention reads the retention_days column straight out of the
+// row, so the assertion is about what was persisted rather than about
+// whatever the in-memory struct happens to hold.
+func storedRetention(t *testing.T, db *gorm.DB, id string) int {
+	t.Helper()
+
+	var got int
+
+	require.NoError(
+		t,
+		db.Model(&database.Webhook{}).
+			Where("id = ?", id).
+			Pluck("retention_days", &got).Error,
+	)
+
+	return got
+}
+
+// newWebhookWithRetention creates a webhook through the ordinary Create
+// path, so the BeforeSave hook and the GORM column default both apply
+// exactly as they do in production.
+func newWebhookWithRetention(
+	t *testing.T,
+	db *gorm.DB,
+	wh *database.Webhook,
+) string {
+	t.Helper()
+
+	wh.UserID = uuid.New().String()
+	wh.Name = testWebhookName
+
+	require.NoError(
+		t,
+		db.Omit(clause.Associations).Create(wh).Error,
+	)
+
+	return wh.ID
+}
+
+func TestWebhookBeforeSave_ZeroBecomesForeverSentinel(t *testing.T) {
+	t.Parallel()
+
+	db := startedTestDB(t)
+
+	wh := &database.Webhook{RetentionDays: 0}
+	id := newWebhookWithRetention(t, db, wh)
+
+	assert.Equal(
+		t,
+		database.RetentionForeverDays,
+		storedRetention(t, db, id),
+		"a zero retention must be stored as the sentinel, "+
+			"not replaced by the column default",
+	)
+}
+
+func TestWebhookBeforeSave_NegativeBecomesForeverSentinel(t *testing.T) {
+	t.Parallel()
+
+	db := startedTestDB(t)
+
+	wh := &database.Webhook{RetentionDays: -5}
+	id := newWebhookWithRetention(t, db, wh)
+
+	assert.Equal(
+		t,
+		database.RetentionForeverDays,
+		storedRetention(t, db, id),
+	)
+}
+
+func TestWebhookBeforeSave_PositiveIsPreserved(t *testing.T) {
+	t.Parallel()
+
+	db := startedTestDB(t)
+
+	wh := &database.Webhook{RetentionDays: 7}
+	id := newWebhookWithRetention(t, db, wh)
+
+	assert.Equal(t, 7, storedRetention(t, db, id))
+}
+
+// TestWebhookBeforeSave_UpdateToZeroBecomesSentinel proves the hook
+// fires on update as well as insert, via the same Save call the edit
+// handler makes.
+func TestWebhookBeforeSave_UpdateToZeroBecomesSentinel(t *testing.T) {
+	t.Parallel()
+
+	db := startedTestDB(t)
+
+	wh := &database.Webhook{RetentionDays: 30}
+	id := newWebhookWithRetention(t, db, wh)
+	require.Equal(t, 30, storedRetention(t, db, id))
+
+	wh.RetentionDays = 0
+	require.NoError(t, db.Omit(clause.Associations).Save(wh).Error)
+
+	assert.Equal(
+		t,
+		database.RetentionForeverDays,
+		storedRetention(t, db, id),
+	)
+}
+
+// TestWebhookRetentionColumnDefaultMatchesConstant guards the one place
+// the default lives twice: a struct tag cannot reference a constant, so
+// this asserts the tag and DefaultRetentionDays agree.
+func TestWebhookRetentionColumnDefaultMatchesConstant(t *testing.T) {
+	t.Parallel()
+
+	field, ok := reflect.TypeFor[database.Webhook]().
+		FieldByName("RetentionDays")
+	require.True(t, ok, "Webhook.RetentionDays must exist")
+
+	assert.Equal(
+		t,
+		"default:"+strconv.Itoa(database.DefaultRetentionDays),
+		field.Tag.Get("gorm"),
+	)
+}
+
+func TestWebhookRetainsForeverAndLabel(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name    string
+		days    int
+		forever bool
+		label   string
+	}{
+		{
+			"sentinel",
+			database.RetentionForeverDays, true, testForeverLabel,
+		},
+		{
+			"above sentinel",
+			database.RetentionForeverDays + 1, true, testForeverLabel,
+		},
+		{"legacy zero", 0, true, testForeverLabel},
+		{"legacy negative", -1, true, testForeverLabel},
+		{"default", database.DefaultRetentionDays, false, "30 days"},
+		{"one day", 1, false, "1 day"},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			wh := database.Webhook{RetentionDays: tc.days}
+
+			assert.Equal(t, tc.forever, wh.RetainsForever())
+			assert.Equal(t, tc.label, wh.RetentionLabel())
+		})
+	}
+}

internal/database/retention.go

@@ -114,7 +114,8 @@ func (r *RetentionReaper) run(ctx context.Context) {
 }
 
 // sweep lists every webhook from the main database and reaps expired
-// rows from each per-webhook database whose RetentionDays is positive.
+// rows from each per-webhook database that has a finite retention
+// policy. Webhooks set to retain forever are skipped entirely.
 func (r *RetentionReaper) sweep(ctx context.Context) {
 	var webhooks []Webhook
 
@@ -139,8 +140,13 @@ func (r *RetentionReaper) sweep(ctx context.Context) {
 
 		wh := webhooks[i]
 
-		// RetentionDays of zero or less means retain forever.
-		if wh.RetentionDays <= 0 {
+		// Skip retain-forever webhooks before building any query.
+		// RetainsForever covers both the RetentionForeverDays
+		// sentinel and the non-positive values that predate it: the
+		// sentinel is a positive number, so without this the reaper
+		// would compute a cutoff a thousand years in the past and
+		// issue a DELETE matching nothing on every single sweep.
+		if wh.RetainsForever() {
 			continue
 		}
 

internal/database/retention_test.go

@@ -77,7 +77,7 @@ func createWebhook(
 
 	wh := &database.Webhook{
 		UserID:        uuid.New().String(),
-		Name:          "test-webhook",
+		Name:          testWebhookName,
 		RetentionDays: retentionDays,
 	}
 	require.NoError(
@@ -85,10 +85,11 @@ func createWebhook(
 		db.Omit(clause.Associations).Create(wh).Error,
 	)
 
-	// The RetentionDays column carries a GORM default of 30, so a
-	// zero (or negative) value passed to Create is replaced by that
-	// default. Force the requested value explicitly so the
-	// retain-forever (<= 0) path can be exercised.
+	// Webhook.BeforeSave rewrites a non-positive RetentionDays to the
+	// retain-forever sentinel, and the column's GORM default would
+	// otherwise substitute 30. Force the requested value with a
+	// column-level update so tests can plant legacy rows that predate
+	// the sentinel and still carry a literal 0 or negative value.
 	require.NoError(
 		t,
 		db.Model(wh).
@@ -98,6 +99,30 @@ func createWebhook(
 	return wh.ID
 }
 
+// createWebhookNormally inserts a webhook through the ordinary Create
+// path, with no column-level forcing, so Webhook.BeforeSave applies
+// exactly as it does in production. Passing 0 therefore yields a row
+// holding the RetentionForeverDays sentinel.
+func createWebhookNormally(
+	t *testing.T,
+	db *gorm.DB,
+	retentionDays int,
+) string {
+	t.Helper()
+
+	wh := &database.Webhook{
+		UserID:        uuid.New().String(),
+		Name:          testWebhookName,
+		RetentionDays: retentionDays,
+	}
+	require.NoError(
+		t,
+		db.Omit(clause.Associations).Create(wh).Error,
+	)
+
+	return wh.ID
+}
+
 // eventChain is the set of row IDs seeded for a single event.
 type eventChain struct {
 	eventID    string
@@ -256,12 +281,59 @@ func TestRetentionReaper_ReapsExpiredKeepsRecent(t *testing.T) {
 	assertChainPresent(t, db, recent)
 }
 
+// TestRetentionReaper_SkipsSentinelReapsFiniteInSameSweep covers the
+// end-to-end retain-forever path: a webhook created the normal way with
+// a requested retention of 0 lands on the RetentionForeverDays
+// sentinel, and the reaper leaves its ancient events alone while still
+// reaping a finite-retention webhook in the very same sweep.
+func TestRetentionReaper_SkipsSentinelReapsFiniteInSameSweep(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	env := setupRetentionTest(t)
+
+	foreverID := createWebhookNormally(t, env.mainDB.DB(), 0)
+
+	var stored database.Webhook
+
+	require.NoError(
+		t,
+		env.mainDB.DB().Where("id = ?", foreverID).
+			First(&stored).Error,
+	)
+	require.Equal(
+		t,
+		database.RetentionForeverDays,
+		stored.RetentionDays,
+		"a requested retention of 0 must persist as the sentinel",
+	)
+
+	finiteID := createWebhookNormally(t, env.mainDB.DB(), 30)
+
+	foreverDB, err := env.mgr.GetDB(foreverID)
+	require.NoError(t, err)
+
+	finiteDB, err := env.mgr.GetDB(finiteID)
+	require.NoError(t, err)
+
+	ancient := time.Now().Add(-365 * 24 * time.Hour)
+	kept := seedEventChain(t, foreverDB, foreverID, ancient)
+	doomed := seedEventChain(t, finiteDB, finiteID, ancient)
+
+	env.reaper.ExportSweep(context.Background())
+
+	assertChainPresent(t, foreverDB, kept)
+	assertChainGone(t, finiteDB, doomed)
+}
+
 func TestRetentionReaper_RetainsForeverWhenNonPositive(t *testing.T) {
 	t.Parallel()
 
 	env := setupRetentionTest(t)
 
-	// RetentionDays of zero means retain forever.
+	// A legacy row written before the sentinel existed still carries a
+	// literal 0; the <= 0 guard must keep honouring it.
 	webhookID := createWebhook(t, env.mainDB.DB(), 0)
 
 	db, err := env.mgr.GetDB(webhookID)