at-container-registry/pkg/appview/db/device_store_test.go

package db

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"strings"
	"testing"
	"time"

	"golang.org/x/crypto/bcrypt"
)

// setupTestDB creates an in-memory SQLite database for testing
func setupTestDB(t *testing.T) *DeviceStore {
	t.Helper()
	// Use a named in-memory DB unique to this test to ensure isolation between tests
	safeName := strings.ReplaceAll(t.Name(), "/", "_")
	db, err := InitDB(fmt.Sprintf("file:%s?mode=memory&cache=shared", safeName), LibsqlConfig{})
	if err != nil {
		t.Fatalf("Failed to initialize test database: %v", err)
	}

	// Limit to single connection to avoid race conditions in tests
	db.SetMaxOpenConns(1)

	t.Cleanup(func() {
		db.Close()
	})
	return NewDeviceStore(db)
}

// createTestUser creates a test user in the database
func createTestUser(t *testing.T, store *DeviceStore, did, handle string) {
	t.Helper()
	_, err := store.db.Exec(`
		INSERT OR IGNORE INTO users (did, handle, pds_endpoint, last_seen)
		VALUES (?, ?, ?, datetime('now'))
	`, did, handle, "https://pds.example.com")
	if err != nil {
		t.Fatalf("Failed to create test user: %v", err)
	}
}

func TestDevice_Struct(t *testing.T) {
	device := &Device{
		DID:       "did:plc:test",
		Handle:    "alice.bsky.social",
		Name:      "My Device",
		CreatedAt: time.Now(),
	}

	if device.DID != "did:plc:test" {
		t.Errorf("Expected DID, got %q", device.DID)
	}
}

func TestGenerateUserCode(t *testing.T) {
	// Generate multiple codes to test
	codes := make(map[string]bool)
	for range 100 {
		code := generateUserCode()

		// Test format: XXXX-XXXX
		if len(code) != 9 {
			t.Errorf("Expected code length 9, got %d for code %q", len(code), code)
		}

		if code[4] != '-' {
			t.Errorf("Expected hyphen at position 4, got %q", string(code[4]))
		}

		// Test valid characters (A-Z, 2-9, no ambiguous chars)
		validChars := "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"
		parts := strings.Split(code, "-")
		if len(parts) != 2 {
			t.Errorf("Expected 2 parts separated by hyphen, got %d", len(parts))
		}

		for _, part := range parts {
			for _, ch := range part {
				if !strings.ContainsRune(validChars, ch) {
					t.Errorf("Invalid character %q in code %q", ch, code)
				}
			}
		}

		// Test uniqueness (should be very rare to get duplicates)
		if codes[code] {
			t.Logf("Warning: duplicate code generated: %q (rare but possible)", code)
		}
		codes[code] = true
	}

	// Verify we got mostly unique codes (at least 95%)
	if len(codes) < 95 {
		t.Errorf("Expected at least 95 unique codes out of 100, got %d", len(codes))
	}
}

func TestGenerateUserCode_Format(t *testing.T) {
	code := generateUserCode()

	// Test exact format
	if len(code) != 9 {
		t.Fatal("Code must be exactly 9 characters")
	}

	if code[4] != '-' {
		t.Fatal("Character at index 4 must be hyphen")
	}

	// Test no ambiguous characters (O, 0, I, 1, L)
	ambiguous := "O01IL"
	for _, ch := range code {
		if strings.ContainsRune(ambiguous, ch) {
			t.Errorf("Code contains ambiguous character %q: %s", ch, code)
		}
	}
}

// TestDeviceStore_CreatePendingAuth tests creating pending authorization
func TestDeviceStore_CreatePendingAuth(t *testing.T) {
	store := setupTestDB(t)

	pending, err := store.CreatePendingAuth("My Device", "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}

	if pending.DeviceCode == "" {
		t.Error("DeviceCode should not be empty")
	}
	if pending.UserCode == "" {
		t.Error("UserCode should not be empty")
	}
	if pending.DeviceName != "My Device" {
		t.Errorf("DeviceName = %v, want My Device", pending.DeviceName)
	}
	if pending.IPAddress != "192.168.1.1" {
		t.Errorf("IPAddress = %v, want 192.168.1.1", pending.IPAddress)
	}
	if pending.UserAgent != "Test Agent" {
		t.Errorf("UserAgent = %v, want Test Agent", pending.UserAgent)
	}
	if pending.ExpiresAt.Before(time.Now()) {
		t.Error("ExpiresAt should be in the future")
	}
}

// TestDeviceStore_GetPendingByUserCode tests retrieving pending auth by user code
func TestDeviceStore_GetPendingByUserCode(t *testing.T) {
	store := setupTestDB(t)

	// Create pending auth
	created, err := store.CreatePendingAuth("My Device", "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}

	tests := []struct {
		name      string
		userCode  string
		wantFound bool
	}{
		{
			name:      "existing user code",
			userCode:  created.UserCode,
			wantFound: true,
		},
		{
			name:      "non-existent user code",
			userCode:  "AAAA-BBBB",
			wantFound: false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			pending, found := store.GetPendingByUserCode(tt.userCode)
			if found != tt.wantFound {
				t.Errorf("GetPendingByUserCode() found = %v, want %v", found, tt.wantFound)
			}
			if tt.wantFound && pending == nil {
				t.Error("Expected pending auth, got nil")
			}
			if tt.wantFound && pending != nil {
				if pending.DeviceName != "My Device" {
					t.Errorf("DeviceName = %v, want My Device", pending.DeviceName)
				}
			}
		})
	}
}

// TestDeviceStore_GetPendingByDeviceCode tests retrieving pending auth by device code
func TestDeviceStore_GetPendingByDeviceCode(t *testing.T) {
	store := setupTestDB(t)

	// Create pending auth
	created, err := store.CreatePendingAuth("My Device", "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}

	tests := []struct {
		name       string
		deviceCode string
		wantFound  bool
	}{
		{
			name:       "existing device code",
			deviceCode: created.DeviceCode,
			wantFound:  true,
		},
		{
			name:       "non-existent device code",
			deviceCode: "invalidcode",
			wantFound:  false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			pending, found := store.GetPendingByDeviceCode(tt.deviceCode)
			if found != tt.wantFound {
				t.Errorf("GetPendingByDeviceCode() found = %v, want %v", found, tt.wantFound)
			}
			if tt.wantFound && pending == nil {
				t.Error("Expected pending auth, got nil")
			}
		})
	}
}

// TestDeviceStore_ApprovePending tests approving pending authorization
func TestDeviceStore_ApprovePending(t *testing.T) {
	store := setupTestDB(t)

	// Create test users
	createTestUser(t, store, "did:plc:alice123", "alice.bsky.social")
	createTestUser(t, store, "did:plc:bob123", "bob.bsky.social")

	// Create pending auth
	pending, err := store.CreatePendingAuth("My Device", "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}

	tests := []struct {
		name      string
		userCode  string
		did       string
		handle    string
		wantErr   bool
		errString string
	}{
		{
			name:     "successful approval",
			userCode: pending.UserCode,
			did:      "did:plc:alice123",
			handle:   "alice.bsky.social",
			wantErr:  false,
		},
		{
			name:      "non-existent user code",
			userCode:  "AAAA-BBBB",
			did:       "did:plc:bob123",
			handle:    "bob.bsky.social",
			wantErr:   true,
			errString: "not found",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			secret, err := store.ApprovePending(tt.userCode, tt.did, tt.handle)
			if (err != nil) != tt.wantErr {
				t.Errorf("ApprovePending() error = %v, wantErr %v", err, tt.wantErr)
				return
			}
			if !tt.wantErr {
				if secret == "" {
					t.Error("Expected device secret, got empty string")
				}
				if !strings.HasPrefix(secret, "atcr_device_") {
					t.Errorf("Secret should start with atcr_device_, got %v", secret)
				}

				// Verify device was created
				devices := store.ListDevices(tt.did)
				if len(devices) != 1 {
					t.Errorf("Expected 1 device, got %d", len(devices))
				}
			}
			if tt.wantErr && tt.errString != "" && err != nil {
				if !strings.Contains(err.Error(), tt.errString) {
					t.Errorf("Error should contain %q, got %v", tt.errString, err)
				}
			}
		})
	}
}

// TestDeviceStore_ApprovePending_AlreadyApproved tests double approval
func TestDeviceStore_ApprovePending_AlreadyApproved(t *testing.T) {
	store := setupTestDB(t)
	createTestUser(t, store, "did:plc:alice123", "alice.bsky.social")

	pending, err := store.CreatePendingAuth("My Device", "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}

	// First approval
	_, err = store.ApprovePending(pending.UserCode, "did:plc:alice123", "alice.bsky.social")
	if err != nil {
		t.Fatalf("First ApprovePending() error = %v", err)
	}

	// Second approval should fail
	_, err = store.ApprovePending(pending.UserCode, "did:plc:alice123", "alice.bsky.social")
	if err == nil {
		t.Error("Expected error for double approval, got nil")
	}
	if !strings.Contains(err.Error(), "already approved") {
		t.Errorf("Error should contain 'already approved', got %v", err)
	}
}

// TestDeviceStore_ValidateDeviceSecret tests device secret validation
func TestDeviceStore_ValidateDeviceSecret(t *testing.T) {
	store := setupTestDB(t)
	createTestUser(t, store, "did:plc:alice123", "alice.bsky.social")

	// Create and approve a device
	pending, err := store.CreatePendingAuth("My Device", "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}

	secret, err := store.ApprovePending(pending.UserCode, "did:plc:alice123", "alice.bsky.social")
	if err != nil {
		t.Fatalf("ApprovePending() error = %v", err)
	}

	tests := []struct {
		name    string
		secret  string
		wantErr bool
	}{
		{
			name:    "valid secret",
			secret:  secret,
			wantErr: false,
		},
		{
			name:    "invalid secret",
			secret:  "atcr_device_invalid",
			wantErr: true,
		},
		{
			name:    "empty secret",
			secret:  "",
			wantErr: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			device, err := store.ValidateDeviceSecret(tt.secret)
			if (err != nil) != tt.wantErr {
				t.Errorf("ValidateDeviceSecret() error = %v, wantErr %v", err, tt.wantErr)
				return
			}
			if !tt.wantErr {
				if device.DID != "did:plc:alice123" {
					t.Errorf("DID = %v, want did:plc:alice123", device.DID)
				}
				if device.Name != "My Device" {
					t.Errorf("Name = %v, want My Device", device.Name)
				}
			}
		})
	}
}

// TestDeviceStore_ListDevices tests listing devices
func TestDeviceStore_ListDevices(t *testing.T) {
	store := setupTestDB(t)
	did := "did:plc:alice123"
	createTestUser(t, store, did, "alice.bsky.social")

	// Initially empty
	devices := store.ListDevices(did)
	if len(devices) != 0 {
		t.Errorf("Expected 0 devices initially, got %d", len(devices))
	}

	// Create 3 devices
	for i := range 3 {
		pending, err := store.CreatePendingAuth("Device "+string(rune('A'+i)), "192.168.1.1", "Agent")
		if err != nil {
			t.Fatalf("CreatePendingAuth() error = %v", err)
		}
		_, err = store.ApprovePending(pending.UserCode, did, "alice.bsky.social")
		if err != nil {
			t.Fatalf("ApprovePending() error = %v", err)
		}
	}

	// List devices
	devices = store.ListDevices(did)
	if len(devices) != 3 {
		t.Errorf("Expected 3 devices, got %d", len(devices))
	}

	// Verify they're sorted by created_at DESC (newest first)
	for i := range len(devices) - 1 {
		if devices[i].CreatedAt.Before(devices[i+1].CreatedAt) {
			t.Error("Devices should be sorted by created_at DESC")
		}
	}

	// List devices for different DID
	otherDevices := store.ListDevices("did:plc:bob123")
	if len(otherDevices) != 0 {
		t.Errorf("Expected 0 devices for different DID, got %d", len(otherDevices))
	}
}

// TestDeviceStore_RevokeDevice tests revoking a device
func TestDeviceStore_RevokeDevice(t *testing.T) {
	store := setupTestDB(t)
	did := "did:plc:alice123"
	createTestUser(t, store, did, "alice.bsky.social")

	// Create device
	pending, err := store.CreatePendingAuth("My Device", "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}
	_, err = store.ApprovePending(pending.UserCode, did, "alice.bsky.social")
	if err != nil {
		t.Fatalf("ApprovePending() error = %v", err)
	}

	devices := store.ListDevices(did)
	if len(devices) != 1 {
		t.Fatalf("Expected 1 device, got %d", len(devices))
	}
	deviceID := devices[0].ID

	tests := []struct {
		name     string
		did      string
		deviceID string
		wantErr  bool
	}{
		{
			name:     "successful revocation",
			did:      did,
			deviceID: deviceID,
			wantErr:  false,
		},
		{
			name:     "non-existent device",
			did:      did,
			deviceID: "non-existent-id",
			wantErr:  true,
		},
		{
			name:     "wrong DID",
			did:      "did:plc:bob123",
			deviceID: deviceID,
			wantErr:  true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			err := store.RevokeDevice(tt.did, tt.deviceID)
			if (err != nil) != tt.wantErr {
				t.Errorf("RevokeDevice() error = %v, wantErr %v", err, tt.wantErr)
			}
		})
	}

	// Verify device was removed (after first successful test)
	devices = store.ListDevices(did)
	if len(devices) != 0 {
		t.Errorf("Expected 0 devices after revocation, got %d", len(devices))
	}
}

// TestDeviceStore_UpdateLastUsed tests updating last used timestamp
func TestDeviceStore_UpdateLastUsed(t *testing.T) {
	store := setupTestDB(t)
	createTestUser(t, store, "did:plc:alice123", "alice.bsky.social")

	// Create device
	pending, err := store.CreatePendingAuth("My Device", "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}
	secret, err := store.ApprovePending(pending.UserCode, "did:plc:alice123", "alice.bsky.social")
	if err != nil {
		t.Fatalf("ApprovePending() error = %v", err)
	}

	// Get device to get secret hash
	device, err := store.ValidateDeviceSecret(secret)
	if err != nil {
		t.Fatalf("ValidateDeviceSecret() error = %v", err)
	}

	initialLastUsed := device.LastUsed

	// Wait a bit to ensure timestamp difference
	time.Sleep(10 * time.Millisecond)

	// Update last used
	store.UpdateLastUsed(device.SecretHash)

	// Verify it was updated
	device2, err := store.ValidateDeviceSecret(secret)
	if err != nil {
		t.Fatalf("ValidateDeviceSecret() error = %v", err)
	}

	if !device2.LastUsed.After(initialLastUsed) {
		t.Error("LastUsed should be updated to later time")
	}
}

// TestDeviceStore_CleanupExpired tests cleanup of expired pending auths
func TestDeviceStore_CleanupExpired(t *testing.T) {
	store := setupTestDB(t)

	// Create pending auth with manual expiration time
	pending, err := store.CreatePendingAuth("My Device", "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}

	// Manually update expiration to the past
	_, err = store.db.Exec(`
		UPDATE pending_device_auth
		SET expires_at = datetime('now', '-1 hour')
		WHERE device_code = ?
	`, pending.DeviceCode)
	if err != nil {
		t.Fatalf("Failed to update expiration: %v", err)
	}

	// Run cleanup
	store.CleanupExpired()

	// Verify it was deleted
	_, found := store.GetPendingByDeviceCode(pending.DeviceCode)
	if found {
		t.Error("Expired pending auth should have been cleaned up")
	}
}

// TestDeviceStore_CleanupExpiredContext tests context-aware cleanup
func TestDeviceStore_CleanupExpiredContext(t *testing.T) {
	store := setupTestDB(t)

	// Create and expire pending auth
	pending, err := store.CreatePendingAuth("My Device", "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}

	_, err = store.db.Exec(`
		UPDATE pending_device_auth
		SET expires_at = datetime('now', '-1 hour')
		WHERE device_code = ?
	`, pending.DeviceCode)
	if err != nil {
		t.Fatalf("Failed to update expiration: %v", err)
	}

	// Run context-aware cleanup
	ctx := context.Background()
	err = store.CleanupExpiredContext(ctx)
	if err != nil {
		t.Errorf("CleanupExpiredContext() error = %v", err)
	}

	// Verify it was deleted
	_, found := store.GetPendingByDeviceCode(pending.DeviceCode)
	if found {
		t.Error("Expired pending auth should have been cleaned up")
	}
}

// TestDeviceStore_SecretHashing tests bcrypt hashing
func TestDeviceStore_SecretHashing(t *testing.T) {
	store := setupTestDB(t)
	createTestUser(t, store, "did:plc:alice123", "alice.bsky.social")

	pending, err := store.CreatePendingAuth("My Device", "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}

	secret, err := store.ApprovePending(pending.UserCode, "did:plc:alice123", "alice.bsky.social")
	if err != nil {
		t.Fatalf("ApprovePending() error = %v", err)
	}

	// Get device via ValidateDeviceSecret to access secret hash
	device, err := store.ValidateDeviceSecret(secret)
	if err != nil {
		t.Fatalf("ValidateDeviceSecret() error = %v", err)
	}

	// Verify bcrypt hash is valid
	err = bcrypt.CompareHashAndPassword([]byte(device.SecretHash), []byte(secret))
	if err != nil {
		t.Error("Secret hash should match secret")
	}

	// Verify wrong secret doesn't match
	err = bcrypt.CompareHashAndPassword([]byte(device.SecretHash), []byte("wrong_secret"))
	if err == nil {
		t.Error("Wrong secret should not match hash")
	}
}

// newDeviceForTest approves a pending auth and returns the device secret.
func newDeviceForTest(t *testing.T, store *DeviceStore, did, handle, name string) string {
	t.Helper()
	pending, err := store.CreatePendingAuth(name, "192.168.1.1", "Test Agent")
	if err != nil {
		t.Fatalf("CreatePendingAuth() error = %v", err)
	}
	secret, err := store.ApprovePending(pending.UserCode, did, handle)
	if err != nil {
		t.Fatalf("ApprovePending() error = %v", err)
	}
	return secret
}

func lookupValueFor(t *testing.T, store *DeviceStore, secret string) string {
	t.Helper()
	var lookup sql.NullString
	err := store.db.QueryRow(
		`SELECT secret_lookup FROM devices WHERE secret_lookup = ?`,
		deviceSecretLookup(secret),
	).Scan(&lookup)
	if errors.Is(err, sql.ErrNoRows) {
		return ""
	}
	if err != nil {
		t.Fatalf("query secret_lookup: %v", err)
	}
	return lookup.String
}

// TestDeviceStore_NewDeviceGetsSecretLookup verifies newly created devices are
// indexed at creation, so they never take the scan path.
func TestDeviceStore_NewDeviceGetsSecretLookup(t *testing.T) {
	store := setupTestDB(t)
	createTestUser(t, store, "did:plc:alice123", "alice.bsky.social")
	secret := newDeviceForTest(t, store, "did:plc:alice123", "alice.bsky.social", "My Device")

	if got := lookupValueFor(t, store, secret); got != deviceSecretLookup(secret) {
		t.Fatalf("secret_lookup not populated at creation, got %q", got)
	}

	device, err := store.ValidateDeviceSecret(secret)
	if err != nil {
		t.Fatalf("ValidateDeviceSecret() error = %v", err)
	}
	if device.DID != "did:plc:alice123" {
		t.Errorf("DID = %v, want did:plc:alice123", device.DID)
	}
}

// TestDeviceStore_LegacyDeviceBackfills covers rows created before migration
// 0028. They have a NULL secret_lookup, so the first authentication falls back
// to the scan and must backfill, and subsequent ones resolve via the index.
func TestDeviceStore_LegacyDeviceBackfills(t *testing.T) {
	store := setupTestDB(t)
	createTestUser(t, store, "did:plc:alice123", "alice.bsky.social")
	secret := newDeviceForTest(t, store, "did:plc:alice123", "alice.bsky.social", "Legacy Device")

	// Simulate a pre-migration row.
	if _, err := store.db.Exec(`UPDATE devices SET secret_lookup = NULL`); err != nil {
		t.Fatalf("clear secret_lookup: %v", err)
	}
	if got := lookupValueFor(t, store, secret); got != "" {
		t.Fatalf("expected no indexed row before backfill, got %q", got)
	}

	device, err := store.ValidateDeviceSecret(secret)
	if err != nil {
		t.Fatalf("ValidateDeviceSecret() on legacy row error = %v", err)
	}
	if device.Name != "Legacy Device" {
		t.Errorf("Name = %v, want Legacy Device", device.Name)
	}

	if got := lookupValueFor(t, store, secret); got != deviceSecretLookup(secret) {
		t.Fatalf("secret_lookup was not backfilled, got %q", got)
	}

	// Second call must still succeed, now via the indexed path.
	if _, err := store.ValidateDeviceSecret(secret); err != nil {
		t.Fatalf("ValidateDeviceSecret() after backfill error = %v", err)
	}
}

// TestDeviceStore_ValidateDoesNotScanIndexedRows is the regression guard for the
// O(n) bcrypt scan. Every device is indexed, so a wrong secret must not compare
// against any of them — it should miss the index and find nothing left to scan.
func TestDeviceStore_ValidateDoesNotScanIndexedRows(t *testing.T) {
	store := setupTestDB(t)
	createTestUser(t, store, "did:plc:alice123", "alice.bsky.social")
	for i := 0; i < 5; i++ {
		newDeviceForTest(t, store, "did:plc:alice123", "alice.bsky.social", fmt.Sprintf("Device %d", i))
	}

	var unindexed int
	if err := store.db.QueryRow(
		`SELECT COUNT(*) FROM devices WHERE secret_lookup IS NULL OR secret_lookup = ''`,
	).Scan(&unindexed); err != nil {
		t.Fatalf("count unindexed: %v", err)
	}
	if unindexed != 0 {
		t.Fatalf("expected all devices indexed, %d still unindexed", unindexed)
	}

	if _, err := store.ValidateDeviceSecret("atcr_device_wrong"); err == nil {
		t.Error("expected error for an unknown secret")
	}
}

// TestDeviceSecretLookup_StableAndDistinct guards the lookup derivation.
func TestDeviceSecretLookup_StableAndDistinct(t *testing.T) {
	a := deviceSecretLookup("atcr_device_aaa")
	if a != deviceSecretLookup("atcr_device_aaa") {
		t.Error("deviceSecretLookup is not deterministic")
	}
	if a == deviceSecretLookup("atcr_device_bbb") {
		t.Error("distinct secrets produced the same lookup")
	}
	if len(a) != 64 {
		t.Errorf("expected 64 hex chars for sha256, got %d", len(a))
	}
}

// TestUpdateLastUsedIsThrottled: callers invoke this on every successful
// authentication, which means every docker push and pull, including each layer's
// re-auth. Writing every time is a network round trip per call against a remote
// primary, for a timestamp read at minute resolution at best.
func TestUpdateLastUsedIsThrottled(t *testing.T) {
	database := deviceThrottleDB(t)
	store := NewDeviceStore(database)
	hash := seedThrottleDevice(t, database, "dev-a", "hash-a")

	store.UpdateLastUsed(hash)
	var first sql.NullTime
	if err := database.QueryRow(`SELECT last_used FROM devices WHERE id = ?`, "dev-a").Scan(&first); err != nil {
		t.Fatalf("read last_used: %v", err)
	}
	if !first.Valid {
		t.Fatal("first call did not write last_used")
	}

	// Force a value the next write would visibly change, then hammer it.
	marker := first.Time.Add(-time.Hour).UTC().Truncate(time.Second)
	if _, err := database.Exec(`UPDATE devices SET last_used = ? WHERE id = ?`, marker, "dev-a"); err != nil {
		t.Fatalf("set marker: %v", err)
	}
	for range 50 {
		store.UpdateLastUsed(hash)
	}

	var after sql.NullTime
	if err := database.QueryRow(`SELECT last_used FROM devices WHERE id = ?`, "dev-a").Scan(&after); err != nil {
		t.Fatalf("read last_used: %v", err)
	}
	if !after.Time.UTC().Truncate(time.Second).Equal(marker) {
		t.Error("last_used was rewritten during 50 back-to-back calls; the throttle is not holding")
	}
}

// TestUpdateLastUsedThrottlesPerDevice: one busy device must not suppress
// another device's first write.
func TestUpdateLastUsedThrottlesPerDevice(t *testing.T) {
	database := deviceThrottleDB(t)
	store := NewDeviceStore(database)
	hashA := seedThrottleDevice(t, database, "dev-a", "hash-a")
	hashB := seedThrottleDevice(t, database, "dev-b", "hash-b")

	store.UpdateLastUsed(hashA)
	store.UpdateLastUsed(hashB)

	for _, id := range []string{"dev-a", "dev-b"} {
		var ts sql.NullTime
		if err := database.QueryRow(`SELECT last_used FROM devices WHERE id = ?`, id).Scan(&ts); err != nil {
			t.Fatalf("read last_used for %s: %v", id, err)
		}
		if !ts.Valid {
			t.Errorf("device %s never got a last_used write", id)
		}
	}
}

func seedThrottleDevice(t *testing.T, database *sql.DB, id, secretHash string) string {
	t.Helper()
	if _, err := database.Exec(`
		INSERT INTO devices (id, did, handle, name, secret_hash, created_at)
		VALUES (?, 'did:plc:throttle', 'throttle.example.com', ?, ?, ?)
	`, id, id, secretHash, time.Now()); err != nil {
		t.Fatalf("seed device %s: %v", id, err)
	}
	return secretHash
}

func deviceThrottleDB(t *testing.T) *sql.DB {
	t.Helper()
	database, err := InitDB(":memory:", LibsqlConfig{})
	if err != nil {
		t.Fatalf("InitDB: %v", err)
	}
	t.Cleanup(func() { database.Close() })
	if err := UpsertUser(database, &User{
		DID:         "did:plc:throttle",
		Handle:      "throttle.example.com",
		PDSEndpoint: "https://pds.example.com",
		LastSeen:    time.Now(),
	}); err != nil {
		t.Fatalf("UpsertUser: %v", err)
	}
	return database
}