watchtower/wtmock: add in-memory impl of Queue

This commit adds an in-memory implementation of the Queue interface.
This can be used for tests.

watchtower/wtclient/interface.go

@@ -131,6 +131,10 @@ type DB interface {
 	// update identified by seqNum was received and saved. The returned
 	// lastApplied will be recorded.
 	AckUpdate(id *wtdb.SessionID, seqNum, lastApplied uint16) error
+
+	// GetDBQueue returns a BackupID Queue instance under the given name
+	// space.
+	GetDBQueue(namespace []byte) wtdb.Queue[*wtdb.BackupID]
 }
 
 // AuthDialer connects to a remote node using an authenticated transport, such

watchtower/wtdb/queue_test.go

@@ -4,7 +4,9 @@ import (
 	"testing"
 
 	"github.com/lightningnetwork/lnd/kvdb"
+	"github.com/lightningnetwork/lnd/watchtower/wtclient"
 	"github.com/lightningnetwork/lnd/watchtower/wtdb"
+	"github.com/lightningnetwork/lnd/watchtower/wtmock"
 	"github.com/stretchr/testify/require"
 )
 
@@ -13,21 +15,53 @@ import (
 func TestDiskQueue(t *testing.T) {
 	t.Parallel()
 
-	// Set up a temporary bolt backend.
-	dbCfg := &kvdb.BoltConfig{DBTimeout: kvdb.DefaultDBTimeout}
+	dbs := []struct {
+		name string
+		init clientDBInit
+	}{
+		{
+			name: "bbolt",
+			init: func(t *testing.T) wtclient.DB {
+				dbCfg := &kvdb.BoltConfig{
+					DBTimeout: kvdb.DefaultDBTimeout,
+				}
+
+				// Construct the ClientDB.
 				bdb, err := wtdb.NewBoltBackendCreator(
 					true, t.TempDir(), "wtclient.db",
 				)(dbCfg)
 				require.NoError(t, err)
 
-	// Construct the ClientDB.
 				db, err := wtdb.OpenClientDB(bdb)
 				require.NoError(t, err)
+
 				t.Cleanup(func() {
 					err = db.Close()
 					require.NoError(t, err)
 				})
 
+				return db
+			},
+		},
+		{
+			name: "mock",
+			init: func(t *testing.T) wtclient.DB {
+				return wtmock.NewClientDB()
+			},
+		},
+	}
+
+	for _, database := range dbs {
+		db := database
+		t.Run(db.name, func(t *testing.T) {
+			t.Parallel()
+
+			testQueue(t, db.init(t))
+		})
+	}
+}
+
+func testQueue(t *testing.T, db wtclient.DB) {
 	namespace := []byte("test-namespace")
 	queue := db.GetDBQueue(namespace)
 

watchtower/wtmock/client_db.go

@@ -49,6 +49,8 @@ type ClientDB struct {
 	nextIndex     uint32
 	indexes       map[keyIndexKey]uint32
 	legacyIndexes map[wtdb.TowerID]uint32
+
+	queues map[string]wtdb.Queue[*wtdb.BackupID]
 }
 
 // NewClientDB initializes a new mock ClientDB.
@@ -68,6 +70,7 @@ func NewClientDB() *ClientDB {
 		indexes:          make(map[keyIndexKey]uint32),
 		legacyIndexes:    make(map[wtdb.TowerID]uint32),
 		closableSessions: make(map[wtdb.SessionID]uint32),
+		queues:           make(map[string]wtdb.Queue[*wtdb.BackupID]),
 	}
 }
 
@@ -568,6 +571,21 @@ func (m *ClientDB) AckUpdate(id *wtdb.SessionID, seqNum,
 	return wtdb.ErrCommittedUpdateNotFound
 }
 
+// GetDBQueue returns a BackupID Queue instance under the given name space.
+func (m *ClientDB) GetDBQueue(namespace []byte) wtdb.Queue[*wtdb.BackupID] {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if q, ok := m.queues[string(namespace)]; ok {
+		return q
+	}
+
+	q := NewQueueDB[*wtdb.BackupID]()
+	m.queues[string(namespace)] = q
+
+	return q
+}
+
 // ListClosableSessions fetches and returns the IDs for all sessions marked as
 // closable.
 func (m *ClientDB) ListClosableSessions() (map[wtdb.SessionID]uint32, error) {

watchtower/wtmock/queue.go

@@ -0,0 +1,92 @@
+package wtmock
+
+import (
+	"container/list"
+	"fmt"
+	"sync"
+
+	"github.com/lightningnetwork/lnd/watchtower/wtdb"
+)
+
+// DiskQueueDB is an in-memory implementation of the wtclient.Queue interface.
+type DiskQueueDB[T any] struct {
+	disk *list.List
+	mu   sync.RWMutex
+}
+
+// NewQueueDB constructs a new DiskQueueDB.
+func NewQueueDB[T any]() wtdb.Queue[T] {
+	return &DiskQueueDB[T]{
+		disk: list.New(),
+	}
+}
+
+// Len returns the number of tasks in the queue.
+//
+// NOTE: This is part of the wtclient.Queue interface.
+func (d *DiskQueueDB[T]) Len() (uint64, error) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	return uint64(d.disk.Len()), nil
+}
+
+// Push adds new T items to the tail of the queue.
+//
+// NOTE: This is part of the wtclient.Queue interface.
+func (d *DiskQueueDB[T]) Push(items ...T) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	for _, item := range items {
+		d.disk.PushBack(item)
+	}
+
+	return nil
+}
+
+// PopUpTo attempts to pop up to n items from the queue. If the queue is empty,
+// then ErrEmptyQueue is returned.
+//
+// NOTE: This is part of the Queue interface.
+func (d *DiskQueueDB[T]) PopUpTo(n int) ([]T, error) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	if d.disk.Len() == 0 {
+		return nil, wtdb.ErrEmptyQueue
+	}
+
+	num := n
+	if d.disk.Len() < n {
+		num = d.disk.Len()
+	}
+
+	tasks := make([]T, 0, num)
+	for i := 0; i < num; i++ {
+		e := d.disk.Front()
+		task, ok := d.disk.Remove(e).(T)
+		if !ok {
+			return nil, fmt.Errorf("queue item not of type %T",
+				task)
+		}
+
+		tasks = append(tasks, task)
+	}
+
+	return tasks, nil
+}
+
+// PushHead pushes new T items to the head of the queue.
+//
+// NOTE: This is part of the wtclient.Queue interface.
+func (d *DiskQueueDB[T]) PushHead(items ...T) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	for i := len(items) - 1; i >= 0; i-- {
+		d.disk.PushFront(items[i])
+	}
+
+	return nil
+}