invoicesrpc: remove direct access to ChannelGraph pointer

Author: ellemouton

Diff for: docs/release-notes/release-notes-0.19.0.md

@@ -245,8 +245,9 @@ config option](https://github.com/lightningnetwork/lnd/pull/9182) and introduce
 a new option `channel-max-fee-exposure` which is unambiguous in its description.
 The underlying functionality between those two options remain the same.
 
-* [Abstraction of graph](https://github.com/lightningnetwork/lnd/pull/9480) 
-  access for autopilot. 
+* Graph abstraction work:
+    - [Abstract autopilot access](https://github.com/lightningnetwork/lnd/pull/9480)
+    - [Abstract invoicerpc server access](https://github.com/lightningnetwork/lnd/pull/9516)
 
 * [Golang was updated to
   `v1.22.11`](https://github.com/lightningnetwork/lnd/pull/9462). 

Diff for: lnrpc/invoicesrpc/addinvoice.go

@@ -18,7 +18,6 @@ import (
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/channeldb"
-	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/graph/db/models"
 	"github.com/lightningnetwork/lnd/invoices"
 	"github.com/lightningnetwork/lnd/lntypes"
@@ -75,8 +74,9 @@ type AddInvoiceConfig struct {
 	// channel graph.
 	ChanDB *channeldb.ChannelStateDB
 
-	// Graph holds a reference to the ChannelGraph database.
-	Graph *graphdb.ChannelGraph
+	// Graph gives the invoice server access to various graph related
+	// queries.
+	Graph GraphSource
 
 	// GenInvoiceFeatures returns a feature containing feature bits that
 	// should be advertised on freshly generated invoices.

Diff for: lnrpc/invoicesrpc/config_active.go

@@ -6,7 +6,6 @@ package invoicesrpc
 import (
 	"github.com/btcsuite/btcd/chaincfg"
 	"github.com/lightningnetwork/lnd/channeldb"
-	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/invoices"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/macaroons"
@@ -52,9 +51,9 @@ type Config struct {
 	// specified.
 	DefaultCLTVExpiry uint32
 
-	// GraphDB is a global database instance which is needed to access the
-	// channel graph.
-	GraphDB *graphdb.ChannelGraph
+	// Graph provides the invoices with information about the current LN
+	// graph.
+	Graph GraphSource
 
 	// ChanStateDB is a possibly replicated db instance which contains the
 	// channel state

Diff for: lnrpc/invoicesrpc/interfaces.go

@@ -0,0 +1,19 @@
+package invoicesrpc
+
+import (
+	"github.com/lightningnetwork/lnd/graph/db/models"
+)
+
+// GraphSource defines the graph interface required by the invoice rpc server.
+type GraphSource interface {
+	// FetchChannelEdgesByID attempts to look up the two directed edges for
+	// the channel identified by the channel ID. If the channel can't be
+	// found, then graphdb.ErrEdgeNotFound is returned.
+	FetchChannelEdgesByID(chanID uint64) (*models.ChannelEdgeInfo,
+		*models.ChannelEdgePolicy, *models.ChannelEdgePolicy, error)
+
+	// IsPublicNode is a helper method that determines whether the node with
+	// the given public key is seen as a public node in the graph from the
+	// graph's source node's point of view.
+	IsPublicNode(pubKey [33]byte) (bool, error)
+}

Diff for: lnrpc/invoicesrpc/invoices_server.go

@@ -346,7 +346,7 @@ func (s *Server) AddHoldInvoice(ctx context.Context,
 		NodeSigner:            s.cfg.NodeSigner,
 		DefaultCLTVExpiry:     s.cfg.DefaultCLTVExpiry,
 		ChanDB:                s.cfg.ChanStateDB,
-		Graph:                 s.cfg.GraphDB,
+		Graph:                 s.cfg.Graph,
 		GenInvoiceFeatures:    s.cfg.GenInvoiceFeatures,
 		GenAmpInvoiceFeatures: s.cfg.GenAmpInvoiceFeatures,
 		GetAlias:              s.cfg.GetAlias,

Diff for: subrpcserver_config.go

@@ -262,7 +262,7 @@ func (s *subRPCServerConfigs) PopulateDependencies(cfg *Config,
 			subCfgValue.FieldByName("DefaultCLTVExpiry").Set(
 				reflect.ValueOf(defaultDelta),
 			)
-			subCfgValue.FieldByName("GraphDB").Set(
+			subCfgValue.FieldByName("Graph").Set(
 				reflect.ValueOf(graphDB),
 			)
 			subCfgValue.FieldByName("ChanStateDB").Set(