diff --git a/graph.go b/graph.go
new file mode 100644
index 0000000..a19250c
--- /dev/null
+++ b/graph.go
@@ -0,0 +1,112 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+type graphBuilder struct {
+	refs    Refs
+	nodeMap NodeMap
+	nodes   []Node
+	edges   []Edge
+}
+
+type NodeMap map[string]int
+
+func NewGraphBuilder(mp PagesRepository) (*graphBuilder, error) {
+	refs := make(Refs)
+
+	f, err := os.Open(filepath.Join(mp.(*FilePages).dirname, "backrefs.json"))
+	if err != nil {
+		return nil, err
+	}
+
+	defer f.Close()
+
+	err = json.NewDecoder(f).Decode(&refs)
+	if err != nil {
+		return nil, err
+	}
+
+	nodeMap := prepareNodeMap(refs)
+	return &graphBuilder{
+		refs:    refs,
+		nodeMap: nodeMap,
+		nodes:   nil,
+		edges:   nil,
+	}, nil
+}
+
+func (gb *graphBuilder) prepareGraph() error {
+	gb.nodes = prepareNodes(gb.nodeMap)
+	gb.edges = prepareEdges(gb.refs, gb.nodeMap)
+	return nil
+}
+
+func (gb *graphBuilder) RemoveNode(name string) {
+	delete(gb.nodeMap, name)
+}
+
+func (gb *graphBuilder) RemoveNodeWithSuffix(suffix string) {
+	for k, _ := range gb.nodeMap {
+		if strings.HasSuffix(k, suffix) {
+			delete(gb.nodeMap, k)
+		}
+	}
+}
+
+func prepareEdges(refs Refs, nodeMap NodeMap) []Edge {
+	var edges []Edge
+	edgeSet := make(map[Edge]bool)
+	for key, references := range refs {
+		if toID, e := nodeMap[key]; e {
+			for _, item := range references {
+				if fromID, e := nodeMap[item.Name]; e {
+					edge := Edge{
+						From: fromID,
+						To:   toID,
+					}
+					if _, e := edgeSet[edge]; !e {
+						edgeSet[edge] = true
+						edges = append(edges, edge)
+					}
+				}
+			}
+		}
+	}
+	return edges
+}
+
+func prepareNodes(nodeMap NodeMap) []Node {
+	var nodes []Node
+	for name, id := range nodeMap {
+		nodes = append(nodes, Node{
+			Id:    id,
+			Label: name,
+		})
+	}
+	return nodes
+}
+
+func prepareNodeMap(refs Refs) NodeMap {
+	nodeCount := 1
+	nodeMap := make(NodeMap)
+
+	for key, references := range refs {
+		if _, e := nodeMap[key]; !e {
+			nodeMap[key] = nodeCount
+			nodeCount += 1
+		}
+		for _, item := range references {
+			if _, e := nodeMap[item.Name]; !e {
+				nodeMap[item.Name] = nodeCount
+				nodeCount += 1
+			}
+		}
+	}
+
+	return nodeMap
+}
diff --git a/main.go b/main.go
index 7cef2c7..40dd5b4 100644
--- a/main.go
+++ b/main.go
@@ -114,7 +114,6 @@ type graphPage struct {
 	Session    *Session
 	Title      string
 	Name       string
-	References Refs
 	Nodes      template.JS
 	Edges      template.JS
 }
@@ -478,17 +477,23 @@ func (h *graphHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	refs := make(Refs)
-
-	f, err := os.Open(filepath.Join(mp.(*FilePages).dirname, "backrefs.json"))
+	gb, err := NewGraphBuilder(mp)
 	if err != nil {
 		http.Error(w, err.Error(), 500)
 		return
 	}
 
-	defer f.Close()
+	gb.RemoveNode("DONE")
+	gb.RemoveNode("TODO")
+	gb.RemoveNode("Home")
+	gb.RemoveNode("Projects")
+	gb.RemoveNode("Notes")
+	gb.RemoveNode("Books")
+	gb.RemoveNode("Daily_Notes")
+	gb.RemoveNode("NewJsonTest")
+	gb.RemoveNodeWithSuffix("_2020")
 
-	err = json.NewDecoder(f).Decode(&refs)
+	err = gb.prepareGraph()
 	if err != nil {
 		http.Error(w, err.Error(), 500)
 		return
@@ -497,85 +502,13 @@ func (h *graphHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	var nodesBuf bytes.Buffer
 	var edgesBuf bytes.Buffer
 
-	var nodes []Node
-	var edges []Edge
-
-	nodeCount := 1
-	nodeMap := make(map[string]int)
-
-	for key, references := range refs {
-		if strings.HasSuffix(key, "_2020") {
-			continue
-		}
-		if _, e := nodeMap[key]; !e {
-			nodeMap[key] = nodeCount
-			nodeCount += 1
-		}
-		for _, item := range references {
-			if strings.HasSuffix(item.Name, "_2020") {
-				continue
-			}
-			if _, e := nodeMap[item.Name]; !e {
-				nodeMap[item.Name] = nodeCount
-				nodeCount += 1
-			}
-		}
-	}
-
-	delete(nodeMap, "DONE")
-	delete(nodeMap, "TODO")
-	delete(nodeMap, "Home")
-	delete(nodeMap, "Projects")
-	delete(nodeMap, "Notes")
-	delete(nodeMap, "Books")
-	delete(nodeMap, "Daily_Notes")
-	delete(nodeMap, "NewJsonTest")
-
-	for name, id := range nodeMap {
-		nodes = append(nodes, Node{
-			Id:    id,
-			Label: name,
-		})
-	}
-
-	edgeSet := make(map[Edge]bool)
-	for key, references := range refs {
-		if key == "DONE" {
-			continue
-		}
-		if strings.HasSuffix(key, "_2020") {
-			continue
-		}
-		if toID, e := nodeMap[key]; e {
-			for _, item := range references {
-				if strings.HasSuffix(item.Name, "_2020") {
-					continue
-				}
-				if fromID, e := nodeMap[item.Name]; e {
-					if fromID == toID {
-						continue
-					}
-					edge := Edge{
-						From: fromID,
-						To:   toID,
-					}
-
-					if _, e := edgeSet[edge]; !e {
-						edgeSet[edge] = true
-						edges = append(edges, edge)
-					}
-				}
-			}
-		}
-	}
-
-	err = json.NewEncoder(&nodesBuf).Encode(&nodes)
+	err = json.NewEncoder(&nodesBuf).Encode(&gb.nodes)
 	if err != nil {
 		http.Error(w, err.Error(), 500)
 		return
 	}
 
-	err = json.NewEncoder(&edgesBuf).Encode(&edges)
+	err = json.NewEncoder(&edgesBuf).Encode(&gb.edges)
 	if err != nil {
 		http.Error(w, err.Error(), 500)
 		return
@@ -587,7 +520,6 @@ func (h *graphHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		Session:      sess,
 		Title:        "Graph",
 		Name:         "Graph",
-		References:   refs,
 		Nodes:        template.JS(nodesBuf.String()),
 		Edges:        template.JS(edgesBuf.String()),
 	}