Fix graph description issue

graph.go

@@ -1,8 +1,12 @@
 package main
 
 import (
+	"encoding/json"
+	"errors"
+	"io"
 	"runtime"
 
+	"github.com/divan/graphx/graph"
 	"github.com/gopherjs/vecty"
 )
 
@@ -37,3 +41,44 @@ func (p *Page) ApplyForces() {
 	p.webgl.updatePositions()
 	p.webgl.rt.Disable()
 }
+
+// GraphFromJSON is a custom version of graphx JSON importer, as we want to use
+// some additional fields (Description).
+// TODO(divan): that's probably can be done better within the limits of graphx library.
+func GraphFromJSON(r io.Reader) (*graph.Graph, string, error) {
+	// decode into temporary struct to process
+	var res struct {
+		Description string             `json:"description"`
+		Nodes       []*graph.BasicNode `json:"nodes"`
+		Links       []*struct {
+			Source string `json:"source"`
+			Target string `json:"target"`
+		} `json:"links"`
+	}
+	err := json.NewDecoder(r).Decode(&res)
+	if err != nil {
+		return nil, "", err
+	}
+
+	if len(res.Nodes) == 0 {
+		return nil, "", errors.New("empty graph")
+	}
+
+	// convert links IDs into indices
+	g := graph.NewGraphMN(len(res.Nodes), len(res.Links))
+
+	for _, node := range res.Nodes {
+		g.AddNode(node)
+	}
+
+	for _, link := range res.Links {
+		err := g.AddLink(link.Source, link.Target)
+		if err != nil {
+			return nil, "", err
+		}
+	}
+
+	g.UpdateCache()
+
+	return g, res.Description, nil
+}

network.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"io"
 
-	"github.com/divan/graphx/formats"
 	"github.com/divan/graphx/graph"
 )
 
@@ -38,12 +37,11 @@ func LoadNetwork(file string) (*Network, error) {
 
 // LoadNetworkFromReader loads network information from the io.Reader.
 func LoadNetworkFromReader(r io.Reader) (*Network, error) {
-	g, err := formats.FromD3JSONReader(r)
+	g, desc, err := GraphFromJSON(r)
 	if err != nil {
 		return nil, fmt.Errorf("parse JSON: %v", err)
 	}
 
-	desc := "TBD"
 	return &Network{
 		Description: desc,
 		Data:        g,

network_selector.go

@@ -16,6 +16,7 @@ const DefaultNetwork = "grid25.json"
 
 // NetworkSelector represents widget for choosing or uploading network topology
 // to be used for visualization.
+// TODO: move to widgets package
 type NetworkSelector struct {
 	vecty.Core