graph/encoding/graphql: add new package for decoding GraphQL output

graph/encoding/graphql/decode.go

@@ -0,0 +1,157 @@
+// Copyright ©2017 The gonum Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package graphql
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+
+	"gonum.org/v1/gonum/graph"
+	"gonum.org/v1/gonum/graph/encoding"
+)
+
+// Unmarshal parses the the JSON-encoded data and stores the result in dst.
+// Node IDs are obtained from the JSON fields identified by the uid parameter.
+// UIDs obtained from the JSON encoding must map to unique node ID values
+// consistently across the JSON-encoded spanning tree.
+func Unmarshal(data []byte, uid string, dst encoding.Builder) error {
+	if uid == "" {
+		return errors.New("graphql: invalid UID field name")
+	}
+	var src json.RawMessage
+	err := json.Unmarshal(data, &src)
+	if err != nil {
+		return err
+	}
+	gen := generator{dst: dst, uidName: uid, nodes: make(map[string]graph.Node)}
+	return gen.walk(src, nil, "")
+}
+
+// StringIDSetter is a graph node that can set its ID based on the given uid string.
+type StringIDSetter interface {
+	SetIDFromString(uid string) error
+}
+
+// LabelSetter is a graph edge that can set its label.
+type LabelSetter interface {
+	SetLabel(string)
+}
+
+type generator struct {
+	dst encoding.Builder
+
+	// uidName is the name of the UID field in the source JSON.
+	uidName string
+	// nodes maps from GraphQL UID string to graph.Node.
+	nodes map[string]graph.Node
+}
+
+func (g *generator) walk(src json.RawMessage, node graph.Node, attr string) error {
+	switch src[0] {
+	case '{':
+		var val map[string]json.RawMessage
+		err := json.Unmarshal(src, &val)
+		if err != nil {
+			return err
+		}
+		if next, ok := val[g.uidName]; !ok {
+			if node != nil {
+				var buf bytes.Buffer
+				err := json.Compact(&buf, src)
+				if err != nil {
+					panic(err)
+				}
+				return fmt.Errorf("graphql: no UID for node: `%s`", &buf)
+			}
+		} else {
+			var v interface{}
+			err = json.Unmarshal(next, &v)
+			if err != nil {
+				return err
+			}
+			value := fmt.Sprint(v)
+			child, ok := g.nodes[value]
+			if !ok {
+				child = g.dst.NewNode()
+				s, ok := child.(StringIDSetter)
+				if !ok {
+					return errors.New("graphql: cannot set UID")
+				}
+				err = s.SetIDFromString(value)
+				if err != nil {
+					return err
+				}
+				g.nodes[value] = child
+				g.dst.AddNode(child)
+			}
+			if node != nil {
+				e := g.dst.NewEdge(node, child)
+				if s, ok := e.(LabelSetter); ok {
+					s.SetLabel(attr)
+				}
+				g.dst.SetEdge(e)
+			}
+			node = child
+		}
+		for attr, src := range val {
+			if attr == g.uidName {
+				continue
+			}
+			err = g.walk(src, node, attr)
+			if err != nil {
+				return err
+			}
+		}
+
+	case '[':
+		var val []json.RawMessage
+		err := json.Unmarshal(src, &val)
+		if err != nil {
+			return err
+		}
+		for _, src := range val {
+			err = g.walk(src, node, attr)
+			if err != nil {
+				return err
+			}
+		}
+
+	default:
+		var v interface{}
+		err := json.Unmarshal(src, &v)
+		if err != nil {
+			return err
+		}
+		if attr == g.uidName {
+			value := fmt.Sprint(v)
+			if s, ok := node.(StringIDSetter); ok {
+				if _, ok := g.nodes[value]; !ok {
+					err = s.SetIDFromString(value)
+					if err != nil {
+						return err
+					}
+					g.nodes[value] = node
+				}
+			} else {
+				return errors.New("graphql: cannot set ID")
+			}
+		} else if s, ok := node.(encoding.AttributeSetter); ok {
+			var value string
+			if _, ok := v.(float64); ok {
+				value = string(src)
+			} else {
+				value = fmt.Sprint(v)
+			}
+			err = s.SetAttribute(encoding.Attribute{Key: attr, Value: value})
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}

graph/encoding/graphql/decode_test.go

@@ -0,0 +1,226 @@
+// Copyright ©2017 The gonum Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package graphql
+
+import (
+	"errors"
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+	"testing"
+
+	"gonum.org/v1/gonum/graph"
+	"gonum.org/v1/gonum/graph/encoding"
+	"gonum.org/v1/gonum/graph/encoding/dot"
+	"gonum.org/v1/gonum/graph/simple"
+)
+
+var decodeTests = []struct {
+	name    string
+	json    string
+	roots   map[uint64]bool
+	wantDOT string
+	wantErr error
+}{
+	{
+		name: "starwars",
+		json: starwars,
+		roots: map[uint64]bool{
+			0xa3cff1a4c3ef3bb6: true,
+			0xb39aa14d66aedad5: true,
+		},
+		wantDOT: `digraph {
+  // Node definitions.
+  0x8a10d5a2611fd03f [name="Richard Marquand"];
+  0xa3cff1a4c3ef3bb6 [
+    name="Star Wars: Episode V - The Empire Strikes Back"
+    release_date=1980-05-21T00:00:00Z
+    revenue=534000000
+    running_time=124
+  ];
+  0xb39aa14d66aedad5 [
+    name="Star Wars: Episode VI - Return of the Jedi"
+    release_date=1983-05-25T00:00:00Z
+    revenue=572000000
+    running_time=131
+  ];
+  0x0312de17a7ee89f9 [name="Luke Skywalker"];
+  0x3da8d1dcab1bb381 [name="Han Solo"];
+  0x4a7d0b5fe91e78a4 [name="Irvin Kernshner"];
+  0x718337b9dcbaa7d9 [name="Princess Leia"];
+
+  // Edge definitions.
+  0xa3cff1a4c3ef3bb6 -> 0x0312de17a7ee89f9 [label=starring];
+  0xa3cff1a4c3ef3bb6 -> 0x3da8d1dcab1bb381 [label=starring];
+  0xa3cff1a4c3ef3bb6 -> 0x4a7d0b5fe91e78a4 [label=director];
+  0xa3cff1a4c3ef3bb6 -> 0x718337b9dcbaa7d9 [label=starring];
+  0xb39aa14d66aedad5 -> 0x8a10d5a2611fd03f [label=director];
+  0xb39aa14d66aedad5 -> 0x0312de17a7ee89f9 [label=starring];
+  0xb39aa14d66aedad5 -> 0x3da8d1dcab1bb381 [label=starring];
+  0xb39aa14d66aedad5 -> 0x718337b9dcbaa7d9 [label=starring];
+}`,
+	},
+	{
+		name: "tutorial",
+		json: dgraphTutorial,
+		roots: map[uint64]bool{
+			0xfd90205a458151f:  true,
+			0x52a80955d40ec819: true,
+		},
+		wantDOT: `digraph {
+  // Node definitions.
+  0x892a6da7ee1fbdec [
+    age=55
+    name=Sarah
+  ];
+  0x99b74c1b5ab100ec [
+    age=35
+    name=Artyom
+  ];
+  0xb9e12a67e34d6acc [
+    age=19
+    name=Catalina
+  ];
+  0xbf104824c777525d [name=Perro];
+  0xf590a923ea1fccaa [name=Goldie];
+  0xf92d7dbe272d680b [name="Hyung Sin"];
+  0x0fd90205a458151f [
+    age=39
+    name=Michael
+  ];
+  0x37734fcf0a6fcc69 [name="Rammy the sheep"];
+  0x52a80955d40ec819 [
+    age=35
+    name=Amit
+  ];
+  0x5e9ad1cd9466228c [
+    age=24
+    name="Sang Hyun"
+  ];
+
+  // Edge definitions.
+  0xb9e12a67e34d6acc -> 0xbf104824c777525d [label=owns_pet];
+  0xb9e12a67e34d6acc -> 0x5e9ad1cd9466228c [label=friend];
+  0xf92d7dbe272d680b -> 0x5e9ad1cd9466228c [label=friend];
+  0x0fd90205a458151f -> 0x892a6da7ee1fbdec [label=friend];
+  0x0fd90205a458151f -> 0x99b74c1b5ab100ec [label=friend];
+  0x0fd90205a458151f -> 0xb9e12a67e34d6acc [label=friend];
+  0x0fd90205a458151f -> 0x37734fcf0a6fcc69 [label=owns_pet];
+  0x0fd90205a458151f -> 0x52a80955d40ec819 [label=friend];
+  0x0fd90205a458151f -> 0x5e9ad1cd9466228c [label=friend];
+  0x52a80955d40ec819 -> 0x99b74c1b5ab100ec [label=friend];
+  0x52a80955d40ec819 -> 0x0fd90205a458151f [label=friend];
+  0x52a80955d40ec819 -> 0x5e9ad1cd9466228c [label=friend];
+  0x5e9ad1cd9466228c -> 0xb9e12a67e34d6acc [label=friend];
+  0x5e9ad1cd9466228c -> 0xf590a923ea1fccaa [label=owns_pet];
+  0x5e9ad1cd9466228c -> 0xf92d7dbe272d680b [label=friend];
+  0x5e9ad1cd9466228c -> 0x52a80955d40ec819 [label=friend];
+}`,
+	},
+	{
+		name:    "tutorial missing IDs",
+		json:    dgraphTutorialMissingIDs,
+		wantErr: errors.New("graphql: no UID for node"), // Incomplete error string.
+	},
+}
+
+func TestDecode(t *testing.T) {
+	for _, test := range decodeTests {
+		dst := newDirectedGraph()
+		err := Unmarshal([]byte(test.json), "_uid_", dst)
+		if test.wantErr == nil && err != nil {
+			t.Errorf("failed to unmarshal GraphQL JSON graph for %q: %v", test.name, err)
+		} else if test.wantErr != nil {
+			if err == nil {
+				t.Errorf("expected error for %q: got:%v want:%v", test.name, err, test.wantErr)
+			}
+			continue
+		}
+		b, err := dot.Marshal(dst, "", "", "  ", false)
+		if err != nil {
+			t.Fatalf("failed to DOT marshal graph %q: %v", test.name, err)
+		}
+		gotDOT := string(b)
+		if gotDOT != test.wantDOT {
+			t.Errorf("unexpected DOT encoding for %q:\ngot:\n%s\nwant:\n%s", test.name, gotDOT, test.wantDOT)
+		}
+	}
+}
+
+type directedGraph struct {
+	*simple.DirectedGraph
+}
+
+func newDirectedGraph() *directedGraph {
+	return &directedGraph{DirectedGraph: simple.NewDirectedGraph(0, 0)}
+}
+
+func (g *directedGraph) NewNode() graph.Node {
+	return &node{attributes: make(attributes)}
+}
+
+func (g *directedGraph) NewEdge(from, to graph.Node) graph.Edge {
+	if e := g.Edge(from, to); e != nil {
+		return e
+	}
+	e := &edge{Edge: simple.Edge{F: from, T: to}}
+	g.SetEdge(e)
+	return e
+}
+
+type node struct {
+	id uint64
+	attributes
+}
+
+func (n *node) ID() int64     { return int64(n.id) }
+func (n *node) DOTID() string { return fmt.Sprintf("0x%016x", uint64(n.id)) }
+
+func (n *node) SetIDFromString(uid string) error {
+	if !strings.HasPrefix(uid, "0x") {
+		return fmt.Errorf("uid is not hex value: %q", uid)
+	}
+	var err error
+	n.id, err = strconv.ParseUint(uid[2:], 16, 64)
+	return err
+}
+
+type edge struct {
+	simple.Edge
+	label string
+}
+
+func (e *edge) SetLabel(l string) {
+	e.label = l
+}
+
+func (e *edge) Attributes() []encoding.Attribute {
+	return []encoding.Attribute{{"label", e.label}}
+}
+
+type attributes map[string]encoding.Attribute
+
+func (a attributes) SetAttribute(attr encoding.Attribute) error {
+	a[attr.Key] = attr
+	return nil
+}
+
+func (a attributes) Attributes() []encoding.Attribute {
+	keys := make([]string, 0, len(a))
+	for k := range a {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	attr := make([]encoding.Attribute, 0, len(keys))
+	for _, k := range keys {
+		v := a[k]
+		if strings.Contains(v.Value, " ") {
+			v.Value = `"` + v.Value + `"`
+		}
+		attr = append(attr, v)
+	}
+	return attr
+}

graph/encoding/graphql/graphql.go

@@ -0,0 +1,7 @@
+// Copyright ©2017 The gonum Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package graphql implements JSON marshaling and unmarshaling of graph as
+// used by GraphQL
+package graphql // import "gonum.org/v1/gonum/graph/encoding/graphql"