terraform/internal/dag/marshal.go

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package dag
import (
"fmt"
"reflect"
"sort"
"strconv"
)
// the marshal* structs are for serialization of the graph data.
type marshalGraph struct {
// Type is always "Graph", for identification as a top level object in the
// JSON stream.
Type string
// Each marshal structure requires a unique ID so that it can be referenced
// by other structures.
ID string `json:",omitempty"`
// Human readable name for this graph.
Name string `json:",omitempty"`
// Arbitrary attributes that can be added to the output.
Attrs map[string]string `json:",omitempty"`
// List of graph vertices, sorted by ID.
Vertices []*marshalVertex `json:",omitempty"`
// List of edges, sorted by Source ID.
Edges []*marshalEdge `json:",omitempty"`
// Any number of subgraphs. A subgraph itself is considered a vertex, and
// may be referenced by either end of an edge.
Subgraphs []*marshalGraph `json:",omitempty"`
// Any lists of vertices that are included in cycles.
Cycles [][]*marshalVertex `json:",omitempty"`
}
func (g *marshalGraph) vertexByID(id string) *marshalVertex {
for _, v := range g.Vertices {
if id == v.ID {
return v
}
}
return nil
}
type marshalVertex struct {
// Unique ID, used to reference this vertex from other structures.
ID string
// Human readable name
Name string `json:",omitempty"`
Attrs map[string]string `json:",omitempty"`
// This is to help transition from the old Dot interfaces. We record if the
// node was a GraphNodeDotter here, so we can call it to get attributes.
graphNodeDotter GraphNodeDotter
}
func newMarshalVertex(v Vertex) *marshalVertex {
dn, ok := v.(GraphNodeDotter)
if !ok {
dn = nil
}
// the name will be quoted again later, so we need to ensure it's properly
// escaped without quotes.
name := strconv.Quote(VertexName(v))
name = name[1 : len(name)-1]
return &marshalVertex{
ID: marshalVertexID(v),
Name: name,
Attrs: make(map[string]string),
graphNodeDotter: dn,
}
}
// vertices is a sort.Interface implementation for sorting vertices by ID
type vertices []*marshalVertex
func (v vertices) Less(i, j int) bool { return v[i].Name < v[j].Name }
func (v vertices) Len() int { return len(v) }
func (v vertices) Swap(i, j int) { v[i], v[j] = v[j], v[i] }
type marshalEdge struct {
// Human readable name
Name string
// Source and Target Vertices by ID
Source string
Target string
Attrs map[string]string `json:",omitempty"`
}
func newMarshalEdge(e Edge) *marshalEdge {
return &marshalEdge{
Name: fmt.Sprintf("%s|%s", VertexName(e.Source()), VertexName(e.Target())),
Source: marshalVertexID(e.Source()),
Target: marshalVertexID(e.Target()),
Attrs: make(map[string]string),
}
}
// edges is a sort.Interface implementation for sorting edges by Source ID
type edges []*marshalEdge
func (e edges) Less(i, j int) bool { return e[i].Name < e[j].Name }
func (e edges) Len() int { return len(e) }
func (e edges) Swap(i, j int) { e[i], e[j] = e[j], e[i] }
// build a marshalGraph structure from a *Graph
func newMarshalGraph(name string, g *Graph) *marshalGraph {
mg := &marshalGraph{
Type: "Graph",
Name: name,
Attrs: make(map[string]string),
}
for _, v := range g.Vertices() {
id := marshalVertexID(v)
if sg, ok := marshalSubgrapher(v); ok {
smg := newMarshalGraph(VertexName(v), sg)
smg.ID = id
mg.Subgraphs = append(mg.Subgraphs, smg)
}
mv := newMarshalVertex(v)
mg.Vertices = append(mg.Vertices, mv)
}
sort.Sort(vertices(mg.Vertices))
for _, e := range g.Edges() {
mg.Edges = append(mg.Edges, newMarshalEdge(e))
}
sort.Sort(edges(mg.Edges))
for _, c := range (&AcyclicGraph{*g}).Cycles() {
var cycle []*marshalVertex
for _, v := range c {
mv := newMarshalVertex(v)
cycle = append(cycle, mv)
}
mg.Cycles = append(mg.Cycles, cycle)
}
return mg
}
// Attempt to return a unique ID for any vertex.
func marshalVertexID(v Vertex) string {
val := reflect.ValueOf(v)
switch val.Kind() {
case reflect.Chan, reflect.Func, reflect.Map, reflect.Ptr, reflect.Slice, reflect.UnsafePointer:
return strconv.Itoa(int(val.Pointer()))
case reflect.Interface:
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// A vertex shouldn't contain another layer of interface, but handle
// this just in case.
return fmt.Sprintf("%#v", val.Interface())
}
if v, ok := v.(Hashable); ok {
h := v.Hashcode()
if h, ok := h.(string); ok {
return h
}
}
// fallback to a name, which we hope is unique.
return VertexName(v)
// we could try harder by attempting to read the arbitrary value from the
// interface, but we shouldn't get here from terraform right now.
}
// check for a Subgrapher, and return the underlying *Graph.
func marshalSubgrapher(v Vertex) (*Graph, bool) {
sg, ok := v.(Subgrapher)
if !ok {
return nil, false
}
switch g := sg.Subgraph().DirectedGraph().(type) {
case *Graph:
return g, true
case *AcyclicGraph:
return &g.Graph, true
}
return nil, false
}