137 lines
2.9 KiB
Go
137 lines
2.9 KiB
Go
package dag
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import (
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"bytes"
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"fmt"
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"sort"
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"sync"
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)
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// Graph is used to represent a dependency graph.
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type Graph struct {
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vertices []Vertex
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edges []Edge
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downEdges map[Vertex]*set
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upEdges map[Vertex]*set
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once sync.Once
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}
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// Vertex of the graph.
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type Vertex interface{}
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// NamedVertex is an optional interface that can be implemented by Vertex
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// to give it a human-friendly name that is used for outputting the graph.
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type NamedVertex interface {
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Vertex
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Name() string
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}
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// Vertices returns the list of all the vertices in the graph.
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func (g *Graph) Vertices() []Vertex {
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return g.vertices
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}
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// Edges returns the list of all the edges in the graph.
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func (g *Graph) Edges() []Edge {
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return g.edges
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}
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// Add adds a vertex to the graph. This is safe to call multiple time with
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// the same Vertex.
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func (g *Graph) Add(v Vertex) Vertex {
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g.once.Do(g.init)
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g.vertices = append(g.vertices, v)
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return v
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}
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// Connect adds an edge with the given source and target. This is safe to
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// call multiple times with the same value. Note that the same value is
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// verified through pointer equality of the vertices, not through the
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// value of the edge itself.
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func (g *Graph) Connect(edge Edge) {
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g.once.Do(g.init)
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source := edge.Source()
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target := edge.Target()
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// Do we have this already? If so, don't add it again.
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if s, ok := g.downEdges[source]; ok && s.Include(target) {
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return
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}
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// TODO: add all edges
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g.edges = append(g.edges, edge)
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// Add the down edge
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s, ok := g.downEdges[source]
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if !ok {
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s = new(set)
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g.downEdges[source] = s
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}
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s.Add(target)
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// Add the up edge
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s, ok = g.upEdges[target]
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if !ok {
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s = new(set)
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g.upEdges[target] = s
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}
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s.Add(source)
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}
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// String outputs some human-friendly output for the graph structure.
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func (g *Graph) String() string {
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var buf bytes.Buffer
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// Build the list of node names and a mapping so that we can more
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// easily alphabetize the output to remain deterministic.
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names := make([]string, 0, len(g.vertices))
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mapping := make(map[string]Vertex, len(g.vertices))
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for _, v := range g.vertices {
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name := vertName(v)
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names = append(names, name)
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mapping[name] = v
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}
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sort.Strings(names)
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// Write each node in order...
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for _, name := range names {
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v := mapping[name]
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targets := g.downEdges[v]
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buf.WriteString(fmt.Sprintf("%s\n", name))
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// Alphabetize dependencies
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deps := make([]string, 0, targets.Len())
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for _, target := range targets.List() {
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deps = append(deps, vertName(target))
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}
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sort.Strings(deps)
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// Write dependencies
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for _, d := range deps {
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buf.WriteString(fmt.Sprintf(" %s\n", d))
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}
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}
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return buf.String()
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}
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func (g *Graph) init() {
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g.vertices = make([]Vertex, 0, 5)
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g.edges = make([]Edge, 0, 2)
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g.downEdges = make(map[Vertex]*set)
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g.upEdges = make(map[Vertex]*set)
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}
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func vertName(raw Vertex) string {
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switch v := raw.(type) {
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case NamedVertex:
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return v.Name()
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case fmt.Stringer:
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return fmt.Sprintf("%s", v)
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default:
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return fmt.Sprintf("%v", v)
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}
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}
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