117 lines
2.7 KiB
Go
117 lines
2.7 KiB
Go
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// Copyright 2019 Drone IO, Inc.
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// Copyright 2018 natessilva
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package dag
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// Dag is a directed acyclic graph.
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type Dag struct {
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graph map[string]*Vertex
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}
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// Vertex is a vetex in the graph.
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type Vertex struct {
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Name string
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Skip bool
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graph []string
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}
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// New creates a new directed acyclic graph (dag) that can
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// determinte if a stage has dependencies.
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func New() *Dag {
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return &Dag{
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graph: make(map[string]*Vertex),
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}
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}
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// Add establishes a dependency between two vertices in the graph.
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func (d *Dag) Add(from string, to ...string) *Vertex {
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vertex := new(Vertex)
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vertex.Name = from
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vertex.Skip = false
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vertex.graph = to
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d.graph[from] = vertex
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return vertex
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}
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// Get returns the vertex from the graph.
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func (d *Dag) Get(name string) (*Vertex, bool) {
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vertex, ok := d.graph[name]
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return vertex, ok
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}
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// Ancestors returns the acentors of the vertex.
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func (d *Dag) Ancestors(name string) []*Vertex {
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vertex := d.graph[name]
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return d.ancestors(vertex)
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}
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func (d *Dag) ancestors(parent *Vertex) []*Vertex {
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if parent == nil {
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return nil
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}
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var combined []*Vertex
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for _, name := range parent.graph {
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vertex, found := d.graph[name]
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if !found {
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continue
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}
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if !vertex.Skip {
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combined = append(combined, vertex)
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}
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combined = append(combined, d.ancestors(vertex)...)
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}
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return combined
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}
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// DetectCycles returns true if cycles are detected in the graph.
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func (d *Dag) DetectCycles() bool {
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visited := make(map[string]bool)
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recStack := make(map[string]bool)
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for vertex := range d.graph {
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if !visited[vertex] {
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if d.detectCycles(vertex, visited, recStack) {
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return true
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}
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}
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}
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return false
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}
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func (d *Dag) detectCycles(name string, visited, recStack map[string]bool) bool {
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visited[name] = true
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recStack[name] = true
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vertex, ok := d.graph[name]
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if !ok {
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return false
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}
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for _, v := range vertex.graph {
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// only check cycles on a vertex one time
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if !visited[v] {
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if d.detectCycles(v, visited, recStack) {
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return true
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}
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// if we've visited this vertex in this recursion
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// stack, then we have a cycle
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} else if recStack[v] {
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return true
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}
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}
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recStack[name] = false
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return false
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}
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