initial commit

.gitignore

@@ -0,0 +1,2 @@
+slacktime
+*.gv

go.mod

@@ -0,0 +1,5 @@
+module scm.dairydemon.net/filifa/slacktime
+
+go 1.19
+
+require gonum.org/v1/gonum v0.15.0 // indirect

go.sum

@@ -0,0 +1,2 @@
+gonum.org/v1/gonum v0.15.0 h1:2lYxjRbTYyxkJxlhC+LvJIx3SsANPdRybu1tGj9/OrQ=
+gonum.org/v1/gonum v0.15.0/go.mod h1:xzZVBJBtS+Mz4q0Yl2LJTk+OxOg4jiXZ7qBoM0uISGo=

main.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+
+	"gonum.org/v1/gonum/graph/encoding/dot"
+)
+
+func main() {
+	f := flag.String("f", "", "graphviz file")
+	flag.Parse()
+
+	if *f == "" {
+		log.Fatal("-f is required")
+	}
+
+	contents, err := os.ReadFile(*f)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	g := newProjectNetwork()
+	err = dot.Unmarshal(contents, g)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	err = g.calculateTimes()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	data, err := dot.Marshal(g, "", "", "\t")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(string(data))
+}

projectnetwork.go

@@ -0,0 +1,124 @@
+package main
+
+import (
+	"errors"
+	"math"
+	"strconv"
+
+	"gonum.org/v1/gonum/graph"
+	"gonum.org/v1/gonum/graph/encoding"
+	"gonum.org/v1/gonum/graph/simple"
+	"gonum.org/v1/gonum/graph/topo"
+)
+
+type projectNetwork struct {
+	*simple.DirectedGraph
+}
+
+func newProjectNetwork() *projectNetwork {
+	return &projectNetwork{DirectedGraph: simple.NewDirectedGraph()}
+}
+
+func (g *projectNetwork) NewNode() graph.Node {
+	return &activity{Node: g.DirectedGraph.NewNode()}
+}
+
+func (g *projectNetwork) calculateTimes() error {
+	sorted, err := topo.Sort(g)
+	if err != nil {
+		return err
+	}
+
+	toposort := make([]*activity, len(sorted))
+	for i := range sorted {
+		toposort[i] = sorted[i].(*activity)
+	}
+
+	g.forwardPass(toposort)
+	g.backwardPass(toposort)
+
+	return nil
+}
+
+func (g *projectNetwork) forwardPass(toposort []*activity) {
+	for _, a := range toposort {
+		g.setEarlyTimes(a)
+	}
+}
+
+func (g *projectNetwork) backwardPass(toposort []*activity) {
+	n := len(toposort)
+
+	end := toposort[n-1]
+	end.lateFinish = end.earlyFinish
+	end.lateStart = end.lateFinish - end.duration
+
+	for i := n - 2; i >= 0; i-- {
+		a := toposort[i]
+		g.setLateTimes(a)
+	}
+}
+
+func (g *projectNetwork) setEarlyTimes(a *activity) {
+	es := 0.0
+	predecessors := g.To(a.ID())
+	for predecessors.Next() {
+		p := predecessors.Node().(*activity)
+		es = math.Max(es, p.earlyFinish)
+	}
+	a.earlyStart = es
+	a.earlyFinish = a.earlyStart + a.duration
+}
+
+func (g *projectNetwork) setLateTimes(a *activity) {
+	lf := math.Inf(1)
+	successors := g.From(a.ID())
+	for successors.Next() {
+		s := successors.Node().(*activity)
+		lf = math.Min(lf, s.lateStart)
+	}
+	a.lateFinish = lf
+	a.lateStart = a.lateFinish - a.duration
+	a.slack = a.lateFinish - a.earlyFinish
+}
+
+type activity struct {
+	graph.Node
+	dotID       string
+	duration    float64
+	earlyStart  float64
+	earlyFinish float64
+	lateStart   float64
+	lateFinish  float64
+	slack	float64
+}
+
+func (a *activity) Attributes() []encoding.Attribute {
+	return []encoding.Attribute{
+		{"DUR", strconv.FormatFloat(a.duration, 'g', -1, 64)},
+		{"ES", strconv.FormatFloat(a.earlyStart, 'g', -1, 64)},
+		{"EF", strconv.FormatFloat(a.earlyStart, 'g', -1, 64)},
+		{"LS", strconv.FormatFloat(a.lateStart, 'g', -1, 64)},
+		{"LF", strconv.FormatFloat(a.lateFinish, 'g', -1, 64)},
+		{"SLACK", strconv.FormatFloat(a.slack, 'g', -1, 64)},
+	}
+}
+
+func (a *activity) SetAttribute(attr encoding.Attribute) error {
+	var err error
+	switch attr.Key {
+	case "DUR":
+		a.duration, err = strconv.ParseFloat(attr.Value, 64)
+	default:
+		err = errors.New("can't set attribute " + attr.Key)
+	}
+	return err
+}
+
+func (a *activity) DOTID() string {
+	return a.dotID
+}
+
+func (a *activity) SetDOTID(id string) {
+	a.dotID = id
+}