forked from hashicorp/terraform
/
dependency.go
46 lines (38 loc) · 975 Bytes
/
dependency.go
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package depgraph
import (
"fmt"
"github.com/hashicorp/terraform/digraph"
)
// Dependency is used to create a directed edge between two nouns.
// One noun may depend on another and provide version constraints
// that cannot be violated
type Dependency struct {
Name string
Meta interface{}
Constraints []Constraint
Source *Noun
Target *Noun
}
// Constraint is used by dependencies to allow arbitrary constraints
// between nouns
type Constraint interface {
Satisfied(head, tail *Noun) (bool, error)
}
// Head returns the source, or dependent noun
func (d *Dependency) Head() digraph.Node {
return d.Source
}
// Tail returns the target, or depended upon noun
func (d *Dependency) Tail() digraph.Node {
return d.Target
}
func (d *Dependency) GoString() string {
return fmt.Sprintf(
"*Dependency{Name: %s, Source: %s, Target: %s}",
d.Name,
d.Source.Name,
d.Target.Name)
}
func (d *Dependency) String() string {
return d.Name
}