graph.go

package xgraph

import "fmt"

// Graph is an execution graph
type Graph struct {
	generators []JobGenerator
	jobs       map[string]Job
}

// New creates a new Graph
func New() *Graph {
	return &Graph{
		generators: []JobGenerator{},
		jobs:       make(map[string]Job),
	}
}

// AddJob adds a Job to the Graph
func (g *Graph) AddJob(job Job) *Graph {
	g.jobs[job.Name()] = job
	return g
}

// AddGenerator adds a JobGenerator to the Graph
func (g *Graph) AddGenerator(generator JobGenerator) *Graph {
	g.generators = append(g.generators, generator)
	return g
}

func (g *Graph) generateJob(name string) (Job, error) {
	for _, gen := range g.generators {
		j, err := gen(name)
		if err != nil {
			return nil, err
		}
		if j != nil {
			g.AddJob(j)
			return j, nil
		}
	}
	return nil, nil
}

// JobNotFoundError is an error type indicating that a job was not found.
// The underlying string is the name of the job.
type JobNotFoundError string

func (err JobNotFoundError) Error() string {
	return fmt.Sprintf("job not found: %q", string(err))
}

func (err JobNotFoundError) String() string {
	return err.Error()
}

// GetJob searches the Graph for a Job with the specified name.
func (g *Graph) GetJob(name string) (j Job, err error) {
	j = g.jobs[name]
	if j == nil {
		j, err = g.generateJob(name)
		if err != nil {
			return
		}
	}
	if j == nil {
		err = JobNotFoundError(name)
	}
	return
}

// JobGenerator is a type which generates Jobs dynamically.
// If a job with the given name should not be generated by this generator, a nil Job should be returned.
// Any errors will be propogated.
type JobGenerator func(name string) (Job, error)