Tiny DSL for describing flows

gistfile1.scala

package graphflow

import org.specs.Specification
class Graph {
    val nodes:scala.collection.mutable.Set[flow.Node] =
        new scala.collection.mutable.HashSet[flow.Node]()
    val edges:scala.collection.mutable.Set[flow.Connection] =
        new scala.collection.mutable.HashSet[flow.Connection]()

    override def toString = "nodes:"+nodes.toString + "\nedges:"+edges.toString
}

object flow {

    private val IN = "_in_"
    private val OUT = "_out_"

    case class Connection(from:Output, to:Input)(implicit g:Graph) {
        if (!g.edges.contains(this)) {
            g.edges.add(this)
        }
        override def toString = from.toString + "-->" + to.toString
    }

    case class Input(node:Node, endpoint:Endpoint) {
        override def toString = endpoint+"-|"+node
    }

    case class Output(node:Node, endpoint:Endpoint) {
        def -->(input:Input)(implicit g:Graph) = Connection(this, input)
        def -->(node:Node)(implicit g:Graph) = Connection(this, Input(node, IN))
        override def toString = node+"|-"+endpoint
    }

    case class Node(name:String) {
        def |-(endpoint:Endpoint):Output = Output(this, endpoint)
        def -->(node:Node)(implicit g:Graph) = Connection(Output(this, OUT), Input(node, IN))
        def -->(input:Input)(implicit g:Graph) = Connection(Output(this, OUT), input)
        override def toString = name
    }

    case class Endpoint(name:String) {
        def -|(node:Node) = Input(node, this)
        override def toString = name
    }

    implicit def string2Endpoint(s:String):Endpoint = Endpoint(s)
    implicit def string2Node(s:String)(implicit g:Graph):Node = {
        val n = Node(s)
        if (!g.nodes.contains(n)) {
            g.nodes.add(n)
        }
        return n
    }

}

import flow._

object FlowSpec extends Specification {
    "a->b" should {
        implicit val g = new Graph
        val a = Node("a")
        val b = Node("b")
        val x = (a|-"x") --> ("y"-|b)

        val x_1 = "a"-->"b"
        val x_2 = ("a")-->("b")

        val x_3 = "a"-->("y"-|b)

        val x_4 = ("a"|-"x") --> ("y"-|"b")

        val x_5 = ("a"|-"x") --> "b"

        println(g)
    }
}