use std::iter;

use abstractgraph;
use abstractgraph::DirectedGraph;
use abstractgraph::OutboundEdge;

// Trivial graph
//
//      A
//
// The simplest possible graph: one node, no edges
//
#[derive(Debug)]
pub struct Trivial();

#[derive(PartialEq, Eq, Hash, Clone, Debug)]
pub enum NoEdge {}

impl OutboundEdge<()> for NoEdge {
    fn destination(&self) -> () {
        unreachable!()
    }
}

impl DirectedGraph for Trivial {
    type Node = ();
    type Edge = NoEdge;
    type Edges = iter::Empty<Self::Edge>;

    fn edges_from(&self, _: &Self::Node) -> Self::Edges {
        iter::empty()
    }
}