## `rust_bounded_graph`
_A thin newtype wrapper for [`petgraph`](https://github.com/petgraph/petgraph) to assist in the creation of graphs with restrictions on their edges_
This crate is a simple wrapper around petgraph's Graph type. It exists to make it simpler to enforce restrictions at the time of edge creation, to ensure that the graph is never in a state with an "invalid" edge between two nodes.
---
In order to do so, your Node type should implement the following trait:
```rust
pub trait BoundedNode<Ix: IndexType = DefaultIx> {
fn can_add_edge(&self, existing_edges: usize, dir: Direction) -> bool;
}
```
Alternatively, for the common and simple situation of a Node with an associated limit on incoming and outgoing edges, one can alternatively implement the following trait:
```rust
pub trait EdgeNumberBoundedNode<Ix: IndexType = DefaultIx> {
fn max_incoming_edges(&self) -> Ix;
fn max_outgoing_edges(&self) -> Ix;
}
```
---
Most methods and traits of [Graph](https://docs.rs/petgraph/latest/petgraph/graph/struct.Graph.html) have been added directly to the BoundedGraph struct provided by this crate, although updating and adding edges is now a failable operation. You may obtain a Graph from a bounded Graph by calling `as_graph()`.
Currently, the following methods are known to be unimplemented:
* update_edge on the Build trait can panic if the edge is new, and invalid.
* `raw_nodes()`, `raw_edges()`, `first_edge()` and `next_edge()` are not implemented on BoundedGraph, as they are low level functions and I currently do not need them. Please file an issue if this is a problem for you.
* `reverse()` is skipped for the first version as its especially likely to break constraits... and I don't need it yet.
* `Arbitrary` trait is unlikely to be implemented at this time.
Please let me know if anything else is missing or incorrect!