//! Generate files suitable for use with [Graphviz](http://www.graphviz.org/)
//!
//! The `render` function generates output (e.g., an `output.dot` file) for
//! use with [Graphviz](http://www.graphviz.org/) by walking a labeled
//! graph. (Graphviz can then automatically lay out the nodes and edges
//! of the graph, and also optionally render the graph as an image or
//! other [output formats](
//! http://www.graphviz.org/content/output-formats), such as SVG.)
//!
//! Rather than impose some particular graph data structure on clients,
//! this library exposes two traits that clients can implement on their
//! own structs before handing them over to the rendering function.
//!
//! Note: This library does not yet provide access to the full
//! expressiveness of the [DOT language](
//! http://www.graphviz.org/doc/info/lang.html). For example, there are
//! many [attributes](http://www.graphviz.org/content/attrs) related to
//! providing layout hints (e.g., left-to-right versus top-down, which
//! algorithm to use, etc). The current intention of this library is to
//! emit a human-readable .dot file with very regular structure suitable
//! for easy post-processing.
//!
//! # Examples
//!
//! The first example uses a very simple graph representation: a list of
//! pairs of ints, representing the edges (the node set is implicit).
//! Each node label is derived directly from the int representing the node,
//! while the edge labels are all empty strings.
//!
//! This example also illustrates how to use `Cow<[T]>` to return
//! an owned vector or a borrowed slice as appropriate: we construct the
//! node vector from scratch, but borrow the edge list (rather than
//! constructing a copy of all the edges from scratch).
//!
//! The output from this example renders five nodes, with the first four
//! forming a diamond-shaped acyclic graph and then pointing to the fifth
//! which is cyclic.
//!
//! ```rust
//! #![feature(rustc_private)]
//!
//! use std::io::Write;
//! use graphviz as dot;
//!
//! type Nd = isize;
//! type Ed = (isize,isize);
//! struct Edges(Vec<Ed>);
//!
//! pub fn render_to<W: Write>(output: &mut W) {
//! let edges = Edges(vec![(0,1), (0,2), (1,3), (2,3), (3,4), (4,4)]);
//! dot::render(&edges, output).unwrap()
//! }
//!
//! impl<'a> dot::Labeller<'a> for Edges {
//! type Node = Nd;
//! type Edge = Ed;
//! fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example1").unwrap() }
//!
//! fn node_id(&'a self, n: &Nd) -> dot::Id<'a> {
//! dot::Id::new(format!("N{}", *n)).unwrap()
//! }
//! }
//!
//! impl<'a> dot::GraphWalk<'a> for Edges {
//! type Node = Nd;
//! type Edge = Ed;
//! fn nodes(&self) -> dot::Nodes<'a,Nd> {
//! // (assumes that |N| \approxeq |E|)
//! let &Edges(ref v) = self;
//! let mut nodes = Vec::with_capacity(v.len());
//! for &(s,t) in v {
//! nodes.push(s); nodes.push(t);
//! }
//! nodes.sort();
//! nodes.dedup();
//! nodes.into()
//! }
//!
//! fn edges(&'a self) -> dot::Edges<'a,Ed> {
//! let &Edges(ref edges) = self;
//! (&edges[..]).into()
//! }
//!
//! fn source(&self, e: &Ed) -> Nd { let &(s,_) = e; s }
//!
//! fn target(&self, e: &Ed) -> Nd { let &(_,t) = e; t }
//! }
//!
//! # pub fn main() { render_to(&mut Vec::new()) }
//! ```
//!
//! ```no_run
//! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
//! pub fn main() {
//! use std::fs::File;
//! let mut f = File::create("example1.dot").unwrap();
//! render_to(&mut f)
//! }
//! ```
//!
//! Output from first example (in `example1.dot`):
//!
//! ```dot
//! digraph example1 {
//! N0[label="N0"];
//! N1[label="N1"];
//! N2[label="N2"];
//! N3[label="N3"];
//! N4[label="N4"];
//! N0 -> N1[label=""];
//! N0 -> N2[label=""];
//! N1 -> N3[label=""];
//! N2 -> N3[label=""];
//! N3 -> N4[label=""];
//! N4 -> N4[label=""];
//! }
//! ```
//!
//! The second example illustrates using `node_label` and `edge_label` to
//! add labels to the nodes and edges in the rendered graph. The graph
//! here carries both `nodes` (the label text to use for rendering a
//! particular node), and `edges` (again a list of `(source,target)`
//! indices).
//!
//! This example also illustrates how to use a type (in this case the edge
//! type) that shares substructure with the graph: the edge type here is a
//! direct reference to the `(source,target)` pair stored in the graph's
//! internal vector (rather than passing around a copy of the pair
//! itself). Note that this implies that `fn edges(&'a self)` must
//! construct a fresh `Vec<&'a (usize,usize)>` from the `Vec<(usize,usize)>`
//! edges stored in `self`.
//!
//! Since both the set of nodes and the set of edges are always
//! constructed from scratch via iterators, we use the `collect()` method
//! from the `Iterator` trait to collect the nodes and edges into freshly
//! constructed growable `Vec` values (rather than using `Cow` as in the
//! first example above).
//!
//! The output from this example renders four nodes that make up the
//! Hasse-diagram for the subsets of the set `{x, y}`. Each edge is
//! labeled with the ⊆ character (specified using the HTML character
//! entity `&sube`).
//!
//! ```rust
//! #![feature(rustc_private)]
//!
//! use std::io::Write;
//! use graphviz as dot;
//!
//! type Nd = usize;
//! type Ed<'a> = &'a (usize, usize);
//! struct Graph { nodes: Vec<&'static str>, edges: Vec<(usize,usize)> }
//!
//! pub fn render_to<W: Write>(output: &mut W) {
//! let nodes = vec!["{x,y}","{x}","{y}","{}"];
//! let edges = vec![(0,1), (0,2), (1,3), (2,3)];
//! let graph = Graph { nodes: nodes, edges: edges };
//!
//! dot::render(&graph, output).unwrap()
//! }
//!
//! impl<'a> dot::Labeller<'a> for Graph {
//! type Node = Nd;
//! type Edge = Ed<'a>;
//! fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example2").unwrap() }
//! fn node_id(&'a self, n: &Nd) -> dot::Id<'a> {
//! dot::Id::new(format!("N{}", n)).unwrap()
//! }
//! fn node_label<'b>(&'b self, n: &Nd) -> dot::LabelText<'b> {
//! dot::LabelText::LabelStr(self.nodes[*n].into())
//! }
//! fn edge_label<'b>(&'b self, _: &Ed) -> dot::LabelText<'b> {
//! dot::LabelText::LabelStr("⊆".into())
//! }
//! }
//!
//! impl<'a> dot::GraphWalk<'a> for Graph {
//! type Node = Nd;
//! type Edge = Ed<'a>;
//! fn nodes(&self) -> dot::Nodes<'a,Nd> { (0..self.nodes.len()).collect() }
//! fn edges(&'a self) -> dot::Edges<'a,Ed<'a>> { self.edges.iter().collect() }
//! fn source(&self, e: &Ed) -> Nd { let & &(s,_) = e; s }
//! fn target(&self, e: &Ed) -> Nd { let & &(_,t) = e; t }
//! }
//!
//! # pub fn main() { render_to(&mut Vec::new()) }
//! ```
//!
//! ```no_run
//! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
//! pub fn main() {
//! use std::fs::File;
//! let mut f = File::create("example2.dot").unwrap();
//! render_to(&mut f)
//! }
//! ```
//!
//! The third example is similar to the second, except now each node and
//! edge now carries a reference to the string label for each node as well
//! as that node's index. (This is another illustration of how to share
//! structure with the graph itself, and why one might want to do so.)
//!
//! The output from this example is the same as the second example: the
//! Hasse-diagram for the subsets of the set `{x, y}`.
//!
//! ```rust
//! #![feature(rustc_private)]
//!
//! use std::io::Write;
//! use graphviz as dot;
//!
//! type Nd<'a> = (usize, &'a str);
//! type Ed<'a> = (Nd<'a>, Nd<'a>);
//! struct Graph { nodes: Vec<&'static str>, edges: Vec<(usize,usize)> }
//!
//! pub fn render_to<W: Write>(output: &mut W) {
//! let nodes = vec!["{x,y}","{x}","{y}","{}"];
//! let edges = vec![(0,1), (0,2), (1,3), (2,3)];
//! let graph = Graph { nodes: nodes, edges: edges };
//!
//! dot::render(&graph, output).unwrap()
//! }
//!
//! impl<'a> dot::Labeller<'a> for Graph {
//! type Node = Nd<'a>;
//! type Edge = Ed<'a>;
//! fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example3").unwrap() }
//! fn node_id(&'a self, n: &Nd<'a>) -> dot::Id<'a> {
//! dot::Id::new(format!("N{}", n.0)).unwrap()
//! }
//! fn node_label<'b>(&'b self, n: &Nd<'b>) -> dot::LabelText<'b> {
//! let &(i, _) = n;
//! dot::LabelText::LabelStr(self.nodes[i].into())
//! }
//! fn edge_label<'b>(&'b self, _: &Ed<'b>) -> dot::LabelText<'b> {
//! dot::LabelText::LabelStr("⊆".into())
//! }
//! }
//!
//! impl<'a> dot::GraphWalk<'a> for Graph {
//! type Node = Nd<'a>;
//! type Edge = Ed<'a>;
//! fn nodes(&'a self) -> dot::Nodes<'a,Nd<'a>> {
//! self.nodes.iter().map(|s| &s[..]).enumerate().collect()
//! }
//! fn edges(&'a self) -> dot::Edges<'a,Ed<'a>> {
//! self.edges.iter()
//! .map(|&(i,j)|((i, &self.nodes[i][..]),
//! (j, &self.nodes[j][..])))
//! .collect()
//! }
//! fn source(&self, e: &Ed<'a>) -> Nd<'a> { let &(s,_) = e; s }
//! fn target(&self, e: &Ed<'a>) -> Nd<'a> { let &(_,t) = e; t }
//! }
//!
//! # pub fn main() { render_to(&mut Vec::new()) }
//! ```
//!
//! ```no_run
//! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
//! pub fn main() {
//! use std::fs::File;
//! let mut f = File::create("example3.dot").unwrap();
//! render_to(&mut f)
//! }
//! ```
//!
//! # References
//!
//! * [Graphviz](http://www.graphviz.org/)
//!
//! * [DOT language](http://www.graphviz.org/doc/info/lang.html)
use *;
use Cow;
use *;
use io;
/// The text for a graphviz label on a node or edge.
/// The style for a node or edge.
/// See <http://www.graphviz.org/doc/info/attrs.html#k:style> for descriptions.
/// Note that some of these are not valid for edges.
// There is a tension in the design of the labelling API.
//
// For example, I considered making a `Labeller<T>` trait that
// provides labels for `T`, and then making the graph type `G`
// implement `Labeller<Node>` and `Labeller<Edge>`. However, this is
// not possible without functional dependencies. (One could work
// around that, but I did not explore that avenue heavily.)
//
// Another approach that I actually used for a while was to make a
// `Label<Context>` trait that is implemented by the client-specific
// Node and Edge types (as well as an implementation on Graph itself
// for the overall name for the graph). The main disadvantage of this
// second approach (compared to having the `G` type parameter
// implement a Labelling service) that I have encountered is that it
// makes it impossible to use types outside of the current crate
// directly as Nodes/Edges; you need to wrap them in newtype'd
// structs. See e.g., the `No` and `Ed` structs in the examples. (In
// practice clients using a graph in some other crate would need to
// provide some sort of adapter shim over the graph anyway to
// interface with this library).
//
// Another approach would be to make a single `Labeller<N,E>` trait
// that provides three methods (graph_label, node_label, edge_label),
// and then make `G` implement `Labeller<N,E>`. At first this did not
// appeal to me, since I had thought I would need separate methods on
// each data variant for dot-internal identifiers versus user-visible
// labels. However, the identifier/label distinction only arises for
// nodes; graphs themselves only have identifiers, and edges only have
// labels.
//
// So in the end I decided to use the third approach described above.
/// `Id` is a Graphviz `ID`.
/// Each instance of a type that implements `Label<C>` maps to a
/// unique identifier with respect to `C`, which is used to identify
/// it in the generated .dot file. They can also provide more
/// elaborate (and non-unique) label text that is used in the graphviz
/// rendered output.
/// The graph instance is responsible for providing the DOT compatible
/// identifiers for the nodes and (optionally) rendered labels for the nodes and
/// edges, as well as an identifier for the graph itself.
/// Escape tags in such a way that it is suitable for inclusion in a
/// Graphviz HTML label.
pub type Nodes<'a,N> = ;
pub type Edges<'a,E> = ;
// (The type parameters in GraphWalk should be associated items,
// when/if Rust supports such.)
/// GraphWalk is an abstraction over a directed graph = (nodes,edges)
/// made up of node handles `N` and edge handles `E`, where each `E`
/// can be mapped to its source and target nodes.
///
/// The lifetime parameter `'a` is exposed in this trait (rather than
/// introduced as a generic parameter on each method declaration) so
/// that a client impl can choose `N` and `E` that have substructure
/// that is bound by the self lifetime `'a`.
///
/// The `nodes` and `edges` method each return instantiations of
/// `Cow<[T]>` to leave implementors the freedom to create
/// entirely new vectors or to pass back slices into internally owned
/// vectors.
/// Returns vec holding all the default render options.
/// Renders directed graph `g` into the writer `w` in DOT syntax.
/// (Simple wrapper around `render_opts` that passes a default set of options.)
/// Renders directed graph `g` into the writer `w` in DOT syntax.
/// (Main entry point for the library.)