//! Simple graphviz dot file format output.

use std::fmt::{self, Display, Write};

use crate::visit::{
    Data, EdgeRef, GraphBase, GraphProp, GraphRef, IntoEdgeReferences, IntoNodeReferences,
    NodeIndexable, NodeRef,
};

/// `Dot` implements output to graphviz .dot format for a graph.
///
/// Formatting and options are rather simple, this is mostly intended
/// for debugging. Exact output may change.
///
/// # Examples
///
/// ```
/// use petgraph::Graph;
/// use petgraph::dot::{Dot, Config};
///
/// let mut graph = Graph::<_, ()>::new();
/// graph.add_node("A");
/// graph.add_node("B");
/// graph.add_node("C");
/// graph.add_node("D");
/// graph.extend_with_edges(&[
///     (0, 1), (0, 2), (0, 3),
///     (1, 2), (1, 3),
///     (2, 3),
/// ]);
///
/// println!("{:?}", Dot::with_config(&graph, &[Config::EdgeNoLabel]));
///
/// // In this case the output looks like this:
/// //
/// // digraph {
/// //     0 [label="\"A\""]
/// //     1 [label="\"B\""]
/// //     2 [label="\"C\""]
/// //     3 [label="\"D\""]
/// //     0 -> 1
/// //     0 -> 2
/// //     0 -> 3
/// //     1 -> 2
/// //     1 -> 3
/// //     2 -> 3
/// // }
///
/// // If you need multiple config options, just list them all in the slice.
/// ```
pub struct Dot<'a, G>
where
    G: IntoEdgeReferences + IntoNodeReferences,
{
    graph: G,
    config: &'a [Config],
    get_edge_attributes: &'a dyn Fn(G, G::EdgeRef) -> String,
    get_node_attributes: &'a dyn Fn(G, G::NodeRef) -> String,
}

static TYPE: [&str; 2] = ["graph", "digraph"];
static EDGE: [&str; 2] = ["--", "->"];
static INDENT: &str = "    ";

impl<'a, G> Dot<'a, G>
where
    G: GraphRef + IntoEdgeReferences + IntoNodeReferences,
{
    /// Create a `Dot` formatting wrapper with default configuration.
    pub fn new(graph: G) -> Self {
        Self::with_config(graph, &[])
    }

    /// Create a `Dot` formatting wrapper with custom configuration.
    pub fn with_config(graph: G, config: &'a [Config]) -> Self {
        Self::with_attr_getters(graph, config, &|_, _| "".to_string(), &|_, _| {
            "".to_string()
        })
    }

    pub fn with_attr_getters(
        graph: G,
        config: &'a [Config],
        get_edge_attributes: &'a dyn Fn(G, G::EdgeRef) -> String,
        get_node_attributes: &'a dyn Fn(G, G::NodeRef) -> String,
    ) -> Self {
        Dot {
            graph,
            config,
            get_edge_attributes,
            get_node_attributes,
        }
    }
}

/// `Dot` configuration.
///
/// This enum does not have an exhaustive definition (will be expanded)
#[derive(Debug, PartialEq, Eq)]
pub enum Config {
    /// Use indices for node labels.
    NodeIndexLabel,
    /// Use indices for edge labels.
    EdgeIndexLabel,
    /// Use no edge labels.
    EdgeNoLabel,
    /// Use no node labels.
    NodeNoLabel,
    /// Do not print the graph/digraph string.
    GraphContentOnly,
    #[doc(hidden)]
    _Incomplete(()),
}

impl<'a, G> Dot<'a, G>
where
    G: GraphBase + IntoNodeReferences + IntoEdgeReferences,
{
    fn graph_fmt<NF, EF, NW, EW>(
        &self,
        g: G,
        f: &mut fmt::Formatter,
        mut node_fmt: NF,
        mut edge_fmt: EF,
    ) -> fmt::Result
    where
        G: NodeIndexable + IntoNodeReferences + IntoEdgeReferences,
        G: GraphProp + GraphBase,
        G: Data<NodeWeight = NW, EdgeWeight = EW>,
        NF: FnMut(&NW, &mut dyn FnMut(&dyn Display) -> fmt::Result) -> fmt::Result,
        EF: FnMut(&EW, &mut dyn FnMut(&dyn Display) -> fmt::Result) -> fmt::Result,
    {
        if !self.config.contains(&Config::GraphContentOnly) {
            writeln!(f, "{} {{", TYPE[g.is_directed() as usize])?;
        }

        // output all labels
        for node in g.node_references() {
            write!(f, "{}{} [ ", INDENT, g.to_index(node.id()),)?;
            if !self.config.contains(&Config::NodeNoLabel) {
                write!(f, "label = \"")?;
                if self.config.contains(&Config::NodeIndexLabel) {
                    write!(f, "{}", g.to_index(node.id()))?;
                } else {
                    node_fmt(node.weight(), &mut |d| Escaped(d).fmt(f))?;
                }
                write!(f, "\" ")?;
            }
            writeln!(f, "{}]", (self.get_node_attributes)(g, node))?;
        }
        // output all edges
        for (i, edge) in g.edge_references().enumerate() {
            write!(
                f,
                "{}{} {} {} [ ",
                INDENT,
                g.to_index(edge.source()),
                EDGE[g.is_directed() as usize],
                g.to_index(edge.target()),
            )?;
            if !self.config.contains(&Config::EdgeNoLabel) {
                write!(f, "label = \"")?;
                if self.config.contains(&Config::EdgeIndexLabel) {
                    write!(f, "{}", i)?;
                } else {
                    edge_fmt(edge.weight(), &mut |d| Escaped(d).fmt(f))?;
                }
                write!(f, "\" ")?;
            }
            writeln!(f, "{}]", (self.get_edge_attributes)(g, edge))?;
        }

        if !self.config.contains(&Config::GraphContentOnly) {
            writeln!(f, "}}")?;
        }
        Ok(())
    }
}

impl<'a, G> fmt::Display for Dot<'a, G>
where
    G: IntoEdgeReferences + IntoNodeReferences + NodeIndexable + GraphProp,
    G::EdgeWeight: fmt::Display,
    G::NodeWeight: fmt::Display,
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.graph_fmt(self.graph, f, |n, cb| cb(n), |e, cb| cb(e))
    }
}

impl<'a, G> fmt::Debug for Dot<'a, G>
where
    G: IntoEdgeReferences + IntoNodeReferences + NodeIndexable + GraphProp,
    G::EdgeWeight: fmt::Debug,
    G::NodeWeight: fmt::Debug,
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.graph_fmt(
            self.graph,
            f,
            |n, cb| cb(&DebugFmt(n)),
            |e, cb| cb(&DebugFmt(e)),
        )
    }
}

/// Escape for Graphviz
struct Escaper<W>(W);

impl<W> fmt::Write for Escaper<W>
where
    W: fmt::Write,
{
    fn write_str(&mut self, s: &str) -> fmt::Result {
        for c in s.chars() {
            self.write_char(c)?;
        }
        Ok(())
    }

    fn write_char(&mut self, c: char) -> fmt::Result {
        match c {
            '"' | '\\' => self.0.write_char('\\')?,
            // \l is for left justified linebreak
            '\n' => return self.0.write_str("\\l"),
            _ => {}
        }
        self.0.write_char(c)
    }
}

/// Pass Display formatting through a simple escaping filter
struct Escaped<T>(T);

impl<T> fmt::Display for Escaped<T>
where
    T: fmt::Display,
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        if f.alternate() {
            writeln!(&mut Escaper(f), "{:#}", &self.0)
        } else {
            write!(&mut Escaper(f), "{}", &self.0)
        }
    }
}

/// Pass Debug formatting to Display
struct DebugFmt<T>(T);

impl<T> fmt::Display for DebugFmt<T>
where
    T: fmt::Debug,
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.0.fmt(f)
    }
}

#[cfg(test)]
mod test {
    use super::{Config, Dot, Escaper};
    use crate::prelude::Graph;
    use crate::visit::NodeRef;
    use std::fmt::Write;

    #[test]
    fn test_escape() {
        let mut buff = String::new();
        {
            let mut e = Escaper(&mut buff);
            let _ = e.write_str("\" \\ \n");
        }
        assert_eq!(buff, "\\\" \\\\ \\l");
    }

    fn simple_graph() -> Graph<&'static str, &'static str> {
        let mut graph = Graph::<&str, &str>::new();
        let a = graph.add_node("A");
        let b = graph.add_node("B");
        graph.add_edge(a, b, "edge_label");
        graph
    }

    #[test]
    fn test_nodeindexlable_option() {
        let graph = simple_graph();
        let dot = format!("{:?}", Dot::with_config(&graph, &[Config::NodeIndexLabel]));
        assert_eq!(dot, "digraph {\n    0 [ label = \"0\" ]\n    1 [ label = \"1\" ]\n    0 -> 1 [ label = \"\\\"edge_label\\\"\" ]\n}\n");
    }

    #[test]
    fn test_edgeindexlable_option() {
        let graph = simple_graph();
        let dot = format!("{:?}", Dot::with_config(&graph, &[Config::EdgeIndexLabel]));
        assert_eq!(dot, "digraph {\n    0 [ label = \"\\\"A\\\"\" ]\n    1 [ label = \"\\\"B\\\"\" ]\n    0 -> 1 [ label = \"0\" ]\n}\n");
    }

    #[test]
    fn test_edgenolable_option() {
        let graph = simple_graph();
        let dot = format!("{:?}", Dot::with_config(&graph, &[Config::EdgeNoLabel]));
        assert_eq!(dot, "digraph {\n    0 [ label = \"\\\"A\\\"\" ]\n    1 [ label = \"\\\"B\\\"\" ]\n    0 -> 1 [ ]\n}\n");
    }

    #[test]
    fn test_nodenolable_option() {
        let graph = simple_graph();
        let dot = format!("{:?}", Dot::with_config(&graph, &[Config::NodeNoLabel]));
        assert_eq!(
            dot,
            "digraph {\n    0 [ ]\n    1 [ ]\n    0 -> 1 [ label = \"\\\"edge_label\\\"\" ]\n}\n"
        );
    }

    #[test]
    fn test_with_attr_getters() {
        let graph = simple_graph();
        let dot = format!(
            "{:?}",
            Dot::with_attr_getters(
                &graph,
                &[Config::NodeNoLabel, Config::EdgeNoLabel],
                &|_, er| format!("label = \"{}\"", er.weight().to_uppercase()),
                &|_, nr| format!("label = \"{}\"", nr.weight().to_lowercase()),
            ),
        );
        assert_eq!(dot, "digraph {\n    0 [ label = \"a\"]\n    1 [ label = \"b\"]\n    0 -> 1 [ label = \"EDGE_LABEL\"]\n}\n");
    }
}