dagre_rust 0.0.5

use graphlib_rust::Graph;
use ordered_hashmap::OrderedHashMap;
use crate::{GraphConfig, GraphEdge, GraphNode};

/*
 * Assigns an initial order value for each node by performing a DFS search
 * starting from nodes in the first rank. Nodes are assigned an order in their
 * rank as they are first visited.
 *
 * This approach comes from Gansner, et al., "A Technique for Drawing Directed
 * Graphs."
 *
 * Returns a layering matrix with an array per layer and each layer sorted by
 * the order of its nodes.
 */

pub fn init_order(g: &Graph<GraphConfig, GraphNode, GraphEdge>) -> Vec<Vec<String>> {
  let mut visited: OrderedHashMap<String, bool> = OrderedHashMap::new();
  let mut simple_nodes: Vec<String> = g.nodes().into_iter().filter(|v| {
    g.children(v).len() == 0
  }).collect();
  let max_rank = simple_nodes.iter().map(|v| {
    g.node(v).unwrap().rank.clone().unwrap_or(0)
  }).max().unwrap_or(0);
  let mut layers: Vec<Vec<String>> = (0..=max_rank).map(|_| -> Vec<String> {
    vec![]
  }).collect();

  fn dfs(v: &String, g: &Graph<GraphConfig, GraphNode, GraphEdge>, visited: &mut OrderedHashMap<String, bool>, layers: &mut Vec<Vec<String>>) {
    if visited.contains_key(v) {
      return ();
    }

    visited.insert(v.clone(), true);
    let node = g.node(v).unwrap();
    let node_rank = node.rank.unwrap_or(0) as usize;
    if layers.get(node_rank.clone()).is_none() {
      layers.insert(node_rank.clone(), vec![]);
    }
    let layer: &mut Vec<String> = layers.get_mut(node_rank.clone()).unwrap();
    layer.push(v.clone());

    let sucs = g.successors(v).unwrap_or(vec![]);
    for sv in sucs.iter() {
      dfs(sv, g, visited, layers)
    }
  }

  simple_nodes.sort_by(|v1, v2| {
    let v1_rank = g.node(v1).unwrap().rank.clone().unwrap_or(0);
    let v2_rank = g.node(v2).unwrap().rank.clone().unwrap_or(0);

    v1_rank.cmp(&v2_rank)
  });

  for v in simple_nodes.iter() {
    dfs(v, g, &mut visited, &mut layers);
  }

  return layers;
}