import * as rankUtil from "./util";
const longestPath = rankUtil.longestPath;
import { feasibleTree } from "./feasible-tree";
import networkSimplex from "./network-simplex";
import { Graph } from "graphlib";

/*
 * Assigns a rank to each node in the input graph that respects the "minlen"
 * constraint specified on edges between nodes.
 *
 * This basic structure is derived from Gansner, et al., "A Technique for
 * Drawing Directed Graphs."
 *
 * Pre-conditions:
 *
 *    1. Graph must be a connected DAG
 *    2. Graph nodes must be objects
 *    3. Graph edges must have "weight" and "minlen" attributes
 *
 * Post-conditions:
 *
 *    1. Graph nodes will have a "rank" attribute based on the results of the
 *       algorithm. Ranks can start at any index (including negative), we'll
 *       fix them up later.
 */
export function rank(g: Graph): void {
  switch ((g.graph() as any).ranker) {
    case "network-simplex":
      networkSimplexRanker(g);
      break;
    case "tight-tree":
      tightTreeRanker(g);
      break;
    case "longest-path":
      longestPathRanker(g);
      break;
    default:
      networkSimplexRanker(g);
  }
}

// A fast and simple ranker, but results are far from optimal.
const longestPathRanker = longestPath;

function tightTreeRanker(g: Graph): void {
  longestPath(g);
  feasibleTree(g);
}

function networkSimplexRanker(g: Graph): void {
  networkSimplex(g);
}