import { DagreGraph } from '../graph';
import { feasibleTreeWithLayer as feasibleTree } from './feasible-tree';
import { networkSimplex } from './network-simplex';
import { longestPath, longestPathWithLayer } from './util';

/*
 * 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 const rank = (
  g: DagreGraph,
  ranker: 'network-simplex' | 'tight-tree' | 'longest-path',
) => {
  switch (ranker) {
    case 'network-simplex':
      networkSimplexRanker(g);
      break;
    case 'tight-tree':
      tightTreeRanker(g);
      break;
    case 'longest-path':
      longestPathRanker(g);
      break;
    // default: networkSimplexRanker(g);
    default:
      tightTreeRanker(g);
  }
};

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

const tightTreeRanker = (g: DagreGraph) => {
  longestPathWithLayer(g);
  feasibleTree(g);
};

const networkSimplexRanker = (g: DagreGraph) => {
  networkSimplex(g);
};