import { longestPath } from './util'
import feasibleTree from './feasible-tree'
import networkSimplex from './network-simplex'

/*
 * 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.
 */
function rank (g) {
  switch (g.graph().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) {
  longestPath(g)
  feasibleTree(g)
}

function networkSimplexRanker (g) {
  networkSimplex(g)
}

export default rank