var _ = require('../lodash')

module.exports = floydWarshall

var DEFAULT_WEIGHT_FUNC = _.constant(1)

function floydWarshall (g, weightFn, edgeFn) {
  return runFloydWarshall(g,
    weightFn || DEFAULT_WEIGHT_FUNC,
    edgeFn || function (v) { return g.outEdges(v) })
}

function runFloydWarshall (g, weightFn, edgeFn) {
  const results = {}
  const nodes = g.nodes()

  nodes.forEach(function (v) {
    results[v] = {}
    results[v][v] = { distance: 0 }
    nodes.forEach(function (w) {
      if (v !== w) {
        results[v][w] = { distance: Number.POSITIVE_INFINITY }
      }
    })
    edgeFn(v).forEach(function (edge) {
      const w = edge.v === v ? edge.w : edge.v
      const d = weightFn(edge)
      results[v][w] = { distance: d, predecessor: v }
    })
  })

  nodes.forEach(function (k) {
    var rowK = results[k]
    nodes.forEach(function (i) {
      var rowI = results[i]
      nodes.forEach(function (j) {
        var ik = rowI[k]
        var kj = rowK[j]
        var ij = rowI[j]
        var altDistance = ik.distance + kj.distance
        if (altDistance < ij.distance) {
          ij.distance = altDistance
          ij.predecessor = kj.predecessor
        }
      })
    })
  })

  return results
}