import _ from 'lodash'

import greedyFAS from './greedy-fas'

function run (g) {
  const fas = (g.graph().acyclicer === 'greedy'
    ? greedyFAS(g, weightFn(g))
    : dfsFAS(g))
  _.forEach(fas, function (e) {
    const label = g.edge(e)
    g.removeEdge(e)
    label.forwardName = e.name
    label.reversed = true
    g.setEdge(e.w, e.v, label, _.uniqueId('rev'))
  })

  function weightFn (g) {
    return function (e) {
      return g.edge(e).weight
    }
  }
}

function dfsFAS (g) {
  const fas = []
  const stack = {}
  const visited = {}

  function dfs (v) {
    if (_.has(visited, v)) {
      return
    }
    visited[v] = true
    stack[v] = true
    _.forEach(g.outEdges(v), function (e) {
      if (_.has(stack, e.w)) {
        fas.push(e)
      } else {
        dfs(e.w)
      }
    })
    delete stack[v]
  }

  _.forEach(g.nodes(), dfs)
  return fas
}

function undo (g) {
  _.forEach(g.edges(), function (e) {
    const label = g.edge(e)
    if (label.reversed) {
      g.removeEdge(e)

      const forwardName = label.forwardName
      delete label.reversed
      delete label.forwardName
      g.setEdge(e.w, e.v, label, forwardName)
    }
  })
}

export default {
  run,
  undo
}