exports.sync = function (store, router, options) {
  var moduleName = (options || {}).moduleName || 'route'

  store.registerModule(moduleName, {
    namespaced: true,
    state: cloneRoute(router.currentRoute),
    mutations: {
      'ROUTE_CHANGED': function ROUTE_CHANGED (state, transition) {
        store.state[moduleName] = cloneRoute(transition.to, transition.from)
      }
    }
  })

  var isTimeTraveling = false
  var currentPath

  // sync router on store change
  var storeUnwatch = store.watch(
    function (state) { return state[moduleName]; },
    function (route) {
      var fullPath = route.fullPath;
      if (fullPath === currentPath) {
        return
      }
      if (currentPath != null) {
        isTimeTraveling = true
        router.push(route)
      }
      currentPath = fullPath
    },
    { sync: true }
  )

  // sync store on router navigation
  var afterEachUnHook = router.afterEach(function (to, from) {
    if (isTimeTraveling) {
      isTimeTraveling = false
      return
    }
    currentPath = to.fullPath
    store.commit(moduleName + '/ROUTE_CHANGED', { to: to, from: from })
  })

  return function unsync () {
    // On unsync, remove router hook
    if (afterEachUnHook != null) {
      afterEachUnHook()
    }

    // On unsync, remove store watch
    if (storeUnwatch != null) {
      storeUnwatch()
    }

    // On unsync, unregister Module with store
    store.unregisterModule(moduleName)
  }
}

function cloneRoute (to, from) {
  var clone = {
    name: to.name,
    path: to.path,
    hash: to.hash,
    query: to.query,
    params: to.params,
    fullPath: to.fullPath,
    meta: to.meta
  }
  if (from) {
    clone.from = cloneRoute(from)
  }
  return Object.freeze(clone)
}