function _applyFragment()

in index.js [844:935]
67 lines of code
16 McCabe index (conditional complexity)

function _applyFragment (fragment) {
  if (!fragment || fragment.substr(0, 2) !== '#?') return
  fragment = fragment.substring(2) // remove the #?

  // use this literal's keys as the source of truth for key-value pairs in the fragment
  var actions = { proposal: [], search: null, status: [], version: [] }

  // parse the fragment as a query string
  Object.keys(actions).forEach(function (action) {
    var pattern = new RegExp(action + '=([^=]+)(&|$)')
    var values = fragment.match(pattern)

    if (values) {
      var value = values[1] // 1st capture group from the RegExp
      if (action === 'search') {
        value = decodeURIComponent(value)
      } else {
        value = value.split(',')
      }

      actions[action] = value
    }
  })

  // perform key-specific parsing and checks

  if (actions.proposal.length) {
    document.querySelector('#search-filter').value = actions.proposal.join(',')
  } else if (actions.search) {
    document.querySelector('#search-filter').value = actions.search
  }

  if (actions.version.length) {
    var versionSelections = actions.version.map(function (version) {
      return document.querySelector('#filter-by-swift-' + _idSafeName(version))
    }).filter(function (version) {
      return !!version
    })

    versionSelections.forEach(function (versionSelection) {
      versionSelection.checked = true
    })

    if (versionSelections.length) {
      document.querySelector(
        '#filter-by-' + states['.implemented'].className
      ).checked = true
    }
  }

  // track this state specifically for toggling the version panel
  var implementedSelected = false

  // update the filter selections in the nav
  if (actions.status.length) {
    var statusSelections = actions.status.map(function (status) {
      var stateName = Object.keys(states).filter(function (state) {
        return states[state].className === status
      })[0]

      if (!stateName) return // fragment contains a nonexistent state
      var state = states[stateName]

      if (stateName === '.implemented') implementedSelected = true

      return document.querySelector('#filter-by-' + state.className)
    }).filter(function (status) {
      return !!status
    })

    statusSelections.forEach(function (statusSelection) {
      statusSelection.checked = true
    })
  }

  // the version panel needs to be activated if any are specified
  if (actions.version.length || implementedSelected) {
    ;['#version-options', '#version-options-label'].forEach(function (selector) {
      document.querySelector('.filter-options')
        .querySelector(selector).classList
        .toggle('hidden')
    })
  }

  // specifying any filter in the fragment should activate the filters in the UI
  if (actions.version.length || actions.status.length) {
    toggleFilterPanel()
    toggleFiltering()
  }

  filterProposals()
}