History.js

var qs = require('qs')
var parseUrl = require('url').parse
var resolveUrl = require('url').resolve
var router = require('./router')
var currentPath = window.location.pathname + window.location.search

// Replace the initial state with the current URL immediately,
// so that it will be rendered if the state is later popped
if (window.history.replaceState) {
  window.history.replaceState({
    $render: true,
    $method: 'get'
  }, null, window.location.href)
}

module.exports = History

function History(app, routes) {
  this.app = app
  this.routes = routes

  if (window.history.pushState) {
    addListeners(this)
    return
  }
  this.push = function(url) {
    window.location.assign(url)
  }
  this.replace = function(url) {
    window.location.replace(url)
  }
}

History.prototype.push = function(url, render, state, e) {
  this._update('pushState', url, render, state, e)
}

History.prototype.replace = function(url, render, state, e) {
  this._update('replaceState', url, render, state, e)
}

// Rerender the current url locally
History.prototype.refresh = function() {
  var path = routePath(window.location.href)
  // Note that we don't pass previous to avoid triggering transitions
  router.render(this, {url: path, method: 'get'})
}

History.prototype.back = function() {
  window.history.back()
}

History.prototype.forward = function() {
  window.history.forward()
}

History.prototype.go = function(i) {
  window.history.go(i)
}

History.prototype._update = function(historyMethod, relativeUrl, render, state, e) {
  var url = resolveUrl(window.location.href, relativeUrl)
  var path = routePath(url)

  // TODO: history.push should set the window.location with external urls
  if (!path) return
  if (render == null) render = true
  if (state == null) state = {}

  // Update the URL
  var options = renderOptions(e, path)
  state.$render = true
  state.$method = options.method
  window.history[historyMethod](state, null, options.url + (url.hash || ''))
  currentPath = window.location.pathname + window.location.search
  if (render) router.render(this, options, e)
  // Jump to named element on new page, to mimic browser behavior
  if (url.hash) {
    var hashElement = document.getElementById(url.hash.substring(1))
    if (hashElement) {
      hashElement.scrollIntoView()
    }
  }
}

History.prototype.page = function() {
  var page = this.app.createPage()
  var history = this

  function redirect(url) {
    if (url === 'back') return history.back()
    // TODO: Add support for `basepath` option like Express
    if (url === 'home') url = '\\'
    history.replace(url, true)
  }

  page.redirect = redirect
  return page
}

// Get the pathname if it is on the same protocol and domain
function routePath(url) {
  var match = parseUrl(url)
  return match &&
    match.protocol === window.location.protocol &&
    match.host === window.location.host &&
    match.pathname + (match.search || '')
}

function renderOptions(e, path) {
  // If this is a form submission, extract the form data and
  // append it to the url for a get or params.body for a post
  if (e && e.type === 'submit') {
    var form = e.target
    var elements = form.elements
    var query = []
    for (var i = 0, len = elements.length, el; i < len; i++) {
      el = elements[i]
      var name = el.name
      if (!name) continue
      var value = el.value
      query.push(encodeURIComponent(name) + '=' + encodeURIComponent(value))
      if (name === '_method') {
        var override = value.toLowerCase()
        if (override === 'delete') override = 'del'
      }
    }
    query = query.join('&')
    if (form.method.toLowerCase() === 'post') {
      var method = override || 'post'
      var body = qs.parse(query)
    } else {
      method = 'get'
      path += '?' + query
    }
  } else {
    method = 'get'
  }
  return {
    method: method
  , url: path
  , previous: window.location.pathname + window.location.search
  , body: body
  , form: form
  , link: e && e._tracksLink
  }
}

function addListeners(history) {

  // Detect clicks on links
  function onClick(e) {
    var el = e.target

    // Ignore command click, control click, and non-left click
    if (e.metaKey || e.which !== 1) return

    // Ignore if already prevented
    if (e.defaultPrevented) return

    // Also look up for parent links (<a><img></a>)
    while (el) {
      var url = el.href
      if (url) {

        // Ignore if created by Tracks
        if (el.hasAttribute && el.hasAttribute('data-router-ignore')) return

        // Ignore links meant to open in a different window or frame
        if (el.target && el.target !== '_self') return

        // Ignore hash links to the same page
        var hashIndex = url.indexOf('#')
        if (~hashIndex && url.slice(0, hashIndex) === window.location.href.replace(/#.*/, '')) {
          return
        }

        e._tracksLink = el
        history.push(url, true, null, e)
        return
      }

      el = el.parentNode
    }
  }

  function onSubmit(e) {
    var target = e.target

    // Ignore if already prevented
    if (e.defaultPrevented) return

    // Only handle if emitted on a form element that isn't multipart
    if (target.tagName.toLowerCase() !== 'form') return
    if (target.enctype === 'multipart/form-data') return

    // Ignore if created by Tracks
    if (target.hasAttribute && target.hasAttribute('data-router-ignore')) return

    // Use the url from the form action, defaulting to the current url
    var url = target.action || window.location.href
    history.push(url, true, null, e)
  }

  function onPopState(e) {
    // HACK: Chrome sometimes does a pop state before the app is set up properly
    if (!history.app.page) return

    var previous = currentPath
    var state = e.state
    currentPath = window.location.pathname + window.location.search

    var options = {
      previous: previous
    , url: currentPath
    }

    if (state) {
      if (!state.$render) return
      options.method = state.$method
      // Note that the post body is only sent on the initial reqest
      // and it is empty if the state is later popped
      return router.render(history, options)
    }

    // The state object will be null for states created by jump links.
    // window.location.hash cannot be used, because it returns nothing
    // if the url ends in just a hash character
    var url = window.location.href
      , hashIndex = url.indexOf('#')
      , el, id
    if (~hashIndex && currentPath !== previous) {
      options.method = 'get'
      router.render(history, options)
      id = url.slice(hashIndex + 1)
      if (el = document.getElementById(id) || document.getElementsByName(id)[0]) {
        el.scrollIntoView()
      }
    }
  }

  document.addEventListener('click', onClick, true)
  document.addEventListener('submit', onSubmit, false)
  window.addEventListener('popstate', onPopState, true)
}