location.js

define(function(require) {
  var findClosest = require('./find-closest')
    , rebind = require('./rebind')
    , dispatcher = require('d3-dispatch').dispatch('statechange')
    , history = window.history
    , location = window.location
    , on = require('./on')
    , base = ''

  on.call(window, 'popstate.location', handleStateChange)
  on.call(document, 'click.location', handleClick)

  if (isHashPath(location.hash)) {
    // Redirect current hash fragment location to "real" path
    history.replaceState(null, null, rebase(fullPath(location)))
  }

  var api =
      { getState: getState
      , setState: setState
      , pushState: deprecatedPushState
      , replaceState: replaceState
      , openNewWindow: openNewWindow
      , basePath: basePath
      }

  return rebind(api, dispatcher, 'on')

  function getState() {
    return unbase(fullPath(location))
  }

  function setState(path) {
    var actual = pushState(path)
    
    if (actual) {
      dispatcher.statechange(actual)
      return actual
    } else {
      return false
    }
  }

  function trimPath(path) {
    return '/' + trimSlashes(~path.indexOf('#/')? path.split('#/')[1] : path)
  }

  function updateState(path, method) {
    path = unbase(trimPath(path))

    if (path === getState()) {
      return false
    } else {
      method({ base: base, path: path }, null, rebase(path))
      return path
    }
  }

  function deprecatedPushState(path) {
    console.warn('deprecated : location.pushState, to be removed in v.4.0.0.')
    return pushState(path)
  }

  function pushState(path) {
    return updateState(path, history.pushState.bind(history))
  }

  function replaceState(path) {
    return updateState(path, history.replaceState.bind(history))
  }

  function openNewWindow(path, target) {
    return window.open(rebase(path), target, '')
  }

  function basePath(path) {
    if (arguments.length === 0) return base

    var cwd = unbase(fullPath(location))

    path = trimSlashes(path)
    base = path? '/' + path : ''

    history.replaceState(null, null, rebase(cwd))
  }

  function handleClick(event) {
    var a
      , target = event.target
      , path

    if (event.ctrlKey) return      // Ignore ctrl+click
    if (event.button !== 0) return // Ignore clicks by buttons other than primary (usually left button)

    a = findClosest.anchor(target)

    if ( !a // non-anchor clicks
      || !!a.target // anchors with specified targets
      || a.hasAttribute('download') // anchors with download attribute
      || !isSameOrigin(a, location) // links to different origins
    ) {
      /* If any of the above conditions are true, we ignore the click and
       * let the browser deal with the navigation as it sees fit
       */
      return
    }

    var path

    if (isHashPath(a.hash)) {
      path = rebase(a.hash.slice(1))
    } else if (a.hash || a.href.slice(location.href.length) === '#') {
      // Ignore links with a non-path hash, and empty hashes (e.g.: `<a href="#"></a>`)
      return 
    } else {
      path = rebase(fullPath(a))
    }

    if (path) {
      event.preventDefault()
      event.stopPropagation()
      var actual = pushState(path)

      if (actual) {
        dispatcher.statechange(actual)
      }
    }
  }

  function handleStateChange(event) {
    var path, base = (event.state && event.state.base) || ''

    if (isHashPath(location.hash)) {
      // "Redirect" current location to a proper path
      path = location.hash.slice(1)

      if (path) {
        var state = { base: base, path: path }
        history.replaceState(state, null, rebase(path))
      }
    } else {
      path = fullPath(location)
    }

    dispatcher.statechange(unbase(path))
  }

  function isHashPath(hash) {
    return (hash || '').slice(0, 2) === '#/'
  }

  function isSameOrigin(a, x) {
    var o = origin(x)
    return a.href.slice(0, o.length) === o
  }

  function origin(url) {
    if (url.origin) {
      return url.origin
    } else {
      var port

      if (url.port && !~url.href.indexOf(':' + url.port)) {
        // IE defaults port values based on protocol, which messes things up
        port = ''
      } else {
        port = ':' + url.port
      }

      return url.protocol + "//" + url.hostname + port
    }
  }

  function fullPath(url) {
    if (isHashPath(url.hash)) {
      return url.hash.slice(1)
    } else {
      return url.href.slice(origin(url).length)
    }
  }

  function rebase(path) {
    return base + '/' + trimSlashes(unbase(path))
  }

  function unbase(path) {
    if (path.slice(0, base.length) === base) {
      return path.slice(base.length)
    } else {
      return path
    }
  }

  function trimSlashes(path) {
    return (path || '').replace(/^\/+|\/+$/g, '')
  }
})