{ipcMain} = require 'electron'

### The history operation in renderer is redirected to browser. ###
ipcMain.on 'ATOM_SHELL_NAVIGATION_CONTROLLER', (event, method, args...) ->
  event.sender[method] args...

ipcMain.on 'ATOM_SHELL_SYNC_NAVIGATION_CONTROLLER', (event, method, args...) ->
  event.returnValue = event.sender[method] args...

###
  JavaScript implementation of Chromium's NavigationController.
  Instead of relying on Chromium for history control, we compeletely do history
  control on user land, and only rely on WebContents.loadURL for navigation.
  This helps us avoid Chromium's various optimizations so we can ensure renderer
  process is restarted everytime.
###
class NavigationController
  constructor: (@webContents) ->
    @clearHistory()

    ### webContents may have already navigated to a page. ###
    if @webContents._getURL()
      @currentIndex++
      @history.push @webContents._getURL()

    @webContents.on 'navigation-entry-commited', (event, url, inPage, replaceEntry) =>
      if @inPageIndex > -1 and not inPage
        ### Navigated to a new page, clear in-page mark. ###
        @inPageIndex = -1
      else if @inPageIndex is -1 and inPage
        ### Started in-page navigations. ###
        @inPageIndex = @currentIndex

      if @pendingIndex >= 0
        ### Go to index. ###
        @currentIndex = @pendingIndex
        @pendingIndex = -1
        @history[@currentIndex] = url
      else if replaceEntry
        ### Non-user initialized navigation. ###
        @history[@currentIndex] = url
      else
        ### Normal navigation. Clear history. ###
        @history = @history.slice 0, @currentIndex + 1
        currentEntry = @history[@currentIndex]
        if currentEntry?.url isnt url
          @currentIndex++
          @history.push url

  loadURL: (url, options={}) ->
    @pendingIndex = -1
    @webContents._loadURL url, options
    @webContents.emit 'load-url', url, options

  getURL: ->
    if @currentIndex is -1
      ''
    else
      @history[@currentIndex]

  stop: ->
    @pendingIndex = -1
    @webContents._stop()

  reload: ->
    @pendingIndex = @currentIndex
    @webContents._loadURL @getURL(), {}

  reloadIgnoringCache: ->
    @pendingIndex = @currentIndex
    @webContents._loadURL @getURL(), {extraHeaders: "pragma: no-cache\n"}

  canGoBack: ->
    @getActiveIndex() > 0

  canGoForward: ->
    @getActiveIndex() < @history.length - 1

  canGoToIndex: (index) ->
    index >=0 and index < @history.length

  canGoToOffset: (offset) ->
    @canGoToIndex @currentIndex + offset

  clearHistory: ->
    @history = []
    @currentIndex = -1
    @pendingIndex = -1
    @inPageIndex = -1

  goBack: ->
    return unless @canGoBack()
    @pendingIndex = @getActiveIndex() - 1
    if @inPageIndex > -1 and @pendingIndex >= @inPageIndex
      @webContents._goBack()
    else
      @webContents._loadURL @history[@pendingIndex], {}

  goForward: ->
    return unless @canGoForward()
    @pendingIndex = @getActiveIndex() + 1
    if @inPageIndex > -1 and @pendingIndex >= @inPageIndex
      @webContents._goForward()
    else
      @webContents._loadURL @history[@pendingIndex], {}

  goToIndex: (index) ->
    return unless @canGoToIndex index
    @pendingIndex = index
    @webContents._loadURL @history[@pendingIndex], {}

  goToOffset: (offset) ->
    return unless @canGoToOffset offset
    pendingIndex = @currentIndex + offset
    if @inPageIndex > -1 and pendingIndex >= @inPageIndex
      @pendingIndex = pendingIndex
      @webContents._goToOffset offset
    else
      @goToIndex pendingIndex

  getActiveIndex: ->
    if @pendingIndex is -1 then @currentIndex else @pendingIndex

  length: ->
    @history.length

module.exports = NavigationController