meteor pagination class

namespace('App.data')

###
Meteor pagination class

Usage 
UsersController = RouteController.extend
  waitOn: ->
    @page = @params.query.page || 1
    @pagination = new App.data.Pagination(Users, selector, {page: @page})
    Meteor.subscribe "users", @pagination.selector, @pagination.getSubscriptionOptions()
    
  data: ->
    pagination: @pagination
    
Then in your template
{{#each pagination.getItems}}
    {{> masterItem}}
{{/each}}

{{> pagination}}
    
###
class @App.data.Pagination

  constructor: (@collection, @selector = {}, options = {}) ->
    @pageSize = options.pageSize || 10
    @page = options.page || 1
    @maxButtonCount = 10
    @totalCountMethod = "totalCount"
    @templateName = options.templateName || "pagination"

    @getPageRange = () ->
      @getPageCount () ->
        beginPage = Math.max(0, @page - Math.ceil(@maxButtonCount / 2))
        endPage = beginPage + @maxButtonCount  - 1
        if endPage >= @pageCount
          endPage = @pageCount - 1
          beginPage = Math.max(0, endPage - @maxButtonCount + 1)
        [beginPage, endPage]

  getItems: () ->
    # Get total and assign buttons as reactive variable to template
    reactivePagerButtons = new ReactiveVar(null)
    @.getButtons (buttons) ->
      reactivePagerButtons.set buttons

    Template[@templateName].helpers
      pagerButtons: ->
        reactivePagerButtons.get();

    @collection.find @selector

  getSubscriptionOptions: () ->
    limit: @pageSize
    skip: (@page - 1) * @pageSize

  getButtons: (cb) ->
    buttons = []
    @getPageCount () ->
      if @pageCount < 2
        return buttons

      currentRoute = Router.current().route.getName()
      currentParams = Router.current().route.params()

      [beginPage, endPage] = @getPageRange()

      while beginPage++ <= endPage
        query = $.query.load(location.href).set("page", beginPage).toString()
        buttons.push
          label: beginPage
          class: if parseInt(beginPage) == parseInt(@page) then "active" else ""
          path: Router.path(currentRoute, currentParams, {"query": query})
      @pagerButtons = buttons
      cb(buttons) if cb

  getPageCount: (cb) ->
    pagination = @
    unless @pageCount
      Meteor.call @totalCountMethod, @collection._name, @selector, (err, total) ->
        pagination.pageCount = Math.floor(total / pagination.pageSize)
        cb.call pagination
    else
      cb.call pagination