Lazy loading backbone collection + infinite scrolling

app.coffee

class LazyCollection extends Backbone.Collection
    indexQuerystring: 'index'
    index: 1
    lastLength: 0
    fetch: (options) ->
        options or= {}
        if options.reset
            @index = 1 
            @lastLength = 0
        else 
            if @lastLength == @length then return
            @lastLength = @length
            @index++
            options.add = true
        options.data or= {}
        options.data[@indexQuerystring] = @index
        success = options.success
        options.success = (model, resp) => 
            @trigger 'fetch:end'
            if success then success model, resp
        error = options.error
        options.error = (originalModel, resp, options) => 
            @trigger 'fetch:end'
            if error then error originalModel, resp, options
        @trigger 'fetch:start'
        Backbone.Collection.prototype.fetch.call @, options

class SearchResults extends LazyCollection
    initialize: ->
        _.bindAll @, 'search'
        @query = ''
    model: Entry
    url: -> "/directory/entries"
    search: (query) -> 
        @query = query ? @query
        @fetch { reset: !!query, data: { query: @query } }

class SearchResultsView extends Backbone.View
    initialize: (options) ->
        _.bindAll @, 'render', 'renderResult'
        @template = options.template
        @collection.on 'reset', @render, @
        @collection.on 'add', @renderResult, @
    render: ->
        @$el.empty()
        @collection.each @renderResult
    renderResult: (result) ->
        view = new SearchResultView 
            template: @template
            model: result
        @$el.append view.render().el

class SearchView extends Backbone.View
    events:
        'click .search': 'search'
    initialize: (options) ->
        _.bindAll @, 'render', 'search', 'toggleSpinner'
        @template = options.template
        @resultTemplate = options.resultTemplate
        options.scrollChannel.subscribe @collection.search
        @collection.on 'fetch:start', @toggleSpinner, @
        @collection.on 'fetch:end', @toggleSpinner, @
    render: ->
        @$el.html @template()
        @resultsView = new SearchResultsView
            el: $ '.search-results'
            template: @resultTemplate
            collection: @collection
    search: (event) ->
        @collection.search $('.search-text').val()
        event.preventDefault()
    toggleSpinner: ->
        @$('.spinner').toggle()

...

start: (results) ->

    container = $ '#container'

    scrollChannel = postal.channel 'scroll.bottom'

    # TODO: Make this a jQuery plugin
    $window = $ window
    $document = $ document
    $window.scroll ->
        scrollTop = $window.scrollTop()
        scrollChannel.publish() unless scrollTop == 0 or scrollTop < ($document.height() - $window.height()) - 100

    @searchResults = new SearchResults

    @searchView = new SearchView
        el: container
        collection: @searchResults
        template: _.template searchTemplate
        resultTemplate: _.template searchResultTemplate
        scrollChannel: scrollChannel
        
    @searchResults.reset results

    ...