'use strict'

module.exports = (impl) ->
    DATA =
        contentItem: null
        scrollElem: null
        yScrollbar: false

    DATA: DATA

    createData: impl.utils.createDataCloner 'Item', DATA

    create: (data) ->
        self = @

        impl.Types.Item.create.call @, data

        scrollElem = data.scrollElem = document.createElement 'div'
        scrollElem.style.overflow = 'hidden'
        scrollElem.style.width = '100%'
        scrollElem.style.height = '100%'
        data.elem.appendChild scrollElem

        @onParentChange ->
            scrollElem.scrollLeft = self._contentX
            scrollElem.scrollTop = self._contentY
            return

        setContentX = (val) ->
            max = self._impl.contentItem?._width - self._width or 0
            if val > max
                val = max
            if val < 0
                val = 0

            oldVal = self.contentX
            if val isnt oldVal
                self._contentX = val
                self.onContentXChange.emit oldVal

        setContentY = (val) ->
            max = self._impl.contentItem?._height - self._height or 0
            if val > max
                val = max
            if val < 0
                val = 0

            oldVal = self.contentY
            if val isnt oldVal
                self._contentY = val
                self.onContentYChange.emit oldVal

        syncScroll = ->
            setContentX @scrollLeft
            setContentY @scrollTop
            return

        # safari scroll event throttling fix
        scrollElem.addEventListener impl.utils.pointerWheelEventName, (e) ->
            if e.deltaX?
                setContentX @scrollLeft + e.deltaX
                setContentY @scrollTop + e.deltaY

        scrollElem.addEventListener 'scroll', syncScroll
        return

    setScrollableContentItem: do ->
        onHeightChange = ->
            data = @_impl
            contentItem = @_contentItem
            if contentItem._height <= @_height
                if data.yScrollbar
                    data.scrollElem.style.overflowY = 'hidden'
                    data.yScrollbar = false
            else
                if not data.yScrollbar
                    data.scrollElem.style.overflowY = 'scroll'
                    data.yScrollbar = true
            return

        (val) ->
            if oldVal = @_impl.contentItem
                if oldVal._impl.elem.parentElement is @_impl.scrollElem
                    @_impl.scrollElem.removeChild oldVal._impl.elem
                oldVal.onHeightChange.disconnect onHeightChange, @

            if val
                val.onHeightChange onHeightChange, @
                @_impl.contentItem = val
                @_impl.scrollElem.appendChild val._impl.elem
            return

    setScrollableContentX: (val) ->
        @_impl.scrollElem.scrollLeft = val
        return

    setScrollableContentY: (val) ->
        @_impl.scrollElem.scrollTop = val
        return

    setScrollableSnap: (val) ->
        return

    setScrollableSnapItem: (val) ->
        return