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local QtCore = require 'qtcore'
local QtGui = require 'qtgui'
local QtWidgets = require 'qtwidgets'

local Class = QtCore.Class('MainWindow', QtWidgets.QMainWindow) {}

function Class:__static_init()
    self:__addslot('selectionChangedSlot(QItemSelection,QItemSelection)'
    	, self.selectionChangedSlot
    )
end

function Class:__init()
	self.treeView = QtWidgets.QTreeView(self)
	self:setCentralWidget(self.treeView)

	local standardModel = QtGui.QStandardItemModel.new()
	local rootNode = standardModel:invisibleRootItem()

    -- defining a couple of items
    local americaItem = QtGui.QStandardItem.new 'America'
    local mexicoItem = QtGui.QStandardItem.new 'Canada'
    local usaItem = QtGui.QStandardItem.new 'USA'
    local bostonItem = QtGui.QStandardItem.new 'Boston'
    local europeItem = QtGui.QStandardItem.new 'Europe'
    local italyItem = QtGui.QStandardItem.new 'Italy'
    local romeItem = QtGui.QStandardItem.new 'Rome'
    local veronaItem = QtGui.QStandardItem.new 'Verona'

    -- building up the hierarchy
    rootNode:appendRow(americaItem)
    rootNode:appendRow(europeItem)
    americaItem:appendRow(mexicoItem)
    americaItem:appendRow(usaItem)
    usaItem:appendRow(bostonItem)
    europeItem:appendRow(italyItem)
    italyItem:appendRow(romeItem)
    italyItem:appendRow(veronaItem)

    -- register the model
    self.treeView:setModel(standardModel)
    -- avoid gc
    self.treeView.model = standardModel

    self.treeView:expandAll()

    -- selection changes shall trigger a slot
    local selectionModel = self.treeView:selectionModel()
    self.connect(selectionModel, SIGNAL 'selectionChanged(QItemSelection,QItemSelection)'
    	, self, SLOT 'selectionChangedSlot(QItemSelection,QItemSelection)'
    )
end

function Class:selectionChangedSlot(newSelection, oldSelection)
    -- get the text of the selected item
    local index = self.treeView:selectionModel():currentIndex()
    local selectedText = index:data(QtCore.DisplayRole):toString()
    -- find out the hierarchy level of the selected item
    local hierarchyLevel = 1
    local seekRoot = index
    while seekRoot:parent() ~= QtCore.QModelIndex() do
    	seekRoot = seekRoot:parent()
    	hierarchyLevel = hierarchyLevel + 1
    end
    local showString = QtCore.QString('%1, Level %2')
    	:arg(selectedText)
    	:arg(tostring(hierarchyLevel))

    self:setWindowTitle(showString)
end

return Class
