import collections
from PySide6 import QtWidgets, QtCore


class Item(object):
    def __init__(self, data, parent):
        self._data = data
        self.parent = parent
        self.children = []
        self.can_fetch_more = True

    def __repr__(self):
        return "Item({!r})".format(self.alias)

    @property
    def alias(self):
        parent = self.parent
        alias = [self.data("name")]
        while parent:
            alias.append(parent.data("name"))
            parent = parent.parent

        return "/".join(reversed(alias))

    def data(self, key, role=QtCore.Qt.DisplayRole):
        if role == QtCore.Qt.DisplayRole:
            return self._data.get(key, "<unknown>")


class TreeModel(QtCore.QAbstractItemModel):
    def __init__(self, columns, parent=None):
        super(TreeModel, self).__init__(parent=parent)
        self.root = Item({"name": "root"}, None)

        self.columns = columns

    def getItem(self, index):
        if index is None or not index.isValid():
            return self.root

        if index.isValid():
            item = index.internalPointer()
            if item:
                return item

        return None

    def data(self, index, role):
        item = self.getItem(index)
        key = list(self.columns.keys())[index.column()]
        return item.data(key, role)

    def index(self, row, column, parent=None):
        item = self.getItem(parent)
        child = item.children[row]
        return self.createIndex(row, column, child)

    def parent(self, index):
        item = self.getItem(index)
        if item.parent == self.root:
            return QtCore.QModelIndex()

        row = item.parent.children.index(item)
        return self.createIndex(row, 0, item.parent)

    def rowCount(self, index):
        return len(self.getItem(index).children)

    def columnCount(self, index):
        return len(list(self.columns.keys()))

    def flags(self, index):
        return QtCore.Qt.ItemIsSelectable \
            | QtCore.Qt.ItemIsEnabled \
            | QtCore.Qt.ItemIsDragEnabled \
            | QtCore.Qt.ItemIsDropEnabled

    def setData(self, index, value, role):
        if role != QtCore.Qt.EditRole:
            return

        item = self.getItem(index)
        item.data[self.columns.keys()[index.column()]] = value

    def headerData(self, section, orientation, role):
        if role == QtCore.Qt.DisplayRole:
            return list(self.columns.values())[section]

    def canFetchMore(self, index):
        item = self.getItem(index)
        return item.can_fetch_more

    def fetchMore(self, index):
        item = self.getItem(index)

        self.beginInsertRows(index, 0, 9)

        for i in range(10):

            item.children.append(Item({"name": "Item #{}".format(i)}, item))

        self.endInsertRows()

        item.can_fetch_more = False

    def hasChildren(self, index):
        item = self.getItem(index)
        return bool(item.children) or item.can_fetch_more


def show(proxy=True):
    app = QtWidgets.QApplication([])
    tree = QtWidgets.QTreeView()

    columns = collections.OrderedDict([
        ["name", "Name"]
    ])

    model = TreeModel(columns)
    if proxy:
        proxy_model = QtCore.QSortFilterProxyModel()
        proxy_model.setSourceModel(model)
        model = proxy_model
    tree.setModel(model)
    tree.show()
    app.exec_()


if __name__ == "__main__":
    show()