# People's Video Editor: high quality, GPU accelerated mp4 editor
# Copyright (C) 2025 Roz K <roz@rozk.net>
#
# This file is part of People's Video Editor.
#
# People's Video Editor is free software: you can redistribute it and/or modify it under the terms of the
# GNU General Public License as published by the Free Software Foundation, either version 3 of the License,
# or (at your option) any later version.
#
# People's Video Editor is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
# without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with People's Video Editor.
# If not, see <https://www.gnu.org/licenses/>.

from weakref import ref

class Node:
    __slots__ = 'parent', 'children', 'state', '__weakref__'

    STATE_NEW      = 0
    STATE_MODIFIED = 1
    STATE_BUILT    = 2

    def __init__(self, parent = None, children = None):
        self.parent = None
        self.children = None
        self.state = Node.STATE_NEW
        if children is not None:
            self.add_children(children)
        if parent is not None:
            parent.add_child(self)

    def __del__(self):
        if self.parent is not None:
            self.parent().remove_child(self)

    def add_child(self, child: Node):
        assert child.parent is None
        child.parent = ref(self)
        if self.children is None:
            self.children = [child]
        else:
            self.children.append(child)
        child.state = Node.STATE_NEW
        self.set_modified()

    def add_children(self, children):
        for child in children:
            self.add_child(child)

    def remove_child(self, child: Node):
        assert child.parent is self
        child.parent = None
        self.children.remove(child)
        self.set_modified()

    def remove_children(self, children):
        for child in children:
            self.remove_child(child)

    def is_new(self):
        return self.state == Node.STATE_NEW

    def needs_rebuilding(self):
        return self.state != Node.STATE_BUILT

    def set_modified(self):
        if self.needs_rebuilding():
            return
        self.state = Node.STATE_MODIFIED
        if self.parent is not None:
            self.set_parent_modified(self.parent())

    def set_parent_modified(self, parent):
        parent.set_modified()

    def rebuild(self):
        if not self.needs_rebuilding():
            return True
        if self.children is not None:
            if not self.rebuild_children(self.children):
                return False
        if not self.build():
            return False
        self.state = Node.STATE_BUILT
        return True

    def rebuild_children(self, children):
        for child in children:
            if not self.rebuild_child(child):
                return False
        return True

    def rebuild_child(self, child):
        return child.rebuild()

    def build(self):
        return True