# This file is part of project Sverchok. It's copyrighted by the contributors
# recorded in the version control history of the file, available from
# its original location https://github.com/nortikin/sverchok/commit/master
#
# SPDX-License-Identifier: GPL3
# License-Filename: LICENSE

# from __future__ import annotations <- Don't use it here, `group node` will loose its `group tree` attribute
import time
from collections import namedtuple
from functools import reduce
from typing import Tuple, List, Set, Dict, Iterator, Optional

import bpy
from bpy.props import BoolProperty, EnumProperty
from sverchok.core.event_system import handle_event
from sverchok.data_structure import extend_blender_class
from mathutils import Vector

from sverchok.core.sockets import socket_type_names
import sverchok.core.events as ev
import sverchok.core.group_update_system as gus
from sverchok.core.update_system import ERROR_KEY
from sverchok.utils.tree_structure import Tree
from sverchok.utils.sv_node_utils import recursive_framed_location_finder
from sverchok.utils.handle_blender_data import BlTrees
from sverchok.node_tree import SvNodeTreeCommon, SverchCustomTreeNode


class SvGroupTree(SvNodeTreeCommon, bpy.types.NodeTree):
    """Separate tree class for sub trees"""
    bl_idname = 'SvGroupTree'
    bl_icon = 'NODETREE'
    bl_label = 'Group tree'

    # should be updated by "Go to edit group tree" operator
    group_node_name: bpy.props.StringProperty(options={'SKIP_SAVE'})

    # Always False, does not have sense to have for nested trees, sine of draft mode refactoring
    sv_draft: bpy.props.BoolProperty(options={'SKIP_SAVE'})
    sv_show_time_nodes: BoolProperty(default=False, options={'SKIP_SAVE'})
    show_time_mode: EnumProperty(
        items=[(n, n, '') for n in ["Per node", "Cumulative"]],
        options={'SKIP_SAVE'},
    )

    @classmethod
    def poll(cls, context):
        return False  # only for inner usage

    sv_show: bpy.props.BoolProperty(name="Show", default=True, description='Show group tree')
    description: bpy.props.StringProperty(
        name="Tree description",
        default="Hover over question mark to read tooltip\n"
                "It's alpha version of group nodes use with caution\n"
                "At this moment only 3 output nodes are supported (Group output, Stethoscope, Debug print)\n"
                "Any node connected to them will be evaluated\n"
                "Viewer nodes are not supported\n"
                "Import into JSON is not supported\n"
                "but it is possible to import group trees via standard Blender append functionality\n"
                "Group trees are using its own update system\n"
                "This system supports canceling processing next nodes by pressing escape during group tree editing")

    @property
    def sv_show_socket_menus(self):
        """It searches root tree and returns its eponymous attribute"""
        for area in bpy.context.screen.areas:
            # this is not Sverchok editor
            if area.ui_type != BlTrees.MAIN_TREE_ID:
                continue

            # editor does not have any active tree
            if not area.spaces[0].node_tree:
                continue

            # this editor edits another trees, What!?
            if self not in (p.node_tree for p in area.spaces[0].path):
                continue

            return area.spaces[0].path[0].node_tree.sv_show_socket_menus
        return False

    def upstream_trees(self) -> List['SvGroupTree']:
        """
        It will try to return all the tree sub trees (in case if there is group nodes)
        and sub trees of sub trees and so on
        The method can help to predict if linking new sub tree can lead to cyclic linking
        """
        next_group_nodes = [node for node in self.nodes if node.bl_idname == 'SvGroupTreeNode']
        trees = [self]
        safe_counter = 0
        while next_group_nodes:
            next_node = next_group_nodes.pop()
            if next_node.node_tree:
                trees.append(next_node.node_tree)
                next_group_nodes.extend([
                    node for node in next_node.node_tree.nodes if node.bl_idname == 'SvGroupTreeNode'])
            safe_counter += 1

            if safe_counter > 1000:
                raise RecursionError(f'Looks like group tree "{self}" has links to itself from other groups')
        return trees

    def can_be_linked(self):
        """trying to avoid creating loops of group trees to each other"""
        # upstream trees of tested treed should nad share trees with downstream trees of current tree
        tested_tree_upstream_trees = {t.name for t in self.upstream_trees()}
        current_tree_downstream_trees = {p.node_tree.name for p in bpy.context.space_data.path}
        shared_trees = tested_tree_upstream_trees & current_tree_downstream_trees
        return not shared_trees

    def update(self):
        """trigger on links or nodes collections changes, on assigning tree to a group node
        also it is triggered when a tree, next in the path, was changed (even if this tree was not effected)"""
        # When group input or output nodes are connected some extra work should be done
        if 'init_tree' in self.id_data:  # tree is building by a script - let it do this
            return

        self.check_last_socket()  # Should not be too expensive to call it each update

        if self.name not in bpy.data.node_groups:  # load new file event
            return
        if not hasattr(bpy.context.space_data, 'path'):  # 3D panel also can call update method O_o
            return
        if not self.group_node_name:  # initialization tree
            return

        group_node: SvGroupTreeNode = None
        # update tree can lead to calling update of previous tree too, so should find position tree in the path
        for i, path in zip(range(-1, -1000, -1), reversed(bpy.context.space_data.path)):
            if path.node_tree == self:
                group_node = bpy.context.space_data.path[i - 1].node_tree.nodes[self.group_node_name]
                break
        if group_node is None:
            # the tree was assigned to a group node, it does not have sense to update
            return

        self.check_reroutes_sockets()
        self.update_sockets()  # probably more precise trigger could be found for calling this method
        handle_event(ev.GroupTreeEvent(self, self.get_update_path()))

    def update_sockets(self):  # todo it lets simplify sockets API
        """Set properties of sockets of parent nodes and of output modes"""
        for node in self.parent_nodes():
            for n_in_s, t_in_s in zip(node.inputs, self.inputs):
                # also before getting data from socket `socket.use_prop` property should be set
                if hasattr(n_in_s, 'default_property'):
                    n_in_s.use_prop = not t_in_s.hide_value
                if hasattr(t_in_s, 'default_type'):
                    n_in_s.default_property_type = t_in_s.default_type
        for out_node in (n for n in self.nodes if n.bl_idname == 'NodeGroupOutput'):
            for n_in_s, t_out_s in zip(out_node.inputs, self.outputs):
                if hasattr(n_in_s, 'default_property'):
                    n_in_s.use_prop = not t_out_s.hide_value
                    if hasattr(t_out_s, 'default_type'):
                        n_in_s.default_property_type = t_out_s.default_type
                else:
                    n_in_s.use_prop = False

    def check_reroutes_sockets(self):
        """
        Fix reroute sockets type
        For now it does work properly in first update
        because all new sockets even if they have links have `is_linked` attribute with False value
        at next update events all works perfectly (skip first update?)

        There is hope this will be fixed https://developer.blender.org/T82390
        """
        tree = Tree(self)
        socket_job = []
        Requirements = namedtuple('Requirements', ['left_n_i', 'left_s_i', 'left_t', 'reroute_n_i',
                                                   'right_n_is', 'right_s_is'])
        # analytical part, it's impossible to use Tree structure and modify the tree
        for node in tree.sorted_walk(tree.output_nodes):
            # walk should be sorted in case if reroute nodes are going one after other
            if node.bl_tween.bl_idname == 'NodeReroute':
                rer_in_s = node.inputs[0]
                rer_out_s = node.outputs[0]
                if rer_in_s.links:
                    left_s = rer_in_s.linked_sockets[0]
                    left_type = left_s.type if hasattr(left_s, 'type') else left_s.bl_tween.bl_idname
                    if left_type != rer_in_s.bl_tween.bl_idname:
                        rer_out_s.type = left_type
                        socket_job.append(Requirements(left_s.node.index, left_s.index, left_type, node.index,
                                                       [s.node.index for s in rer_out_s.linked_sockets],
                                                       [s.index for s in rer_out_s.linked_sockets]))

        # regenerating sockets
        for props in socket_job:
            left_s = self.nodes[props.left_n_i].outputs[props.left_s_i]
            reroute = self.nodes[props.reroute_n_i]

            # handle input socket
            in_s = reroute.inputs.new(props.left_t, left_s.name)
            self.links.new(in_s, left_s)
            reroute.inputs.remove(reroute.inputs[0])

            # handle output sockets
            out_s = reroute.outputs.new(props.left_t, left_s.name)
            for right_n_i, right_s_i in zip(props.right_n_is, props.right_s_is):
                left_s = self.nodes[right_n_i].inputs[right_s_i]
                self.links.new(left_s, out_s)
            reroute.outputs.remove(reroute.outputs[0])

    def check_last_socket(self):
        """Override socket creation of standard operator in Node interface menu"""
        if self.inputs:
            if self.inputs[-1].bl_socket_idname == 'NodeSocketFloat':
                # This is wrong socket type -> fixing
                self.inputs.remove(self.inputs[-1])
                self.inputs.new('SvStringsSocket', 'Value')
        if self.outputs:
            if self.outputs[-1].bl_socket_idname == 'NodeSocketFloat':
                self.outputs.remove(self.outputs[-1])
                self.outputs.new('SvStringsSocket', 'Value')

    def update_nodes(self, nodes: list):
        """
        This method expect to get list of its nodes which should be updated
        Execution won't be immediately, use cases -
        1. Node property of was changed
        2. ???
        """
        # the method can be called during tree reconstruction from JSON file
        # in this case we does not intend doing any updates
        if not self.group_node_name:  # initialization tree
            return

        handle_event(ev.GroupPropertyEvent(self, self.get_update_path(), nodes))

    def parent_nodes(self) -> Iterator['SvGroupTreeNode']:
        """Returns all parent nodes"""
        # todo optimisation?
        for tree in (t for t in bpy.data.node_groups if t.bl_idname in {'SverchCustomTreeType', 'SvGroupTree'}):
            for node in tree.nodes:
                if hasattr(node, 'node_tree') and node.node_tree and node.node_tree.name == self.name:
                    yield node

    def get_update_path(self) -> List['SvGroupTreeNode']:
        """
        Should be called only when the tree is opened in one of tree editors
        returns list of group nodes in path of current screen
        """
        for area in bpy.context.screen.areas:
            # this is not Sverchok editor
            if area.ui_type != BlTrees.MAIN_TREE_ID:
                continue

            # editor does not have any active tree
            if not area.spaces[0].node_tree:
                continue

            # this editor edits another tree, What!?
            if self not in (p.node_tree for p in area.spaces[0].path):
                continue

            group_nodes = []
            paths = area.spaces[0].path
            for path, next_path in zip(paths[:-1], paths[1:]):
                group_nodes.append(path.node_tree.nodes[next_path.node_tree.group_node_name])
                if next_path.node_tree == self:
                    break  # the tree is no last in the path
            return group_nodes
        raise LookupError(f'Path the group tree: {self} was not found')

    if bpy.app.version >= (3, 2):  # in 3.1 this can lead to a crash
        @classmethod
        def valid_socket_type(cls, socket_type: str):
            # https://docs.blender.org/api/master/bpy.types.NodeTree.html#bpy.types.NodeTree.valid_socket_type
            return socket_type in socket_type_names()


class BaseNode:
    n_id: bpy.props.StringProperty(options={'SKIP_SAVE'})

    @property
    def node_id(self):
        """Identifier of the node"""
        if not self.n_id:
            self.n_id = str(hash(self) ^ hash(time.monotonic()))
        return self.n_id

    def process_node(self, context):
        """update properties of socket of the node trigger this method"""
        self.id_data.update_nodes([self])

    def copy(self, original):
        self.n_id = ''

    sv_default_color = SverchCustomTreeNode.sv_default_color

    set_temp_color = SverchCustomTreeNode.set_temp_color

    @property
    def absolute_location(self):
        return recursive_framed_location_finder(self, self.location[:])


class SvGroupTreeNode(SverchCustomTreeNode, bpy.types.NodeCustomGroup):
    """Node for keeping sub trees"""
    bl_idname = 'SvGroupTreeNode'
    bl_label = 'Group node (Alpha)'

    # todo add methods: switch_on_off

    def nested_tree_filter(self, context):
        """Define which tree we would like to use as nested trees."""
        tested_tree = context
        if tested_tree.bl_idname == SvGroupTree.bl_idname:  # It should be our dedicated to this class
            return tested_tree.can_be_linked()
        else:
            return False

    def update_group_tree(self, context):
        """Apply filtered tree to `node_tree` attribute.
        By this attribute Blender is aware of linking between the node and nested tree."""
        handle_event(ev.TreesGraphEvent())
        self.node_tree: SvGroupTree = self.group_tree
        # also default values should be fixed
        if self.node_tree:
            self.node_tree.use_fake_user = True
            for node_sock, interface_sock in zip(self.inputs, self.node_tree.inputs):
                if hasattr(interface_sock, 'default_value') and hasattr(node_sock, 'default_property'):
                    node_sock.default_property = interface_sock.default_value
                self.node_tree.update_sockets()  # properties of input socket properties should be updated
        else:  # in case if None is assigned to node_tree
            self.inputs.clear()
            self.outputs.clear()

    group_tree: bpy.props.PointerProperty(type=SvGroupTree, poll=nested_tree_filter, update=update_group_tree)

    def toggle_active(self, state: bool, to_update: bool = True):
        """This function can change state of `is_active` attribute without node updating"""
        if 'toggle_active' in self:
            # avoiding recursion
            del self['toggle_active']
            return
        else:
            self['toggle_active'] = True
            self.is_active = state  # it will call the method again and will delete 'toggle_active' key
            if state and to_update:
                self.id_data.update_nodes([self])

    is_active: bpy.props.BoolProperty(name="Live", description='Update realtime if active', default=True,
                                      update=lambda s, c: s.toggle_active(s.is_active))

    def switch_viewers(self, context):
        """Turn on/off displaying objects in viewport generated by viewer nodes inside group tree"""
        for node in self.node_tree.nodes:
            try:
                node.show_viewport(self.show)
            except AttributeError:
                pass

    show: bpy.props.BoolProperty(default=True, description="On/off viewer nodes inside", update=switch_viewers)

    def draw_buttons(self, context, layout):
        if self.node_tree:
            row_description = layout.row()

            row = row_description.row(align=True)
            row.prop(self, 'is_active', toggle=True)
            row = row.row(align=True)
            # row.prop(self, 'show', text="", icon=f'RESTRICT_VIEW_{"OFF" if self.show else "ON"}')
            row.prop(self.node_tree, 'use_fake_user', text='')

            add_description = row_description.operator('node.add_tree_description', text='', icon='QUESTION')
            add_description.tree_name = self.node_tree.name
            add_description.description = self.node_tree.description

        col = layout.column()
        # col.template_ID(self, 'group_tree')
        row_name = col.row()
        row_ops = col.row()
        row_search = row_ops.row(align=True)
        row_search.operator('node.search_group_tree', text='', icon='VIEWZOOM')
        if self.group_tree:
            row_name.prop(self.group_tree, 'name', text='')
            row_search.operator('node.edit_group_tree', text='Edit', icon='FILE_PARENT')
            row_ops.operator('node.ungroup_group_tree', text='', icon='MOD_PHYSICS')
        else:
            row_search.operator('node.add_group_tree', text='New', icon='ADD')

    def process(self):
        """
        This method is going to be called only by update system of main tree
        Calling this method means that input group node should fetch data from group node
        """
        # it's better process the node even if it is switched off in case when tree is just opened
        should_update_output_data = False
        if self.outputs:
            try:
                self.outputs[0].sv_get(deepcopy=False)
            except LookupError:
                should_update_output_data = True

        if not self.node_tree or (not self.is_active and not should_update_output_data):
            return

        self.node_tree: SvGroupTree

        # most simple way to pass data about whether node group should show timings
        self.node_tree.sv_show_time_nodes = self.id_data.sv_show_time_nodes
        self.node_tree.show_time_mode = self.id_data.show_time_mode

        input_node = self.active_input()
        output_node = self.active_output()
        if not input_node or not output_node:
            return

        for in_s, out_s in zip(self.inputs, input_node.outputs):
            if out_s.identifier == '__extend__':  # virtual socket
                break
            out_s.sv_set(in_s.sv_get(deepcopy=False))

        tree = gus.GroupUpdateTree.get(self.node_tree, refresh_tree=True)
        tree.add_outdated([input_node])
        tree.update(self)

        for node in self.node_tree.nodes:
            if err := node.get(ERROR_KEY):
                raise Exception(err)
        else:
            for in_s, out_s in zip(output_node.inputs, self.outputs):
                if in_s.identifier == '__extend__':  # virtual socket
                    break
                out_s.sv_set(in_s.sv_get(deepcopy=False))

    def active_input(self) -> Optional[bpy.types.Node]:
        # https://developer.blender.org/T82350
        for node in reversed(self.node_tree.nodes):
            if node.bl_idname == 'NodeGroupInput':
                return node

    def active_output(self) -> Optional[bpy.types.Node]:
        for node in reversed(self.node_tree.nodes):
            if node.bl_idname == 'NodeGroupOutput':
                return node

    def sv_update(self):
        # this code should work only first time a socket was added
        if self.node_tree:
            for n_in_s, t_in_s in zip(self.inputs, self.node_tree.inputs):
                # also before getting data from socket `socket.use_prop` property should be set
                if hasattr(n_in_s, 'default_property'):
                    n_in_s.use_prop = not t_in_s.hide_value
                if hasattr(t_in_s, 'default_type'):
                    n_in_s.default_property_type = t_in_s.default_type

    def sv_copy(self, original):
        handle_event(ev.TreesGraphEvent())

    def sv_free(self):
        handle_event(ev.TreesGraphEvent())


class PlacingNodeOperator:
    """Helper class for locating nodes in a node tree"""
    # quite basic operator can be moved to some more general module
    @staticmethod
    def placing_node(context, node_type: str):
        tree = context.space_data.path[-1].node_tree
        bpy.ops.node.select_all(action='DESELECT')
        group_node = tree.nodes.new(node_type)
        group_node.location = context.space_data.cursor_location

    @staticmethod
    def store_mouse_cursor(context, event):
        # convert mouse position to the View2D for later node placement
        space = context.space_data
        space.cursor_location_from_region(event.mouse_region_x, event.mouse_region_y)

    # Default invoke stores the mouse position to place the node correctly
    # and invokes the transform operator
    def invoke(self, context, event):
        self.store_mouse_cursor(context, event)
        result = self.execute(context)

        if 'FINISHED' in result:
            # removes the node again if transform is canceled
            bpy.ops.node.translate_attach_remove_on_cancel('INVOKE_DEFAULT')

        return result


class AddGroupNode(PlacingNodeOperator, bpy.types.Operator):
    """Creating just group node without linking any sub tree to it"""
    bl_idname = "node.add_group_node"
    bl_label = "Add group node"

    def execute(self, context):
        self.placing_node(context, 'SvGroupTreeNode')
        return {'FINISHED'}

    @classmethod
    def poll(cls, context):
        return cls.can_be_added(context)[0]

    @classmethod
    def description(cls, context, properties):
        return cls.can_be_added(context)[1]

    @classmethod
    def can_be_added(cls, context) -> Tuple[bool, str]:
        path = context.space_data.path[-1] if len(context.space_data.path) else None
        if not path:
            return False, ''
        tree = path.node_tree
        if tree.bl_idname == 'SverchCustomTreeType':
            return True, 'Add group node'
        elif tree.bl_idname == 'SvGroupTree':
            return True, "Add group node"
        else:
            return False, f"Can't add in '{tree.bl_idname}' type"


class AddNodeOutputInput(PlacingNodeOperator, bpy.types.Operator):
    """Operator for creating output and input nodes in sub trees"""
    bl_idname = "node.add_node_output_input"
    bl_label = "Add output input nodes"

    node_type: bpy.props.EnumProperty(items=[(i, i, '') for i in ['input', 'output']])

    def execute(self, context):
        if self.node_type == 'input':
            node_type = 'NodeGroupInput'
        else:
            node_type = 'NodeGroupOutput'
        self.placing_node(context, node_type)
        return {'FINISHED'}

    @classmethod
    def poll(cls, context):
        path = context.space_data.path
        if len(path):
            if path[-1].node_tree.bl_idname == SvGroupTree.bl_idname:
                return True
        return False

    @classmethod
    def description(cls, context, properties):
        return f'Add group {properties.node_type} node'


class AddGroupTree(bpy.types.Operator):
    """Create empty sub tree for group node"""
    bl_idname = "node.add_group_tree"
    bl_label = "Add group tree"

    def execute(self, context):
        """Link new sub tree to group node, create input and output nodes in sub tree and go to edit one"""
        sub_tree = bpy.data.node_groups.new('Sverchok group', 'SvGroupTree')  # creating sub tree
        sub_tree.use_fake_user = True
        context.node.group_tree = sub_tree  # link sub tree to group node
        sub_tree.nodes.new('NodeGroupInput').location = (-250, 0)  # create node for putting data into sub tree
        sub_tree.nodes.new('NodeGroupOutput').location = (250, 0)  # create node for getting data from sub tree
        return bpy.ops.node.edit_group_tree({'node': context.node})


class AddGroupTreeFromSelected(bpy.types.Operator):
    """Create instead of select nodes group node and placing them into sub tree"""
    bl_idname = "node.add_group_tree_from_selected"
    bl_label = "Add group tree from selected"

    @classmethod
    def poll(cls, context):
        path = context.space_data.path
        if len(path):
            if path[-1].node_tree.bl_idname in {'SverchCustomTreeType', SvGroupTree.bl_idname}:
                return bool(cls.filter_selected_nodes(path[-1].node_tree))
        return False

    def execute(self, context):
        """
        Add group tree from selected:
        01. Deselect group Input and Output nodes
        02. Copy nodes into clipboard
        03. Create group tree and move into one
        04. Past nodes from clipboard
        05. Move nodes into tree center
        06. Add group "input" and "output" outside of bounding box of the nodes
        07. Connect "input" and "output" sockets with group nodes
        08. Add Group tree node in center of selected node in initial tree
        09. Link the node with appropriate sockets
        10. Cleaning
        """
        base_tree = context.space_data.path[-1].node_tree
        if not self.can_be_grouped(base_tree):
            self.report({'WARNING'}, 'Current selection can not be converted to group')
            return {'CANCELLED'}
        sub_tree: SvGroupTree = bpy.data.node_groups.new('Sverchok group', SvGroupTree.bl_idname)

        # deselect group nodes if selected
        [setattr(n, 'select', False) for n in base_tree.nodes
         if n.select and n.bl_idname in {'NodeGroupInput', 'NodeGroupOutput'}]

        # Frames can't be just copied because they does not have absolute location, but they can be recreated
        frame_names = {n.name for n in base_tree.nodes if n.select and n.bl_idname == 'NodeFrame'}
        [setattr(n, 'select', False) for n in base_tree.nodes if n.bl_idname == 'NodeFrame']

        with base_tree.init_tree(), sub_tree.init_tree():
            # copy and past nodes into group tree
            bpy.ops.node.clipboard_copy()
            context.space_data.path.append(sub_tree)
            bpy.ops.node.clipboard_paste()
            context.space_data.path.pop()  # will enter later via operator

            # move nodes in tree center
            sub_tree_nodes = self.filter_selected_nodes(sub_tree)
            center = reduce(lambda v1, v2: v1 + v2, [n.location for n in sub_tree_nodes]) / len(sub_tree_nodes)
            [setattr(n, 'location', n.location - center) for n in sub_tree_nodes]

            # recreate frames
            node_name_mapping = {n.name: n.name for n in sub_tree.nodes}  # all nodes have the same name as in base tree
            self.recreate_frames(base_tree, sub_tree, frame_names, node_name_mapping)

            # add group input and output nodes
            min_x = min(n.location[0] for n in sub_tree_nodes)
            max_x = max(n.location[0] for n in sub_tree_nodes)
            input_node = sub_tree.nodes.new('NodeGroupInput')
            input_node.location = (min_x - 250, 0)
            output_node = sub_tree.nodes.new('NodeGroupOutput')
            output_node.location = (max_x + 250, 0)

            # add group tree node
            initial_nodes = self.filter_selected_nodes(base_tree)
            center = reduce(lambda v1, v2: v1 + v2,
                            [Vector(n.absolute_location) for n in initial_nodes]) / len(initial_nodes)
            group_node = base_tree.nodes.new(SvGroupTreeNode.bl_idname)
            group_node.select = False
            group_node.group_tree = sub_tree
            group_node.location = center
            sub_tree.group_node_name = group_node.name

            # linking, linking should be ordered from first socket to last (in case like `join list` nodes)
            py_base_tree = Tree(base_tree)
            [setattr(py_base_tree.nodes[n.name], 'select', n.select) for n in base_tree.nodes]
            input_node['connected_sockets'] = dict()  # Dict[node.name + socket.identifier, socket index of input node]
            for py_node in py_base_tree.nodes:  # is selected
                if not py_node.select:
                    continue
                for in_s in py_node.inputs:
                    for out_s in in_s.linked_sockets:  # only one link always
                        if out_s.node.select:
                            continue
                        out_s_key = out_s.node.name + out_s.identifier
                        if out_s_key in input_node['connected_sockets']:  # protect from creating extra input sockets
                            input_out_s_index = input_node['connected_sockets'][out_s_key]
                            sub_tree.links.new(in_s.get_bl_socket(sub_tree), input_node.outputs[input_out_s_index])
                        else:
                            input_out_s_index = len(input_node.outputs) - 1
                            input_node['connected_sockets'][out_s_key] = input_out_s_index
                            sub_tree.links.new(in_s.get_bl_socket(sub_tree), input_node.outputs[input_out_s_index])
                            base_tree.links.new(group_node.inputs[-1], out_s.get_bl_socket(base_tree))

                for out_py_socket in py_node.outputs:
                    if any(not s.node.select for s in out_py_socket.linked_sockets):
                        sub_tree.links.new(output_node.inputs[-1], out_py_socket.get_bl_socket(sub_tree))
                    for in_py_socket in out_py_socket.linked_sockets:
                        if not in_py_socket.node.select:
                            base_tree.links.new(in_py_socket.get_bl_socket(base_tree), group_node.outputs[-1])

            # delete selected nodes and copied frames without children
            [base_tree.nodes.remove(n) for n in self.filter_selected_nodes(base_tree)]
            with_children_frames = {n.parent.name for n in base_tree.nodes if n.parent}
            [base_tree.nodes.remove(n) for n in base_tree.nodes
             if n.name in frame_names and n.name not in with_children_frames]

        # todo one ui update (useless) will be done by the operator and another with update system of main handler
        bpy.ops.node.edit_group_tree({'node': group_node})

        return {'FINISHED'}

    @staticmethod
    def filter_selected_nodes(tree) -> list:
        """Avoiding selecting nodes which should not be copied into sub tree"""
        return [n for n in tree.nodes if n.select and n.bl_idname not in {'NodeGroupInput', 'NodeGroupOutput'}]

    @staticmethod
    def can_be_grouped(tree) -> bool:
        """True if selected nodes can be putted into group (does not produce cyclic links)"""
        # if there is one or more unselected nodes between nodes to be grouped
        # then current selection can't be grouped
        py_tree = Tree(tree)
        [setattr(py_tree.nodes[n.name], 'select', n.select) for n in tree.nodes]
        for node in py_tree.nodes:
            if not node.select:
                continue
            for neighbour_node in node.next_nodes:
                if neighbour_node.select:
                    continue
                for next_node in py_tree.bfs_walk([neighbour_node]):
                    if next_node.select:
                        return False
        return True

    @staticmethod
    def recreate_frames(from_tree: bpy.types.NodeTree,
                        to_tree: bpy.types.NodeTree,
                        frame_names: Set[str],
                        from_to_node_names: Dict[str, str]):
        """
        It will copy frames from one tree to another
        from_to_node_names - mapping of node names between two trees
        """
        new_frame_names = {n: to_tree.nodes.new('NodeFrame').name for n in frame_names}
        frame_attributes = ['label', 'use_custom_color', 'color', 'label_size', 'text']
        for frame_name in frame_names:
            old_frame = from_tree.nodes[frame_name]
            new_frame = to_tree.nodes[new_frame_names[frame_name]]
            for attr in frame_attributes:
                setattr(new_frame, attr, getattr(old_frame, attr))
        for from_node in from_tree.nodes:
            if from_node.name not in from_to_node_names:
                continue
            if from_node.parent and from_node.parent.name in new_frame_names:
                if from_node.bl_idname == 'NodeFrame':
                    to_node = to_tree.nodes[new_frame_names[from_node.name]]
                else:
                    to_node = to_tree.nodes[from_to_node_names[from_node.name]]
                to_node.parent = to_tree.nodes[new_frame_names[from_node.parent.name]]


class UngroupGroupTree(bpy.types.Operator):
    """Put sub nodes into current layout and delete current group node"""
    bl_idname = 'node.ungroup_group_tree'
    bl_label = "Ungroup group tree"

    @classmethod
    def poll(cls, context):
        if context.active_node and hasattr(context.active_node, 'node_tree'):
            return True
        elif context.node:
            return True
        return False

    def execute(self, context):
        """Similar to AddGroupTreeFromSelected operator but in backward direction (from sub tree to tree)"""

        # go to sub tree, select all except input and output groups and mark nodes to be copied
        group_node = context.node
        sub_tree = group_node.node_tree
        bpy.ops.node.edit_group_tree({'node': group_node})
        [setattr(n, 'select', False) for n in sub_tree.nodes]
        group_nodes_filter = filter(lambda n: n.bl_idname not in {'NodeGroupInput', 'NodeGroupOutput'}, sub_tree.nodes)
        for node in group_nodes_filter:
            node.select = True
            node['sub_node_name'] = node.name  # this will be copied within the nodes

        # the attribute should be empty in destination tree
        tree = context.space_data.path[-2].node_tree
        for node in tree.nodes:
            if 'sub_node_name' in node:
                del node['sub_node_name']

        # Frames can't be just copied because they does not have absolute location, but they can be recreated
        frame_names = {n.name for n in sub_tree.nodes if n.select and n.bl_idname == 'NodeFrame'}
        [setattr(n, 'select', False) for n in sub_tree.nodes if n.bl_idname == 'NodeFrame']

        if any(n for n in sub_tree.nodes if n.select):  # if no selection copy operator will raise error
            # copy and past nodes into group tree
            bpy.ops.node.clipboard_copy()
            context.space_data.path.pop()
            bpy.ops.node.clipboard_paste()  # this will deselect all and select only pasted nodes

            # move nodes in group node center
            tree_select_nodes = [n for n in tree.nodes if n.select]
            center = reduce(lambda v1, v2: v1 + v2,
                            [Vector(n.absolute_location) for n in tree_select_nodes]) / len(tree_select_nodes)
            [setattr(n, 'location', n.location - (center - group_node.location)) for n in tree_select_nodes]

            # recreate frames
            node_name_mapping = {n['sub_node_name']: n.name for n in tree.nodes if 'sub_node_name' in n}
            AddGroupTreeFromSelected.recreate_frames(sub_tree, tree, frame_names, node_name_mapping)
        else:
            context.space_data.path.pop()  # should exit from sub tree anywhere

        # recreate py tree structure
        sub_py_tree = Tree(sub_tree)
        [setattr(sub_py_tree.nodes[n.name], 'type', n.bl_idname) for n in sub_tree.nodes]
        py_tree = Tree(tree)
        [setattr(py_tree.nodes[n.name], 'select', n.select) for n in tree.nodes]
        group_py_node = py_tree.nodes[group_node.name]
        for node in tree.nodes:
            if 'sub_node_name' in node:
                sub_py_tree.nodes[node['sub_node_name']].twin = py_tree.nodes[node.name]
                py_tree.nodes[node.name].twin = sub_py_tree.nodes[node['sub_node_name']]

        # create in links
        for group_input_py_node in [n for n in sub_py_tree.nodes if n.type == 'NodeGroupInput']:
            for group_in_s, input_out_s in zip(group_py_node.inputs, group_input_py_node.outputs):
                if group_in_s.links and input_out_s.links:
                    link_out_s = group_in_s.linked_sockets[0]
                    for twin_in_s in input_out_s.linked_sockets:
                        if twin_in_s.node.type == 'NodeGroupOutput':  # node should be searched in above tree
                            group_out_s = group_py_node.outputs[twin_in_s.index]
                            for link_in_s in group_out_s.linked_sockets:
                                tree.links.new(link_in_s.get_bl_socket(tree), link_out_s.get_bl_socket(tree))
                        else:
                            link_in_s = twin_in_s.node.twin.inputs[twin_in_s.index]
                            tree.links.new(link_in_s.get_bl_socket(tree), link_out_s.get_bl_socket(tree))

        # create out links
        for group_output_py_node in [n for n in sub_py_tree.nodes if n.type == 'NodeGroupOutput']:
            for group_out_s, output_in_s in zip(group_py_node.outputs, group_output_py_node.inputs):
                if group_out_s.links and output_in_s.links:
                    twin_out_s = output_in_s.linked_sockets[0]
                    if twin_out_s.node.type == 'NodeGroupInput':
                        continue  # we already added this link
                    for link_in_s in group_out_s.linked_sockets:
                        link_out_s = twin_out_s.node.twin.outputs[twin_out_s.index]
                        tree.links.new(link_in_s.get_bl_socket(tree), link_out_s.get_bl_socket(tree))

        # delete group node
        tree.nodes.remove(group_node)
        for node in tree.nodes:
            if 'sub_node_name' in node:
                del node['sub_node_name']

        tree.update()

        return {'FINISHED'}


class EditGroupTree(bpy.types.Operator):
    """Go into sub tree to edit"""
    bl_idname = 'node.edit_group_tree'
    bl_label = 'Edit group tree'

    def execute(self, context):
        group_node = context.node
        sub_tree: SvGroupTree = context.node.node_tree
        context.space_data.path.append(sub_tree, node=group_node)
        sub_tree.group_node_name = group_node.name
        event = ev.GroupTreeEvent(sub_tree, sub_tree.get_update_path())
        handle_event(event)
        # todo make protection from editing the same trees in more then one area
        # todo add the same logic to exit from tree operator
        return {'FINISHED'}


class AddTreeDescription(bpy.types.Operator):
    """UI for filling Group tree description"""
    bl_idname = 'node.add_tree_description'
    bl_label = "Tree description"

    tree_name: bpy.props.StringProperty(options={'HIDDEN'})

    from_file: bpy.props.BoolProperty()
    text_name: bpy.props.StringProperty(description="Text with description of the node")
    description: bpy.props.StringProperty()

    @classmethod
    def description(cls, context, properties):
        return properties.description

    def execute(self, context):
        tree = bpy.data.node_groups[self.tree_name]
        if self.from_file:
            tree.description = bpy.data.texts[self.text_name].as_string()
        else:
            tree.description = self.description
        return {'FINISHED'}

    def invoke(self, context, event):
        return context.window_manager.invoke_props_dialog(self)

    def draw(self, context):
        col = self.layout.column()
        col.use_property_split = True
        row = col.row()
        row.active = not self.from_file
        row.prop(self, 'description')
        col.prop(self, 'from_file')
        row = col.row()
        row.active = self.from_file
        row.prop_search(self, 'text_name', bpy.data, 'texts', text="Description")


class SearchGroupTree(bpy.types.Operator):
    """Browse group trees to be linked"""
    bl_idname = 'node.search_group_tree'
    bl_label = 'Search group tree'
    bl_property = 'tree_name'

    def available_trees(self, context):
        linkable_trees = filter(lambda t: hasattr(t, 'can_be_linked') and t.can_be_linked(), bpy.data.node_groups)
        return [(t.name, t.name, '') for t in linkable_trees]

    tree_name: bpy.props.EnumProperty(items=available_trees)

    group_node_name: bpy.props.StringProperty(options={'SKIP_SAVE'})

    def execute(self, context):
        tree = context.space_data.path[-1].node_tree
        tree_to_link = bpy.data.node_groups[self.tree_name]
        group_node = tree.nodes[self.group_node_name]
        group_node.group_tree = tree_to_link
        return {'FINISHED'}

    def invoke(self, context, event):
        self.group_node_name = context.node.name  # execute context does not have the attribute -_-
        context.window_manager.invoke_search_popup(self)
        return {'FINISHED'}


classes = [SvGroupTree, SvGroupTreeNode, AddGroupNode, AddGroupTree, EditGroupTree, AddTreeDescription,
           AddNodeOutputInput, AddGroupTreeFromSelected, SearchGroupTree, UngroupGroupTree]


@extend_blender_class
class NodeGroupOutput(BaseNode):  # todo copy node id problem
    def process(self):
        return


@extend_blender_class
class NodeGroupInput(BaseNode):
    def process(self):
        return


@extend_blender_class
class NodeReroute(BaseNode):
    """Add sv logic"""
    # `copy` attribute can't be overridden for this class


@extend_blender_class
class NodeFrame(BaseNode):
    # for API consistency, it's much simpler way then create extra conditions everywhere
    pass


register, unregister = bpy.utils.register_classes_factory(classes)
