import bpy

import re
import itertools
import bisect
import json

from .errors import MetarigError
from .naming import strip_prefix, make_derived_name
from .mechanism import MechanismUtilityMixin
from .misc import map_list, map_apply

from ..base_rig import *
from ..base_generate import GeneratorPlugin

from collections import defaultdict
from itertools import count, repeat, chain

def _auto_call(value):
    if callable(value):
        return value()
    else:
        return value

def _rig_is_child(rig, parent):
    if parent is None:
        return True

    while rig:
        if rig is parent:
            return True

        rig = rig.rigify_parent

    return False


class SwitchParentBuilder(GeneratorPlugin, MechanismUtilityMixin):
    """
    Implements centralized generation of switchable parent mechanisms.
    Allows all rigs to register their bones as possible parents for other rigs.
    """

    def __init__(self, generator):
        super().__init__(generator)

        self.child_list = []
        self.global_parents = []
        self.local_parents = defaultdict(list)
        self.child_map = {}
        self.frozen = False

        self.register_parent(None, 'root', name='Root', is_global=True)


    ##############################
    # API

    def register_parent(self, rig, bone, *, name=None, is_global=False, exclude_self=False):
        """
        Registers a bone of the specified rig as a possible parent.

        Parameters:
          rig               Owner of the bone.
          bone              Actual name of the parent bone.
          name              Name of the parent for mouse-over hint.
          is_global         The parent is accessible to all rigs, instead of just children of owner.
          exclude_self      The parent is invisible to the owner rig itself.

        Lazy creation:
          The bone parameter may be a function creating the bone on demand and
          returning its name. It is guaranteed to be called at most once.
        """

        assert not self.frozen
        assert isinstance(bone, str) or callable(bone)

        entry = {
            'rig': rig, 'bone': bone, 'name': name,
            'is_global': is_global, 'exclude_self': exclude_self, 'used': False,
        }

        if is_global:
            self.global_parents.append(entry)
        else:
            self.local_parents[id(rig)].append(entry)


    def build_child(self, rig, bone, *, use_parent_mch=True, **options):
        """
        Build a switchable parent mechanism for the specified bone.

        Parameters:
          rig               Owner of the child bone.
          bone              Name of the child bone.
          extra_parents     List of bone names or (name, user_name) pairs to use as additional parents.
          use_parent_mch    Create an intermediate MCH bone for the constraints and parent the child to it.
          select_parent     Select the specified bone instead of the last one.
          ignore_global     Ignore the is_global flag of potential parents.
          exclude_self      Ignore parents registered by the rig itself.
          context_rig       Rig to use for selecting parents.

          prop_bone         Name of the bone to add the property to.
          prop_id           Actual name of the control property.
          prop_name         Name of the property to use in the UI script.
          controls          Collection of controls to bind property UI to.

          ctrl_bone         User visible control bone that depends on this parent (for switch & keep transform)
          no_fix_*          Disable "Switch and Keep Transform" correction for specific channels.
          copy_*            Override the specified components by copying from another bone.
          inherit_scale     Inherit scale mode for the child bone (default: AVERAGE).

        Lazy parameters:
          'extra_parents', 'select_parent', 'prop_bone', 'controls', 'copy_*'
          may be a function returning the value. They are called in the configure_bones stage.
        """
        assert self.generator.stage == 'generate_bones' and not self.frozen
        assert rig is not None
        assert isinstance(bone, str)
        assert bone not in self.child_map

        # Create MCH proxy
        if use_parent_mch:
            mch_bone = rig.copy_bone(bone, make_derived_name(bone, 'mch', '.parent'), scale=1/3)
        else:
            mch_bone = bone

        child = {
            **self.child_option_table,
            'rig':rig, 'bone': bone, 'mch_bone': mch_bone,
            'is_done': False, 'is_configured': False,
        }
        self.assign_child_options(child, options)
        self.child_list.append(child)
        self.child_map[bone] = child


    def amend_child(self, rig, bone, **options):
        """
        Change parameters assigned in a previous build_child call.

        Provided to make it more convenient to change rig behavior by subclassing.
        """
        assert self.generator.stage == 'generate_bones' and not self.frozen
        child = self.child_map[bone]
        assert child['rig'] == rig
        self.assign_child_options(child, options)


    def rig_child_now(self, bone):
        """Create the constraints immediately."""
        assert self.generator.stage == 'rig_bones'
        child = self.child_map[bone]
        assert not child['is_done']
        self.__rig_child(child)

    ##############################
    # Implementation

    child_option_table = {
        'extra_parents': None,
        'prop_bone': None, 'prop_id': None, 'prop_name': None, 'controls': None,
        'select_parent': None, 'ignore_global': False, 'exclude_self': False, 'context_rig': None,
        'ctrl_bone': None,
        'no_fix_location': False, 'no_fix_rotation': False, 'no_fix_scale': False,
        'copy_location': None, 'copy_rotation': None, 'copy_scale': None,
        'inherit_scale': 'AVERAGE',
    }

    def assign_child_options(self, child, options):
        if 'context_rig' in options:
            assert _rig_is_child(child['rig'], options['context_rig'])

        for name, value in options.items():
            if name not in self.child_option_table:
                raise AttributeError('invalid child option: '+name)

            child[name] = value

    def get_rig_parent_candidates(self, rig):
        candidates = []

        # Build a list in parent hierarchy order
        while rig:
            candidates.append(self.local_parents[id(rig)])
            rig = rig.rigify_parent

        candidates.append(self.global_parents)

        return list(chain.from_iterable(reversed(candidates)))

    def generate_bones(self):
        self.frozen = True
        self.parent_list = self.global_parents + list(chain.from_iterable(self.local_parents.values()))

        # Link children to parents
        for child in self.child_list:
            child_rig = child['context_rig'] or child['rig']
            parents = []

            for parent in self.get_rig_parent_candidates(child_rig):
                if parent['rig'] is child_rig:
                    if parent['exclude_self'] or child['exclude_self']:
                        continue
                elif parent['is_global'] and not child['ignore_global']:
                    # Can't use parents from own children, even if global (cycle risk)
                    if _rig_is_child(parent['rig'], child_rig):
                        continue
                else:
                    # Required to be a child of the parent's rig
                    if not _rig_is_child(child_rig, parent['rig']):
                        continue

                parent['used'] = True
                parents.append(parent)

            child['parents'] = parents

        # Call lazy creation for parents
        for parent in self.parent_list:
            if parent['used']:
                parent['bone'] = _auto_call(parent['bone'])

    def parent_bones(self):
        for child in self.child_list:
            rig = child['rig']
            mch = child['mch_bone']

            # Remove real parent from the child
            rig.set_bone_parent(mch, None)
            self.generator.disable_auto_parent(mch)

            # Parent child to the MCH proxy
            if mch != child['bone']:
                rig.set_bone_parent(child['bone'], mch, inherit_scale=child['inherit_scale'])

    def configure_bones(self):
        for child in self.child_list:
            self.__configure_child(child)

    def __configure_child(self, child):
        if child['is_configured']:
            return

        child['is_configured'] = True

        bone = child['bone']

        # Build the final list of parent bone names
        parent_map = dict()

        for parent in child['parents']:
            if parent['bone'] not in parent_map:
                parent_map[parent['bone']] = parent['name']

        last_main_parent_bone = child['parents'][-1]['bone']
        num_main_parents = len(parent_map.items())

        for parent in _auto_call(child['extra_parents'] or []):
            if not isinstance(parent, tuple):
                parent = (parent, None)
            if parent[0] not in parent_map:
                parent_map[parent[0]] = parent[1]

        parent_bones = list(parent_map.items())
        child['parent_bones'] = parent_bones

        # Find which bone to select
        select_bone = _auto_call(child['select_parent']) or last_main_parent_bone
        select_index = num_main_parents

        try:
            select_index = 1 + next(i for i, (bone, _) in enumerate(parent_bones) if bone == select_bone)
        except StopIteration:
            print("RIGIFY ERROR: Can't find bone '%s' to select as default parent of '%s'\n" % (select_bone, bone))

        # Create the controlling property
        prop_bone = child['prop_bone'] = _auto_call(child['prop_bone']) or bone
        prop_name = child['prop_name'] or child['prop_id'] or 'Parent Switch'
        prop_id = child['prop_id'] = child['prop_id'] or 'parent_switch'

        parent_names = [ parent[1] or strip_prefix(parent[0]) for parent in [(None, 'None'), *parent_bones] ]
        parent_str = ', '.join([ '%s (%d)' % (name, i) for i, name in enumerate(parent_names) ])

        ctrl_bone = child['ctrl_bone'] or bone

        self.make_property(
            prop_bone, prop_id, select_index,
            min=0, max=len(parent_bones),
            description='Switch parent of %s: %s' % (ctrl_bone, parent_str)
        )

        # Find which channels don't depend on the parent

        no_fix = [ child[n] for n in ['no_fix_location', 'no_fix_rotation', 'no_fix_scale'] ]

        child['copy'] = [ _auto_call(child[n]) for n in ['copy_location', 'copy_rotation', 'copy_scale'] ]

        locks = tuple(bool(nofix or copy) for nofix, copy in zip(no_fix, child['copy']))

        # Create the script for the property
        controls = _auto_call(child['controls']) or set([prop_bone, bone])

        script = self.generator.script
        panel = script.panel_with_selected_check(child['rig'], controls)

        panel.use_bake_settings()
        script.add_utilities(SCRIPT_UTILITIES_OP_SWITCH_PARENT)
        script.register_classes(SCRIPT_REGISTER_OP_SWITCH_PARENT)

        op_props = {
            'bone': ctrl_bone, 'prop_bone': prop_bone, 'prop_id': prop_id,
            'parent_names': json.dumps(parent_names), 'locks': locks,
        }

        row = panel.row(align=True)
        lsplit = row.split(factor=0.75, align=True)
        lsplit.operator('pose.rigify_switch_parent_{rig_id}', text=prop_name, icon='DOWNARROW_HLT', properties=op_props)
        lsplit.custom_prop(prop_bone, prop_id, text='')
        row.operator('pose.rigify_switch_parent_bake_{rig_id}', text='', icon='ACTION_TWEAK', properties=op_props)

    def rig_bones(self):
        for child in self.child_list:
            self.__rig_child(child)

    def __rig_child(self, child):
        if child['is_done']:
            return

        child['is_done'] = True

        # Implement via an Armature constraint
        mch = child['mch_bone']
        con = self.make_constraint(mch, 'ARMATURE', name='SWITCH_PARENT')

        prop_var = [(child['prop_bone'], child['prop_id'])]

        for i, (parent, parent_name) in enumerate(child['parent_bones']):
            tgt = con.targets.new()

            tgt.target = self.obj
            tgt.subtarget = parent
            tgt.weight = 0.0

            expr = 'var == %d' % (i+1)
            self.make_driver(tgt, 'weight', expression=expr, variables=prop_var)

        # Add copy constraints
        copy = child['copy']

        if copy[0]:
            self.make_constraint(mch, 'COPY_LOCATION', copy[0])
        if copy[1]:
            self.make_constraint(mch, 'COPY_ROTATION', copy[1])
        if copy[2]:
            self.make_constraint(mch, 'COPY_SCALE', copy[2])


SCRIPT_REGISTER_OP_SWITCH_PARENT = ['POSE_OT_rigify_switch_parent', 'POSE_OT_rigify_switch_parent_bake']

SCRIPT_UTILITIES_OP_SWITCH_PARENT = ['''
################################
## Switchable Parent operator ##
################################

class RigifySwitchParentBase:
    bone:         StringProperty(name="Control Bone")
    prop_bone:    StringProperty(name="Property Bone")
    prop_id:      StringProperty(name="Property")
    parent_names: StringProperty(name="Parent Names")
    locks:        bpy.props.BoolVectorProperty(name="Locked", size=3, default=[False,False,False])

    parent_items = [('0','None','None')]

    selected: bpy.props.EnumProperty(
        name='Selected Parent',
        items=lambda s,c: RigifySwitchParentBase.parent_items
    )

    keyflags = None
    keyflags_switch = None

    def save_frame_state(self, context, obj):
        return get_transform_matrix(obj, self.bone, with_constraints=False)

    def apply_frame_state(self, context, obj, old_matrix):
        # Change the parent
        set_custom_property_value(
            obj, self.prop_bone, self.prop_id, int(self.selected),
            keyflags=self.keyflags_switch
        )

        context.view_layer.update()

        # Set the transforms to restore position
        set_transform_from_matrix(
            obj, self.bone, old_matrix, keyflags=self.keyflags,
            no_loc=self.locks[0], no_rot=self.locks[1], no_scale=self.locks[2]
        )

    def get_bone_props(self):
        props = set()
        if not self.locks[0]:
            props |= TRANSFORM_PROPS_LOCATION
        if not self.locks[1]:
            props |= TRANSFORM_PROPS_ROTATION
        if not self.locks[2]:
            props |= TRANSFORM_PROPS_SCALE
        return props

    def init_invoke(self, context):
        pose = context.active_object.pose

        if (not pose or not self.parent_names
            or self.bone not in pose.bones
            or self.prop_bone not in pose.bones
            or self.prop_id not in pose.bones[self.prop_bone]):
            self.report({'ERROR'}, "Invalid parameters")
            return {'CANCELLED'}

        parents = json.loads(self.parent_names)
        pitems = [(str(i), name, name) for i, name in enumerate(parents)]

        RigifySwitchParentBase.parent_items = pitems

        self.selected = str(pose.bones[self.prop_bone][self.prop_id])


class POSE_OT_rigify_switch_parent(RigifySwitchParentBase, RigifySingleUpdateMixin, bpy.types.Operator):
    bl_idname = "pose.rigify_switch_parent_" + rig_id
    bl_label = "Switch Parent (Keep Transform)"
    bl_options = {'REGISTER', 'UNDO', 'INTERNAL'}
    bl_description = "Switch parent, preserving the bone position and orientation"

    def draw(self, _context):
        col = self.layout.column()
        col.prop(self, 'selected', expand=True)


class POSE_OT_rigify_switch_parent_bake(RigifySwitchParentBase, RigifyBakeKeyframesMixin, bpy.types.Operator):
    bl_idname = "pose.rigify_switch_parent_bake_" + rig_id
    bl_label = "Apply Switch Parent To Keyframes"
    bl_options = {'UNDO', 'INTERNAL'}
    bl_description = "Switch parent over a frame range, adjusting keys to preserve the bone position and orientation"

    def execute_scan_curves(self, context, obj):
        return self.bake_add_bone_frames(self.bone, self.get_bone_props())

    def execute_before_apply(self, context, obj, range, range_raw):
        self.bake_replace_custom_prop_keys_constant(self.prop_bone, self.prop_id, int(self.selected))

    def draw(self, context):
        self.layout.prop(self, 'selected', text='')
''']
