# -*- coding: utf-8 -*-
# MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
#
# Copyright (c) 2014-2021 Megvii Inc. All rights reserved.
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

import collections
from collections import OrderedDict
from typing import Callable, NamedTuple

import numpy as np

from ...core._imperative_rt.common import CompNode
from ...core._imperative_rt.core2 import Tensor as RawTensor
from ...core._wrap import Device
from ...core.tensor.dtype import QuantDtypeMeta
from ...module import Module
from ...quantization.utils import LSQParams, QParams, QuantMode
from ...tensor import Parameter, Tensor
from .node import ModuleNode, Node, NodeMixin, TensorNode

SUPPORTED_TYPE = {}

# if type(object) or obj in SUPPORTED_LEAF_TYPE, the object could be treated as leaf node of pytree
SUPPORTED_LEAF_TYPE = {
    RawTensor,
    Tensor,
    Parameter,
    str,
    int,
    float,
    bool,
    QuantDtypeMeta,
    CompNode,
    Device,
    type(None),
    type(Ellipsis),
    QuantMode,
}

# if isinstance(object, SUPPORTED_LEAF_CLS) or issubclass(obj, SUPPORTED_LEAF_CLS) is True, the object could be threated as leaf node of pytree
SUPPORTED_LEAF_CLS = [Module, Node, NodeMixin, np.dtype, np.ndarray, np.number]

NodeType = NamedTuple("NodeType", [("flatten", Callable), ("unflatten", Callable)])


def register_supported_type(type, flatten=None, unflatten=None):
    if flatten and unflatten:
        SUPPORTED_TYPE[type] = NodeType(flatten, unflatten)
    else:
        SUPPORTED_LEAF_CLS.append(type)


def _dict_flatten(inp):
    aux_data = []
    results = []
    for key, value in sorted(inp.items()):
        results.append(value)
        aux_data.append(key)
    return results, tuple(aux_data)


def _dict_unflatten(inps, aux_data):
    return dict(zip(aux_data, inps))


def _ordereddict_flatten(inp):
    aux_data = []
    results = []
    for key, value in inp.items():
        results.append(value)
        aux_data.append(key)
    return results, tuple(aux_data)


def _ordereddict_unflatten(inps, aux_data):
    return OrderedDict(zip(aux_data, inps))


def qparams_flatten(inp):
    aux_data = []
    results = []
    for key in inp.__slots__:
        aux_data.append(key)
        results.append(getattr(inp, key, None))
    return results, tuple(aux_data)


def qparams_unflatten(inp, aux_data):
    obj = QParams.__new__(QParams)
    for k, v in zip(aux_data, inp):
        setattr(obj, k, v)
    return obj


register_supported_type(list, lambda x: (x, None), lambda x, aux_data: list(x))
register_supported_type(tuple, lambda x: (x, None), lambda x, aux_data: tuple(x))
register_supported_type(dict, _dict_flatten, _dict_unflatten)
register_supported_type(
    collections.OrderedDict, _ordereddict_flatten, _ordereddict_unflatten
)
register_supported_type(
    slice,
    lambda x: ([x.start, x.stop, x.step], None),
    lambda x, aux_data: slice(x[0], x[1], x[2]),
)

register_supported_type(QParams, qparams_flatten, qparams_unflatten)


def _is_leaf(obj):
    if isinstance(obj, type):
        return issubclass(obj, tuple(SUPPORTED_LEAF_CLS)) or obj in SUPPORTED_LEAF_TYPE
    return (
        isinstance(obj, tuple(SUPPORTED_LEAF_CLS)) or type(obj) in SUPPORTED_LEAF_TYPE
    )


def _leaf_type(node):
    if isinstance(node, (RawTensor, TensorNode)):
        return (Tensor, TensorNode)
    elif isinstance(node, (NodeMixin, Module)):
        return (Module, ModuleNode, NodeMixin)
    else:
        return type(node)


def _is_const_leaf(node):
    if isinstance(node, (RawTensor, NodeMixin, Module)):
        return False
    return True


def tree_flatten(
    values,
    leaf_type: Callable = _leaf_type,
    is_leaf: Callable = _is_leaf,
    is_const_leaf: Callable = _is_const_leaf,
):
    if type(values) not in SUPPORTED_TYPE:
        assert is_leaf(values), values
        node = LeafDef(leaf_type(values))
        if is_const_leaf(values):
            if isinstance(values, np.ndarray):
                node.const_val = str(values)
            else:
                node.const_val = values
        return [values,], node

    rst = []
    children_defs = []
    children_values, aux_data = SUPPORTED_TYPE[type(values)].flatten(values)
    for v in children_values:
        v_list, treedef = tree_flatten(v, leaf_type, is_leaf, is_const_leaf)
        rst.extend(v_list)
        children_defs.append(treedef)

    return rst, TreeDef(type(values), aux_data, children_defs)


class TreeDef:
    def __init__(self, type, aux_data, children_defs):
        self.type = type
        self.aux_data = aux_data
        self.children_defs = children_defs
        self.num_leaves = sum(ch.num_leaves for ch in children_defs)

    def unflatten(self, leaves):
        assert len(leaves) == self.num_leaves
        start = 0
        children = []
        for ch in self.children_defs:
            children.append(ch.unflatten(leaves[start : start + ch.num_leaves]))
            start += ch.num_leaves
        return SUPPORTED_TYPE[self.type].unflatten(children, self.aux_data)

    def __hash__(self):
        return hash(
            tuple(
                [
                    self.type,
                    self.aux_data,
                    self.num_leaves,
                    tuple([hash(x) for x in self.children_defs]),
                ]
            )
        )

    def __lt__(self, other):
        return self.__hash__() < other.__hash__()

    def __gt__(self, other):
        return self.__hash__() > other.__hash__()

    def __eq__(self, other):
        return (
            self.type == other.type
            and self.aux_data == other.aux_data
            and self.num_leaves == other.num_leaves
            and self.children_defs == other.children_defs
        )

    def __repr__(self):
        return "{}[{}]".format(self.type.__name__, self.children_defs)


class LeafDef(TreeDef):
    def __init__(self, type):
        if not isinstance(type, collections.abc.Sequence):
            type = (type,)
        super().__init__(type, None, [])
        self.num_leaves = 1
        self.const_val = None

    def unflatten(self, leaves):
        assert len(leaves) == 1
        assert isinstance(leaves[0], self.type), self.type
        return leaves[0]

    def __eq__(self, other):
        return self.type == other.type and self.const_val == other.const_val

    def __hash__(self):
        return hash(tuple([self.type, self.const_val]))

    def __repr__(self):
        return "Leaf({}[{}])".format(
            ", ".join(t.__name__ for t in self.type), self.const_val
        )