# Copyright (c) Facebook, Inc. and its affiliates.

import contextlib
from unittest import mock
import torch

from detectron2.modeling import poolers
from detectron2.modeling.proposal_generator import rpn
from detectron2.modeling.roi_heads import keypoint_head, mask_head
from detectron2.modeling.roi_heads.fast_rcnn import FastRCNNOutputLayers

from .c10 import (
    Caffe2Compatible,
    Caffe2FastRCNNOutputsInference,
    Caffe2KeypointRCNNInference,
    Caffe2MaskRCNNInference,
    Caffe2ROIPooler,
    Caffe2RPN,
)


class GenericMixin(object):
    pass


class Caffe2CompatibleConverter(object):
    """
    A GenericUpdater which implements the `create_from` interface, by modifying
    module object and assign it with another class replaceCls.
    """

    def __init__(self, replaceCls):
        self.replaceCls = replaceCls

    def create_from(self, module):
        # update module's class to the new class
        assert isinstance(module, torch.nn.Module)
        if issubclass(self.replaceCls, GenericMixin):
            # replaceCls should act as mixin, create a new class on-the-fly
            new_class = type(
                "{}MixedWith{}".format(self.replaceCls.__name__, module.__class__.__name__),
                (self.replaceCls, module.__class__),
                {},  # {"new_method": lambda self: ...},
            )
            module.__class__ = new_class
        else:
            # replaceCls is complete class, this allow arbitrary class swap
            module.__class__ = self.replaceCls

        # initialize Caffe2Compatible
        if isinstance(module, Caffe2Compatible):
            module.tensor_mode = False

        return module


def patch(model, target, updater, *args, **kwargs):
    """
    recursively (post-order) update all modules with the target type and its
    subclasses, make a initialization/composition/inheritance/... via the
    updater.create_from.
    """
    for name, module in model.named_children():
        model._modules[name] = patch(module, target, updater, *args, **kwargs)
    if isinstance(model, target):
        return updater.create_from(model, *args, **kwargs)
    return model


def patch_generalized_rcnn(model):
    ccc = Caffe2CompatibleConverter
    model = patch(model, rpn.RPN, ccc(Caffe2RPN))
    model = patch(model, poolers.ROIPooler, ccc(Caffe2ROIPooler))

    return model


@contextlib.contextmanager
def mock_fastrcnn_outputs_inference(
    tensor_mode, check=True, box_predictor_type=FastRCNNOutputLayers
):
    with mock.patch.object(
        box_predictor_type,
        "inference",
        autospec=True,
        side_effect=Caffe2FastRCNNOutputsInference(tensor_mode),
    ) as mocked_func:
        yield
    if check:
        assert mocked_func.call_count > 0


@contextlib.contextmanager
def mock_mask_rcnn_inference(tensor_mode, patched_module, check=True):
    with mock.patch(
        "{}.mask_rcnn_inference".format(patched_module), side_effect=Caffe2MaskRCNNInference()
    ) as mocked_func:
        yield
    if check:
        assert mocked_func.call_count > 0


@contextlib.contextmanager
def mock_keypoint_rcnn_inference(tensor_mode, patched_module, use_heatmap_max_keypoint, check=True):
    with mock.patch(
        "{}.keypoint_rcnn_inference".format(patched_module),
        side_effect=Caffe2KeypointRCNNInference(use_heatmap_max_keypoint),
    ) as mocked_func:
        yield
    if check:
        assert mocked_func.call_count > 0


class ROIHeadsPatcher:
    def __init__(self, heads, use_heatmap_max_keypoint):
        self.heads = heads
        self.use_heatmap_max_keypoint = use_heatmap_max_keypoint

    @contextlib.contextmanager
    def mock_roi_heads(self, tensor_mode=True):
        """
        Patching several inference functions inside ROIHeads and its subclasses

        Args:
            tensor_mode (bool): whether the inputs/outputs are caffe2's tensor
                format or not. Default to True.
        """
        # NOTE: this requries the `keypoint_rcnn_inference` and `mask_rcnn_inference`
        # are called inside the same file as BaseXxxHead due to using mock.patch.
        kpt_heads_mod = keypoint_head.BaseKeypointRCNNHead.__module__
        mask_head_mod = mask_head.BaseMaskRCNNHead.__module__

        mock_ctx_managers = [
            mock_fastrcnn_outputs_inference(
                tensor_mode=tensor_mode,
                check=True,
                box_predictor_type=type(self.heads.box_predictor),
            )
        ]
        if getattr(self.heads, "keypoint_on", False):
            mock_ctx_managers += [
                mock_keypoint_rcnn_inference(
                    tensor_mode, kpt_heads_mod, self.use_heatmap_max_keypoint
                )
            ]
        if getattr(self.heads, "mask_on", False):
            mock_ctx_managers += [mock_mask_rcnn_inference(tensor_mode, mask_head_mod)]

        with contextlib.ExitStack() as stack:  # python 3.3+
            for mgr in mock_ctx_managers:
                stack.enter_context(mgr)
            yield
