# Copyright (c) Microsoft Corporation.
# Licensed under the MIT License.

import torch
import torch.nn.parallel
import numpy as np
import torch.nn as nn
import torch.nn.functional as F


class Downsample(nn.Module):
    # https://github.com/adobe/antialiased-cnns

    def __init__(self, pad_type="reflect", filt_size=3, stride=2, channels=None, pad_off=0):
        super(Downsample, self).__init__()
        self.filt_size = filt_size
        self.pad_off = pad_off
        self.pad_sizes = [
            int(1.0 * (filt_size - 1) / 2),
            int(np.ceil(1.0 * (filt_size - 1) / 2)),
            int(1.0 * (filt_size - 1) / 2),
            int(np.ceil(1.0 * (filt_size - 1) / 2)),
        ]
        self.pad_sizes = [pad_size + pad_off for pad_size in self.pad_sizes]
        self.stride = stride
        self.off = int((self.stride - 1) / 2.0)
        self.channels = channels

        # print('Filter size [%i]'%filt_size)
        if self.filt_size == 1:
            a = np.array([1.0,])
        elif self.filt_size == 2:
            a = np.array([1.0, 1.0])
        elif self.filt_size == 3:
            a = np.array([1.0, 2.0, 1.0])
        elif self.filt_size == 4:
            a = np.array([1.0, 3.0, 3.0, 1.0])
        elif self.filt_size == 5:
            a = np.array([1.0, 4.0, 6.0, 4.0, 1.0])
        elif self.filt_size == 6:
            a = np.array([1.0, 5.0, 10.0, 10.0, 5.0, 1.0])
        elif self.filt_size == 7:
            a = np.array([1.0, 6.0, 15.0, 20.0, 15.0, 6.0, 1.0])

        filt = torch.Tensor(a[:, None] * a[None, :])
        filt = filt / torch.sum(filt)
        self.register_buffer("filt", filt[None, None, :, :].repeat((self.channels, 1, 1, 1)))

        self.pad = get_pad_layer(pad_type)(self.pad_sizes)

    def forward(self, inp):
        if self.filt_size == 1:
            if self.pad_off == 0:
                return inp[:, :, :: self.stride, :: self.stride]
            else:
                return self.pad(inp)[:, :, :: self.stride, :: self.stride]
        else:
            return F.conv2d(self.pad(inp), self.filt, stride=self.stride, groups=inp.shape[1])


def get_pad_layer(pad_type):
    if pad_type in ["refl", "reflect"]:
        PadLayer = nn.ReflectionPad2d
    elif pad_type in ["repl", "replicate"]:
        PadLayer = nn.ReplicationPad2d
    elif pad_type == "zero":
        PadLayer = nn.ZeroPad2d
    else:
        print("Pad type [%s] not recognized" % pad_type)
    return PadLayer