#!/usr/bin/env python

import torch

import getopt
import math
import numpy
import os
import PIL
import PIL.Image
import sys

# try:
from .correlation import correlation # the custom cost volume layer
# except:
# 	sys.path.insert(0, './correlation'); import correlation # you should consider upgrading python
# end

##########################################################

# assert(int(str('').join(torch.__version__.split('.')[0:2])) >= 13) # requires at least pytorch version 1.3.0

# torch.set_grad_enabled(False) # make sure to not compute gradients for computational performance

# torch.backends.cudnn.enabled = True # make sure to use cudnn for computational performance

# ##########################################################

# arguments_strModel = 'default' # 'default', or 'chairs-things'
# arguments_strFirst = './images/first.png'
# arguments_strSecond = './images/second.png'
# arguments_strOut = './out.flo'

# for strOption, strArgument in getopt.getopt(sys.argv[1:], '', [ strParameter[2:] + '=' for strParameter in sys.argv[1::2] ])[0]:
# 	if strOption == '--model' and strArgument != '': arguments_strModel = strArgument # which model to use
# 	if strOption == '--first' and strArgument != '': arguments_strFirst = strArgument # path to the first frame
# 	if strOption == '--second' and strArgument != '': arguments_strSecond = strArgument # path to the second frame
# 	if strOption == '--out' and strArgument != '': arguments_strOut = strArgument # path to where the output should be stored
# end

##########################################################



def backwarp(tenInput, tenFlow):
	backwarp_tenGrid = {}
	backwarp_tenPartial = {}
	if str(tenFlow.shape) not in backwarp_tenGrid:
		tenHor = torch.linspace(-1.0 + (1.0 / tenFlow.shape[3]), 1.0 - (1.0 / tenFlow.shape[3]), tenFlow.shape[3]).view(1, 1, 1, -1).expand(-1, -1, tenFlow.shape[2], -1)
		tenVer = torch.linspace(-1.0 + (1.0 / tenFlow.shape[2]), 1.0 - (1.0 / tenFlow.shape[2]), tenFlow.shape[2]).view(1, 1, -1, 1).expand(-1, -1, -1, tenFlow.shape[3])

		backwarp_tenGrid[str(tenFlow.shape)] = torch.cat([ tenHor, tenVer ], 1).cuda()
	# end

	if str(tenFlow.shape) not in backwarp_tenPartial:
		backwarp_tenPartial[str(tenFlow.shape)] = tenFlow.new_ones([ tenFlow.shape[0], 1, tenFlow.shape[2], tenFlow.shape[3] ])
	# end

	tenFlow = torch.cat([ tenFlow[:, 0:1, :, :] / ((tenInput.shape[3] - 1.0) / 2.0), tenFlow[:, 1:2, :, :] / ((tenInput.shape[2] - 1.0) / 2.0) ], 1)
	tenInput = torch.cat([ tenInput, backwarp_tenPartial[str(tenFlow.shape)] ], 1)

	tenOutput = torch.nn.functional.grid_sample(input=tenInput, grid=(backwarp_tenGrid[str(tenFlow.shape)] + tenFlow).permute(0, 2, 3, 1), mode='bilinear', padding_mode='zeros', align_corners=False)

	tenMask = tenOutput[:, -1:, :, :]; tenMask[tenMask > 0.999] = 1.0; tenMask[tenMask < 1.0] = 0.0

	return tenOutput[:, :-1, :, :] * tenMask
# end

##########################################################

class Network(torch.nn.Module):
	def __init__(self):
		super(Network, self).__init__()

		class Extractor(torch.nn.Module):
			def __init__(self):
				super(Extractor, self).__init__()

				self.netOne = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=3, out_channels=16, kernel_size=3, stride=2, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=16, out_channels=16, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=16, out_channels=16, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1)
				)

				self.netTwo = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=16, out_channels=32, kernel_size=3, stride=2, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=32, out_channels=32, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=32, out_channels=32, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1)
				)

				self.netThr = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=32, out_channels=64, kernel_size=3, stride=2, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=64, out_channels=64, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=64, out_channels=64, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1)
				)

				self.netFou = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=64, out_channels=96, kernel_size=3, stride=2, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=96, out_channels=96, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=96, out_channels=96, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1)
				)

				self.netFiv = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=96, out_channels=128, kernel_size=3, stride=2, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=128, out_channels=128, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=128, out_channels=128, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1)
				)

				self.netSix = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=128, out_channels=196, kernel_size=3, stride=2, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=196, out_channels=196, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=196, out_channels=196, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1)
				)
			# end

			def forward(self, tenInput):
				tenOne = self.netOne(tenInput)
				tenTwo = self.netTwo(tenOne)
				tenThr = self.netThr(tenTwo)
				tenFou = self.netFou(tenThr)
				tenFiv = self.netFiv(tenFou)
				tenSix = self.netSix(tenFiv)

				return [ tenOne, tenTwo, tenThr, tenFou, tenFiv, tenSix ]
			# end
		# end

		class Decoder(torch.nn.Module):
			def __init__(self, intLevel):
				super(Decoder, self).__init__()

				intPrevious = [ None, None, 81 + 32 + 2 + 2, 81 + 64 + 2 + 2, 81 + 96 + 2 + 2, 81 + 128 + 2 + 2, 81, None ][intLevel + 1]
				intCurrent = [ None, None, 81 + 32 + 2 + 2, 81 + 64 + 2 + 2, 81 + 96 + 2 + 2, 81 + 128 + 2 + 2, 81, None ][intLevel + 0]

				if intLevel < 6: self.netUpflow = torch.nn.ConvTranspose2d(in_channels=2, out_channels=2, kernel_size=4, stride=2, padding=1)
				if intLevel < 6: self.netUpfeat = torch.nn.ConvTranspose2d(in_channels=intPrevious + 128 + 128 + 96 + 64 + 32, out_channels=2, kernel_size=4, stride=2, padding=1)
				if intLevel < 6: self.fltBackwarp = [ None, None, None, 5.0, 2.5, 1.25, 0.625, None ][intLevel + 1]

				self.netOne = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=intCurrent, out_channels=128, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1)
				)

				self.netTwo = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=intCurrent + 128, out_channels=128, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1)
				)

				self.netThr = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=intCurrent + 128 + 128, out_channels=96, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1)
				)

				self.netFou = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=intCurrent + 128 + 128 + 96, out_channels=64, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1)
				)

				self.netFiv = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=intCurrent + 128 + 128 + 96 + 64, out_channels=32, kernel_size=3, stride=1, padding=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1)
				)

				self.netSix = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=intCurrent + 128 + 128 + 96 + 64 + 32, out_channels=2, kernel_size=3, stride=1, padding=1)
				)
			# end

			def forward(self, tenFirst, tenSecond, objPrevious):
				tenFlow = None
				tenFeat = None

				if objPrevious is None:
					tenFlow = None
					tenFeat = None

					tenVolume = torch.nn.functional.leaky_relu(input=correlation.FunctionCorrelation(tenFirst=tenFirst, tenSecond=tenSecond), negative_slope=0.1, inplace=False)

					tenFeat = torch.cat([ tenVolume ], 1)

				elif objPrevious is not None:
					tenFlow = self.netUpflow(objPrevious['tenFlow'])
					tenFeat = self.netUpfeat(objPrevious['tenFeat'])

					tenVolume = torch.nn.functional.leaky_relu(input=correlation.FunctionCorrelation(tenFirst=tenFirst, tenSecond=backwarp(tenInput=tenSecond, tenFlow=tenFlow * self.fltBackwarp)), negative_slope=0.1, inplace=False)

					tenFeat = torch.cat([ tenVolume, tenFirst, tenFlow, tenFeat ], 1)

				# end

				tenFeat = torch.cat([ self.netOne(tenFeat), tenFeat ], 1)
				tenFeat = torch.cat([ self.netTwo(tenFeat), tenFeat ], 1)
				tenFeat = torch.cat([ self.netThr(tenFeat), tenFeat ], 1)
				tenFeat = torch.cat([ self.netFou(tenFeat), tenFeat ], 1)
				tenFeat = torch.cat([ self.netFiv(tenFeat), tenFeat ], 1)

				tenFlow = self.netSix(tenFeat)

				return {
					'tenFlow': tenFlow,
					'tenFeat': tenFeat
				}
			# end
		# end

		class Refiner(torch.nn.Module):
			def __init__(self):
				super(Refiner, self).__init__()

				self.netMain = torch.nn.Sequential(
					torch.nn.Conv2d(in_channels=81 + 32 + 2 + 2 + 128 + 128 + 96 + 64 + 32, out_channels=128, kernel_size=3, stride=1, padding=1, dilation=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=128, out_channels=128, kernel_size=3, stride=1, padding=2, dilation=2),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=128, out_channels=128, kernel_size=3, stride=1, padding=4, dilation=4),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=128, out_channels=96, kernel_size=3, stride=1, padding=8, dilation=8),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=96, out_channels=64, kernel_size=3, stride=1, padding=16, dilation=16),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=64, out_channels=32, kernel_size=3, stride=1, padding=1, dilation=1),
					torch.nn.LeakyReLU(inplace=False, negative_slope=0.1),
					torch.nn.Conv2d(in_channels=32, out_channels=2, kernel_size=3, stride=1, padding=1, dilation=1)
				)
			# end

			def forward(self, tenInput):
				return self.netMain(tenInput)
			# end
		# end

		self.netExtractor = Extractor()

		self.netTwo = Decoder(2)
		self.netThr = Decoder(3)
		self.netFou = Decoder(4)
		self.netFiv = Decoder(5)
		self.netSix = Decoder(6)

		self.netRefiner = Refiner()

		self.load_state_dict({ strKey.replace('module', 'net'): tenWeight for strKey, tenWeight in torch.hub.load_state_dict_from_url(url='http://content.sniklaus.com/github/pytorch-pwc/network-' + 'default' + '.pytorch').items() })
	# end

	def forward(self, tenFirst, tenSecond):
		intWidth = tenFirst.shape[3]
		intHeight = tenFirst.shape[2]

		intPreprocessedWidth = int(math.floor(math.ceil(intWidth / 64.0) * 64.0))
		intPreprocessedHeight = int(math.floor(math.ceil(intHeight / 64.0) * 64.0))

		tenPreprocessedFirst = torch.nn.functional.interpolate(input=tenFirst, size=(intPreprocessedHeight, intPreprocessedWidth), mode='bilinear', align_corners=False)
		tenPreprocessedSecond = torch.nn.functional.interpolate(input=tenSecond, size=(intPreprocessedHeight, intPreprocessedWidth), mode='bilinear', align_corners=False)
		
		tenFirst = self.netExtractor(tenPreprocessedFirst)
		tenSecond = self.netExtractor(tenPreprocessedSecond)


		objEstimate = self.netSix(tenFirst[-1], tenSecond[-1], None)
		objEstimate = self.netFiv(tenFirst[-2], tenSecond[-2], objEstimate)
		objEstimate = self.netFou(tenFirst[-3], tenSecond[-3], objEstimate)
		objEstimate = self.netThr(tenFirst[-4], tenSecond[-4], objEstimate)
		objEstimate = self.netTwo(tenFirst[-5], tenSecond[-5], objEstimate)

		tenFlow = objEstimate['tenFlow'] + self.netRefiner(objEstimate['tenFeat'])
		tenFlow = 20.0 * torch.nn.functional.interpolate(input=tenFlow, size=(intHeight, intWidth), mode='bilinear', align_corners=False)
		tenFlow[:, 0, :, :] *= float(intWidth) / float(intPreprocessedWidth)
		tenFlow[:, 1, :, :] *= float(intHeight) / float(intPreprocessedHeight)

		return tenFlow
	# end
# end

netNetwork = None

##########################################################

def estimate(tenFirst, tenSecond):
	global netNetwork

	if netNetwork is None:
		netNetwork = Network().cuda().eval()
	# end

	assert(tenFirst.shape[1] == tenSecond.shape[1])
	assert(tenFirst.shape[2] == tenSecond.shape[2])

	intWidth = tenFirst.shape[2]
	intHeight = tenFirst.shape[1]

	assert(intWidth == 1024) # remember that there is no guarantee for correctness, comment this line out if you acknowledge this and want to continue
	assert(intHeight == 436) # remember that there is no guarantee for correctness, comment this line out if you acknowledge this and want to continue

	tenPreprocessedFirst = tenFirst.cuda().view(1, 3, intHeight, intWidth)
	tenPreprocessedSecond = tenSecond.cuda().view(1, 3, intHeight, intWidth)

	intPreprocessedWidth = int(math.floor(math.ceil(intWidth / 64.0) * 64.0))
	intPreprocessedHeight = int(math.floor(math.ceil(intHeight / 64.0) * 64.0))

	tenPreprocessedFirst = torch.nn.functional.interpolate(input=tenPreprocessedFirst, size=(intPreprocessedHeight, intPreprocessedWidth), mode='bilinear', align_corners=False)
	tenPreprocessedSecond = torch.nn.functional.interpolate(input=tenPreprocessedSecond, size=(intPreprocessedHeight, intPreprocessedWidth), mode='bilinear', align_corners=False)

	tenFlow = 20.0 * torch.nn.functional.interpolate(input=netNetwork(tenPreprocessedFirst, tenPreprocessedSecond), size=(intHeight, intWidth), mode='bilinear', align_corners=False)

	tenFlow[:, 0, :, :] *= float(intWidth) / float(intPreprocessedWidth)
	tenFlow[:, 1, :, :] *= float(intHeight) / float(intPreprocessedHeight)

	return tenFlow[0, :, :, :].cpu()
# end

##########################################################

# if __name__ == '__main__':
# 	tenFirst = torch.FloatTensor(numpy.ascontiguousarray(numpy.array(PIL.Image.open(arguments_strFirst))[:, :, ::-1].transpose(2, 0, 1).astype(numpy.float32) * (1.0 / 255.0)))
# 	tenSecond = torch.FloatTensor(numpy.ascontiguousarray(numpy.array(PIL.Image.open(arguments_strSecond))[:, :, ::-1].transpose(2, 0, 1).astype(numpy.float32) * (1.0 / 255.0)))

# 	tenOutput = estimate(tenFirst, tenSecond)

# 	objOutput = open(arguments_strOut, 'wb')

# 	numpy.array([ 80, 73, 69, 72 ], numpy.uint8).tofile(objOutput)
# 	numpy.array([ tenOutput.shape[2], tenOutput.shape[1] ], numpy.int32).tofile(objOutput)
# 	numpy.array(tenOutput.numpy().transpose(1, 2, 0), numpy.float32).tofile(objOutput)

# 	objOutput.close()
# end