import argparse
import os
import sys
import logging
import numpy
import numpy as np
import torch
import torch.utils.data
import torchvision
from torch.utils.data import DataLoader
from tensorboardX import SummaryWriter
from tqdm import tqdm

# Only if the files are in example folder.
BASE_DIR = os.path.dirname(os.path.abspath(__file__))
if BASE_DIR[-8:] == 'examples':
	sys.path.append(os.path.join(BASE_DIR, os.pardir))
	os.chdir(os.path.join(BASE_DIR, os.pardir))
	
from learning3d.models import PRNet
from learning3d.data_utils import RegistrationData, ModelNet40Data

def _init_(args):
	if not os.path.exists('checkpoints'):
		os.makedirs('checkpoints')
	if not os.path.exists('checkpoints/' + args.exp_name):
		os.makedirs('checkpoints/' + args.exp_name)
	if not os.path.exists('checkpoints/' + args.exp_name + '/' + 'models'):
		os.makedirs('checkpoints/' + args.exp_name + '/' + 'models')
	os.system('cp train_dcp.py checkpoints' + '/' + args.exp_name + '/' + 'train.py.backup')

class IOStream:
	def __init__(self, path):
		self.f = open(path, 'a')

	def cprint(self, text):
		print(text)
		self.f.write(text + '\n')
		self.f.flush()

	def close(self):
		self.f.close()

def get_transformations(igt):
	R_ba = igt[:, 0:3, 0:3]								# Ps = R_ba * Pt
	translation_ba = igt[:, 0:3, 3].unsqueeze(2)		# Ps = Pt + t_ba
	R_ab = R_ba.permute(0, 2, 1)						# Pt = R_ab * Ps
	translation_ab = -torch.bmm(R_ab, translation_ba)	# Pt = Ps + t_ab
	return R_ab, translation_ab, R_ba, translation_ba

def test_one_epoch(device, model, test_loader):
	model.eval()
	test_loss = 0.0
	pred  = 0.0
	count = 0
	for i, data in enumerate(tqdm(test_loader)):
		template, source, igt = data
		transformations = get_transformations(igt)
		transformations = [t.to(device) for t in transformations]
		R_ab, translation_ab, R_ba, translation_ba = transformations

		template = template.to(device)
		source = source.to(device)
		igt = igt.to(device)

		output = model(template, source, R_ab, translation_ab.squeeze(2))
		loss_val = output['loss']

		test_loss += loss_val.item()
		count += 1

	test_loss = float(test_loss)/count
	return test_loss

def test(args, model, test_loader, textio):
	test_loss = test_one_epoch(args.device, model, test_loader)
	textio.cprint('Validation Loss: %f & Validation Accuracy: %f'%(test_loss, test_accuracy))

def train_one_epoch(device, model, train_loader, optimizer):
	model.train()
	train_loss = 0.0
	pred  = 0.0
	count = 0
	for i, data in enumerate(tqdm(train_loader)):
		template, source, igt = data
		transformations = get_transformations(igt)
		transformations = [t.to(device) for t in transformations]
		R_ab, translation_ab, R_ba, translation_ba = transformations

		template = template.to(device)
		source = source.to(device)
		igt = igt.to(device)

		output = model(template, source, R_ab, translation_ab.squeeze(2))
		loss_val = output['loss']

		# forward + backward + optimize
		optimizer.zero_grad()
		loss_val.backward()
		optimizer.step()

		train_loss += loss_val.item()
		count += 1

	train_loss = float(train_loss)/count
	return train_loss

def train(args, model, train_loader, test_loader, boardio, textio, checkpoint):
	learnable_params = filter(lambda p: p.requires_grad, model.parameters())
	if args.optimizer == 'Adam':
		optimizer = torch.optim.Adam(learnable_params)
	else:
		optimizer = torch.optim.SGD(learnable_params, lr=0.1)

	if checkpoint is not None:
		min_loss = checkpoint['min_loss']
		optimizer.load_state_dict(checkpoint['optimizer'])

	best_test_loss = np.inf

	for epoch in range(args.start_epoch, args.epochs):
		train_loss = train_one_epoch(args.device, model, train_loader, optimizer)
		test_loss = test_one_epoch(args.device, model, test_loader)

		if test_loss<best_test_loss:
			best_test_loss = test_loss
			snap = {'epoch': epoch + 1,
					'model': model.state_dict(),
					'min_loss': best_test_loss,
					'optimizer' : optimizer.state_dict(),}
			torch.save(snap, 'checkpoints/%s/models/best_model_snap.t7' % (args.exp_name))
			torch.save(model.state_dict(), 'checkpoints/%s/models/best_model.t7' % (args.exp_name))
			torch.save(model.feature_model.state_dict(), 'checkpoints/%s/models/best_ptnet_model.t7' % (args.exp_name))

		torch.save(snap, 'checkpoints/%s/models/model_snap.t7' % (args.exp_name))
		torch.save(model.state_dict(), 'checkpoints/%s/models/model.t7' % (args.exp_name))
		torch.save(model.feature_model.state_dict(), 'checkpoints/%s/models/ptnet_model.t7' % (args.exp_name))
		
		boardio.add_scalar('Train Loss', train_loss, epoch+1)
		boardio.add_scalar('Test Loss', test_loss, epoch+1)
		boardio.add_scalar('Best Test Loss', best_test_loss, epoch+1)

		textio.cprint('EPOCH:: %d, Traininig Loss: %f, Testing Loss: %f, Best Loss: %f'%(epoch+1, train_loss, test_loss, best_test_loss))

def options():
	parser = argparse.ArgumentParser(description='Point Cloud Registration')
	parser.add_argument('--exp_name', type=str, default='exp_prnet', metavar='N',
						help='Name of the experiment')
	parser.add_argument('--dataset_path', type=str, default='ModelNet40',
						metavar='PATH', help='path to the input dataset') # like '/path/to/ModelNet40'
	parser.add_argument('--eval', type=bool, default=False, help='Train or Evaluate the network.')

	# settings for input data
	parser.add_argument('--dataset_type', default='modelnet', choices=['modelnet', 'shapenet2'],
						metavar='DATASET', help='dataset type (default: modelnet)')
	parser.add_argument('--emb_dims', default=512, type=int,
						metavar='K', help='dim. of the feature vector (default: 1024)')
	parser.add_argument('--num_iterations', default=3, type=int,
						help='Number of Iterations')

	# settings for on training
	parser.add_argument('--seed', type=int, default=1234)
	parser.add_argument('-j', '--workers', default=4, type=int,
						metavar='N', help='number of data loading workers (default: 4)')
	parser.add_argument('-b', '--batch_size', default=32, type=int,
						metavar='N', help='mini-batch size (default: 32)')
	parser.add_argument('--epochs', default=200, type=int,
						metavar='N', help='number of total epochs to run')
	parser.add_argument('--start_epoch', default=0, type=int,
						metavar='N', help='manual epoch number (useful on restarts)')
	parser.add_argument('--optimizer', default='Adam', choices=['Adam', 'SGD'],
						metavar='METHOD', help='name of an optimizer (default: Adam)')
	parser.add_argument('--resume', default='', type=str,
						metavar='PATH', help='path to latest checkpoint (default: null (no-use))')
	parser.add_argument('--pretrained', default='', type=str,
						metavar='PATH', help='path to pretrained model file (default: null (no-use))')
	parser.add_argument('--device', default='cuda:0', type=str,
						metavar='DEVICE', help='use CUDA if available')

	args = parser.parse_args()
	return args

def main():
	args = options()

	torch.backends.cudnn.deterministic = True
	torch.manual_seed(args.seed)
	torch.cuda.manual_seed_all(args.seed)
	np.random.seed(args.seed)

	boardio = SummaryWriter(log_dir='checkpoints/' + args.exp_name)
	_init_(args)

	textio = IOStream('checkpoints/' + args.exp_name + '/run.log')
	textio.cprint(str(args))

	
	trainset = RegistrationData('PRNet', ModelNet40Data(train=True), partial_source=True, partial_template=True)
	testset = RegistrationData('PRNet', ModelNet40Data(train=False), partial_source=True, partial_template=True)
	train_loader = DataLoader(trainset, batch_size=args.batch_size, shuffle=True, drop_last=True, num_workers=args.workers)
	test_loader = DataLoader(testset, batch_size=args.batch_size, shuffle=False, drop_last=False, num_workers=args.workers)

	if not torch.cuda.is_available():
		args.device = 'cpu'
	args.device = torch.device(args.device)

	# Create PointNet Model.
	model = PRNet(emb_dims=args.emb_dims, num_iters=args.num_iterations)
	model = model.to(args.device)

	checkpoint = None
	if args.resume:
		assert os.path.isfile(args.resume)
		checkpoint = torch.load(args.resume)
		args.start_epoch = checkpoint['epoch']
		model.load_state_dict(checkpoint['model'])

	if args.pretrained:
		assert os.path.isfile(args.pretrained)
		model.load_state_dict(torch.load(args.pretrained, map_location='cpu'))
	model.to(args.device)

	if args.eval:
		test(args, model, test_loader, textio)
	else:
		train(args, model, train_loader, test_loader, boardio, textio, checkpoint)

if __name__ == '__main__':
	main()