import sys, os, argparse, time

import numpy as np
import cv2
import matplotlib.pyplot as plt

import torch
import torch.nn as nn
from torch.autograd import Variable
from torch.utils.data import DataLoader
from torchvision import transforms
import torchvision
import torch.backends.cudnn as cudnn
import torch.nn.functional as F

import datasets, hopenet
import torch.utils.model_zoo as model_zoo

def parse_args():
    """Parse input arguments."""
    parser = argparse.ArgumentParser(description='Head pose estimation using the Hopenet network.')
    parser.add_argument('--gpu', dest='gpu_id', help='GPU device id to use [0]',
            default=0, type=int)
    parser.add_argument('--num_epochs', dest='num_epochs', help='Maximum number of training epochs.',
          default=5, type=int)
    parser.add_argument('--batch_size', dest='batch_size', help='Batch size.',
          default=16, type=int)
    parser.add_argument('--lr', dest='lr', help='Base learning rate.',
          default=0.001, type=float)
    parser.add_argument('--data_dir', dest='data_dir', help='Directory path for data.',
          default='', type=str)
    parser.add_argument('--filename_list', dest='filename_list', help='Path to text file containing relative paths for every example.',
          default='', type=str)
    parser.add_argument('--output_string', dest='output_string', help='String appended to output snapshots.', default = '', type=str)
    parser.add_argument('--dataset', dest='dataset', help='Dataset type.', default='Pose_300W_LP', type=str)

    args = parser.parse_args()
    return args

def get_ignored_params(model):
    # Generator function that yields ignored params.
    b = [model.conv1, model.bn1]
    for i in range(len(b)):
        for module_name, module in b[i].named_modules():
            if 'bn' in module_name:
                module.eval()
            for name, param in module.named_parameters():
                yield param

def get_non_ignored_params(model):
    # Generator function that yields params that will be optimized.
    b = [model.layer1, model.layer2, model.layer3, model.layer4]
    for i in range(len(b)):
        for module_name, module in b[i].named_modules():
            if 'bn' in module_name:
                module.eval()
            for name, param in module.named_parameters():
                yield param

def get_fc_params(model):
    # Generator function that yields fc layer params.
    b = [model.fc_angles]
    for i in range(len(b)):
        for module_name, module in b[i].named_modules():
            for name, param in module.named_parameters():
                yield param

def load_filtered_state_dict(model, snapshot):
    # By user apaszke from discuss.pytorch.org
    model_dict = model.state_dict()
    snapshot = {k: v for k, v in snapshot.items() if k in model_dict}
    model_dict.update(snapshot)
    model.load_state_dict(model_dict)

if __name__ == '__main__':
    args = parse_args()

    cudnn.enabled = True
    num_epochs = args.num_epochs
    batch_size = args.batch_size
    gpu = args.gpu_id

    if not os.path.exists('output/snapshots'):
        os.makedirs('output/snapshots')

    # ResNet50
    model = hopenet.ResNet(torchvision.models.resnet.Bottleneck, [3, 4, 6, 3], 3)
    load_filtered_state_dict(model, model_zoo.load_url('https://download.pytorch.org/models/resnet50-19c8e357.pth'))

    print 'Loading data.'

    transformations = transforms.Compose([transforms.Scale(240),
    transforms.RandomCrop(224), transforms.ToTensor(),
    transforms.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225])])

    if args.dataset == 'Pose_300W_LP':
        pose_dataset = datasets.Pose_300W_LP(args.data_dir, args.filename_list, transformations)
    elif args.dataset == 'Pose_300W_LP_random_ds':
        pose_dataset = datasets.Pose_300W_LP_random_ds(args.data_dir, args.filename_list, transformations)
    elif args.dataset == 'AFLW2000':
        pose_dataset = datasets.AFLW2000(args.data_dir, args.filename_list, transformations)
    elif args.dataset == 'BIWI':
        pose_dataset = datasets.BIWI(args.data_dir, args.filename_list, transformations)
    elif args.dataset == 'AFLW':
        pose_dataset = datasets.AFLW(args.data_dir, args.filename_list, transformations)
    elif args.dataset == 'AFLW_aug':
        pose_dataset = datasets.AFLW_aug(args.data_dir, args.filename_list, transformations)
    elif args.dataset == 'AFW':
        pose_dataset = datasets.AFW(args.data_dir, args.filename_list, transformations)
    else:
        print 'Error: not a valid dataset name'
        sys.exit()
    train_loader = torch.utils.data.DataLoader(dataset=pose_dataset,
                                               batch_size=batch_size,
                                               shuffle=True,
                                               num_workers=2)

    model.cuda(gpu)
    criterion = nn.MSELoss().cuda(gpu)

    optimizer = torch.optim.Adam([{'params': get_ignored_params(model), 'lr': 0},
                                  {'params': get_non_ignored_params(model), 'lr': args.lr},
                                  {'params': get_fc_params(model), 'lr': args.lr * 5}],
                                   lr = args.lr)

    print 'Ready to train network.'
    print 'First phase of training.'
    for epoch in range(num_epochs):
        for i, (images, labels, cont_labels, name) in enumerate(train_loader):
            images = Variable(images).cuda(gpu)

            label_angles = Variable(cont_labels[:,:3]).cuda(gpu)
            angles = model(images)

            loss = criterion(angles, label_angles)
            optimizer.zero_grad()
            loss.backward()
            optimizer.step()

            if (i+1) % 100 == 0:
                print ('Epoch [%d/%d], Iter [%d/%d] Loss: %.4f'
                       %(epoch+1, num_epochs, i+1, len(pose_dataset)//batch_size, loss.data[0]))

        # Save models at numbered epochs.
        if epoch % 1 == 0 and epoch < num_epochs:
            print 'Taking snapshot...'
            torch.save(model.state_dict(),
            'output/snapshots/' + args.output_string + '_epoch_'+ str(epoch+1) + '.pkl')