import torch
import torch.nn as nn
import numpy as np
from torch.optim import AdamW
import torch.optim as optim
import itertools
from model.warplayer import warp
from torch.nn.parallel import DistributedDataParallel as DDP
from train_log.IFNet_HDv3 import *
import torch.nn.functional as F
from model.loss import *

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
    
class Model:
    def __init__(self, local_rank=-1):
        self.flownet = IFNet()
        self.device()
        self.optimG = AdamW(self.flownet.parameters(), lr=1e-6, weight_decay=1e-4)
        self.epe = EPE()
        self.version = 4.25
        # self.vgg = VGGPerceptualLoss().to(device)
        self.sobel = SOBEL()
        if local_rank != -1:
            self.flownet = DDP(self.flownet, device_ids=[local_rank], output_device=local_rank)

    def train(self):
        self.flownet.train()

    def eval(self):
        self.flownet.eval()

    def device(self):
        self.flownet.to(device)

    def load_model(self, path, rank=0):
        def convert(param):
            if rank == -1:
                return {
                    k.replace("module.", ""): v
                    for k, v in param.items()
                    if "module." in k
                }
            else:
                return param
        if rank <= 0:
            if torch.cuda.is_available():
                self.flownet.load_state_dict(convert(torch.load('{}/flownet.pkl'.format(path))), False)
            else:
                self.flownet.load_state_dict(convert(torch.load('{}/flownet.pkl'.format(path), map_location ='cpu')), False)
        
    def save_model(self, path, rank=0):
        if rank == 0:
            torch.save(self.flownet.state_dict(),'{}/flownet.pkl'.format(path))

    def inference(self, img0, img1, timestep=0.5, scale=1.0):
        imgs = torch.cat((img0, img1), 1)
        scale_list = [16/scale, 8/scale, 4/scale, 2/scale, 1/scale]
        flow, mask, merged = self.flownet(imgs, timestep, scale_list)
        return merged[-1]
    
    def update(self, imgs, gt, learning_rate=0, mul=1, training=True, flow_gt=None):
        for param_group in self.optimG.param_groups:
            param_group['lr'] = learning_rate
        img0 = imgs[:, :3]
        img1 = imgs[:, 3:]
        if training:
            self.train()
        else:
            self.eval()
        scale = [16, 8, 4, 2, 1]
        flow, mask, merged = self.flownet(torch.cat((imgs, gt), 1), scale=scale, training=training)
        loss_l1 = (merged[-1] - gt).abs().mean()
        loss_smooth = self.sobel(flow[-1], flow[-1]*0).mean()
        # loss_vgg = self.vgg(merged[-1], gt)
        if training:
            self.optimG.zero_grad()
            loss_G = loss_l1 + loss_cons + loss_smooth * 0.1
            loss_G.backward()
            self.optimG.step()
        else:
            flow_teacher = flow[2]
        return merged[-1], {
            'mask': mask,
            'flow': flow[-1][:, :2],
            'loss_l1': loss_l1,
            'loss_cons': loss_cons,
            'loss_smooth': loss_smooth,
            }
