import os.path as osp
from pathlib import Path

import mmcv
import torch
from mmcv.runner import auto_fp16
from torchvision.utils import save_image

from mmedit.core import L1Evaluation, psnr, ssim, tensor2img
from ..base import BaseModel
from ..builder import build_backbone, build_component, build_loss
from ..common import set_requires_grad
from ..registry import MODELS


@MODELS.register_module()
class OneStageInpaintor(BaseModel):
    """Standard one-stage inpaintor with commonly used losses.

    An inpaintor must contain an encoder-decoder style generator to
    inpaint masked regions. A discriminator will be adopted when
    adversarial training is needed.

    In this class, we provide a common interface for inpaintors.
    For other inpaintors, only some funcs may be modified to fit the
    input style or training schedule.

    Args:
        generator (dict): Config for encoder-decoder style generator.
        disc (dict): Config for discriminator.
        loss_gan (dict): Config for adversarial loss.
        loss_gp (dict): Config for gradient penalty loss.
        loss_disc_shift (dict): Config for discriminator shift loss.
        loss_composed_percep (dict): Config for perceptural and style loss with
            composed image as input.
        loss_out_percep (dict): Config for perceptural and style loss with
            direct output as input.
        loss_l1_hole (dict): Config for l1 loss in the hole.
        loss_l1_valid (dict): Config for l1 loss in the valid region.
        loss_tv (dict): Config for total variation loss.
        train_cfg (dict): Configs for training scheduler. `disc_step` must be
            contained for indicates the discriminator updating steps in each
            training step.
        test_cfg (dict): Configs for testing scheduler.
        pretrained (str): Path for pretrained model. Default None.
    """
    _eval_metrics = dict(l1=L1Evaluation, psnr=psnr, ssim=ssim)

    def __init__(self,
                 encdec,
                 disc=None,
                 loss_gan=None,
                 loss_gp=None,
                 loss_disc_shift=None,
                 loss_composed_percep=None,
                 loss_out_percep=False,
                 loss_l1_hole=None,
                 loss_l1_valid=None,
                 loss_tv=None,
                 train_cfg=None,
                 test_cfg=None,
                 pretrained=None):
        super().__init__()
        self.with_l1_hole_loss = loss_l1_hole is not None
        self.with_l1_valid_loss = loss_l1_valid is not None
        self.with_tv_loss = loss_tv is not None
        self.with_composed_percep_loss = loss_composed_percep is not None
        self.with_out_percep_loss = loss_out_percep
        self.with_gan = disc is not None and loss_gan is not None
        self.with_gp_loss = loss_gp is not None
        self.with_disc_shift_loss = loss_disc_shift is not None
        self.is_train = train_cfg is not None
        self.train_cfg = train_cfg
        self.test_cfg = test_cfg
        self.eval_with_metrics = ('metrics' in self.test_cfg) and (
            self.test_cfg['metrics'] is not None)

        self.generator = build_backbone(encdec)

        # support fp16
        self.fp16_enabled = False

        # build loss modules
        if self.with_gan:
            self.disc = build_component(disc)
            self.loss_gan = build_loss(loss_gan)

        if self.with_l1_hole_loss:
            self.loss_l1_hole = build_loss(loss_l1_hole)

        if self.with_l1_valid_loss:
            self.loss_l1_valid = build_loss(loss_l1_valid)

        if self.with_composed_percep_loss:
            self.loss_percep = build_loss(loss_composed_percep)

        if self.with_gp_loss:
            self.loss_gp = build_loss(loss_gp)

        if self.with_disc_shift_loss:
            self.loss_disc_shift = build_loss(loss_disc_shift)

        if self.with_tv_loss:
            self.loss_tv = build_loss(loss_tv)

        self.disc_step_count = 0
        self.init_weights(pretrained=pretrained)

    def init_weights(self, pretrained=None):
        """Init weights for models.

        Args:
            pretrained (str, optional): Path for pretrained weights. If given
                None, pretrained weights will not be loaded. Defaults to None.
        """
        self.generator.init_weights(pretrained=pretrained)
        if self.with_gan:
            self.disc.init_weights(pretrained=pretrained)

    @auto_fp16(apply_to=('masked_img', 'mask'))
    def forward(self, masked_img, mask, test_mode=True, **kwargs):
        """Forward function.

        Args:
            masked_img (torch.Tensor): Image with hole as input.
            mask (torch.Tensor): Mask as input.
            test_mode (bool, optional): Whether use testing mode.
                Defaults to True.

        Returns:
            dict: Dict contains output results.
        """
        if test_mode:
            return self.forward_test(masked_img, mask, **kwargs)

        return self.forward_train(masked_img, mask, **kwargs)

    def forward_train(self, *args, **kwargs):
        """Forward function for training.

        In this version, we do not use this interface.
        """
        raise NotImplementedError('This interface should not be used in '
                                  'current training schedule. Please use '
                                  '`train_step` for training.')

    def forward_train_d(self, data_batch, is_real, is_disc):
        """Forward function in discriminator training step.

        In this function, we compute the prediction for each data batch (real
        or fake). Meanwhile, the standard gan loss will be computed with
        several proposed losses fro stable training.

        Args:
            data (torch.Tensor): Batch of real data or fake data.
            is_real (bool): If True, the gan loss will regard this batch as
                real data. Otherwise, the gan loss will regard this batch as
                fake data.
            is_disc (bool): If True, this function is called in discriminator
                training step. Otherwise, this function is called in generator
                training step. This will help us to compute different types of
                adversarial loss, like LSGAN.

        Returns:
            dict: Contains the loss items computed in this function.
        """
        pred = self.disc(data_batch)
        loss_ = self.loss_gan(pred, is_real, is_disc)

        loss = dict(real_loss=loss_) if is_real else dict(fake_loss=loss_)

        if self.with_disc_shift_loss:
            loss_d_shift = self.loss_disc_shift(loss_)
            # 0.5 for average the fake and real data
            loss.update(loss_disc_shift=loss_d_shift * 0.5)

        return loss

    def generator_loss(self, fake_res, fake_img, data_batch):
        """Forward function in generator training step.

        In this function, we mainly compute the loss items for generator with
        the given (fake_res, fake_img). In general, the `fake_res` is the
        direct output of the generator and the `fake_img` is the composition of
        direct output and ground-truth image.

        Args:
            fake_res (torch.Tensor): Direct output of the generator.
            fake_img (torch.Tensor): Composition of `fake_res` and
                ground-truth image.
            data_batch (dict): Contain other elements for computing losses.

        Returns:
            tuple(dict): Dict contains the results computed within this \
                function for visualization and dict contains the loss items \
                computed in this function.
        """
        gt = data_batch['gt_img']
        mask = data_batch['mask']
        masked_img = data_batch['masked_img']

        loss = dict()

        if self.with_gan:
            g_fake_pred = self.disc(fake_img)
            loss_g_fake = self.loss_gan(g_fake_pred, True, is_disc=False)
            loss['loss_g_fake'] = loss_g_fake

        if self.with_l1_hole_loss:
            loss_l1_hole = self.loss_l1_hole(fake_res, gt, weight=mask)
            loss['loss_l1_hole'] = loss_l1_hole

        if self.with_l1_valid_loss:
            loss_loss_l1_valid = self.loss_l1_valid(
                fake_res, gt, weight=1. - mask)
            loss['loss_l1_valid'] = loss_loss_l1_valid

        if self.with_composed_percep_loss:
            loss_pecep, loss_style = self.loss_percep(fake_img, gt)
            if loss_pecep is not None:
                loss['loss_composed_percep'] = loss_pecep
            if loss_style is not None:
                loss['loss_composed_style'] = loss_style

        if self.with_out_percep_loss:
            loss_out_percep, loss_out_style = self.loss_percep(fake_res, gt)
            if loss_out_percep is not None:
                loss['loss_out_percep'] = loss_out_percep
            if loss_out_style is not None:
                loss['loss_out_style'] = loss_out_style

        if self.with_tv_loss:
            loss_tv = self.loss_tv(fake_img, mask=mask)
            loss['loss_tv'] = loss_tv

        res = dict(
            gt_img=gt.cpu(),
            masked_img=masked_img.cpu(),
            fake_res=fake_res.cpu(),
            fake_img=fake_img.cpu())

        return res, loss

    def forward_test(self,
                     masked_img,
                     mask,
                     save_image=False,
                     save_path=None,
                     iteration=None,
                     **kwargs):
        """Forward function for testing.

        Args:
            masked_img (torch.Tensor): Tensor with shape of (n, 3, h, w).
            mask (torch.Tensor): Tensor with shape of (n, 1, h, w).
            save_image (bool, optional): If True, results will be saved as
                image. Defaults to False.
            save_path (str, optional): If given a valid str, the reuslts will
                be saved in this path. Defaults to None.
            iteration (int, optional): Iteration number. Defaults to None.

        Returns:
            dict: Contain output results and eval metrics (if have).
        """
        input_x = torch.cat([masked_img, mask], dim=1)
        fake_res = self.generator(input_x)
        fake_img = fake_res * mask + masked_img * (1. - mask)

        output = dict()
        eval_results = {}
        if self.eval_with_metrics:
            gt_img = kwargs['gt_img']
            data_dict = dict(gt_img=gt_img, fake_res=fake_res, mask=mask)
            for metric_name in self.test_cfg['metrics']:
                if metric_name in ['ssim', 'psnr']:
                    eval_results[metric_name] = self._eval_metrics[
                        metric_name](tensor2img(fake_img, min_max=(-1, 1)),
                                     tensor2img(gt_img, min_max=(-1, 1)))
                else:
                    eval_results[metric_name] = self._eval_metrics[
                        metric_name]()(data_dict).item()
            output['eval_results'] = eval_results
        else:
            output['fake_res'] = fake_res
            output['fake_img'] = fake_img

        output['meta'] = None if 'meta' not in kwargs else kwargs['meta'][0]

        if save_image:
            assert save_image and save_path is not None, (
                'Save path should been given')
            assert output['meta'] is not None, (
                'Meta information should be given to save image.')

            tmp_filename = output['meta']['gt_img_path']
            filestem = Path(tmp_filename).stem
            if iteration is not None:
                filename = f'{filestem}_{iteration}.png'
            else:
                filename = f'{filestem}.png'
            mmcv.mkdir_or_exist(save_path)
            img_list = [kwargs['gt_img']] if 'gt_img' in kwargs else []
            img_list.extend(
                [masked_img,
                 mask.expand_as(masked_img), fake_res, fake_img])
            img = torch.cat(img_list, dim=3).cpu()
            self.save_visualization(img, osp.join(save_path, filename))
            output['save_img_path'] = osp.abspath(
                osp.join(save_path, filename))

        return output

    def save_visualization(self, img, filename):
        """Save visualization results.

        Args:
            img (torch.Tensor): Tensor with shape of (n, 3, h, w).
            filename (str): Path to save visualization.
        """
        if self.test_cfg.get('img_rerange', True):
            img = (img + 1) / 2
        if self.test_cfg.get('img_bgr2rgb', True):
            img = img[:, [2, 1, 0], ...]
        save_image(img, filename, nrow=1, padding=0)

    def train_step(self, data_batch, optimizer):
        """Train step function.

        In this function, the inpaintor will finish the train step following
        the pipeline:

            1. get fake res/image
            2. optimize discriminator (if have)
            3. optimize generator

        If `self.train_cfg.disc_step > 1`, the train step will contain multiple
        iterations for optimizing discriminator with different input data and
        only one iteration for optimizing gerator after `disc_step` iterations
        for discriminator.

        Args:
            data_batch (torch.Tensor): Batch of data as input.
            optimizer (dict[torch.optim.Optimizer]): Dict with optimizers for
                generator and discriminator (if have).

        Returns:
            dict: Dict with loss, information for logger, the number of \
                samples and results for visualization.
        """
        log_vars = {}

        gt_img = data_batch['gt_img']
        mask = data_batch['mask']
        masked_img = data_batch['masked_img']

        # get common output from encdec
        input_x = torch.cat([masked_img, mask], dim=1)
        fake_res = self.generator(input_x)
        fake_img = gt_img * (1. - mask) + fake_res * mask

        # discriminator training step
        if self.train_cfg.disc_step > 0:
            set_requires_grad(self.disc, True)
            disc_losses = self.forward_train_d(
                fake_img.detach(), False, is_disc=True)
            loss_disc, log_vars_d = self.parse_losses(disc_losses)
            log_vars.update(log_vars_d)
            optimizer['disc'].zero_grad()
            loss_disc.backward()

            disc_losses = self.forward_train_d(gt_img, True, is_disc=True)
            loss_disc, log_vars_d = self.parse_losses(disc_losses)
            log_vars.update(log_vars_d)
            loss_disc.backward()

            if self.with_gp_loss:
                loss_d_gp = self.loss_gp(
                    self.disc, gt_img, fake_img, mask=mask)
                loss_disc, log_vars_d = self.parse_losses(
                    dict(loss_gp=loss_d_gp))
                log_vars.update(log_vars_d)
                loss_disc.backward()

            optimizer['disc'].step()

            self.disc_step_count = (self.disc_step_count +
                                    1) % self.train_cfg.disc_step
            if self.disc_step_count != 0:
                # results contain the data for visualization
                results = dict(
                    gt_img=gt_img.cpu(),
                    masked_img=masked_img.cpu(),
                    fake_res=fake_res.cpu(),
                    fake_img=fake_img.cpu())
                outputs = dict(
                    log_vars=log_vars,
                    num_samples=len(data_batch['gt_img'].data),
                    results=results)

                return outputs

        # generator (encdec) training step, results contain the data
        # for visualization
        if self.with_gan:
            set_requires_grad(self.disc, False)
        results, g_losses = self.generator_loss(fake_res, fake_img, data_batch)
        loss_g, log_vars_g = self.parse_losses(g_losses)
        log_vars.update(log_vars_g)
        optimizer['generator'].zero_grad()
        loss_g.backward()
        optimizer['generator'].step()

        outputs = dict(
            log_vars=log_vars,
            num_samples=len(data_batch['gt_img'].data),
            results=results)

        return outputs

    def val_step(self, data_batch, **kwargs):
        """Forward function for evaluation.

        Args:
            data_batch (dict): Contain data for forward.

        Returns:
            dict: Contain the results from model.
        """
        output = self.forward_test(**data_batch, **kwargs)

        return output

    def forward_dummy(self, x):
        """Forward dummy function for getting flops.

        Args:
            x (torch.Tensor): Input tensor with shape of (n, c, h, w).

        Returns:
            torch.Tensor: Results tensor with shape of (n, 3, h, w).
        """
        res = self.generator(x)

        return res
