"""SAMPLING ONLY."""

import numpy as np
import torch
from tqdm import tqdm

from ..ldm.modules.diffusionmodules.util import (extract_into_tensor,
                                                 make_ddim_sampling_parameters,
                                                 make_ddim_timesteps,
                                                 noise_like)


class DDIMSampler(object):

    def __init__(self, model, schedule='linear', **kwargs):
        super().__init__()
        self.model = model
        self.ddpm_num_timesteps = model.num_timesteps
        self.schedule = schedule

    def register_buffer(self, name, attr):
        if type(attr) == torch.Tensor:
            if attr.device != torch.device('cuda'):
                attr = attr.to(torch.device('cuda'))
        setattr(self, name, attr)

    def make_schedule(self,
                      ddim_num_steps,
                      ddim_discretize='uniform',
                      ddim_eta=0.,
                      verbose=True):
        self.ddim_timesteps = make_ddim_timesteps(
            ddim_discr_method=ddim_discretize,
            num_ddim_timesteps=ddim_num_steps,
            num_ddpm_timesteps=self.ddpm_num_timesteps,
            verbose=verbose)
        alphas_cumprod = self.model.alphas_cumprod
        assert alphas_cumprod.shape[
            0] == self.ddpm_num_timesteps, 'alphas have to be defined for each timestep'

        def to_torch(x):
            return x.clone().detach().to(torch.float32).to(self.model.device)

        self.register_buffer('betas', to_torch(self.model.betas))
        self.register_buffer('alphas_cumprod', to_torch(alphas_cumprod))
        self.register_buffer('alphas_cumprod_prev',
                             to_torch(self.model.alphas_cumprod_prev))

        # calculations for diffusion q(x_t | x_{t-1}) and others
        self.register_buffer('sqrt_alphas_cumprod',
                             to_torch(np.sqrt(alphas_cumprod.cpu())))
        self.register_buffer('sqrt_one_minus_alphas_cumprod',
                             to_torch(np.sqrt(1. - alphas_cumprod.cpu())))
        self.register_buffer('log_one_minus_alphas_cumprod',
                             to_torch(np.log(1. - alphas_cumprod.cpu())))
        self.register_buffer('sqrt_recip_alphas_cumprod',
                             to_torch(np.sqrt(1. / alphas_cumprod.cpu())))
        self.register_buffer('sqrt_recipm1_alphas_cumprod',
                             to_torch(np.sqrt(1. / alphas_cumprod.cpu() - 1)))

        # ddim sampling parameters
        ddim_sigmas, ddim_alphas, ddim_alphas_prev = make_ddim_sampling_parameters(
            alphacums=alphas_cumprod.cpu(),
            ddim_timesteps=self.ddim_timesteps,
            eta=ddim_eta,
            verbose=verbose)
        self.register_buffer('ddim_sigmas', ddim_sigmas)
        self.register_buffer('ddim_alphas', ddim_alphas)
        self.register_buffer('ddim_alphas_prev', ddim_alphas_prev)
        self.register_buffer('ddim_sqrt_one_minus_alphas',
                             np.sqrt(1. - ddim_alphas))
        tmp1 = (1 - self.alphas_cumprod_prev) / (1 - self.alphas_cumprod)
        tmp2 = (1 - self.alphas_cumprod / self.alphas_cumprod_prev)
        sigmas_for_original_sampling_steps = ddim_eta * torch.sqrt(tmp1 * tmp2)
        self.register_buffer('ddim_sigmas_for_original_num_steps',
                             sigmas_for_original_sampling_steps)

    @torch.no_grad()
    def sample(
            self,
            S,
            batch_size,
            shape,
            conditioning=None,
            callback=None,
            normals_sequence=None,
            img_callback=None,
            quantize_x0=False,
            eta=0.,
            mask=None,
            x0=None,
            temperature=1.,
            noise_dropout=0.,
            score_corrector=None,
            corrector_kwargs=None,
            verbose=True,
            x_T=None,
            log_every_t=100,
            unconditional_guidance_scale=1.,
            unconditional_conditioning=None,  # this has to come in the same format as the conditioning
            dynamic_threshold=None,
            ucg_schedule=None,
            **kwargs):
        if conditioning is not None:
            if isinstance(conditioning, dict):
                ctmp = conditioning[list(conditioning.keys())[0]]
                while isinstance(ctmp, list):
                    ctmp = ctmp[0]
                cbs = ctmp.shape[0]
                if cbs != batch_size:
                    print(
                        f'Warning: Got {cbs} conditionings but batch-size is {batch_size}'
                    )

            elif isinstance(conditioning, list):
                for ctmp in conditioning:
                    if ctmp.shape[0] != batch_size:
                        print(
                            f'Warning: Got {cbs} conditionings but batch-size is {batch_size}'
                        )

            else:
                if conditioning.shape[0] != batch_size:
                    print(
                        f'Warning: Got {conditioning.shape[0]} conditionings but batch-size is {batch_size}'
                    )

        self.make_schedule(ddim_num_steps=S, ddim_eta=eta, verbose=verbose)
        # sampling
        C, H, W = shape
        size = (batch_size, C, H, W)
        print(f'Data shape for DDIM sampling is {size}, eta {eta}')

        samples, intermediates = self.ddim_sampling(
            conditioning,
            size,
            callback=callback,
            img_callback=img_callback,
            quantize_denoised=quantize_x0,
            mask=mask,
            x0=x0,
            ddim_use_original_steps=False,
            noise_dropout=noise_dropout,
            temperature=temperature,
            score_corrector=score_corrector,
            corrector_kwargs=corrector_kwargs,
            x_T=x_T,
            log_every_t=log_every_t,
            unconditional_guidance_scale=unconditional_guidance_scale,
            unconditional_conditioning=unconditional_conditioning,
            dynamic_threshold=dynamic_threshold,
            ucg_schedule=ucg_schedule)
        return samples, intermediates

    @torch.no_grad()
    def ddim_sampling(self,
                      cond,
                      shape,
                      x_T=None,
                      ddim_use_original_steps=False,
                      callback=None,
                      timesteps=None,
                      quantize_denoised=False,
                      mask=None,
                      x0=None,
                      img_callback=None,
                      log_every_t=100,
                      temperature=1.,
                      noise_dropout=0.,
                      score_corrector=None,
                      corrector_kwargs=None,
                      unconditional_guidance_scale=1.,
                      unconditional_conditioning=None,
                      dynamic_threshold=None,
                      ucg_schedule=None):
        device = self.model.betas.device
        b = shape[0]
        # x_T 1,4,64,64
        if x_T is None:
            img = torch.randn(shape, device=device)
        else:
            img = x_T

        if timesteps is None:
            timesteps = self.ddpm_num_timesteps if ddim_use_original_steps else self.ddim_timesteps
        elif timesteps is not None and not ddim_use_original_steps:
            subset_end = int(
                min(timesteps / self.ddim_timesteps.shape[0], 1)
                * self.ddim_timesteps.shape[0]) - 1
            timesteps = self.ddim_timesteps[:subset_end]

        intermediates = {'x_inter': [img], 'pred_x0': [img]}
        time_range = reversed(range(
            0, timesteps)) if ddim_use_original_steps else np.flip(timesteps)
        total_steps = timesteps if ddim_use_original_steps else timesteps.shape[
            0]
        print(f'Running DDIM Sampling with {total_steps} timesteps')

        iterator = tqdm(time_range, desc='DDIM Sampler', total=total_steps)

        for i, step in enumerate(iterator):
            index = total_steps - i - 1
            ts = torch.full((b, ), step, device=device, dtype=torch.long)

            if mask is not None:
                assert x0 is not None
                img_orig = self.model.q_sample(
                    x0, ts)  # TODO: deterministic forward pass?
                img = img_orig * mask + (1. - mask) * img

            if ucg_schedule is not None:
                assert len(ucg_schedule) == len(time_range)
                unconditional_guidance_scale = ucg_schedule[i]

            outs = self.p_sample_ddim(
                img,
                cond,
                ts,
                index=index,
                use_original_steps=ddim_use_original_steps,
                quantize_denoised=quantize_denoised,
                temperature=temperature,
                noise_dropout=noise_dropout,
                score_corrector=score_corrector,
                corrector_kwargs=corrector_kwargs,
                unconditional_guidance_scale=unconditional_guidance_scale,
                unconditional_conditioning=unconditional_conditioning,
                dynamic_threshold=dynamic_threshold)
            img, pred_x0 = outs
            if callback:
                callback(i)
            if img_callback:
                img_callback(pred_x0, i)

            if index % log_every_t == 0 or index == total_steps - 1:
                intermediates['x_inter'].append(img)
                intermediates['pred_x0'].append(pred_x0)

        return img, intermediates

    @torch.no_grad()
    def p_sample_ddim(self,
                      x,
                      c,
                      t,
                      index,
                      repeat_noise=False,
                      use_original_steps=False,
                      quantize_denoised=False,
                      temperature=1.,
                      noise_dropout=0.,
                      score_corrector=None,
                      corrector_kwargs=None,
                      unconditional_guidance_scale=1.,
                      unconditional_conditioning=None,
                      dynamic_threshold=None):
        b, *_, device = *x.shape, x.device

        if unconditional_conditioning is None or unconditional_guidance_scale == 1.:
            model_output = self.model.apply_model(x, t, c)
        else:
            model_t = self.model.apply_model(x, t, c)
            model_uncond = self.model.apply_model(x, t,
                                                  unconditional_conditioning)
            model_output = model_uncond + unconditional_guidance_scale * (
                model_t - model_uncond)

        if self.model.parameterization == 'v':
            e_t = self.model.predict_eps_from_z_and_v(x, t, model_output)
        else:
            e_t = model_output

        if score_corrector is not None:
            assert self.model.parameterization == 'eps', 'not implemented'
            e_t = score_corrector.modify_score(self.model, e_t, x, t, c,
                                               **corrector_kwargs)

        alphas = self.model.alphas_cumprod if use_original_steps else self.ddim_alphas
        alphas_prev = self.model.alphas_cumprod_prev if use_original_steps else self.ddim_alphas_prev
        sqrt_one_minus_alphas = self.model.sqrt_one_minus_alphas_cumprod \
            if use_original_steps else self.ddim_sqrt_one_minus_alphas
        sigmas = self.model.ddim_sigmas_for_original_num_steps if use_original_steps else self.ddim_sigmas
        # select parameters corresponding to the currently considered timestep
        a_t = torch.full((b, 1, 1, 1), alphas[index], device=device)
        a_prev = torch.full((b, 1, 1, 1), alphas_prev[index], device=device)
        sigma_t = torch.full((b, 1, 1, 1), sigmas[index], device=device)
        sqrt_one_minus_at = torch.full((b, 1, 1, 1),
                                       sqrt_one_minus_alphas[index],
                                       device=device)

        # current prediction for x_0
        if self.model.parameterization != 'v':
            pred_x0 = (x - sqrt_one_minus_at * e_t) / a_t.sqrt()
        else:
            pred_x0 = self.model.predict_start_from_z_and_v(x, t, model_output)

        if quantize_denoised:
            pred_x0, _, *_ = self.model.first_stage_model.quantize(pred_x0)

        if dynamic_threshold is not None:
            raise NotImplementedError()

        # direction pointing to x_t
        dir_xt = (1. - a_prev - sigma_t**2).sqrt() * e_t
        noise = sigma_t * noise_like(x.shape, device,
                                     repeat_noise) * temperature
        if noise_dropout > 0.:
            noise = torch.nn.functional.dropout(noise, p=noise_dropout)
        x_prev = a_prev.sqrt() * pred_x0 + dir_xt + noise
        return x_prev, pred_x0

    @torch.no_grad()
    def encode(self,
               x0,
               c,
               t_enc,
               use_original_steps=False,
               return_intermediates=None,
               unconditional_guidance_scale=1.0,
               unconditional_conditioning=None,
               callback=None):
        timesteps = np.arange(self.ddpm_num_timesteps
                              ) if use_original_steps else self.ddim_timesteps
        num_reference_steps = timesteps.shape[0]

        assert t_enc <= num_reference_steps
        num_steps = t_enc

        if use_original_steps:
            alphas_next = self.alphas_cumprod[:num_steps]
            alphas = self.alphas_cumprod_prev[:num_steps]
        else:
            alphas_next = self.ddim_alphas[:num_steps]
            alphas = torch.tensor(self.ddim_alphas_prev[:num_steps])

        x_next = x0
        intermediates = []
        inter_steps = []
        for i in tqdm(range(num_steps), desc='Encoding Image'):
            t = torch.full((x0.shape[0], ),
                           timesteps[i],
                           device=self.model.device,
                           dtype=torch.long)
            if unconditional_guidance_scale == 1.:
                noise_pred = self.model.apply_model(x_next, t, c)
            else:
                assert unconditional_conditioning is not None
                e_t_uncond, noise_pred = torch.chunk(
                    self.model.apply_model(
                        torch.cat((x_next, x_next)), torch.cat((t, t)),
                        torch.cat((unconditional_conditioning, c))), 2)
                noise_pred = e_t_uncond + unconditional_guidance_scale * (
                    noise_pred - e_t_uncond)

            xt_weighted = (alphas_next[i] / alphas[i]).sqrt() * x_next
            tmp = (1 / alphas_next[i] - 1).sqrt() - (1 / alphas[i] - 1).sqrt()
            weighted_noise_pred = alphas_next[i].sqrt() * tmp * noise_pred
            x_next = xt_weighted + weighted_noise_pred
            if return_intermediates and i % (num_steps // return_intermediates
                                             ) == 0 and i < num_steps - 1:
                intermediates.append(x_next)
                inter_steps.append(i)
            elif return_intermediates and i >= num_steps - 2:
                intermediates.append(x_next)
                inter_steps.append(i)
            if callback:
                callback(i)

        out = {'x_encoded': x_next, 'intermediate_steps': inter_steps}
        if return_intermediates:
            out.update({'intermediates': intermediates})
        return x_next, out

    @torch.no_grad()
    def stochastic_encode(self, x0, t, use_original_steps=False, noise=None):
        # fast, but does not allow for exact reconstruction
        # t serves as an index to gather the correct alphas
        if use_original_steps:
            sqrt_alphas_cumprod = self.sqrt_alphas_cumprod
            sqrt_one_minus_alphas_cumprod = self.sqrt_one_minus_alphas_cumprod
        else:
            sqrt_alphas_cumprod = torch.sqrt(self.ddim_alphas)
            sqrt_one_minus_alphas_cumprod = self.ddim_sqrt_one_minus_alphas

        if noise is None:
            noise = torch.randn_like(x0)
        return (
            extract_into_tensor(sqrt_alphas_cumprod, t, x0.shape) * x0
            + extract_into_tensor(sqrt_one_minus_alphas_cumprod, t, x0.shape)
            * noise)

    @torch.no_grad()
    def decode(self,
               x_latent,
               cond,
               t_start,
               unconditional_guidance_scale=1.0,
               unconditional_conditioning=None,
               use_original_steps=False,
               callback=None):

        timesteps = np.arange(self.ddpm_num_timesteps
                              ) if use_original_steps else self.ddim_timesteps
        timesteps = timesteps[:t_start]

        time_range = np.flip(timesteps)
        total_steps = timesteps.shape[0]
        print(f'Running DDIM Sampling with {total_steps} timesteps')

        iterator = tqdm(time_range, desc='Decoding image', total=total_steps)
        x_dec = x_latent
        for i, step in enumerate(iterator):
            index = total_steps - i - 1
            ts = torch.full((x_latent.shape[0], ),
                            step,
                            device=x_latent.device,
                            dtype=torch.long)
            x_dec, _ = self.p_sample_ddim(
                x_dec,
                cond,
                ts,
                index=index,
                use_original_steps=use_original_steps,
                unconditional_guidance_scale=unconditional_guidance_scale,
                unconditional_conditioning=unconditional_conditioning)
            if callback:
                callback(i)
        return x_dec
