# download from https://github.com/Doubiiu/DynamiCrafter
import numpy as np
from tqdm import tqdm
import torch
from lvdm.models.utils_diffusion import make_ddim_sampling_parameters, make_ddim_timesteps, rescale_noise_cfg
from lvdm.common import noise_like
from lvdm.common import extract_into_tensor
import copy


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
        self.counter = 0

    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'
        to_torch = lambda x: x.clone().detach().to(torch.float32).to(self.model.device)

        if self.model.use_dynamic_rescale:
            self.ddim_scale_arr = self.model.scale_arr[self.ddim_timesteps] # extract the index by a list from a tensor
            #print(self.ddim_scale_arr)
            #print(self.ddim_scale_arr.shape) 50
            #print(self.ddim_timesteps)
            #[ 19  39  59  79  99 119 139 159 179 199 219 239 259 279 299 319 339 359
            #379 399 419 439 459 479 499 519 539 559 579 599 619 639 659 679 699 719
            #739 759 779 799 819 839 859 879 899 919 939 959 979 999]
            # index = total_steps - i - 1 thus no need reverse 
 
            self.ddim_scale_arr_prev = torch.cat([self.ddim_scale_arr[0:1], self.ddim_scale_arr[:-1]])

        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())))
        #print(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
        #print(verbose) # False
        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)

        #print(ddim_sigmas)
        #tensor([0.0285, 0.1005, 0.1222, 0.1360, 0.1471, 0.1570, 0.1661, 0.1749, 0.1833,
        #0.1916, 0.1998, 0.2079, 0.2160, 0.2240, 0.2320, 0.2400, 0.2481, 0.2561,
        #0.2642, 0.2723, 0.2805, 0.2887, 0.2970, 0.3054, 0.3139, 0.3225, 0.3312,
        #0.3401, 0.3492, 0.3585, 0.3680, 0.3779, 0.3881, 0.3987, 0.4099, 0.4216,
        #0.4341, 0.4476, 0.4621, 0.4781, 0.4959, 0.5160, 0.5392, 0.5666, 0.5997,
        #0.6411, 0.6952, 0.7697, 0.8781, 1.0000], dtype=torch.float64)


        # not use this since v prediction
        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))
        sigmas_for_original_sampling_steps = ddim_eta * torch.sqrt(
            (1 - self.alphas_cumprod_prev) / (1 - self.alphas_cumprod) * (
                        1 - self.alphas_cumprod / self.alphas_cumprod_prev))
        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,
               schedule_verbose=False,
               x_T=None,
               log_every_t=100,
               unconditional_guidance_scale=1.,
               unconditional_conditioning=None,
               precision=None,
               fs=None,
               timestep_spacing='uniform', #uniform_trailing for starting from last timestep
               guidance_rescale=0.0,
               **kwargs
               ):
        
        # check condition bs
        if conditioning is not None:
            if isinstance(conditioning, dict):
                try:
                    cbs = conditioning[list(conditioning.keys())[0]].shape[0]
                except:
                    cbs = conditioning[list(conditioning.keys())[0]][0].shape[0]

                if cbs != 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_discretize=timestep_spacing, ddim_eta=eta, verbose=schedule_verbose)
        
        # make shape
        if len(shape) == 3:
            C, H, W = shape
            size = (batch_size, C, H, W)
        elif len(shape) == 4:
            C, T, H, W = shape
            size = (batch_size, C, T, H, W)

        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,
                                                    verbose=verbose,
                                                    precision=precision,
                                                    fs=fs,
                                                    guidance_rescale=guidance_rescale,
                                                    **kwargs)
        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, verbose=True,precision=None,fs=None,guidance_rescale=0.0,
                      **kwargs):
        device = self.model.betas.device        
        b = shape[0]
        #print(x_T)
        # x_T is None
        if x_T is None:
            img = torch.randn(shape, device=device)
        else:
            img = x_T
        if precision is not None:
            if precision == 16:
                img = img.to(dtype=torch.float16)

        #print(timesteps)
        #print(self.ddpm_num_timesteps) 50
        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(total_steps) 50
        #print(timesteps) 
        if verbose:
            iterator = tqdm(time_range, desc='DDIM Sampler', total=total_steps)
        else:
            iterator = time_range

        clean_cond = kwargs.pop("clean_cond", False)
        #print(iterator) 50 numbers
        #[999 979 959 939 919 899 879 859 839 819 799 779 759 739 719 699 679 659
        #639 619 599 579 559 539 519 499 479 459 439 419 399 379 359 339 319 299
        #279 259 239 219 199 179 159 139 119  99  79  59  39  19]

        # cond_copy, unconditional_conditioning_copy = copy.deepcopy(cond), copy.deepcopy(unconditional_conditioning)
        #print(total_steps) 50 not 1000
        for i, step in enumerate(iterator):
            #print(step)
            index = total_steps - i - 1
            ts = torch.full((b,), step, device=device, dtype=torch.long)


            ## use mask to blend noised original latent (img_orig) & new sampled latent (img)
            if mask is not None: # This code not use this
                assert x0 is not None
                if clean_cond:
                    img_orig = x0
                else:
                    img_orig = self.model.q_sample(x0, ts)  # TODO: deterministic forward pass? <ddim inversion>
                img = img_orig * mask + (1. - mask) * img # keep original & modify use img

            #print(self.ddim_alphas)
            #print(self.ddim_alphas_prev)

            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,
                                      mask=mask,x0=x0,fs=fs,guidance_rescale=guidance_rescale,
                                      **kwargs)
            

            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,
                      uc_type=None, conditional_guidance_scale_temporal=None,mask=None,x0=None,guidance_rescale=0.0,**kwargs):
        b, *_, device = *x.shape, x.device
        if x.dim() == 5:
            is_video = True
        else:
            is_video = False

        if unconditional_conditioning is None or unconditional_guidance_scale == 1.:
            model_output = self.model.apply_model(x, t, c, **kwargs) # unet denoiser
        else:
            ### do_classifier_free_guidance
            if isinstance(c, torch.Tensor) or isinstance(c, dict):
                #print(x.shape)
                # x: torch.Size([1, 4, 16, 40, 64])
                e_t_cond = self.model.apply_model(x, t, c, **kwargs)
                e_t_uncond = self.model.apply_model(x, t, unconditional_conditioning, **kwargs)
            else:
                raise NotImplementedError

            model_output = e_t_uncond + unconditional_guidance_scale * (e_t_cond - e_t_uncond)

            if guidance_rescale > 0.0:
                model_output = rescale_noise_cfg(model_output, e_t_cond, guidance_rescale=guidance_rescale)

        if self.model.parameterization == "v":
            e_t = self.model.predict_eps_from_z_and_v(x, t, model_output)
        else:
            e_t = model_output
        
        # score_corrector is None
        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)

        #print('use_original_steps', use_original_steps) 

        # use_original_steps False
        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
        # xₜ = √(ᾱₜ) · x₀ + √(1 - ᾱₜ) · ε
        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
        sigmas = self.ddim_sigmas_for_original_num_steps if use_original_steps else self.ddim_sigmas
        # select parameters corresponding to the currently considered timestep

        #print(alphas, alphas_prev, sqrt_one_minus_alphas, sigmas)
        
        if is_video:
            size = (b, 1, 1, 1, 1)
        else:
            size = (b, 1, 1, 1)
        #print(index)
        # index: 50 -> 0
        # alphas: [tensor([9.8101e-01, 9.6026e-01, 9.3784e-01, 9.1376e-01, 8.8809e-01, 8.6088e-01,
        #8.3223e-01, 8.0223e-01, 7.7101e-01, 7.3870e-01, 7.0545e-01, 6.7144e-01,
        #6.3682e-01, 6.0178e-01, 5.6652e-01, 5.3122e-01, 4.9608e-01, 4.6130e-01,
        #4.2706e-01, 3.9354e-01, 3.6092e-01, 3.2936e-01, 2.9899e-01, 2.6996e-01,
        #2.4236e-01, 2.1629e-01, 1.9183e-01, 1.6901e-01, 1.4788e-01, 1.2845e-01,
        #1.1070e-01, 9.4605e-02, 8.0129e-02, 6.7212e-02, 5.5783e-02, 4.5762e-02,
        #3.7059e-02, 2.9578e-02, 2.3220e-02, 1.7883e-02, 1.3466e-02, 9.8669e-03,
        #6.9896e-03, 4.7409e-03, 3.0331e-03, 1.7848e-03, 9.2135e-04, 3.7515e-04,
        #8.5788e-05, 0.0000e+00]]
        #print('alphas', alphas)
        #print('alphas_prev[index])', alphas_prev[index])
        #print('sigmas[index]', sigmas[index])

        # not use this since v prediction
        #print(alphas) # 50 numbers
        #print(index)
        #print(alphas[index], alphas_prev[index], sigmas[index], sqrt_one_minus_alphas[index])

        a_t = torch.full(size, alphas[index], device=device)
        a_prev = torch.full(size, alphas_prev[index], device=device)
        sigma_t = torch.full(size, sigmas[index], device=device)
        sqrt_one_minus_at = torch.full(size, sqrt_one_minus_alphas[index],device=device)

        # current prediction v for predicting 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)
        
        # True
        if self.model.use_dynamic_rescale:
            #print(self.ddim_scale_arr)
            scale_t = torch.full(size, self.ddim_scale_arr[index], device=device)
            prev_scale_t = torch.full(size, self.ddim_scale_arr_prev[index], device=device)
            rescale = (prev_scale_t / scale_t)
            pred_x0 *= rescale


        #print('quantize_denoised', quantize_denoised)
        # False
        if quantize_denoised:
            pred_x0, _, *_ = self.model.first_stage_model.quantize(pred_x0)

        #sigma_t = 1 if eta = 0
        # direction pointing to x_t
        dir_xt = (1. - a_prev - sigma_t**2).sqrt() * e_t


        #print(noise_like(x.shape, device, False))

        #print(temperature)

        noise = sigma_t * noise_like(x.shape, device, repeat_noise) * temperature
        if noise_dropout > 0.:
            noise = torch.nn.functional.dropout(noise, p=noise_dropout)
        
        #print(noise_dropout)
        # noise_dropout 0
        x_prev = a_prev.sqrt() * pred_x0 + dir_xt + noise # construct Xt-1

        return x_prev, pred_x0

    @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

    @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)
