# SPDX-FileCopyrightText: Copyright (c) 2024 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
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"""The causal continuous video tokenizer with VAE or AE formulation for 3D data.."""

import logging
import torch
from torch import nn
from enum import Enum
import math

from .cosmos_tokenizer.layers3d import (
    EncoderFactorized,
    DecoderFactorized,
    CausalConv3d,
)

logger = logging.getLogger(__name__)

class IdentityDistribution(torch.nn.Module):
    def __init__(self):
        super().__init__()

    def forward(self, parameters):
        return parameters, (torch.tensor([0.0]), torch.tensor([0.0]))


class GaussianDistribution(torch.nn.Module):
    def __init__(self, min_logvar: float = -30.0, max_logvar: float = 20.0):
        super().__init__()
        self.min_logvar = min_logvar
        self.max_logvar = max_logvar

    def sample(self, mean, logvar):
        std = torch.exp(0.5 * logvar)
        return mean + std * torch.randn_like(mean)

    def forward(self, parameters):
        mean, logvar = torch.chunk(parameters, 2, dim=1)
        logvar = torch.clamp(logvar, self.min_logvar, self.max_logvar)
        return self.sample(mean, logvar), (mean, logvar)


class ContinuousFormulation(Enum):
    VAE = GaussianDistribution
    AE = IdentityDistribution


class CausalContinuousVideoTokenizer(nn.Module):
    def __init__(
        self, z_channels: int, z_factor: int, latent_channels: int, **kwargs
    ) -> None:
        super().__init__()
        self.name = kwargs.get("name", "CausalContinuousVideoTokenizer")
        self.latent_channels = latent_channels
        self.sigma_data = 0.5

        # encoder_name = kwargs.get("encoder", Encoder3DType.BASE.name)
        self.encoder = EncoderFactorized(
            z_channels=z_factor * z_channels, **kwargs
        )
        if kwargs.get("temporal_compression", 4) == 4:
            kwargs["channels_mult"] = [2, 4]
        # decoder_name = kwargs.get("decoder", Decoder3DType.BASE.name)
        self.decoder = DecoderFactorized(
            z_channels=z_channels, **kwargs
        )

        self.quant_conv = CausalConv3d(
            z_factor * z_channels,
            z_factor * latent_channels,
            kernel_size=1,
            padding=0,
        )
        self.post_quant_conv = CausalConv3d(
            latent_channels, z_channels, kernel_size=1, padding=0
        )

        # formulation_name = kwargs.get("formulation", ContinuousFormulation.AE.name)
        self.distribution = IdentityDistribution()  # ContinuousFormulation[formulation_name].value()

        num_parameters = sum(param.numel() for param in self.parameters())
        logger.debug(f"model={self.name}, num_parameters={num_parameters:,}")
        logger.debug(
            f"z_channels={z_channels}, latent_channels={self.latent_channels}."
        )

        latent_temporal_chunk = 16
        self.latent_mean = nn.Parameter(torch.zeros([self.latent_channels * latent_temporal_chunk], dtype=torch.float32))
        self.latent_std = nn.Parameter(torch.ones([self.latent_channels * latent_temporal_chunk], dtype=torch.float32))


    def encode(self, x):
        h = self.encoder(x)
        moments = self.quant_conv(h)
        z, posteriors = self.distribution(moments)
        latent_ch = z.shape[1]
        latent_t = z.shape[2]
        in_dtype = z.dtype
        mean = self.latent_mean.view(latent_ch, -1)
        std = self.latent_std.view(latent_ch, -1)

        mean = mean.repeat(1, math.ceil(latent_t / mean.shape[-1]))[:, : latent_t].reshape([1, latent_ch, -1, 1, 1]).to(dtype=in_dtype, device=z.device)
        std = std.repeat(1, math.ceil(latent_t / std.shape[-1]))[:, : latent_t].reshape([1, latent_ch, -1, 1, 1]).to(dtype=in_dtype, device=z.device)
        return ((z - mean) / std) * self.sigma_data

    def decode(self, z):
        in_dtype = z.dtype
        latent_ch = z.shape[1]
        latent_t = z.shape[2]
        mean = self.latent_mean.view(latent_ch, -1)
        std = self.latent_std.view(latent_ch, -1)

        mean = mean.repeat(1, math.ceil(latent_t / mean.shape[-1]))[:, : latent_t].reshape([1, latent_ch, -1, 1, 1]).to(dtype=in_dtype, device=z.device)
        std = std.repeat(1, math.ceil(latent_t / std.shape[-1]))[:, : latent_t].reshape([1, latent_ch, -1, 1, 1]).to(dtype=in_dtype, device=z.device)

        z = z / self.sigma_data
        z = z * std + mean
        z = self.post_quant_conv(z)
        return self.decoder(z)

