from diffusers.training_utils import *


# https://github.com/huggingface/diffusers/pull/9812: fix `self.use_ema_warmup`
class MyEMAModel(EMAModel):
    """
    Exponential Moving Average of models weights
    """

    def __init__(
        self,
        parameters: Iterable[torch.nn.Parameter],
        decay: float = 0.9999,
        min_decay: float = 0.0,
        update_after_step: int = 0,
        use_ema_warmup: bool = False,
        inv_gamma: Union[float, int] = 1.0,
        power: Union[float, int] = 2 / 3,
        foreach: bool = False,
        model_cls: Optional[Any] = None,
        model_config: Dict[str, Any] = None,
        **kwargs,
    ):
        """
        Args:
            parameters (Iterable[torch.nn.Parameter]): The parameters to track.
            decay (float): The decay factor for the exponential moving average.
            min_decay (float): The minimum decay factor for the exponential moving average.
            update_after_step (int): The number of steps to wait before starting to update the EMA weights.
            use_ema_warmup (bool): Whether to use EMA warmup.
            inv_gamma (float):
                Inverse multiplicative factor of EMA warmup. Default: 1. Only used if `use_ema_warmup` is True.
            power (float): Exponential factor of EMA warmup. Default: 2/3. Only used if `use_ema_warmup` is True.
            foreach (bool): Use torch._foreach functions for updating shadow parameters. Should be faster.
            device (Optional[Union[str, torch.device]]): The device to store the EMA weights on. If None, the EMA
                        weights will be stored on CPU.

        @crowsonkb's notes on EMA Warmup:
            If gamma=1 and power=1, implements a simple average. gamma=1, power=2/3 are good values for models you plan
            to train for a million or more steps (reaches decay factor 0.999 at 31.6K steps, 0.9999 at 1M steps),
            gamma=1, power=3/4 for models you plan to train for less (reaches decay factor 0.999 at 10K steps, 0.9999
            at 215.4k steps).
        """

        if isinstance(parameters, torch.nn.Module):
            deprecation_message = (
                "Passing a `torch.nn.Module` to `ExponentialMovingAverage` is deprecated. "
                "Please pass the parameters of the module instead."
            )
            deprecate(
                "passing a `torch.nn.Module` to `ExponentialMovingAverage`",
                "1.0.0",
                deprecation_message,
                standard_warn=False,
            )
            parameters = parameters.parameters()

            # # set use_ema_warmup to True if a torch.nn.Module is passed for backwards compatibility
            # use_ema_warmup = True

        if kwargs.get("max_value", None) is not None:
            deprecation_message = "The `max_value` argument is deprecated. Please use `decay` instead."
            deprecate("max_value", "1.0.0", deprecation_message, standard_warn=False)
            decay = kwargs["max_value"]

        if kwargs.get("min_value", None) is not None:
            deprecation_message = "The `min_value` argument is deprecated. Please use `min_decay` instead."
            deprecate("min_value", "1.0.0", deprecation_message, standard_warn=False)
            min_decay = kwargs["min_value"]

        parameters = list(parameters)
        self.shadow_params = [p.clone().detach() for p in parameters]

        if kwargs.get("device", None) is not None:
            deprecation_message = "The `device` argument is deprecated. Please use `to` instead."
            deprecate("device", "1.0.0", deprecation_message, standard_warn=False)
            self.to(device=kwargs["device"])

        self.temp_stored_params = None

        self.decay = decay
        self.min_decay = min_decay
        self.update_after_step = update_after_step
        self.use_ema_warmup = use_ema_warmup
        self.inv_gamma = inv_gamma
        self.power = power
        self.optimization_step = 0
        self.cur_decay_value = None  # set in `step()`
        self.foreach = foreach

        self.model_cls = model_cls
        self.model_config = model_config

    def get_decay(self, optimization_step: int) -> float:
        """
        Compute the decay factor for the exponential moving average.
        """
        step = max(0, optimization_step - self.update_after_step - 1)

        if step <= 0:
            return 0.0

        if self.use_ema_warmup:
            cur_decay_value = 1 - (1 + step / self.inv_gamma) ** -self.power
        else:
            # cur_decay_value = (1 + step) / (10 + step)
            cur_decay_value = self.decay

        cur_decay_value = min(cur_decay_value, self.decay)
        # make sure decay is not smaller than min_decay
        cur_decay_value = max(cur_decay_value, self.min_decay)
        return cur_decay_value