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# Copyright 2025 Google LLC and HuggingFace Inc. team.
#
# 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,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import math
from collections.abc import Callable, Sequence
from dataclasses import dataclass

import torch
import torch.nn as nn
import torch.nn.functional as F

from ... import initialization as init
from ...integrations import use_kernel_forward_from_hub
from ...modeling_flash_attention_utils import FlashAttentionKwargs
from ...modeling_outputs import BaseModelOutput
from ...modeling_utils import ALL_ATTENTION_FUNCTIONS, PreTrainedModel
from ...processing_utils import Unpack
from ...utils import TransformersKwargs, auto_docstring, can_return_tuple, logging
from .configuration_timesfm import TimesFmConfig


logger = logging.get_logger(__name__)


@dataclass
@auto_docstring
class TimesFmOutput(BaseModelOutput):
    r"""
    loc (`torch.Tensor` of shape `(batch_size, )`):
        The mean of the time series inputs.
    scale (`torch.Tensor` of shape `(batch_size,)`):
        The scale of the time series inputs.
    """

    loc: torch.Tensor | None = None
    scale: torch.Tensor | None = None


@dataclass
@auto_docstring
class TimesFmOutputForPrediction(BaseModelOutput):
    r"""
    mean_predictions (`torch.Tensor` of shape `(batch_size, sequence_length)`):
        The mean predictions of the time series.
    full_predictions (`torch.Tensor` of shape `(batch_size, sequence_length)`):
        The full predictions of the time series including the mean and the quantiles.
    loss (`torch.Tensor` of shape `(1,)`, *optional*, returned when `future_values` is provided):
        The loss of the TimesFM model.
    """

    mean_predictions: torch.Tensor | None = None
    full_predictions: torch.Tensor | None = None
    loss: torch.Tensor | float | None = None


class TimesFmMLP(nn.Module):
    """Pax MLP in pytorch."""

    def __init__(self, config: TimesFmConfig):
        super().__init__()
        hidden_size = config.hidden_size
        intermediate_size = config.intermediate_size

        self.gate_proj = nn.Linear(hidden_size, intermediate_size)
        self.down_proj = nn.Linear(intermediate_size, hidden_size)
        self.layer_norm = nn.LayerNorm(normalized_shape=hidden_size, eps=1e-6)

    def forward(self, x, paddings=None):
        gate_inp = self.layer_norm(x)
        gate = self.gate_proj(gate_inp)
        gate = F.relu(gate)
        outputs = self.down_proj(gate)
        if paddings is not None:
            outputs = outputs * (1.0 - paddings[:, :, None])
        return outputs + x


class TimesFmResidualBlock(nn.Module):
    """TimesFM residual block."""

    def __init__(self, input_dims, hidden_dims, output_dims):
        super().__init__()
        self.input_dims = input_dims
        self.hidden_dims = hidden_dims
        self.output_dims = output_dims

        self.input_layer = nn.Linear(input_dims, hidden_dims)
        self.activation = nn.SiLU()
        self.output_layer = nn.Linear(hidden_dims, output_dims)
        self.residual_layer = nn.Linear(input_dims, output_dims)

    def forward(self, x):
        hidden = self.input_layer(x)
        hidden = self.activation(hidden)
        output = self.output_layer(hidden)
        residual = self.residual_layer(x)
        return output + residual


@use_kernel_forward_from_hub("RMSNorm")
class TimesFmRMSNorm(nn.Module):
    def __init__(self, hidden_size, eps: float = 1e-6) -> None:
        """
        TimesFmRMSNorm is equivalent to T5LayerNorm
        """
        super().__init__()
        self.weight = nn.Parameter(torch.ones(hidden_size))
        self.variance_epsilon = eps

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        input_dtype = hidden_states.dtype
        hidden_states = hidden_states.to(torch.float32)
        variance = hidden_states.pow(2).mean(-1, keepdim=True)
        hidden_states = hidden_states * torch.rsqrt(variance + self.variance_epsilon)
        return self.weight * hidden_states.to(input_dtype)

    def extra_repr(self):
        return f"{tuple(self.weight.shape)}, eps={self.variance_epsilon}"


class TimesFmPositionalEmbedding(nn.Module):
    """Generates position embedding for a given 1-d sequence."""

    def __init__(self, config: TimesFmConfig):
        super().__init__()
        min_timescale = config.min_timescale
        max_timescale = config.max_timescale
        self.min_timescale, self.max_timescale = min_timescale, max_timescale
        self.embedding_dims = config.hidden_size

        num_timescales = self.embedding_dims // 2
        log_timescale_increment = math.log(float(max_timescale) / float(min_timescale)) / max(num_timescales - 1, 1)
        self.register_buffer(
            "inv_timescales",
            min_timescale * torch.exp(torch.arange(num_timescales, dtype=torch.float32) * -log_timescale_increment),
        )

    def forward(self, seq_length=None, position=None):
        """Generates a Tensor of sinusoids with different frequencies.

        Args:
            seq_length: an optional Python int defining the output sequence length.
              if the `position` argument is specified.
            position: [B, seq_length], optional position for each token in the
              sequence, only required when the sequence is packed.

        Returns:
            [B, seqlen, D] if `position` is specified, else [1, seqlen, D]
        """
        if position is None and seq_length is None:
            raise ValueError("Either position or seq_length must be provided")

        if position is None:
            # [1, seqlen]
            position = torch.arange(seq_length, dtype=torch.float32, device=self.inv_timescales.device).unsqueeze(0)
        elif position.ndim != 2:
            raise ValueError(f"position must be 2-dimensional, got shape {position.shape}")

        scaled_time = position.view(*position.shape, 1) * self.inv_timescales.view(1, 1, -1)
        signal = torch.cat([torch.sin(scaled_time), torch.cos(scaled_time)], dim=2)

        # Padding to ensure correct embedding dimension
        signal = F.pad(signal, (0, 0, 0, self.embedding_dims % 2))
        return signal


def simple_eager_attention_forward(
    module: nn.Module,
    query_states: torch.Tensor,
    key_states: torch.Tensor,
    value_states: torch.Tensor,
    attention_mask: torch.Tensor | None,
    scaling: float,
    dropout: float = 0.0,
    **kwargs: Unpack[TransformersKwargs],
):
    attn_weights = torch.matmul(query_states, key_states.transpose(2, 3)) * scaling
    if attention_mask is not None:
        attn_weights = attn_weights + attention_mask

    attn_weights = nn.functional.softmax(attn_weights, dim=-1, dtype=torch.float32).to(query_states.dtype)
    attn_weights = nn.functional.dropout(attn_weights, p=dropout, training=module.training)
    attn_output = torch.matmul(attn_weights, value_states)
    attn_output = attn_output.transpose(1, 2).contiguous()

    return attn_output, attn_weights


class TimesFmAttention(nn.Module):
    """Implements the attention used in TimesFM. One key difference is that there is _per_dim_scaling of the query."""

    def __init__(self, config: TimesFmConfig, layer_idx: int):
        super().__init__()
        self.config = config
        self.is_causal = True
        self.attention_dropout = config.attention_dropout
        self.layer_idx = layer_idx

        self.num_heads = config.num_attention_heads
        self.hidden_size = config.hidden_size
        self.head_dim = config.head_dim

        self.q_size = self.num_heads * self.head_dim
        self.kv_size = self.num_heads * self.head_dim
        self.scaling = nn.Parameter(torch.empty((self.head_dim,)))

        self.q_proj = nn.Linear(self.hidden_size, self.num_heads * self.head_dim)
        self.k_proj = nn.Linear(self.hidden_size, self.num_heads * self.head_dim)
        self.v_proj = nn.Linear(self.hidden_size, self.num_heads * self.head_dim)
        self.o_proj = nn.Linear(self.num_heads * self.head_dim, self.hidden_size)

    def _scale_query(self, query: torch.Tensor) -> torch.Tensor:
        scale = F.softplus(self.scaling).mul(1.442695041 / math.sqrt(self.head_dim))
        return query * scale[None, None, None, :]

    def forward(
        self,
        hidden_states: torch.Tensor,
        attention_mask: torch.Tensor | None = None,
        **kwargs: Unpack[FlashAttentionKwargs],
    ) -> tuple[torch.Tensor, torch.Tensor | None]:
        input_shape = hidden_states.shape[:-1]
        hidden_shape = (*input_shape, -1, self.head_dim)

        query_states = self.q_proj(hidden_states).view(hidden_shape).transpose(1, 2)
        query_states = self._scale_query(query_states)
        key_states = self.k_proj(hidden_states).view(hidden_shape).transpose(1, 2)
        value_states = self.v_proj(hidden_states).view(hidden_shape).transpose(1, 2)

        attention_interface: Callable = ALL_ATTENTION_FUNCTIONS.get_interface(
            self.config._attn_implementation, simple_eager_attention_forward
        )

        attn_output, attn_weights = attention_interface(
            self,
            query_states,
            key_states,
            value_states,
            attention_mask,
            dropout=0.0 if not self.training else self.attention_dropout,
            scaling=1.0,
            **kwargs,
        )
        attn_output = attn_output.reshape(*input_shape, -1).contiguous()
        attn_output = self.o_proj(attn_output)
        return attn_output, attn_weights


class TimesFmDecoderLayer(nn.Module):
    """Transformer layer."""

    def __init__(self, config: TimesFmConfig, layer_idx: int):
        super().__init__()

        self.self_attn = TimesFmAttention(config, layer_idx=layer_idx)
        self.mlp = TimesFmMLP(config)
        self.input_layernorm = TimesFmRMSNorm(config.hidden_size, eps=config.rms_norm_eps)

    def forward(
        self,
        hidden_states: torch.Tensor,
        attention_mask: torch.Tensor,
        paddings: torch.Tensor,
        output_attentions: bool = False,
    ) -> tuple[torch.Tensor | None, torch.Tensor]:
        # Self Attention
        residual = hidden_states
        hidden_states = self.input_layernorm(hidden_states)
        hidden_states, scores = self.self_attn(
            hidden_states=hidden_states,
            attention_mask=attention_mask,
            output_attentions=output_attentions,
        )
        hidden_states = residual + hidden_states

        # MLP
        hidden_states = self.mlp(hidden_states, paddings=paddings)

        return scores, hidden_states


@auto_docstring
class TimesFmPreTrainedModel(PreTrainedModel):
    config: TimesFmConfig
    base_model_prefix = "timesfm"
    _no_split_modules = ["TimesFmDecoderLayer"]
    main_input_name = "past_values"
    input_modalities = ("time",)
    _supports_sdpa = True

    @torch.no_grad()
    def _init_weights(self, module):
        super()._init_weights(module)
        if isinstance(module, TimesFmAttention):
            # Initialize scaling parameter
            init.ones_(module.scaling)
        elif isinstance(module, TimesFmPositionalEmbedding):
            num_timescales = module.embedding_dims // 2
            max_timescale, min_timescale = module.max_timescale, module.min_timescale
            log_timescale_increment = math.log(float(max_timescale) / float(min_timescale)) / max(
                num_timescales - 1, 1
            )
            init.copy_(
                module.inv_timescales,
                min_timescale
                * torch.exp(torch.arange(num_timescales, dtype=torch.float32) * -log_timescale_increment),
            )


@auto_docstring
class TimesFmModel(TimesFmPreTrainedModel):
    def __init__(self, config: TimesFmConfig):
        super().__init__(config)

        self.config = config
        self.input_ff_layer = TimesFmResidualBlock(
            input_dims=2 * config.patch_length,
            output_dims=config.hidden_size,
            hidden_dims=config.intermediate_size,
        )
        self.freq_emb = nn.Embedding(num_embeddings=config.freq_size, embedding_dim=config.hidden_size)
        self.layers = nn.ModuleList(
            [TimesFmDecoderLayer(config, layer_idx) for layer_idx in range(config.num_hidden_layers)]
        )
        if self.config.use_positional_embedding:
            self.position_emb = TimesFmPositionalEmbedding(config=config)

        # Initialize weights and apply final processing
        self.post_init()

    def _forward_transform(
        self, inputs: torch.Tensor, patched_pads: torch.Tensor
    ) -> tuple[torch.Tensor, tuple[torch.Tensor, torch.Tensor]]:
        """Input is of shape [B, N, P]."""
        mu, sigma = self._timesfm_masked_mean_std(inputs, patched_pads)
        sigma = torch.clamp(sigma, min=self.config.tolerance)

        # Normalize each patch
        outputs = (inputs - mu[:, None, None]) / sigma[:, None, None]
        outputs = torch.where(
            torch.abs(inputs - self.config.pad_val) < self.config.tolerance,
            torch.tensor(self.config.pad_val, dtype=outputs.dtype, device=outputs.device),
            outputs,
        )
        return outputs, (mu, sigma)

    @can_return_tuple
    @auto_docstring
    def forward(
        self,
        past_values: torch.Tensor,
        past_values_padding: torch.LongTensor,
        freq: torch.Tensor,
        output_attentions: bool = False,
        output_hidden_states: bool = False,
        **kwargs,
    ) -> TimesFmOutput:
        r"""
        past_values (`torch.FloatTensor` of shape `(batch_size, sequence_length)`):
            Past values of the time series that serves as input to the model.
        past_values_padding (`torch.LongTensor` of shape `(batch_size, sequence_length)`):
            The padding indicator of the time series.
        freq (`torch.LongTensor` of shape `(batch_size,)`):
            Frequency indices for the time series data.
        """
        # Reshape into patches (using view for efficiency)
        bsize = past_values.shape[0]
        patched_inputs = past_values.view(bsize, -1, self.config.patch_length)
        patched_pads = past_values_padding.view(bsize, -1, self.config.patch_length)

        patched_inputs = torch.where(
            torch.abs(patched_pads - 1.0) < self.config.tolerance,
            torch.tensor(0.0, dtype=patched_inputs.dtype, device=patched_inputs.device),
            patched_inputs,
        )
        patched_pads = torch.where(
            torch.abs(patched_inputs - self.config.pad_val) < self.config.tolerance,
            torch.tensor(1.0, dtype=patched_pads.dtype, device=patched_pads.device),
            patched_pads,
        )
        patched_inputs, stats = self._forward_transform(patched_inputs, patched_pads)

        # B x N x D
        patched_inputs = patched_inputs * (1.0 - patched_pads)
        concat_inputs = torch.cat([patched_inputs, patched_pads], dim=-1)
        model_input = self.input_ff_layer(concat_inputs)

        # A patch should not be padded even if there is at least one zero.
        patched_padding = torch.min(patched_pads, dim=-1)[0]  # Get the values from the min result
        if self.config.use_positional_embedding:
            pos_emb = self.position_emb(model_input.shape[1])
            pos_emb = torch.concat([pos_emb] * model_input.shape[0], dim=0)
            pos_emb = self._timesfm_shift_padded_seq(patched_padding, pos_emb)
            model_input += pos_emb

        f_emb = self.freq_emb(freq)  # B x 1 x D
        model_input += f_emb

        # Convert paddings to attention mask and combine with causal mask
        hidden_states = model_input
        attention_mask = self._prepare_4d_attention_mask(
            attention_mask=patched_padding,
            sequence_length=hidden_states.shape[1],
            dtype=hidden_states.dtype,
            device=hidden_states.device,
            is_causal=True,
        )

        all_attentions = []
        all_hidden_states = []

        for layer in self.layers[: self.config.num_hidden_layers]:
            scores, hidden_states = layer(
                hidden_states=hidden_states,
                attention_mask=attention_mask,
                paddings=patched_padding,
                output_attentions=output_attentions,
            )
            if output_attentions:
                all_attentions.append(scores)
            if output_hidden_states:
                all_hidden_states.append(hidden_states)

        if output_hidden_states:
            all_hidden_states = [model_input] + all_hidden_states
        else:
            all_hidden_states = None

        return TimesFmOutput(
            last_hidden_state=hidden_states,
            hidden_states=all_hidden_states,
            attentions=all_attentions if output_attentions else None,
            loc=stats[0],
            scale=stats[1],
        )

    @staticmethod
    def _prepare_4d_attention_mask(
        attention_mask: torch.Tensor | None,
        sequence_length: int,
        dtype: torch.dtype,
        device: torch.device,
        is_causal: bool = True,
    ) -> torch.Tensor | None:
        """
        Creates 4D attention mask and combines causal and padding masks if needed.

        Args:
            attention_mask: Optional tensor of shape (batch_size, seq_length) containing padding mask
            sequence_length: Length of the sequence
            dtype: Data type of the mask
            device: Device of the mask
            is_causal: Whether to apply causal masking

        Returns:
            4D attention mask of shape (batch_size, 1, seq_length, seq_length)
        """
        # Get minimum value for the dtype
        min_value = torch.finfo(dtype).min if dtype.is_floating_point else torch.iinfo(dtype).min

        # Handle padding mask
        if attention_mask is not None:
            # Convert 2D padding mask to 4D attention mask
            attention_mask = attention_mask.view(attention_mask.shape[0], 1, 1, -1)
            attention_mask = attention_mask * min_value

        # Create causal mask if needed
        if is_causal:
            causal_mask = torch.triu(
                torch.ones((sequence_length, sequence_length), dtype=dtype, device=device) * min_value,
                diagonal=1,
            )
            causal_mask = causal_mask.view(1, 1, sequence_length, sequence_length)

            # Combine with padding mask if it exists
            if attention_mask is not None:
                attention_mask = torch.minimum(attention_mask, causal_mask)
            else:
                attention_mask = causal_mask

        return attention_mask

    @staticmethod
    def _timesfm_masked_mean_std(inputs: torch.Tensor, padding: torch.Tensor) -> tuple[torch.Tensor, torch.Tensor]:
        """Calculates mean and standard deviation of `inputs` across axis 1.

        It excludes values where `padding` is 1.

        Args:
            inputs: A PyTorch tensor of shape [b, n, p].
            padding: A PyTorch tensor of shape [b, n, p] with values 0 or 1.

        Returns:
            A tuple containing the mean and standard deviation.
            We return the statistics of the first patch with more than three non-padded values.
        """

        # Selecting the first patch with more than 3 unpadded values.
        def _get_patch_index(arr: torch.Tensor):
            indices = torch.argmax((arr >= 3).to(torch.int32), dim=1)
            row_sum = (arr >= 3).to(torch.int32).sum(dim=1)
            return torch.where(row_sum == 0, arr.shape[1] - 1, indices)

        pad_sum = torch.sum(1 - padding, dim=2)
        patch_indices = _get_patch_index(pad_sum)
        bidxs = torch.arange(inputs.shape[0])

        arr = inputs[bidxs, patch_indices, :]
        pad = padding[bidxs, patch_indices, :]

        # Create a mask where padding is 0
        mask = 1 - pad

        # Calculate the number of valid elements
        num_valid_elements = torch.sum(mask, dim=1)
        num_valid_elements = torch.clamp(num_valid_elements, min=1.0)

        # Calculate the masked sum and mean
        masked_sum = torch.sum(arr * mask, dim=1)
        masked_mean = masked_sum / num_valid_elements  # [b]

        # Calculate the masked variance using centered values
        masked_centered_arr = (arr - masked_mean.unsqueeze(-1)) * mask
        masked_var = torch.sum(masked_centered_arr**2, dim=1) / num_valid_elements
        masked_var = torch.clamp(masked_var, min=0.0)
        masked_std = torch.sqrt(masked_var)

        return masked_mean, masked_std

    @staticmethod
    def _timesfm_shift_padded_seq(mask: torch.Tensor, seq: torch.Tensor) -> torch.Tensor:
        """Shifts rows of seq based on the first 0 in each row of the mask.

        Args:
            mask: mask tensor of shape [B, N]
            seq: seq tensor of shape [B, N, P]

        Returns:
            The shifted sequence.
        """
        batch_size, num_seq, feature_dim = seq.shape

        new_mask: torch.BoolTensor = mask == 0

        # Use argmax to find the first True value in each row
        indices = new_mask.to(torch.int32).argmax(dim=1)

        # Handle rows with all zeros
        indices[~new_mask.any(dim=1)] = -1

        # Create index ranges for each sequence in the batch
        idx_range = torch.arange(num_seq, device=seq.device).view(1, -1, 1).expand(batch_size, -1, feature_dim)

        # Calculate shifted indices for each element in each sequence
        shifted_idx = (idx_range - indices[:, None, None]) % num_seq

        # Gather values from seq using shifted indices
        shifted_seq = seq.gather(1, shifted_idx)

        return shifted_seq


class TimesFmModelForPrediction(TimesFmPreTrainedModel):
    """TimesFM model for quantile and mean prediction."""

    def __init__(self, config: TimesFmConfig):
        super().__init__(config)

        self.config = config
        self.context_len = config.context_length
        self.horizon_len = config.horizon_length

        self.decoder = TimesFmModel(config)

        # quantile and mean output
        self.horizon_ff_layer = TimesFmResidualBlock(
            input_dims=config.hidden_size,
            output_dims=config.horizon_length * (1 + len(config.quantiles)),
            hidden_dims=config.intermediate_size,
        )

        # Initialize weights and apply final processing
        self.post_init()

    def _preprocess(
        self, inputs: Sequence[torch.Tensor], freq: Sequence[int] | None = None, context_len: int | None = None
    ) -> tuple[torch.Tensor, ...]:
        """Pad/truncate input time series to `context_len` and build a padding mask.

        Args:
            inputs: A list of 1d Tensors. Each Tensor is the context time series of a single forecast task.
            freq: Optional list of frequencies (returned as a tensor when provided).
            context_len: Optional context length override (defaults to `self.context_len`).

        Returns:
            Tuple of (padded_inputs, padding_mask) and optionally a freq tensor.
        """
        if context_len is None:
            context_len = self.context_len

        input_ts, input_padding = [], []

        for ts in inputs:
            input_len = ts.shape[0]
            padding = torch.zeros(input_len + self.horizon_len, dtype=ts.dtype, device=ts.device)
            if input_len < context_len:
                num_front_pad = context_len - input_len
                ts = torch.cat([torch.zeros(num_front_pad, dtype=ts.dtype, device=ts.device), ts], dim=0)
                padding = torch.cat([torch.ones(num_front_pad, dtype=ts.dtype, device=padding.device), padding], dim=0)
            elif input_len > context_len:
                ts = ts[-context_len:]
                padding = padding[-(context_len + self.horizon_len) :]

            input_ts.append(ts)
            input_padding.append(padding)

        result = (torch.stack(input_ts, dim=0), torch.stack(input_padding, dim=0))
        if freq is not None:
            result = result + (torch.tensor(freq[: len(inputs)], dtype=torch.int32).reshape(-1, 1),)
        return result

    def _postprocess_output(
        self, model_output: torch.Tensor, stats: tuple[torch.Tensor, torch.Tensor]
    ) -> torch.Tensor:
        """Postprocess output of stacked transformer."""

        # B x N x (H.Q)
        output_ts = self.horizon_ff_layer(model_output)

        # Reshape using view
        b, n, _ = output_ts.shape
        output_ts = output_ts.view(b, n, self.config.horizon_length, len(self.config.quantiles) + 1)

        mu, sigma = stats
        return output_ts * sigma[:, None, None, None] + mu[:, None, None, None]

    def _quantile_loss(self, predictions: torch.Tensor, targets: torch.Tensor) -> torch.Tensor:
        losses = []
        for i, q in enumerate(self.config.quantiles):
            errors = targets - predictions[..., i]
            loss = torch.max((q - 1) * errors, q * errors)
            losses.append(loss.mean())
        return torch.stack(losses).mean()

    @can_return_tuple
    @auto_docstring
    def forward(
        self,
        past_values: Sequence[torch.Tensor],
        freq: Sequence[torch.Tensor | int] | None = None,
        window_size: int | None = None,
        future_values: torch.Tensor | None = None,
        forecast_context_len: int | None = None,
        return_forecast_on_context: bool = False,
        truncate_negative: bool = False,
        output_attentions: bool | None = None,
        output_hidden_states: bool | None = None,
        **kwargs,
    ) -> TimesFmOutputForPrediction:
        r"""
        past_values (`torch.FloatTensor` of shape `(batch_size, sequence_length)`):
            Past values of the time series that serves as input to the model.
        freq (`torch.LongTensor` of shape `(batch_size,)`):
            Frequency indices for the time series data.
        window_size (`int`, *optional*):
            Window size of trend + residual decomposition. If None then we do not do decomposition.
        future_values (`torch.Tensor`, *optional*):
            Optional future time series values to be used for loss computation.
        forecast_context_len (`int`, *optional*):
            Optional max context length.
        return_forecast_on_context (`bool`, *optional*):
            True to return the forecast on the context when available, i.e. after the first input patch.
        truncate_negative (`bool`, *optional*):
            Truncate to only non-negative values if any of the contexts have non-negative values,
            otherwise do nothing.
        output_attentions (`bool`, *optional*):
            Whether to output the attentions.
        output_hidden_states (`bool`, *optional*):
            Whether to output the hidden states.

        Example:

        ```python
        >>> from transformers import TimesFmModelForPrediction

        >>> model = TimesFmModelForPrediction.from_pretrained("google/timesfm-2.0-500m-pytorch")

        >>> forecast_input = [torch.linspace(0, 20, 100).sin(), torch.linspace(0, 20, 200).sin(), torch.linspace(0, 20, 400).sin()]
        >>> frequency_input = torch.tensor([0, 1, 2], dtype=torch.long)

        >>> # Generate
        >>> with torch.no_grad():
        >>>     outputs = model(past_values=forecast_input, freq=frequency_input, return_dict=True)
        >>>     point_forecast_conv = outputs.mean_predictions
        >>>     quantile_forecast_conv = outputs.full_predictions
        ```
        """
        if forecast_context_len is None:
            fcontext_len = self.context_len
        else:
            fcontext_len = forecast_context_len

        # Get device from first input tensor
        device = past_values[0].device

        # Truncate inputs to forecast_context_len
        inputs = [ts[-fcontext_len:] for ts in past_values]
        inp_min = torch.min(torch.stack([torch.min(ts) for ts in inputs]))

        if window_size is not None:
            new_inputs = []
            new_freqs = []
            for i, ts in enumerate(inputs):
                new_inputs.extend(self._timesfm_moving_average(ts, window_size))
                if freq is not None:
                    new_freqs.extend([freq[i]] * 2)
            inputs = new_inputs
            if freq is not None:
                freq = new_freqs

        if freq is None:
            logger.info("No frequency provided via `freq`. Default to high (0).")
            freq = [0] * len(inputs)

        if output_attentions is None:
            output_attentions = self.config.output_attentions
        if output_hidden_states is None:
            output_hidden_states = self.config.output_hidden_states

        input_ts, input_padding, inp_freq = self._preprocess(inputs, freq)
        # Move tensors to the same device as input
        input_ts = input_ts.to(device)
        input_padding = input_padding.to(device)
        inp_freq = inp_freq.to(device)

        final_out = input_ts
        context_len = final_out.shape[1]
        full_outputs = []

        if input_padding.shape[1] != final_out.shape[1] + self.horizon_len:
            raise ValueError(
                "Length of paddings must match length of input + horizon_len:"
                f" {input_padding.shape[1]} != {final_out.shape[1]} + {self.horizon_len}"
            )
        output_patch_len = self.config.horizon_length

        num_decode_patches = (self.horizon_len + output_patch_len - 1) // output_patch_len
        for step_index in range(num_decode_patches):
            current_padding = input_padding[:, 0 : final_out.shape[1]]
            input_ts = final_out[:, -fcontext_len:]
            input_padding = current_padding[:, -fcontext_len:]
            decoder_output = self.decoder(
                past_values=input_ts,
                past_values_padding=input_padding,
                freq=inp_freq,
                output_attentions=output_attentions,
                output_hidden_states=output_hidden_states,
            )
            fprop_outputs = self._postprocess_output(
                decoder_output.last_hidden_state,
                (decoder_output.loc, decoder_output.scale),
            )

            if return_forecast_on_context and step_index == 0:
                # For the first decodings step, collect the model forecast on the
                # context except the unavailable first input batch forecast.
                new_full_ts = fprop_outputs[:, :-1, : self.config.patch_length, :]
                # We have to use reshape and not view for non-contiguous memory
                new_full_ts = new_full_ts.reshape(new_full_ts.size(0), -1, new_full_ts.size(3))

                full_outputs.append(new_full_ts)

            # (full batch, last patch, output_patch_len, index of mean forecast = 0)
            new_ts = fprop_outputs[:, -1, :output_patch_len, 0]
            new_full_ts = fprop_outputs[:, -1, :output_patch_len, :]
            # (full batch, last patch, output_patch_len, all output indices)
            full_outputs.append(new_full_ts)
            final_out = torch.concatenate([final_out, new_ts], axis=-1)

        if return_forecast_on_context:
            # `full_outputs` indexing starts at after the first input patch.
            full_outputs = torch.concatenate(full_outputs, axis=1)[
                :, : (context_len - self.config.patch_length + self.horizon_len), :
            ]
        else:
            # `full_outputs` indexing starts at the forecast horizon.
            full_outputs = torch.concatenate(full_outputs, axis=1)[:, 0 : self.horizon_len, :]

        mean_outputs = full_outputs[:, :, 0]
        if window_size is not None:
            mean_outputs = mean_outputs[0::2, ...] + mean_outputs[1::2, ...]
            full_outputs = full_outputs[0::2, ...] + full_outputs[1::2, ...]
        if inp_min >= 0 and truncate_negative:
            mean_outputs = torch.maximum(mean_outputs, 0.0)
            full_outputs = torch.maximum(full_outputs, 0.0)

        loss = None
        if future_values is not None:
            mse_loss = F.mse_loss(mean_outputs, future_values)
            quantile_loss = self._quantile_loss(full_outputs[:, :, 1:], future_values)
            loss = mse_loss + quantile_loss

        return TimesFmOutputForPrediction(
            last_hidden_state=decoder_output.last_hidden_state,
            attentions=decoder_output.attentions if output_attentions else None,
            hidden_states=decoder_output.hidden_states if output_hidden_states else None,
            mean_predictions=mean_outputs,
            full_predictions=full_outputs,
            loss=loss,
        )

    @staticmethod
    def _timesfm_moving_average(arr: torch.Tensor, window_size: int) -> list[torch.Tensor]:
        """Calculates the moving average using PyTorch's convolution function."""
        # Pad with zeros to handle initial window positions
        arr_padded = F.pad(arr, (window_size - 1, 0), "constant", 0)
        # Create a convolution kernel
        kernel = torch.ones(window_size, dtype=arr.dtype, device=arr.device) / window_size
        # Apply convolution to calculate the moving average
        smoothed_arr = F.conv1d(arr_padded.view(1, 1, -1), kernel.view(1, 1, -1)).squeeze()
        return [smoothed_arr, arr - smoothed_arr]


__all__ = ["TimesFmModelForPrediction", "TimesFmPreTrainedModel", "TimesFmModel"]
