# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
from vllm.distributed import divide


class MambaStateShapeCalculator:

    @classmethod
    def mamba1_state_shape(
        cls,
        tp_world_size: int,
        intermediate_size: int,
        state_size: int,
        conv_kernel: int,
        use_v1: bool = True,
    ) -> tuple[tuple[int, int], tuple[int, int]]:
        conv_state_shape = (divide(intermediate_size,
                                   tp_world_size), conv_kernel - 1)

        temporal_state_shape = (divide(intermediate_size,
                                       tp_world_size), state_size)

        # In V0, the conv_state shape was swapped during allocation in
        # MambaCacheManager, but in V1 it needs to be determined here at the
        # calculation level
        if use_v1:
            conv_state_shape = conv_state_shape[1], conv_state_shape[0]

        return conv_state_shape, temporal_state_shape

    @classmethod
    def mamba2_state_shape(
        cls,
        tp_world_size: int,
        intermediate_size: int,
        n_groups: int,
        num_heads: int,
        head_dim: int,
        state_size: int,
        conv_kernel: int,
        use_v1: bool = True,
    ) -> tuple[tuple[int, int], tuple[int, int, int]]:
        # if n_groups is not divisible by world_size, need to extend the shards
        # to ensure all groups needed by a head is sharded along with it
        n_groups = n_groups + cls.extra_groups_for_head_shards(
            n_groups, tp_world_size)
        # heads and n_groups are TP-ed
        conv_dim = intermediate_size + 2 * n_groups * state_size

        # contiguous along 'dim' axis
        conv_state_shape = (conv_kernel - 1, divide(conv_dim, tp_world_size))
        if not use_v1:
            conv_state_shape = conv_state_shape[1], conv_state_shape[0]

        # These are not TP-ed as they depend on A, dt_bias, D
        # - they are typically small
        #   e.g., (h_heads, head_dim, state_size) = (128, 64, 128)
        temporal_state_shape = (divide(num_heads,
                                       tp_world_size), head_dim, state_size)
        return conv_state_shape, temporal_state_shape

    @classmethod
    def extra_groups_for_head_shards(cls, ngroups: int, tp_size: int):
        """Compute the increase in group numbers to account for
        replication in order to accompany the head shards."""

        # in the case ngoups % tp_size == 0, this will be zero
        if ngroups % tp_size == 0:
            return 0

        # for n_groups == 1, this is exactly tp_size - n_groups
        return tp_size - ngroups
