# SPDX-License-Identifier: Apache-2.0

import torch

from vllm.model_executor.models.utils import AutoWeightsLoader


class ModuleWithBatchNorm(torch.nn.Module):

    def __init__(self):
        super().__init__()
        self.bn = torch.nn.BatchNorm1d(2)

    def forward(self, x):
        return self.bn(x)


class ModuleWithNestedBatchNorm(torch.nn.Module):

    def __init__(self):
        super().__init__()
        self.nested_mod = ModuleWithBatchNorm()

    def forward(self, x):
        return self.nested_mod(x)


def test_module_with_batchnorm_can_load():
    """Ensure the auto weight loader can load batchnorm stats."""
    mod = ModuleWithBatchNorm()
    # Run some data through the module with batchnorm
    mod(torch.Tensor([[1, 2], [3, 4]]))

    # Try to load the weights to a new instance
    def weight_generator():
        yield from mod.state_dict().items()

    new_mod = ModuleWithBatchNorm()

    assert not torch.all(new_mod.bn.running_mean == mod.bn.running_mean)
    assert not torch.all(new_mod.bn.running_var == mod.bn.running_var)
    assert new_mod.bn.num_batches_tracked.item() == 0

    loader = AutoWeightsLoader(new_mod)
    loader.load_weights(weight_generator())

    # Ensure the stats are updated
    assert torch.all(new_mod.bn.running_mean == mod.bn.running_mean)
    assert torch.all(new_mod.bn.running_var == mod.bn.running_var)
    assert new_mod.bn.num_batches_tracked.item() == 1


def test_module_with_child_containing_batchnorm_can_autoload():
    """Ensure the auto weight loader can load nested modules batchnorm stats."""
    mod = ModuleWithNestedBatchNorm()
    # Run some data through the module with batchnorm
    mod(torch.Tensor([[1, 2], [3, 4]]))

    # Try to load the weights to a new instance
    def weight_generator():
        yield from mod.state_dict().items()

    new_mod = ModuleWithNestedBatchNorm()

    assert not torch.all(
        new_mod.nested_mod.bn.running_mean == mod.nested_mod.bn.running_mean)
    assert not torch.all(
        new_mod.nested_mod.bn.running_var == mod.nested_mod.bn.running_var)
    assert new_mod.nested_mod.bn.num_batches_tracked.item() == 0

    loader = AutoWeightsLoader(new_mod)
    loader.load_weights(weight_generator())

    # Ensure the stats are updated
    assert torch.all(
        new_mod.nested_mod.bn.running_mean == mod.nested_mod.bn.running_mean)
    assert torch.all(
        new_mod.nested_mod.bn.running_var == mod.nested_mod.bn.running_var)
    assert new_mod.nested_mod.bn.num_batches_tracked.item() == 1