# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0

from __future__ import annotations

from typing import cast

import pytest
from gpu_memory_service.client.memory_manager import GMSClientMemoryManager
from gpu_memory_service.client.torch.module import (
    materialize_module_from_gms,
    register_module_tensors,
)
from gpu_memory_service.client.torch.tensor import _tensor_from_pointer
from gpu_memory_service.common.types import RequestedLockType

from tests.gms.harness.gms import GMSServerProcess

torch = pytest.importorskip("torch", reason="torch is required")

pytestmark = [
    pytest.mark.pre_merge,
    pytest.mark.unit,
    pytest.mark.gpu_1,
]


if not torch.cuda.is_available():
    pytest.skip(
        "CUDA is required for torch GMS integration tests", allow_module_level=True
    )


class _TinyModule(torch.nn.Module):
    def __init__(self) -> None:
        super().__init__()
        self.linear = torch.nn.Linear(8, 4, bias=False, device="cuda")
        self.register_buffer(
            "scale",
            torch.linspace(0.5, 2.0, steps=4, device="cuda", dtype=torch.float32),
        )
        self.extra = torch.arange(1, 5, device="cuda", dtype=torch.float32)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        y = self.linear(x)
        y = y + self.scale
        y = y * self.extra
        return torch.relu(y)


@pytest.fixture
def running_gms(request):
    with GMSServerProcess(request, device=0, tag="weights") as server:
        yield server.socket_path


def _make_gms_tensor(
    manager: GMSClientMemoryManager,
    tensor: torch.Tensor,
    *,
    tag: str,
) -> tuple[str, torch.Tensor]:
    storage_bytes = tensor.untyped_storage().nbytes()
    va = manager.create_mapping(size=storage_bytes, tag=tag)
    allocation_id = manager.mappings[va].allocation_id
    gms_tensor = _tensor_from_pointer(
        va,
        list(tensor.shape),
        list(tensor.stride()),
        tensor.dtype,
        tensor.device.index or 0,
    )
    gms_tensor.copy_(tensor)
    return allocation_id, gms_tensor


def _assert_exact_tensor_equal(expected: torch.Tensor, actual: torch.Tensor) -> None:
    torch.testing.assert_close(expected, actual, rtol=0, atol=0)


def test_gms_tensor_matches_plain_torch_ops(running_gms):
    socket_path = running_gms
    baseline = torch.arange(64, device="cuda", dtype=torch.float32).reshape(8, 8)
    rhs = torch.arange(32, device="cuda", dtype=torch.float32).reshape(8, 4)

    writer = GMSClientMemoryManager(socket_path, device=0)
    writer.connect(RequestedLockType.RW)
    allocation_id, _writer_tensor = _make_gms_tensor(writer, baseline, tag="weights")
    assert writer.commit()

    reader = GMSClientMemoryManager(socket_path, device=0)
    reader.connect(RequestedLockType.RO)
    va = reader.create_mapping(allocation_id=allocation_id)
    gms_tensor = _tensor_from_pointer(
        va,
        list(baseline.shape),
        list(baseline.stride()),
        baseline.dtype,
        0,
    )

    _assert_exact_tensor_equal(
        torch.relu((baseline + 3.0) @ rhs), torch.relu((gms_tensor + 3.0) @ rhs)
    )
    _assert_exact_tensor_equal(
        baseline.transpose(0, 1).contiguous(), gms_tensor.transpose(0, 1).contiguous()
    )
    _assert_exact_tensor_equal(
        baseline[:, 2:6].sum(dim=1), gms_tensor[:, 2:6].sum(dim=1)
    )
    _assert_exact_tensor_equal(
        (baseline * 2.0 - 5.0).square(), (gms_tensor * 2.0 - 5.0).square()
    )

    reader.close()


def test_live_gms_tensor_survives_unmap_and_remap(running_gms):
    socket_path = running_gms
    baseline = torch.arange(64, device="cuda", dtype=torch.float32).reshape(8, 8)

    writer = GMSClientMemoryManager(socket_path, device=0)
    writer.connect(RequestedLockType.RW)
    allocation_id, _ = _make_gms_tensor(writer, baseline, tag="weights")
    assert writer.commit()

    reader = GMSClientMemoryManager(socket_path, device=0)
    reader.connect(RequestedLockType.RO)
    va = reader.create_mapping(allocation_id=allocation_id)
    gms_tensor = _tensor_from_pointer(
        va,
        list(baseline.shape),
        list(baseline.stride()),
        baseline.dtype,
        0,
    )
    pointer_before = gms_tensor.data_ptr()
    expected = torch.relu((baseline + 7.0).square())

    reader.unmap_all_vas()
    reader.abort()
    reader.connect(RequestedLockType.RO)
    reader.remap_all_vas()

    assert gms_tensor.data_ptr() == pointer_before
    _assert_exact_tensor_equal(expected, torch.relu((gms_tensor + 7.0).square()))

    reader.close()


def test_materialized_module_from_gms_matches_plain_module_forward(running_gms):
    socket_path = running_gms
    torch.manual_seed(7)
    baseline = _TinyModule().cuda()
    gms_model = _TinyModule().cuda()
    gms_model.load_state_dict(baseline.state_dict())
    inputs = torch.randn(3, 8, device="cuda", dtype=torch.float32)
    expected = baseline(inputs).detach().clone()

    writer = GMSClientMemoryManager(socket_path, device=0)
    writer.connect(RequestedLockType.RW)

    baseline_weight = cast(torch.Tensor, baseline.linear.weight)
    baseline_scale = cast(torch.Tensor, baseline.scale)
    baseline_extra = cast(torch.Tensor, baseline.extra)

    _, gms_weight = _make_gms_tensor(writer, baseline_weight, tag="weights")
    gms_model.linear.weight = torch.nn.Parameter(
        gms_weight, requires_grad=baseline_weight.requires_grad
    )
    _, gms_scale = _make_gms_tensor(writer, baseline_scale, tag="weights")
    gms_model._buffers["scale"] = gms_scale
    _, gms_extra = _make_gms_tensor(writer, baseline_extra, tag="weights")
    gms_model.extra = gms_extra

    register_module_tensors(writer, gms_model)
    _assert_exact_tensor_equal(expected, gms_model(inputs))
    assert writer.commit()

    reader = GMSClientMemoryManager(socket_path, device=0)
    reader.connect(RequestedLockType.RO)
    materialized = _TinyModule().cuda()
    materialize_module_from_gms(reader, materialized, device_index=0)

    _assert_exact_tensor_equal(expected, materialized(inputs))
    _assert_exact_tensor_equal(baseline_scale, cast(torch.Tensor, materialized.scale))
    _assert_exact_tensor_equal(baseline_extra, cast(torch.Tensor, materialized.extra))
    _assert_exact_tensor_equal(
        baseline_weight,
        cast(torch.Tensor, materialized.linear.weight),
    )

    reader.close()
