# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""
Tests that triton_kernel_moe_forward correctly applies expert_map
remapping when expert parallelism (EP) is enabled.

Previously, legacy_routing was always used and it produced routing data
with global expert IDs that didn't correspond to local weight indices,
causing illegal memory access with EP.  The fix splits routing: when
expert_map is provided, topk selection is performed first, expert_map is
applied to remap global→local IDs, and make_routing_data builds routing
structures from the local IDs.
"""

from unittest.mock import MagicMock, patch

import pytest
import torch


class TestTritonMoeForwardExpertMap:
    """Test that triton_kernel_moe_forward applies expert_map remapping
    when expert_map is provided (EP active)."""

    @pytest.mark.parametrize("expert_map_present", [False, True])
    def test_routing_path_selection(self, expert_map_present):
        """Verify that the EP-aware routing path is taken when expert_map
        is present, and the legacy_routing path is taken otherwise."""

        device = "cuda" if torch.cuda.is_available() else "cpu"
        # This is a structural test: we mock the routing functions to
        # verify the correct path is exercised.
        mock_expert_map = (
            torch.tensor([0, -1, 1, -1], device=device) if expert_map_present else None
        )

        with (
            patch(
                "vllm.model_executor.layers.fused_moe."
                "gpt_oss_triton_kernels_moe.legacy_routing"
            ) as mock_legacy,
            patch("triton_kernels.topk.topk") as mock_topk,
            patch(
                "vllm.model_executor.layers.fused_moe."
                "gpt_oss_triton_kernels_moe.make_routing_data"
            ) as mock_make_routing,
            patch(
                "vllm.model_executor.layers.fused_moe."
                "gpt_oss_triton_kernels_moe.triton_kernel_fused_experts"
            ) as mock_fused_experts,
        ):
            from vllm.model_executor.layers.fused_moe.gpt_oss_triton_kernels_moe import (  # noqa: E501
                triton_kernel_moe_forward,
            )

            # Set up return values
            mock_routing_data = MagicMock()
            mock_gather = MagicMock()
            mock_scatter = MagicMock()

            if expert_map_present:
                sparse_result = MagicMock()
                sparse_result.indx = torch.tensor([[0, 2]], dtype=torch.int32)
                sparse_result.vals = torch.tensor([[0.6, 0.4]])
                mock_topk.return_value = sparse_result
                mock_make_routing.return_value = (
                    mock_routing_data,
                    mock_gather,
                    mock_scatter,
                )
            else:
                mock_legacy.return_value = (
                    mock_routing_data,
                    mock_gather,
                    mock_scatter,
                )

            mock_fused_experts.return_value = torch.zeros((1, 8), device=device)

            hidden = torch.randn((1, 8), device=device)
            w1 = torch.randn((2, 8, 16), device=device)
            w2 = torch.randn((2, 8, 8), device=device)
            logits = torch.randn((1, 4), device=device)

            triton_kernel_moe_forward(
                hidden_states=hidden,
                w1=w1,
                w2=w2,
                gating_output=logits,
                topk=2,
                renormalize=True,
                expert_map=mock_expert_map,
            )

            if expert_map_present:
                # EP path: should use topk + make_routing_data, NOT
                # legacy_routing
                mock_topk.assert_called_once()
                mock_make_routing.assert_called_once()
                mock_legacy.assert_not_called()
                # expert_map should be None in the fused_experts call
                # (already applied)
                call_kwargs = mock_fused_experts.call_args
                assert call_kwargs[1].get("expert_map") is None or (
                    len(call_kwargs[0]) > 0
                )
            else:
                # Non-EP path: should use legacy_routing
                mock_legacy.assert_called_once()
                mock_topk.assert_not_called()
                mock_make_routing.assert_not_called()
