#!/usr/bin/env python3
# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""
Test script for the token-to-expert routing simulator.

This script demonstrates how to use the routing simulator to test
different routing strategies and analyze their performance, including
integration tests with FusedMoE layer.
"""

import tempfile

import pytest
import torch

from vllm.config import VllmConfig, set_current_vllm_config
from vllm.distributed import (
    init_distributed_environment,
    initialize_model_parallel,
)
from vllm.model_executor.layers.fused_moe.routing_simulator import (
    DistributionBasedRouting,
    RoutingSimulator,
)


@pytest.fixture
def device():
    """Fixture to provide the appropriate device for testing."""
    return torch.device("cuda" if torch.cuda.is_available() else "cpu")


@pytest.mark.parametrize("num_tokens", [1, 16, 256])
@pytest.mark.parametrize("hidden_size", [64, 1024])
@pytest.mark.parametrize("num_experts", [16, 128])
@pytest.mark.parametrize("top_k", [1, 4])
def test_basic_functionality(
    num_tokens: int,
    hidden_size: int,
    num_experts: int,
    top_k: int,
    device,
):
    """Test basic functionality of the routing simulator."""
    # Test each routing strategy
    strategies = RoutingSimulator.get_available_strategies()

    hidden_states = torch.randn(num_tokens, hidden_size, device=device)
    router_logits = torch.randn(num_tokens, num_experts, device=device)

    for strategy in strategies:
        # Simulate routing
        topk_weights, topk_ids = RoutingSimulator.simulate_routing(
            hidden_states=hidden_states,
            router_logits=router_logits,
            strategy_name=strategy,
            top_k=top_k,
        )

        # Check output shapes
        assert topk_weights.shape == (
            num_tokens,
            top_k,
        ), f"Wrong weights shape for {strategy}"
        assert topk_ids.shape == (
            num_tokens,
            top_k,
        ), f"Wrong ids shape for {strategy}"

        # Check that expert IDs are valid
        assert topk_ids.min() >= 0, f"Invalid expert ID (negative) for {strategy}"
        assert topk_ids.max() < num_experts, (
            f"Invalid expert ID (too large) for {strategy}"
        )


def test_routing_strategy_integration(monkeypatch, device):
    """Test that the routing strategy environment variable works with
    FusedMoE."""
    pytest.importorskip("vllm.model_executor.layers.fused_moe.layer")

    import vllm.envs as envs
    from vllm.model_executor.layers.fused_moe.layer import FusedMoE

    # Test parameters
    num_tokens = 32
    hidden_size = 16
    num_experts = 4
    top_k = 2

    # Create test data
    hidden_states = torch.randn(num_tokens, hidden_size, device=device)
    router_logits = torch.randn(num_tokens, num_experts, device=device)

    # Test different routing strategies
    strategies = RoutingSimulator.get_available_strategies()

    vllm_config = VllmConfig()
    with set_current_vllm_config(vllm_config):
        temp_file = tempfile.mkstemp()[1]
        init_distributed_environment(
            world_size=1,
            rank=0,
            local_rank=0,
            distributed_init_method=f"file://{temp_file}",
        )
        initialize_model_parallel(
            tensor_model_parallel_size=1,
            pipeline_model_parallel_size=1,
        )
        fused_moe = FusedMoE(
            num_experts=num_experts,
            top_k=top_k,
            hidden_size=hidden_size,
            intermediate_size=0,
            use_grouped_topk=False,
            renormalize=True,
        )

    for strategy in strategies:
        # Set environment variable
        env_name = "VLLM_MOE_ROUTING_SIMULATION_STRATEGY"
        monkeypatch.setenv(env_name, strategy)

        # Force reload of environment variable
        envs.environment_variables[env_name] = lambda s=strategy: s

        # Test the select_experts method
        topk_weights, topk_ids = fused_moe.router.select_experts(
            hidden_states=hidden_states,
            router_logits=router_logits,
        )

        # Verify output shapes
        assert topk_weights.shape == (num_tokens, top_k), (
            f"Wrong weights shape for {strategy}"
        )
        assert topk_ids.shape == (num_tokens, top_k), f"Wrong ids shape for {strategy}"

        # Verify expert IDs are valid
        assert topk_ids.min() >= 0, f"Invalid expert ID (negative) for {strategy}"
        assert topk_ids.max() < num_experts, (
            f"Invalid expert ID (too large) for {strategy}"
        )


def test_distribution_based_routing_with_custom_strategy():
    """Test registering and using DistributionBasedRouting with custom
    parameters."""
    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

    # Register custom distribution-based strategy
    custom_strategy = DistributionBasedRouting(distribution="normal", mean=2.0, std=0.5)
    RoutingSimulator.register_strategy("custom_normal", custom_strategy)

    # Test data
    num_tokens = 60
    hidden_size = 48
    num_experts = 6
    top_k = 3

    hidden_states = torch.randn(num_tokens, hidden_size, device=device)
    router_logits = torch.randn(num_tokens, num_experts, device=device)

    # Use the custom strategy
    topk_weights, topk_ids = RoutingSimulator.simulate_routing(
        hidden_states=hidden_states,
        router_logits=router_logits,
        strategy_name="custom_normal",
        top_k=top_k,
    )

    # Check output shapes
    assert topk_weights.shape == (num_tokens, top_k)
    assert topk_ids.shape == (num_tokens, top_k)

    # Check that expert IDs are valid
    assert topk_ids.min() >= 0
    assert topk_ids.max() < num_experts


def test_instance_compatibility():
    """Test that static methods work correctly."""
    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

    # Test static method directly
    hidden_states = torch.randn(10, 8, device=device)
    router_logits = torch.randn(10, 4, device=device)

    topk_weights, topk_ids = RoutingSimulator.simulate_routing(
        hidden_states=hidden_states,
        router_logits=router_logits,
        strategy_name="uniform_random",
        top_k=2,
    )

    assert topk_weights.shape == (10, 2)
    assert topk_ids.shape == (10, 2)
