# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project

import fnmatch
import multiprocessing as mp
import os
import shutil
from tempfile import TemporaryDirectory

import pytest
import torch
from huggingface_hub import snapshot_download

from vllm import LLM, SamplingParams
from vllm.model_executor.model_loader import ShardedStateLoader

prompts = [
    "Hello, my name is",
    "The president of the United States is",
    "The capital of France is",
    "The future of AI is",
]

# Create a sampling params object.
sampling_params = SamplingParams(
    temperature=0,
    max_tokens=256,
    ignore_eos=True,
)


def test_filter_subtensors():
    state_dict = {
        "a": torch.empty(2),
        "b": torch.empty((2, 4)),
        "c": torch.empty((2, 4, 8)),
    }
    state_dict.update(
        {
            "x": state_dict["b"],
            "y": state_dict["c"][1, 2, :],
            "z": state_dict["c"][1, :, 4],
        }
    )
    filtered_state_dict = ShardedStateLoader._filter_subtensors(state_dict)
    assert tuple(filtered_state_dict.keys()) == ("a", "b", "c")
    for key, tensor in filtered_state_dict.items():
        # NOTE: don't use `equal` here, as the tensor might contain NaNs
        assert tensor is state_dict[key]


@pytest.fixture(scope="module")
def llama_3p2_1b_files():
    input_dir = snapshot_download(
        "meta-llama/Llama-3.2-1B-Instruct", ignore_patterns=["*.bin*", "original/*"]
    )

    yield input_dir


def _run_writer(input_dir, output_dir, weights_patterns, **kwargs):
    llm_sharded_writer = LLM(model=input_dir, **kwargs)
    # Check which engine version is being used
    is_v1_engine = hasattr(llm_sharded_writer.llm_engine, "engine_core")
    # Dump worker states to output directory
    if is_v1_engine:
        # For V1 engine, we need to use engine_core.save_sharded_state
        print("Using V1 engine save path")
        llm_sharded_writer.llm_engine.engine_core.save_sharded_state(path=output_dir)
    else:
        # For V0 engine
        print("Using V0 engine save path")
        model_executor = llm_sharded_writer.llm_engine.model_executor
        model_executor.save_sharded_state(path=output_dir)

    # Copy metadata files to output directory
    for file in os.listdir(input_dir):
        if os.path.isdir(os.path.join(input_dir, file)):
            shutil.copytree(
                os.path.join(input_dir, file), os.path.join(output_dir, file)
            )
        elif not any(fnmatch.fnmatch(file, ext) for ext in weights_patterns):
            shutil.copy(os.path.join(input_dir, file), output_dir)


def _run_generate(input_dir, queue: mp.Queue, **kwargs):
    llm = LLM(model=input_dir, **kwargs)
    gen = llm.generate(prompts, sampling_params)
    queue.put([g.outputs[0].__dict__ for g in gen])
    queue.close()
    queue.join_thread()


@pytest.mark.parametrize("enable_lora", [False, True])
@pytest.mark.parametrize("tp_size", [1, 2])
def test_sharded_state_loader(
    enable_lora, tp_size, num_gpus_available, llama_3p2_1b_files
):
    if num_gpus_available < tp_size:
        pytest.skip(f"Not enough GPUs for tensor parallelism {tp_size}")

    weights_patterns = ("*.safetensors",)
    gpu_memory_utilization = 0.8
    input_dir = llama_3p2_1b_files
    ctx = mp.get_context("spawn")

    # Run in separate processes for memory & CUDA isolation
    with TemporaryDirectory() as output_dir:
        p = ctx.Process(
            target=_run_writer,
            args=(input_dir, output_dir, weights_patterns),
            kwargs=dict(
                tensor_parallel_size=tp_size,
                gpu_memory_utilization=gpu_memory_utilization,
                enforce_eager=True,
            ),
        )
        p.start()
        p.join()

        queue = ctx.Queue()

        p = ctx.Process(
            target=_run_generate,
            args=(input_dir, queue),
            kwargs=dict(
                enable_lora=enable_lora,
                gpu_memory_utilization=gpu_memory_utilization,
                tensor_parallel_size=tp_size,
            ),
        )
        p.start()
        # Call queue.get() before p.join() to prevent deadlock:
        # If p.join() is called before queue.get() and the queue is full,
        # the child process may block while writing to the queue and never
        # terminate, causing the parent to wait indefinitely on p.join().
        # See: https://github.com/vllm-project/vllm/pull/22371#discussion_r2257773814
        out_before = queue.get()
        p.join()
        queue.close()
        queue.join_thread()

        queue = ctx.Queue()

        p = ctx.Process(
            target=_run_generate,
            args=(output_dir, queue),
            kwargs=dict(
                enable_lora=enable_lora,
                gpu_memory_utilization=gpu_memory_utilization,
                tensor_parallel_size=tp_size,
                load_format="sharded_state",
            ),
        )
        p.start()
        # Call queue.get() before p.join() to prevent deadlock:
        # If p.join() is called before queue.get() and the queue is full,
        # the child process may block while writing to the queue and never
        # terminate, causing the parent to wait indefinitely on p.join().
        # See: https://github.com/vllm-project/vllm/pull/22371#discussion_r2257773814
        out_after = queue.get()
        p.join()
        queue.close()
        queue.join_thread()

        assert out_before == out_after
