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

import random

import pytest
import torch

from vllm import LLM, SamplingParams
from vllm.config import CompilationConfig, CompilationMode
from vllm.distributed import cleanup_dist_env_and_memory

from ...utils import fork_new_process_for_each_test

# global seed
SEED = 42


@pytest.fixture
def test_prompts():
    """
    Adapted from tests/v1/e2e/test_spec_decode.py
    """
    prompt_types = ["repeat", "sentence"]
    # Setting higher num prompts increases the chance of numerics mismatch
    # due to matrix multiplication numerics depending on batch dimension
    num_prompts = 10
    prompts = []

    random.seed(0)
    random_prompt_type_choices = random.choices(prompt_types, k=num_prompts)

    for kind in random_prompt_type_choices:
        word_choices = ["test", "temp", "hello", "where"]
        word = random.choice(word_choices)
        if kind == "repeat":
            prompt = f"""please repeat the word '{word}' 10 times."""
        elif kind == "sentence":
            prompt = f"""please give a ten-word sentence that
            uses the word {word} at least once."""
        else:
            raise ValueError(f"Unknown prompt type: {kind}")
        prompts.append(prompt)

    return prompts


def cleanup(llm: LLM, compilation_config: CompilationConfig):
    # hacky: below lines are required to free up memory for the next test
    # when setting VLLM_ENABLE_V1_MULTIPROCESSING=0, del llm is not sufficient
    # TODO(sarckk): when enforce_eager=False, memory is not freed:
    # find out why and re-enable test for enforce_eager=False case
    llm_engine = llm.llm_engine.engine_core.engine_core
    model_runner = llm_engine.model_executor.driver_worker.worker.model_runner
    del model_runner.model
    del model_runner.kv_caches
    del compilation_config.static_forward_context
    compilation_config.static_forward_context = {}

    del llm
    torch.cuda.empty_cache()
    cleanup_dist_env_and_memory()


@fork_new_process_for_each_test
@pytest.mark.parametrize("enforce_eager", [True])
@pytest.mark.skip(reason="Disable until Gemma3n supports fast prefill")
def test_kv_sharing_fast_prefill(
    monkeypatch: pytest.MonkeyPatch,
    enforce_eager: bool,
    test_prompts: list[str],
):
    sampling_params = SamplingParams(temperature=0.0, max_tokens=100)
    compilation_config = CompilationConfig(
        # This allows vLLM compilation backend to handle allocating and
        # managing buffers for cudagraph
        cudagraph_copy_inputs=True,
        mode=CompilationMode.VLLM_COMPILE
        if not enforce_eager
        else CompilationMode.NONE,
    )

    with monkeypatch.context() as m:
        # Make scheduling deterministic for reproducibility
        m.setenv("VLLM_ENABLE_V1_MULTIPROCESSING", "0")

        llm = LLM(
            model="google/gemma-3n-E2B-it",
            enforce_eager=enforce_eager,
            compilation_config=compilation_config,
            seed=SEED,
        )
        ref_responses = llm.generate(test_prompts, sampling_params)

        cleanup(llm, compilation_config)

        llm = LLM(
            model="google/gemma-3n-E2B-it",
            enforce_eager=enforce_eager,
            compilation_config=compilation_config,
            seed=SEED,
            kv_sharing_fast_prefill=True,
        )
        optimized_responses = llm.generate(test_prompts, sampling_params)

        cleanup(llm, compilation_config)

        misses = 0

        for ref_response, optimized_response in zip(ref_responses, optimized_responses):
            if ref_response.outputs[0].text != optimized_response.outputs[0].text:
                misses += 1

        assert misses == 0
