import torch
from torch.utils import benchmark
from transformers import AutoTokenizer, AutoModelForCausalLM, Mxfp4Config

# ============ CONFIGURATION ============
MODEL_ID = "openai/gpt-oss-20b"
MAX_NEW_TOKENS = 256
BENCHMARK_RUNS = 5

SOURCE_FILES = [
    "/fsx/aritra/git-repos/transformers/src/transformers/models/gpt_oss/modeling_gpt_oss.py",  # Fixed: missing comma
    "/fsx/aritra/git-repos/transformers/src/transformers/models/gpt_oss/modular_gpt_oss.py",
]


# ============ MODEL LOADING ============
def load_model(model_id: str, use_attn_kernels: bool):
    """Load model with optional attention kernel optimization."""
    quantization_config = Mxfp4Config(dequantize=True)
    
    kwargs = {
        "dtype": "auto",
        "device_map": "cuda:0",
        "use_kernels": False,
        "quantization_config": quantization_config,
    }
    
    if use_attn_kernels:
        kwargs["attn_implementation"] = "kernels-community/vllm-flash-attn3"

    return AutoModelForCausalLM.from_pretrained(model_id, **kwargs).eval()


def unload_model(model):
    """Move model to CPU and free GPU memory."""
    model.to("cpu")
    del model
    torch.cuda.empty_cache()


# ============ GENERATION ============
def generate(model, model_inputs: dict, max_new_tokens: int):
    """Run inference without sampling."""
    with torch.inference_mode():
        model.generate(
            **model_inputs,
            do_sample=False,
            temperature=None,
            max_new_tokens=max_new_tokens,
            eos_token_id=-1,
            disable_compile=True,
        )


# ============ DATA PREPARATION ============
def load_prompts(filepaths: list[str]) -> list[str]:
    """Read source files and create summarization prompts."""
    prompts = []
    for filepath in filepaths:
        with open(filepath, "r") as f:
            prompts.append(f"{f.read()}\nSummarize this for me.")
    return prompts


def tokenize_prompts(tokenizer, prompts: list[str]) -> list[tuple[dict, int]]:
    """Tokenize prompts and return inputs with their prefill sizes."""
    tokenizer.padding_side = "left"
    tokenized = []

    for prompt in prompts:
        message = [{"role": "user", "content": prompt}]
        text = tokenizer.apply_chat_template(
            message,  # Fixed: was `m`
            add_generation_prompt=True,
            tokenize=False,
            reasoning_effort="low",
        )
        inputs = tokenizer(text, return_tensors="pt", padding=True)
        prefill_size = inputs.input_ids.size(1)  # Fixed: was `input` and `.size[1]`
        tokenized.append((inputs, prefill_size))

    return tokenized


# ============ BENCHMARKING ============
def run_benchmarks(model, tokenized_inputs: list[tuple], use_attn_kernels: bool) -> list:
    """Run timing benchmarks for each input."""
    results = []

    for inputs, prefill_size in tokenized_inputs:
        timer = benchmark.Timer(
            stmt="generate(model, model_inputs, max_new_tokens)",
            setup="from __main__ import generate",
            globals={
                "model": model,
                "model_inputs": inputs.to(model.device),
                "max_new_tokens": MAX_NEW_TOKENS,
            },
            num_threads=torch.get_num_threads(),
            label=f"Time to generate {MAX_NEW_TOKENS} tokens",
            sub_label=f"prefill_size={prefill_size}",
            description=f"attn_kernels={use_attn_kernels}",
        )
        results.append(timer.timeit(BENCHMARK_RUNS))

    return results


# ============ MAIN ============
def main():
    prompts = load_prompts(SOURCE_FILES)

    tokenizer = AutoTokenizer.from_pretrained(MODEL_ID)
    tokenized_inputs = tokenize_prompts(tokenizer, prompts)

    all_results = []
    for use_attn_kernels in [True, False]:
        print(f"\nBenchmarking with attn_kernels={use_attn_kernels}...")

        model = load_model(MODEL_ID, use_attn_kernels)
        results = run_benchmarks(model, tokenized_inputs, use_attn_kernels)
        all_results.extend(results)
        unload_model(model)

    benchmark.Compare(all_results).print()


if __name__ == "__main__":
    main()

# [------------------ Time to generate 256 tokens -------------------]
#                          |  attn_kernels=True  |  attn_kernels=False
# 12 threads: --------------------------------------------------------
#       prefill_size=7353  |         8.3         |         10.2       
#       prefill_size=4225  |         8.3         |          9.0       

# Times are in seconds (s).