# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0

import logging
from typing import Optional

import sglang as sgl
from sglang.srt.server_args import ServerArgs

from dynamo._core import Endpoint
from dynamo.llm import ModelRuntimeConfig, ModelType, register_llm


async def register_llm_with_runtime_config(
    engine: sgl.Engine,
    endpoint: Endpoint,
    server_args: ServerArgs,
    migration_limit: int,
):
    """Register LLM with runtime config"""
    runtime_config = await _get_runtime_config(engine)
    try:
        await register_llm(
            ModelType.Backend,
            endpoint,
            server_args.model_path,
            server_args.served_model_name,
            kv_cache_block_size=server_args.page_size,
            migration_limit=migration_limit,
            runtime_config=runtime_config,
        )
    except Exception as e:
        logging.error(f"Failed to register with runtime config: {e}")
        return None


async def _get_runtime_config(engine: sgl.Engine) -> Optional[ModelRuntimeConfig]:
    """Get runtime config from SGLang engine"""
    try:
        # Try to check if the engine has a scheduler attribute with the computed values
        if hasattr(engine, "scheduler_info") and engine.scheduler_info is not None:
            runtime_config = ModelRuntimeConfig()

            # Get max_total_num_tokens from scheduler_info
            if "max_total_num_tokens" in engine.scheduler_info:
                max_total_tokens = engine.scheduler_info["max_total_num_tokens"]
                if max_total_tokens and hasattr(
                    engine.tokenizer_manager, "server_args"
                ):
                    page_size = engine.tokenizer_manager.server_args.page_size
                    if page_size:
                        runtime_config.total_kv_blocks = (
                            max_total_tokens + page_size - 1
                        ) // page_size
                        logging.info(
                            f"Got total KV blocks from scheduler: {runtime_config.total_kv_blocks} "
                            f"(max_total_tokens={max_total_tokens}, page_size={page_size})"
                        )

            # Note: max_running_requests and max_prefill_tokens are NOT available in scheduler_info

            return runtime_config

        # If scheduler approach doesn't work, log and return None to indicate we'll skip runtime config
        logging.warning(
            "Could not access runtime config from SGLang engine. "
            "The engine may compute these values internally after initialization. "
            "Proceeding without runtime config - SGLang will use its internal defaults."
        )
        return None

    except Exception as e:
        logging.warning(f"Failed to get runtime config: {e}. Proceeding without it.")
        return None
