import gc
import json
import os
import time
from pathlib import Path
from typing import Any, Callable, Dict, Optional, Sequence

from llama_index.bridge.pydantic import Field, PrivateAttr
from llama_index.callbacks import CallbackManager
from llama_index.constants import DEFAULT_CONTEXT_WINDOW, DEFAULT_NUM_OUTPUTS
from llama_index.llms.base import (
    ChatMessage,
    ChatResponse,
    CompletionResponse,
    LLMMetadata,
    llm_chat_callback,
    llm_completion_callback,
)
from llama_index.llms.custom import CustomLLM
from llama_index.llms.generic_utils import completion_response_to_chat_response
from llama_index.llms.nvidia_tensorrt_utils import (
    generate_completion_dict,
    get_output,
    parse_input,
)

EOS_TOKEN = 2
PAD_TOKEN = 2


class LocalTensorRTLLM(CustomLLM):
    model_path: Optional[str] = Field(description="The path to the trt engine.")
    temperature: float = Field(description="The temperature to use for sampling.")
    max_new_tokens: int = Field(description="The maximum number of tokens to generate.")
    context_window: int = Field(
        description="The maximum number of context tokens for the model."
    )
    messages_to_prompt: Callable = Field(
        description="The function to convert messages to a prompt.", exclude=True
    )
    completion_to_prompt: Callable = Field(
        description="The function to convert a completion to a prompt.", exclude=True
    )
    generate_kwargs: Dict[str, Any] = Field(
        default_factory=dict, description="Kwargs used for generation."
    )
    model_kwargs: Dict[str, Any] = Field(
        default_factory=dict, description="Kwargs used for model initialization."
    )
    verbose: bool = Field(description="Whether to print verbose output.")

    _model: Any = PrivateAttr()
    _model_config: Any = PrivateAttr()
    _tokenizer: Any = PrivateAttr()
    _max_new_tokens = PrivateAttr()
    _sampling_config = PrivateAttr()
    _verbose = PrivateAttr()

    def __init__(
        self,
        model_path: Optional[str] = None,
        engine_name: Optional[str] = None,
        tokenizer_dir: Optional[str] = None,
        temperature: float = 0.1,
        max_new_tokens: int = DEFAULT_NUM_OUTPUTS,
        context_window: int = DEFAULT_CONTEXT_WINDOW,
        messages_to_prompt: Optional[Callable] = None,
        completion_to_prompt: Optional[Callable] = None,
        callback_manager: Optional[CallbackManager] = None,
        generate_kwargs: Optional[Dict[str, Any]] = None,
        model_kwargs: Optional[Dict[str, Any]] = None,
        verbose: bool = False,
    ) -> None:
        try:
            import torch
            from transformers import AutoTokenizer
        except ImportError:
            raise ImportError(
                "nvidia_tensorrt requires `pip install torch` and `pip install transformers`."
            )

        try:
            import tensorrt_llm
            from tensorrt_llm.runtime import ModelConfig, SamplingConfig
        except ImportError:
            print(
                "Unable to import `tensorrt_llm` module. Please ensure you have\
                  `tensorrt_llm` installed in your environment. You can run\
                  `pip3 install tensorrt_llm -U --extra-index-url https://pypi.nvidia.com` to install."
            )

        model_kwargs = model_kwargs or {}
        model_kwargs.update({"n_ctx": context_window, "verbose": verbose})
        self._max_new_tokens = max_new_tokens
        self._verbose = verbose
        # check if model is cached
        if model_path is not None:
            if not os.path.exists(model_path):
                raise ValueError(
                    "Provided model path does not exist. "
                    "Please check the path or provide a model_url to download."
                )
            else:
                engine_dir = model_path
                engine_dir_path = Path(engine_dir)
                config_path = engine_dir_path / "config.json"

                # config function
                with open(config_path) as f:
                    config = json.load(f)
                use_gpt_attention_plugin = config["plugin_config"][
                    "gpt_attention_plugin"
                ]
                remove_input_padding = config["plugin_config"]["remove_input_padding"]
                tp_size = config["builder_config"]["tensor_parallel"]
                pp_size = config["builder_config"]["pipeline_parallel"]
                world_size = tp_size * pp_size
                assert (
                    world_size == tensorrt_llm.mpi_world_size()
                ), f"Engine world size ({world_size}) != Runtime world size ({tensorrt_llm.mpi_world_size()})"
                num_heads = config["builder_config"]["num_heads"] // tp_size
                hidden_size = config["builder_config"]["hidden_size"] // tp_size
                vocab_size = config["builder_config"]["vocab_size"]
                num_layers = config["builder_config"]["num_layers"]
                num_kv_heads = config["builder_config"].get("num_kv_heads", num_heads)
                paged_kv_cache = config["plugin_config"]["paged_kv_cache"]
                if config["builder_config"].get("multi_query_mode", False):
                    tensorrt_llm.logger.warning(
                        "`multi_query_mode` config is deprecated. Please rebuild the engine."
                    )
                    num_kv_heads = 1
                num_kv_heads = (num_kv_heads + tp_size - 1) // tp_size

                self._model_config = ModelConfig(
                    num_heads=num_heads,
                    num_kv_heads=num_kv_heads,
                    hidden_size=hidden_size,
                    vocab_size=vocab_size,
                    num_layers=num_layers,
                    gpt_attention_plugin=use_gpt_attention_plugin,
                    paged_kv_cache=paged_kv_cache,
                    remove_input_padding=remove_input_padding,
                )

                assert (
                    pp_size == 1
                ), "Python runtime does not support pipeline parallelism"
                world_size = tp_size * pp_size

                runtime_rank = tensorrt_llm.mpi_rank()
                runtime_mapping = tensorrt_llm.Mapping(
                    world_size, runtime_rank, tp_size=tp_size, pp_size=pp_size
                )

                # TensorRT-LLM must run on a GPU.
                assert (
                    torch.cuda.is_available()
                ), "LocalTensorRTLLM requires a Nvidia CUDA enabled GPU to operate"
                torch.cuda.set_device(runtime_rank % runtime_mapping.gpus_per_node)
                self._tokenizer = AutoTokenizer.from_pretrained(
                    tokenizer_dir, legacy=False
                )
                self._sampling_config = SamplingConfig(
                    end_id=EOS_TOKEN,
                    pad_id=PAD_TOKEN,
                    num_beams=1,
                    temperature=temperature,
                )

                serialize_path = engine_dir_path / (engine_name if engine_name else "")
                with open(serialize_path, "rb") as f:
                    engine_buffer = f.read()
                decoder = tensorrt_llm.runtime.GenerationSession(
                    self._model_config, engine_buffer, runtime_mapping, debug_mode=False
                )
                self._model = decoder

        generate_kwargs = generate_kwargs or {}
        generate_kwargs.update(
            {"temperature": temperature, "max_tokens": max_new_tokens}
        )

        super().__init__(
            model_path=model_path,
            temperature=temperature,
            context_window=context_window,
            max_new_tokens=max_new_tokens,
            messages_to_prompt=messages_to_prompt,
            completion_to_prompt=completion_to_prompt,
            callback_manager=callback_manager,
            generate_kwargs=generate_kwargs,
            model_kwargs=model_kwargs,
            verbose=verbose,
        )

    @classmethod
    def class_name(cls) -> str:
        """Get class name."""
        return "LocalTensorRTLLM"

    @property
    def metadata(self) -> LLMMetadata:
        """LLM metadata."""
        return LLMMetadata(
            context_window=self.context_window,
            num_output=self.max_new_tokens,
            model_name=self.model_path,
        )

    @llm_chat_callback()
    def chat(self, messages: Sequence[ChatMessage], **kwargs: Any) -> ChatResponse:
        prompt = self.messages_to_prompt(messages)
        completion_response = self.complete(prompt, formatted=True, **kwargs)
        return completion_response_to_chat_response(completion_response)

    @llm_completion_callback()
    def complete(
        self, prompt: str, formatted: bool = False, **kwargs: Any
    ) -> CompletionResponse:
        try:
            import torch
        except ImportError:
            raise ImportError("nvidia_tensorrt requires `pip install torch`.")

        self.generate_kwargs.update({"stream": False})

        if not formatted:
            prompt = self.completion_to_prompt(prompt)

        input_text = prompt
        input_ids, input_lengths = parse_input(
            input_text, self._tokenizer, EOS_TOKEN, self._model_config
        )

        max_input_length = torch.max(input_lengths).item()
        self._model.setup(
            input_lengths.size(0), max_input_length, self._max_new_tokens, 1
        )  # beam size is set to 1
        if self._verbose:
            start_time = time.time()

        output_ids = self._model.decode(input_ids, input_lengths, self._sampling_config)
        torch.cuda.synchronize()

        elapsed_time = -1.0
        if self._verbose:
            end_time = time.time()
            elapsed_time = end_time - start_time

        output_txt, output_token_ids = get_output(
            output_ids, input_lengths, self._max_new_tokens, self._tokenizer
        )

        if self._verbose:
            print(f"Input context length  : {input_ids.shape[1]}")
            print(f"Inference time        : {elapsed_time:.2f} seconds")
            print(f"Output context length : {len(output_token_ids)} ")
            print(
                f"Inference token/sec   : {(len(output_token_ids) / elapsed_time):2f}"
            )

        # call garbage collected after inference
        torch.cuda.empty_cache()
        gc.collect()

        return CompletionResponse(
            text=output_txt,
            raw=generate_completion_dict(output_txt, self._model, self.model_path),
        )

    @llm_completion_callback()
    def stream_complete(self, prompt: str, **kwargs: Any) -> CompletionResponse:
        raise NotImplementedError(
            "Nvidia TensorRT-LLM does not currently support streaming completion."
        )