# Copyright (c) 2024, NVIDIA CORPORATION. All rights reserved.

"""Sample Generate GPT"""
import os
import sys
sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__),
                                             os.path.pardir)))
from megatron.training import get_args
from megatron.training import print_rank_0
from megatron.core import mpu
from megatron.training.checkpointing import load_checkpoint
from megatron.training.initialize import initialize_megatron
from megatron.core.models.gpt import GPTModel
from megatron.training import get_model
from megatron.training.arguments import core_transformer_config_from_args
from megatron.training.yaml_arguments import core_transformer_config_from_yaml
from megatron.inference.text_generation_server import MegatronServer
from megatron.inference.text_generation import generate_and_post_process
from megatron.inference.text_generation import beam_search_and_post_process
from megatron.core.transformer.spec_utils import import_module
from megatron.core.models.gpt.gpt_layer_specs import (
    get_gpt_layer_local_spec,
    get_gpt_layer_with_transformer_engine_spec,
)

from contextlib import nullcontext
import torch
from typing import Union
import megatron


def model_provider(pre_process=True, post_process=True) -> Union[GPTModel, megatron.legacy.model.GPTModel]:
    """Builds the model.

        If you set the use_legacy_models to True, it will return the legacy GPT model and if not the core GPT model.

        Args:
            pre_process (bool, optional): Set to true if you need to compute embedings. Defaults to True.
            post_process (bool, optional): Set to true if you need to want to compute output logits/loss. Defaults to True.


        Returns:
            Union[GPTModel, megatron.legacy.model.GPTModel]: The returned model
        """

    args = get_args()
    use_te = args.transformer_impl == "transformer_engine"

    print_rank_0('building GPT model ...')

    # Experimental loading arguments from yaml
    if args.yaml_cfg is not None:
        config = core_transformer_config_from_yaml(args, "language_model")
    else:
        config = core_transformer_config_from_args(args)

    if args.use_legacy_models:
        model = megatron.legacy.model.GPTModel(
            config,
            num_tokentypes=0,
            parallel_output=False,
            pre_process=pre_process,
            post_process=post_process
        )
    else:
        if args.spec is not None:
            transformer_layer_spec = import_module(args.spec)
        else:
            if use_te:
                transformer_layer_spec = get_gpt_layer_with_transformer_engine_spec(args.num_experts, args.moe_grouped_gemm, args.qk_layernorm)
            else:
                transformer_layer_spec = get_gpt_layer_local_spec(args.num_experts, args.moe_grouped_gemm, args.qk_layernorm)

        model = GPTModel(
            config=config,
            transformer_layer_spec=transformer_layer_spec,
            vocab_size=args.padded_vocab_size,
            max_sequence_length=args.max_position_embeddings,
            pre_process=pre_process,
            post_process=post_process,
            fp16_lm_cross_entropy=args.fp16_lm_cross_entropy,
            parallel_output=False,
            share_embeddings_and_output_weights=not args.untie_embeddings_and_output_weights,
            position_embedding_type=args.position_embedding_type,
            rotary_percent=args.rotary_percent,
            rotary_base=args.rotary_base
        )

    return model

def add_text_generate_args(parser):
    group = parser.add_argument_group(title='text generation')
    group.add_argument("--port", type=int, default=5000,
                       help='port for text generation server to run on')
    return parser


if __name__ == "__main__":
    initialize_megatron(extra_args_provider=add_text_generate_args,
                        args_defaults={'tokenizer_type': 'GPT2BPETokenizer',
                                       'no_load_rng': True,
                                       'no_load_optim': True})

    args = get_args()
    if args.num_layers_per_virtual_pipeline_stage is not None:
        print("Interleaved pipeline schedule is not yet supported for text generation.")
        exit()
    print_rank_0("WARNING: Forcing exit_on_missing_checkpoint to True for text "
                 "generation.")
    args.exit_on_missing_checkpoint = True

    # Set up model and load checkpoint
    load_context = nullcontext()
    if args.fp8:
        from transformer_engine.pytorch.fp8 import fp8_model_init
        load_context = fp8_model_init()
    with load_context:
        model = get_model(model_provider, wrap_with_ddp=False)

    if args.load is not None:
        _ = load_checkpoint(model, None, None)

    assert len(model) == 1, "Above condition should have caught this"
    model = model[0]
    if mpu.is_pipeline_first_stage() and mpu.get_tensor_model_parallel_rank() == 0:
        server = MegatronServer(model)
        server.run("0.0.0.0",port=args.port)

    while True:
        choice = torch.tensor(1, dtype=torch.long, device='cuda')
        torch.distributed.broadcast(choice, 0)
        if choice.item() == 0:
            try:
                generate_and_post_process(model)
            except ValueError as ve:
                pass
        elif choice.item() == 1:
            try:
                beam_search_and_post_process(model)
            except ValueError as ve:
                pass
