# Copyright 2024 Bytedance Ltd. and/or its affiliates
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
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import os
from transformers import AutoTokenizer, AutoConfig, AutoModelForCausalLM
from torch.distributed.fsdp import FullyShardedDataParallel as FSDP, ShardingStrategy, MixedPrecision, CPUOffload
from torch.distributed.fsdp.api import ShardingStrategy, ShardedStateDictConfig, StateDictType
import torch

from verl.utils.distributed import initialize_global_process_group
from verl.third_party.vllm import LLM

from vllm import SamplingParams

import time
import torch.distributed as dist


def main():
    assert torch.cuda.is_available(), 'CUDA must be present to run FSDP vLLM example'
    local_rank, rank, world_size = initialize_global_process_group()

    local_cache_path = '~/.cache/verl/rlhf'
    local_cache_path = os.path.expanduser(local_cache_path)
    hdfs_path = 'Qwen/Qwen2-7B-Instruct'

    from verl.utils.fs import copy_to_local
    local_model_path = copy_to_local(src=hdfs_path, cache_dir=local_cache_path)
    tokenizer = AutoTokenizer.from_pretrained(local_model_path, trust_remote_code=True)
    actor_model_config = AutoConfig.from_pretrained(local_model_path, trust_remote_code=True)
    with torch.device("cuda"):
        actor_model = AutoModelForCausalLM.from_pretrained(local_model_path, trust_remote_code=True)
        actor_model.to(torch.bfloat16)

    max_prompt_length = 16
    response_length = 32
    preencode_prompts = [
        "The president of the United States is",
        "The capital of France is",
        "The future of AI is",
    ]
    tokenizer.pad_token = tokenizer.eos_token
    prompts = tokenizer(preencode_prompts, return_tensors='pt', padding=True)
    input_ids = prompts['input_ids']
    attention_mask = prompts['attention_mask']
    from verl.utils.torch_functional import pad_sequence_to_length
    input_ids = pad_sequence_to_length(input_ids, max_prompt_length, tokenizer.pad_token_id, left_pad=True).cuda()
    attention_mask = pad_sequence_to_length(attention_mask, max_prompt_length, 0, left_pad=True).cuda()

    from transformers import GenerationConfig
    generation_config = GenerationConfig(do_sample=False)
    actor_model.cuda()
    output = actor_model.generate(
        input_ids=input_ids,
        attention_mask=attention_mask,
        max_new_tokens=32,
        # max_length=max_length,
        eos_token_id=tokenizer.eos_token_id,
        pad_token_id=tokenizer.pad_token_id,
        generation_config=generation_config,
        # renormalize_logits=True,
        output_scores=False,  # this is potentially very large
        return_dict_in_generate=True,
        use_cache=False)  # may OOM when use_cache = True
    seq = output.sequences
    response = seq[:, max_prompt_length:]

    print(f'hf response: {tokenizer.batch_decode(response)}')

    tensor_model_parallel_size = 4
    from torch.distributed.device_mesh import init_device_mesh
    device_mesh = init_device_mesh('cuda', mesh_shape=(world_size,), mesh_dim_names=['fsdp'])

    mixed_precision = MixedPrecision(param_dtype=torch.bfloat16, reduce_dtype=torch.float32, buffer_dtype=torch.float32)
    fsdp_model = FSDP(actor_model,
                      use_orig_params=True,
                      auto_wrap_policy=None,
                      device_id=torch.cuda.current_device(),
                      sharding_strategy=ShardingStrategy.FULL_SHARD,
                      mixed_precision=mixed_precision,
                      cpu_offload=CPUOffload(offload_params=False),
                      sync_module_states=False,
                      device_mesh=device_mesh)

    FSDP.set_state_dict_type(fsdp_model,
                             state_dict_type=StateDictType.SHARDED_STATE_DICT,
                             state_dict_config=ShardedStateDictConfig())

    state_dict = fsdp_model.state_dict()

    sampling_params = SamplingParams(temperature=0,
                                     top_p=1,
                                     n=1,
                                     max_tokens=response_length,
                                     logprobs=1,
                                     ignore_eos=True,
                                     detokenize=False)

    print(actor_model_config)
    llm = LLM(model=None,
              tokenizer=tokenizer,
              model_hf_config=actor_model_config,
              tensor_parallel_size=tensor_model_parallel_size,
              enforce_eager=True,
              dtype='bfloat16',
              load_format='dummy_dtensor',
              gpu_memory_utilization=0.8,
              trust_remote_code=True)

    # Warmup iterations
    for _ in range(10):
        torch.cuda.synchronize()
        llm.sync_model_weights(actor_weights=state_dict, load_format='dtensor')
        torch.cuda.synchronize()
        dist.barrier()

    start_time = time.time()
    llm.sync_model_weights(actor_weights=state_dict, load_format='dtensor')
    torch.cuda.synchronize()
    dist.barrier()
    end_time = time.time()

    # Calculate elapsed time
    elapsed_time = end_time - start_time
    print(f"Time taken: {elapsed_time:.6f} seconds")

    input_ids = input_ids.cuda()
    attention_mask = attention_mask.cuda()
    idx_list = []
    batch_size = input_ids.shape[0]

    pad_token_id = tokenizer.pad_token_id if tokenizer.pad_token_id is not None else tokenizer.eos_token_id
    from verl.workers.rollout.vllm_rollout.vllm_rollout import _pre_process_inputs
    for i in range(batch_size):
        idx_list.append(_pre_process_inputs(pad_token_id, input_ids[i]))
    print('start generation')
    outputs = llm.generate(prompt_token_ids=idx_list, sampling_params=sampling_params, use_tqdm=False)
    vllm_output = outputs[0].cuda()
    if torch.distributed.get_rank() == 0:
        print(f'hf response: {tokenizer.batch_decode(response)}')
        print(f'vllm response: {tokenizer.batch_decode(vllm_output)}')


if __name__ == "__main__":
    main()