# Copyright 2023-2024 SGLang Team
# 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
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#     http://www.apache.org/licenses/LICENSE-2.0
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# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# limitations under the License.
# ==============================================================================
# Copyright 2024 Bytedance Ltd. and/or its affiliates
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# 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
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#     http://www.apache.org/licenses/LICENSE-2.0
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# 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
# limitations under the License.

from __future__ import annotations
import os
from contextlib import contextmanager
from typing import TYPE_CHECKING, List
from omegaconf import DictConfig
from tensordict import TensorDict
from verl import DataProto
from verl.workers.rollout.base import BaseRollout
from verl.utils.torch_functional import get_eos_mask, pad_sequence_to_length, pad_2d_list_to_length
from sglang.srt.entrypoints.verl_engine import VerlEngine
from torch.distributed.device_mesh import init_device_mesh
from sglang.srt.sampling.sampling_params import SamplingParams
from verl.third_party.sglang import parallel_state as sglang_ps
import torch.distributed
from torch.nn.utils.rnn import pad_sequence

if TYPE_CHECKING:
    from torch import nn


# NOTE(sgm): add for verl. We can optimize it by making the dataloader yield List[int] without padding.
def _pre_process_inputs(pad_token_id, prompt_token_ids: torch.Tensor) -> List[int]:
    # remove the left padding in the prompt token_id
    # pad_token_id = self.llm_engine.tokenizer.pad_token_id if self.llm_engine.tokenizer.pad_token_id is not None else self.llm_engine.tokenizer.eos_token_id
    non_pad_index = torch.nonzero(prompt_token_ids != pad_token_id, as_tuple=False)[0][0]
    token_ids = prompt_token_ids[non_pad_index:].tolist()
    return token_ids


# NOTE(linjunrong): adhoc
def _post_process_outputs(tokenizer, output):

    def _map_each_response(l):
        # output_token_ids = torch.tensor(l['token_ids'])
        log_probs = []
        output_token_ids = []
        for log_prob, token_ids, _ in l["meta_info"]["output_token_logprobs"]:
            log_probs.append(log_prob)
            output_token_ids.append(token_ids)
        log_probs = torch.tensor(log_probs)
        output_token_ids = torch.tensor(output_token_ids)
        return output_token_ids, log_probs

    out_map = map(lambda x: _map_each_response(x), output)
    batched_output_token_ids = []
    batched_logprobs = []
    for output_token_ids, log_probs in out_map:
        batched_output_token_ids.append(output_token_ids)
        batched_logprobs.append(log_probs)
    pad_token_id = (tokenizer.pad_token_id if tokenizer.pad_token_id is not None else tokenizer.eos_token_id)
    batched_output_token_ids = pad_sequence(batched_output_token_ids, batch_first=True, padding_value=pad_token_id)
    if len(batched_logprobs) > 0:
        batched_logprobs = pad_sequence(batched_logprobs, batch_first=True, padding_value=pad_token_id)
    return batched_output_token_ids, batched_logprobs


class SGLangRollout(BaseRollout):

    def __init__(
        self,
        actor_module: nn.Module | str,
        config: DictConfig,
        tokenizer,
        model_hf_config,
        **kwargs,
    ):
        """A SGLang rollout. It requires the module is supported by the SGLang.

        Args:
            actor_module: module here follows huggingface APIs
            config: DictConfig
            tokenizer: the task/model tokenizer
            model_hf_config: the huggingface config to initiallize the generating model in SGLang
            **kwargs: train_tp, for Megatron Backend to initialize hybrid engine (zero redundancy) process group
        """
        super().__init__()
        self.config = config

        # TODO(linjunrong.ocss884): this substitution is left for resolving SGLang conflict with ray devices
        # isolation, will solve in the future
        del os.environ["CUDA_VISIBLE_DEVICES"]
        if os.environ["ENSURE_CUDA_VISIBLE_DEVICES"]:
            os.environ["CUDA_VISIBLE_DEVICES"] = os.environ["ENSURE_CUDA_VISIBLE_DEVICES"]

        assert not (not config.enforce_eager and
                    config.free_cache_engine), "disable CUDA graph (enforce_eager = False) if free cache engine"

        tensor_parallel_size = self.config.get("tensor_model_parallel_size", 1)
        assert (tensor_parallel_size <= torch.distributed.get_world_size()
               ), "tensor parallel size should be less than or equal to the world size"

        if kwargs.get("train_tp", None) is not None:
            # deployed with megatron
            os.environ["CUDA_TIMER_STREAM_KAFKA_ENABLE"] = "0"
            os.environ["MEGATRON_IMPORT_TIMERS"] = "0"
            train_tp = kwargs.get("train_tp", None)
            num_tp_per_train_tp = train_tp // tensor_parallel_size
            sglang_ps.initialize_parallel_state(
                tensor_model_parallel_size=tensor_parallel_size,
                num_tp_per_train_tp=num_tp_per_train_tp,
            )

        assert (model_hf_config.max_position_embeddings >= config.prompt_length +
                config.response_length), "model context length should be greater than total sequence length"

        tp_size = tensor_parallel_size
        world_size = int(os.getenv("WORLD_SIZE", "-1"))

        # init device mesh
        device_mesh_kwargs = dict(
            mesh_shape=(world_size // tp_size, tp_size, 1),
            mesh_dim_names=["dp", "tp", "pp"],
        )
        device_mesh_cpu = init_device_mesh("cpu", **device_mesh_kwargs)
        # device_mesh_device = init_device_mesh("cuda", **device_mesh_kwargs)

        # get tp_rank of this process in this tp group
        global_rank = device_mesh_cpu.get_rank()
        tp_size = device_mesh_cpu["tp"].mesh.size()[0]
        src_rank = global_rank // tp_size * tp_size

        self.inference_engine = VerlEngine(
            model_path=actor_module,
            dtype=config.dtype,
            mem_fraction_static=config.gpu_memory_utilization,
            device_mesh_cpu=device_mesh_cpu["tp"],
            base_gpu_id=src_rank,
            gpu_id_step=1,
            # NOTE(Chenyang): if you want to debug the sglang engine
            # please set the following parameters
            # Otherwise, it will make the engine run too slow
            # log_level="INFO",
            # log_requests=True,
            # log_requests_level=2,
            # max_running_requests=1,
        )

        # offload
        self.inference_engine.release_memory_occupation()

        kwargs = dict(n=1,
                      max_new_tokens=config.response_length,
                      presence_penalty=0.0,
                      frequency_penalty=0.0,
                      repetition_penalty=1.0)
        # supporting adding any sampling params from the config file
        for k in config.keys():
            if hasattr(SamplingParams(), str(k)):
                kwargs[k] = config.get(k)
        print(f"kwargs: {kwargs}")
        self.sampling_params = kwargs

        self.tokenizer = tokenizer
        self.pad_token_id = tokenizer.pad_token_id

    @contextmanager
    def update_sampling_params(self, **kwargs):
        # update sampling params
        old_sampling_params_args = {}
        if kwargs:
            for key, value in kwargs.items():
                if key in self.sampling_params:
                    old_value = self.sampling_params[key]
                    old_sampling_params_args[key] = old_value
                    self.sampling_params[key] = value
        yield
        # roll back to previous sampling params
        # if len(old_sampling_params_args):
        for key, value in old_sampling_params_args.items():
            self.sampling_params[key] = value

    @torch.no_grad()
    def generate_sequences(self, prompts: DataProto, **kwargs) -> DataProto:
        # if self.config.free_cache_engine:

        idx = prompts.batch["input_ids"]  # (bs, prompt_length)
        # left-padded attention_mask
        attention_mask = prompts.batch["attention_mask"]
        position_ids = prompts.batch["position_ids"]

        # used to construct attention_mask
        eos_token_id = prompts.meta_info["eos_token_id"]

        batch_size = idx.size(0)
        idx_list = []
        # parse idx from torch.Tensor to List[List[str]]
        for i in range(batch_size):
            idx_list.append(_pre_process_inputs(self.pad_token_id, idx[i]))

        do_sample = prompts.meta_info.get("do_sample", True)
        if not do_sample:
            # kwargs = {
            #     'top_p': 1.0,
            #     'top_k': -1,
            #     'min_p': 0.0,
            #     'temperature': 0,
            #     'n': 1  # if greedy, only 1 response
            # }
            kwargs = dict(
                n=1,
                presence_penalty=0.0,
                frequency_penalty=0.0,
                repetition_penalty=1.0,
                temperature=0,
                top_p=1,
                top_k=-1,
                ignore_eos=False,
                min_new_tokens=0,
                max_new_tokens=4096,
                skip_special_tokens=True,
                spaces_between_special_tokens=True,
            )
        # users can customize different sampling_params at different run
        with self.update_sampling_params(**kwargs):
            print(f"{self.sampling_params=}")
            output = self.inference_engine.generate(
                prompt=None,  # because we have already convert it to prompt token id
                sampling_params=self.sampling_params,
                return_logprob=True,
                input_ids=idx_list,
            )

        out = _post_process_outputs(self.tokenizer, output)

        response = out[0].to(idx.device)
        log_probs = out[1].to(idx.device)

        if response.shape[1] < self.config.response_length:
            response = pad_sequence_to_length(response, self.config.response_length, self.pad_token_id)
            log_probs = pad_sequence_to_length(log_probs, self.config.response_length, self.pad_token_id)
        if self.config.n > 1 and do_sample:
            idx = idx.repeat_interleave(self.config.n, dim=0)
            attention_mask = attention_mask.repeat_interleave(self.config.n, dim=0)
            position_ids = position_ids.repeat_interleave(self.config.n, dim=0)
            batch_size = batch_size * self.config.n
        seq = torch.cat([idx, response], dim=-1)

        response_length = response.size(1)
        delta_position_id = torch.arange(1, response_length + 1, device=position_ids.device)
        delta_position_id = delta_position_id.unsqueeze(0).repeat(batch_size, 1)

        # TODO(sgm): fix position_ids on right_pad
        # prompt: left pad + response: right pad
        # attention_mask: [0,0,0,0,1,1,1,1, | 1,1,1,0,0,0,0,0]
        # position_ids:   [0,0,0,0,0,1,2,3, | 4,5,6,7,8,9,10,11]
        response_position_ids = position_ids[:, -1:] + delta_position_id
        position_ids = torch.cat([position_ids, response_position_ids], dim=-1)
        response_attention_mask = get_eos_mask(response_id=response, eos_token=eos_token_id, dtype=attention_mask.dtype)
        attention_mask = torch.cat((attention_mask, response_attention_mask), dim=-1)

        # all the tp ranks should contain the same data here. data in all ranks are valid
        batch = TensorDict(
            {
                "prompts": idx,
                "responses": response,
                "input_ids": seq,  # here input_ids become the whole sentences
                # 'old_log_probs': log_probs, # we will recompute old log prob with actor
                "attention_mask": attention_mask,
                "position_ids": position_ids,
            },
            batch_size=batch_size,
        )

        # free cache engine
        if self.config.free_cache_engine and self.inference_engine._engine is not None:
            self.inference_engine._engine.tokenizer_manager.flush_cache()

        return DataProto(batch=batch)
