# 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
# limitations under the License.
"""
FSDP PPO Trainer with Ray-based single controller.
This trainer supports model-agonistic model initialization with huggingface
"""

import os
import uuid
from contextlib import contextmanager
from dataclasses import dataclass, field
from enum import Enum
from pprint import pprint
from typing import Type, Dict
from copy import deepcopy

import ray
import numpy as np
from codetiming import Timer
from omegaconf import OmegaConf, open_dict
from verl import DataProto
from verl.protocol import pad_dataproto_to_divisor, unpad_dataproto, DataProtoItem
from verl.single_controller.base import Worker
from verl.single_controller.ray import RayResourcePool, RayWorkerGroup, RayClassWithInitArgs
from verl.single_controller.ray.base import create_colocated_worker_cls
from verl.trainer.ppo import core_algos
from verl.trainer.ppo.metric_utils import compute_data_metrics, compute_throughout_metrics, compute_timing_metrics, reduce_metrics
from verl.utils.seqlen_balancing import get_seqlen_balanced_partitions, log_seqlen_unbalance
from verl.utils.checkpoint.checkpoint_manager import find_latest_ckpt_path
from verl.utils.dataset.rl_dataset import RLHFDataset, collate_fn
from verl.utils.tracking import ValidationGenerationsLogger
from torch.utils.data import RandomSampler, SequentialSampler
from torchdata.stateful_dataloader import StatefulDataLoader

WorkerType = Type[Worker]


def dataprotoitem_to_dataproto(item: DataProtoItem) -> DataProto:
    """Convert a DataProtoItem to a DataProto object"""
    return DataProto.from_dict(
        tensors=item.batch,  # TensorDict is already in correct format
        non_tensors=item.non_tensor_batch,  # Dict is already in correct format 
        meta_info=item.meta_info
    )

class Role(Enum):
    """
    To create more roles dynamically, you can subclass Role and add new members
    """
    Actor = 0
    Rollout = 1
    ActorRollout = 2
    Critic = 3
    RefPolicy = 4
    RewardModel = 5
    ActorRolloutRef = 6


class AdvantageEstimator(str, Enum):
    """
    Using an enumeration class to avoid spelling errors in adv_estimator
    """
    GAE = 'gae'
    GRPO = 'grpo'
    REINFORCE_PLUS_PLUS = 'reinforce_plus_plus'
    REMAX = 'remax'
    RLOO = 'rloo'
    LOOP = 'loop'


@dataclass
class ResourcePoolManager:
    """
    Define a resource pool specification. Resource pool will be initialized first.
    Mapping
    """
    resource_pool_spec: dict[str, list[int]]
    mapping: dict[Role, str]
    resource_pool_dict: dict[str, RayResourcePool] = field(default_factory=dict)

    def create_resource_pool(self):
        for resource_pool_name, process_on_nodes in self.resource_pool_spec.items():
            # max_colocate_count means the number of WorkerGroups (i.e. processes) in each RayResourcePool
            # For FSDP backend, we recommend using max_colocate_count=1 that merge all WorkerGroups into one.
            # For Megatron backend, we recommend using max_colocate_count>1 that can utilize different WorkerGroup for differnt models
            resource_pool = RayResourcePool(process_on_nodes=process_on_nodes,
                                            use_gpu=True,
                                            max_colocate_count=1,
                                            name_prefix=resource_pool_name)
            self.resource_pool_dict[resource_pool_name] = resource_pool

        self._check_resource_available()

    def get_resource_pool(self, role: Role) -> RayResourcePool:
        """Get the resource pool of the worker_cls"""
        return self.resource_pool_dict[self.mapping[role]]

    def get_n_gpus(self) -> int:
        """Get the number of gpus in this cluster."""
        return sum([n_gpus for process_on_nodes in self.resource_pool_spec.values() for n_gpus in process_on_nodes])

    def _check_resource_available(self):
        """Check if the resource pool can be satisfied in this ray cluster."""
        node_available_resources = ray.state.available_resources_per_node()
        node_available_gpus = {node: node_info.get('GPU', 0) for node, node_info in node_available_resources.items()}

        # check total required gpus can be satisfied
        total_available_gpus = sum(node_available_gpus.values())
        total_required_gpus = sum(
            [n_gpus for process_on_nodes in self.resource_pool_spec.values() for n_gpus in process_on_nodes])
        if total_available_gpus < total_required_gpus:
            raise ValueError(
                f"Total available GPUs {total_available_gpus} is less than total desired GPUs {total_required_gpus}")

        # check each resource pool can be satisfied, O(#resource_pools * #nodes)
        for resource_pool_name, process_on_nodes in self.resource_pool_spec.items():
            num_gpus, num_nodes = process_on_nodes[0], len(process_on_nodes)
            for node, available_gpus in node_available_gpus.items():
                if available_gpus >= num_gpus:
                    node_available_gpus[node] -= num_gpus
                    num_nodes -= 1
                    if num_nodes == 0:
                        break
            if num_nodes > 0:
                raise ValueError(
                    f"Resource pool {resource_pool_name}: {num_gpus}*{num_nodes} cannot be satisfied in this ray cluster"
                )


import torch
from verl.utils.torch_functional import masked_mean


def apply_kl_penalty(data: DataProto, kl_ctrl: core_algos.AdaptiveKLController, kl_penalty='kl'):
    responses = data.batch['responses']
    response_length = responses.size(1)
    token_level_scores = data.batch['token_level_scores']
    batch_size = data.batch.batch_size[0]
    attention_mask = data.batch['attention_mask']
    response_mask = attention_mask[:, -response_length:]

    # compute kl between ref_policy and current policy
    if 'ref_log_prob' in data.batch.keys():
        kld = core_algos.kl_penalty(data.batch['old_log_probs'], data.batch['ref_log_prob'],
                                    kl_penalty=kl_penalty)  # (batch_size, response_length)
        kld = kld * response_mask
        beta = kl_ctrl.value
    else:
        beta = 0
        kld = torch.zeros_like(response_mask, dtype=torch.float32)

    token_level_rewards = token_level_scores - beta * kld

    current_kl = masked_mean(kld, mask=response_mask, axis=-1)  # average over sequence
    current_kl = torch.mean(current_kl, dim=0).item()

    # according to https://github.com/huggingface/trl/blob/951ca1841f29114b969b57b26c7d3e80a39f75a0/trl/trainer/ppo_trainer.py#L837
    kl_ctrl.update(current_kl=current_kl, n_steps=batch_size)
    data.batch['token_level_rewards'] = token_level_rewards

    metrics = {'critic/kl': current_kl, 'critic/kl_coeff': beta}

    return data, metrics


def compute_advantage(data: DataProto, adv_estimator, gamma=1.0, lam=1.0, mask_truncated_samples=False):
    # prepare response group
    # TODO: add other ways to estimate advantages
    if adv_estimator == AdvantageEstimator.GAE:
        values = data.batch['values']
        responses = data.batch['responses']
        response_length = responses.size(-1)
        attention_mask = data.batch['attention_mask']
        response_mask = attention_mask[:, -response_length:]
        token_level_rewards = data.batch['token_level_rewards']
        advantages, returns = core_algos.compute_gae_advantage_return(token_level_rewards=token_level_rewards,
                                                                      values=values,
                                                                      eos_mask=response_mask,
                                                                      gamma=gamma,
                                                                      lam=lam)
        data.batch['advantages'] = advantages
        data.batch['returns'] = returns
    elif adv_estimator == AdvantageEstimator.GRPO:
        token_level_rewards = data.batch['token_level_rewards']
        index = data.non_tensor_batch['uid']
        responses = data.batch['responses']
        response_length = responses.size(-1)
        attention_mask = data.batch['attention_mask']
        response_mask = attention_mask[:, -response_length:]
        advantages, returns = core_algos.compute_grpo_outcome_advantage(token_level_rewards=token_level_rewards,
                                                                        eos_mask=response_mask,
                                                                        index=index,
                                                                        mask_truncated_samples=mask_truncated_samples)
        data.batch['advantages'] = advantages
        data.batch['returns'] = returns
    elif adv_estimator == AdvantageEstimator.REINFORCE_PLUS_PLUS:
        token_level_rewards = data.batch['token_level_rewards']
        responses = data.batch['responses']
        response_length = responses.size(-1)
        attention_mask = data.batch['attention_mask']
        response_mask = attention_mask[:, -response_length:]
        advantages, returns = core_algos.compute_reinforce_plus_plus_outcome_advantage(
            token_level_rewards=token_level_rewards, eos_mask=response_mask, gamma=gamma)
        data.batch['advantages'] = advantages
        data.batch['returns'] = returns
    elif adv_estimator == AdvantageEstimator.REMAX:
        token_level_rewards = data.batch['token_level_rewards']
        index = data.non_tensor_batch['uid']
        responses = data.batch['responses']
        response_length = responses.size(-1)
        attention_mask = data.batch['attention_mask']
        response_mask = attention_mask[:, -response_length:]

        reward_baselines = data.batch['reward_baselines']

        advantages, returns = core_algos.compute_remax_outcome_advantage(token_level_rewards=token_level_rewards,
                                                                         reward_baselines=reward_baselines,
                                                                         eos_mask=response_mask)

        data.batch['advantages'] = advantages
        data.batch['returns'] = returns
    elif adv_estimator == AdvantageEstimator.RLOO:
        token_level_rewards = data.batch['token_level_rewards']
        index = data.non_tensor_batch['uid']
        responses = data.batch['responses']
        response_length = responses.size(-1)
        attention_mask = data.batch['attention_mask']
        response_mask = attention_mask[:, -response_length:]
        advantages, returns = core_algos.compute_rloo_outcome_advantage(token_level_rewards=token_level_rewards,
                                                                        eos_mask=response_mask,
                                                                        index=index)
        data.batch['advantages'] = advantages
        data.batch['returns'] = returns
    elif adv_estimator == AdvantageEstimator.LOOP:
        # same as grpo but without normalization
        token_level_rewards = data.batch['token_level_rewards']
        index = data.non_tensor_batch['uid']
        responses = data.batch['responses']
        response_length = responses.size(-1)
        attention_mask = data.batch['attention_mask']
        response_mask = attention_mask[:, -response_length:]
        advantages, returns = core_algos.compute_loop_outcome_advantage(token_level_rewards=token_level_rewards,
                                                                        eos_mask=response_mask,
                                                                        index=index)
        data.batch['advantages'] = advantages
        data.batch['returns'] = returns
    else:
        raise NotImplementedError
    return data


@contextmanager
def _timer(name: str, timing_raw: Dict[str, float]):
    with Timer(name=name, logger=None) as timer:
        yield
    timing_raw[name] = timer.last


class RayPPOTrainer(object):
    """
    Note that this trainer runs on the driver process on a single CPU/GPU node.
    """

    # TODO: support each role have individual ray_worker_group_cls,
    # i.e., support different backend of different role
    def __init__(self,
                 config,
                 tokenizer,
                 role_worker_mapping: dict[Role, WorkerType],
                 resource_pool_manager: ResourcePoolManager,
                 ray_worker_group_cls: RayWorkerGroup = RayWorkerGroup,
                 processor=None,
                 reward_fn=None,
                 val_reward_fn=None):

        # assert torch.cuda.is_available(), 'cuda must be available on driver'

        self.tokenizer = tokenizer
        self.processor = processor
        self.config = config
        self.reward_fn = reward_fn
        self.val_reward_fn = val_reward_fn

        self.hybrid_engine = config.actor_rollout_ref.hybrid_engine
        # TODO: now we also support hybrid engine
        # assert self.hybrid_engine, 'Currently, only support hybrid engine'

        if self.hybrid_engine:
            assert Role.ActorRollout in role_worker_mapping, f'{role_worker_mapping.keys()=}'

        self.role_worker_mapping = role_worker_mapping
        self.resource_pool_manager = resource_pool_manager
        self.use_reference_policy = Role.RefPolicy in role_worker_mapping
        self.use_rm = Role.RewardModel in role_worker_mapping
        self.ray_worker_group_cls = ray_worker_group_cls
        self.validation_generations_logger = ValidationGenerationsLogger()

        # define KL control
        if self.use_reference_policy:
            if config.algorithm.kl_ctrl.type == 'fixed':
                self.kl_ctrl = core_algos.FixedKLController(kl_coef=config.algorithm.kl_ctrl.kl_coef)
            elif config.algorithm.kl_ctrl.type == 'adaptive':
                assert config.algorithm.kl_ctrl.horizon > 0, f'horizon must be larger than 0. Got {config.critic.kl_ctrl.horizon}'
                self.kl_ctrl = core_algos.AdaptiveKLController(init_kl_coef=config.algorithm.kl_ctrl.kl_coef,
                                                               target_kl=config.algorithm.kl_ctrl.target_kl,
                                                               horizon=config.algorithm.kl_ctrl.horizon)
            else:
                raise NotImplementedError
        else:
            self.kl_ctrl = core_algos.FixedKLController(kl_coef=0.)

        if self.config.algorithm.adv_estimator == AdvantageEstimator.GAE:
            self.use_critic = True
        elif self.config.algorithm.adv_estimator in [
                AdvantageEstimator.GRPO, AdvantageEstimator.REINFORCE_PLUS_PLUS, AdvantageEstimator.REMAX,
                AdvantageEstimator.RLOO, AdvantageEstimator.LOOP
        ]:
            self.use_critic = False
        else:
            raise NotImplementedError

        self._validate_config()
        self._create_dataloader()

    def _validate_config(self):
        config = self.config
        # number of GPUs total
        n_gpus = config.trainer.n_gpus_per_node * config.trainer.nnodes

        # 1. Check total batch size for data correctness
        real_train_batch_size = config.data.train_batch_size * config.actor_rollout_ref.rollout.n
        # assert real_train_batch_size % n_gpus == 0, \
        #     f"real_train_batch_size ({real_train_batch_size}) must be divisible by total n_gpus ({n_gpus})."

        # A helper function to check "micro_batch_size" vs "micro_batch_size_per_gpu"
        # We throw an error if the user sets both. The new convention is "..._micro_batch_size_per_gpu".
        def check_mutually_exclusive(mbs, mbs_per_gpu, name: str):
            if mbs is None and mbs_per_gpu is None:
                raise ValueError(f"[{name}] Please set at least one of '{name}.micro_batch_size' or "
                                 f"'{name}.micro_batch_size_per_gpu'.")

            if mbs is not None and mbs_per_gpu is not None:
                raise ValueError(f"[{name}] You have set both '{name}.micro_batch_size' AND "
                                 f"'{name}.micro_batch_size_per_gpu'. Please remove '{name}.micro_batch_size' "
                                 f"because only '*_micro_batch_size_per_gpu' is supported (the former is deprecated).")

        if not config.actor_rollout_ref.actor.use_dynamic_bsz:
            # actor: ppo_micro_batch_size vs. ppo_micro_batch_size_per_gpu
            check_mutually_exclusive(config.actor_rollout_ref.actor.ppo_micro_batch_size,
                                     config.actor_rollout_ref.actor.ppo_micro_batch_size_per_gpu,
                                     "actor_rollout_ref.actor")

            # reference: log_prob_micro_batch_size vs. log_prob_micro_batch_size_per_gpu
            check_mutually_exclusive(config.actor_rollout_ref.ref.log_prob_micro_batch_size,
                                     config.actor_rollout_ref.ref.log_prob_micro_batch_size_per_gpu,
                                     "actor_rollout_ref.ref")

            #  The rollout section also has log_prob_micro_batch_size vs. log_prob_micro_batch_size_per_gpu
            check_mutually_exclusive(config.actor_rollout_ref.rollout.log_prob_micro_batch_size,
                                     config.actor_rollout_ref.rollout.log_prob_micro_batch_size_per_gpu,
                                     "actor_rollout_ref.rollout")

        if self.use_critic and not config.critic.use_dynamic_bsz:
            # Check for critic micro-batch size conflicts
            check_mutually_exclusive(config.critic.ppo_micro_batch_size, config.critic.ppo_micro_batch_size_per_gpu,
                                     "critic")

        # Check for reward model micro-batch size conflicts
        if config.reward_model.enable and not config.reward_model.use_dynamic_bsz:
            check_mutually_exclusive(config.reward_model.micro_batch_size, config.reward_model.micro_batch_size_per_gpu,
                                     "reward_model")

        # Actor
        # check if train_batch_size is larger than ppo_mini_batch_size
        # if NOT dynamic_bsz, we must ensure:
        #    ppo_mini_batch_size is divisible by ppo_micro_batch_size
        #    ppo_micro_batch_size * sequence_parallel_size >= n_gpus
        if not config.actor_rollout_ref.actor.use_dynamic_bsz:
            assert config.data.train_batch_size >= config.actor_rollout_ref.actor.ppo_mini_batch_size
            sp_size = config.actor_rollout_ref.actor.get('ulysses_sequence_parallel_size', 1)
            if config.actor_rollout_ref.actor.ppo_micro_batch_size is not None:
                assert config.actor_rollout_ref.actor.ppo_mini_batch_size % config.actor_rollout_ref.actor.ppo_micro_batch_size == 0
                assert config.actor_rollout_ref.actor.ppo_micro_batch_size * sp_size >= n_gpus

        # critic
        if self.use_critic and not config.critic.use_dynamic_bsz:
            assert config.data.train_batch_size >= config.critic.ppo_mini_batch_size
            sp_size = config.critic.get('ulysses_sequence_parallel_size', 1)
            if config.critic.ppo_micro_batch_size is not None:
                assert config.critic.ppo_mini_batch_size % config.critic.ppo_micro_batch_size == 0
                assert config.critic.ppo_micro_batch_size * sp_size >= n_gpus

        # Check if use_remove_padding is enabled when using sequence parallelism for fsdp
        if config.actor_rollout_ref.actor.strategy == 'fsdp':
            if config.actor_rollout_ref.actor.get('ulysses_sequence_parallel_size', 1) > 1 or \
                    config.actor_rollout_ref.ref.get('ulysses_sequence_parallel_size', 1) > 1:
                assert config.actor_rollout_ref.model.use_remove_padding, \
                    "When using sequence parallelism for actor/ref policy, you must enable `use_remove_padding`."

        if self.use_critic and config.critic.strategy == 'fsdp':
            if config.critic.get('ulysses_sequence_parallel_size', 1) > 1:
                assert config.critic.model.use_remove_padding, \
                    "When using sequence parallelism for critic, you must enable `use_remove_padding`."

        if config.data.get('val_batch_size', None) is not None:
            print(
                f"WARNING: val_batch_size is deprecated. Validation datasets are sent to inference engines as a whole batch, which will schedule the memory themselves."
            )

        # check eval config
        if config.actor_rollout_ref.rollout.val_kwargs.do_sample:
            assert config.actor_rollout_ref.rollout.temperature > 0, \
                "validation gen temperature should be greater than 0 when enabling do_sample"

        print("[validate_config] All configuration checks passed successfully!")

    def _create_dataloader(self):
        # TODO: we have to make sure the batch size is divisible by the dp size
        self.train_dataset = RLHFDataset(parquet_files=self.config.data.train_files,
                                         tokenizer=self.tokenizer,
                                         processor=self.processor,
                                         prompt_key=self.config.data.prompt_key,
                                         image_key=self.config.data.get('image_key', 'images'),
                                         max_prompt_length=self.config.data.max_prompt_length,
                                         filter_prompts=True,
                                         return_raw_chat=self.config.data.get('return_raw_chat', False),
                                         truncation=self.config.data.get('truncation', 'error'),
                                         filter_overlong_prompts=self.config.data.filter_overlong_prompts)
        assert self.train_dataset.truncation == self.config.data.get(
            'truncation', 'error'
        ), f'dataset truncation {self.train_dataset.truncation} must be the same as config {self.config.data.get("truncation", "error")}'
        # use sampler for better ckpt resume
        if self.config.data.shuffle:
            train_dataloader_generator = torch.Generator()
            train_dataloader_generator.manual_seed(self.config.data.get('seed', 1))
            sampler = RandomSampler(data_source=self.train_dataset, generator=train_dataloader_generator)
        else:
            sampler = SequentialSampler(data_source=self.train_dataset)

        train_batch_size = self.config.data.train_batch_size
        if self.config.trainer.rejection_sample:
            train_batch_size *= self.config.trainer.rejection_sample_multiplier
            train_batch_size = int(train_batch_size)

        self.train_dataloader = StatefulDataLoader(dataset=self.train_dataset,
                                                   batch_size=train_batch_size,
                                                   num_workers=8,
                                                   drop_last=True,
                                                   collate_fn=collate_fn,
                                                   sampler=sampler)
        self.val_dataset = RLHFDataset(parquet_files=self.config.data.val_files,
                                       tokenizer=self.tokenizer,
                                       processor=self.processor,
                                       prompt_key=self.config.data.prompt_key,
                                       image_key=self.config.data.get('image_key', 'images'),
                                       max_prompt_length=self.config.data.max_prompt_length,
                                       filter_prompts=True,
                                       return_raw_chat=self.config.data.get('return_raw_chat', False),
                                       truncation=self.config.data.get('truncation', 'error'),
                                       filter_overlong_prompts=self.config.data.filter_overlong_prompts)
        assert self.val_dataset.truncation == self.config.data.get(
            'truncation', 'error'
        ), f'dataset truncation {self.val_dataset.truncation} must be the same as config {self.config.data.get("truncation", "error")}'
        self.val_dataloader = StatefulDataLoader(
            dataset=self.val_dataset,
            # Validation datasets are sent to inference engines as a whole batch,
            # which will schedule the memory themselves.
            batch_size=len(self.val_dataset),
            num_workers=8,
            shuffle=False,
            drop_last=False,
            collate_fn=collate_fn)

        assert len(self.train_dataloader) >= 1
        assert len(
            self.val_dataloader
        ) == 1, "Validation dataloader must have a single batch, which inference engines will schedule the memory themselves."

        print(f'Size of train dataloader: {len(self.train_dataloader)}')

        # inject total_training_steps to actor/critic optim_config. This is hacky.
        total_training_steps = len(self.train_dataloader) * self.config.trainer.total_epochs

        if self.config.trainer.total_training_steps is not None:
            total_training_steps = self.config.trainer.total_training_steps

        self.total_training_steps = total_training_steps
        print(f'Total training steps: {self.total_training_steps}')

        OmegaConf.set_struct(self.config, True)
        with open_dict(self.config):
            self.config.actor_rollout_ref.actor.optim.total_training_steps = total_training_steps
            self.config.critic.optim.total_training_steps = total_training_steps

    def _maybe_log_val_generations(self, inputs, outputs, scores):
        """Log a table of validation samples to the configured logger (wandb or swanlab)"""

        generations_to_log = self.config.trainer.val_generations_to_log_to_wandb

        if generations_to_log == 0:
            return

        import numpy as np

        # Create tuples of (input, output, score) and sort by input text
        samples = list(zip(inputs, outputs, scores))
        samples.sort(key=lambda x: x[0])  # Sort by input text

        # Use fixed random seed for deterministic shuffling
        rng = np.random.RandomState(42)
        rng.shuffle(samples)

        # Take first N samples after shuffling
        samples = samples[:generations_to_log]

        # Log to each configured logger
        self.validation_generations_logger.log(self.config.trainer.logger, samples, self.global_steps)

    def _validate(self):
        reward_tensor_lst = []
        data_source_lst = []

        # Lists to collect samples for the table
        sample_inputs = []
        sample_outputs = []
        sample_scores = []

        for test_data in self.val_dataloader:
            test_batch = DataProto.from_single_dict(test_data)

            # we only do validation on rule-based rm
            if self.config.reward_model.enable and test_batch[0].non_tensor_batch['reward_model']['style'] == 'model':
                return {}

            n_val_samples = self.config.actor_rollout_ref.rollout.val_kwargs.n
            test_batch = test_batch.repeat(repeat_times=n_val_samples, interleave=True)
            # Store original inputs
            input_ids = test_batch.batch['input_ids']
            input_texts = [self.tokenizer.decode(ids, skip_special_tokens=True) for ids in input_ids]
            sample_inputs.extend(input_texts)

            test_batch.meta_info = {
                'eos_token_id': self.tokenizer.eos_token_id,
                'pad_token_id': self.tokenizer.pad_token_id,
                'recompute_log_prob': False,
                'do_sample': self.config.actor_rollout_ref.rollout.val_kwargs.do_sample,
                'validate': True,
            }
            print(f'test_batch meta info: {test_batch.meta_info}')

            if self.hybrid_engine:
                validate_wg = self.actor_rollout_wg
            else:
                validate_wg = self.rollout_wg
            
            # pad to be divisible by dp_size
            test_batch_padded, pad_size = pad_dataproto_to_divisor(test_batch, validate_wg.world_size)
            
            if self.config.actor_rollout_ref.rollout.async_engine:
                gen_seq_generator = validate_wg.generate_sequences_async(prompts=test_batch_padded)
                outputs = []
                for item in gen_seq_generator:
                    if item is None:
                        break
                    outputs.append(item)
                test_output_gen_batch_padded = DataProto.concat(outputs)
            else:
                test_output_gen_batch_padded = validate_wg.generate_sequences(test_batch_padded)

            # unpad
            test_output_gen_batch = unpad_dataproto(test_output_gen_batch_padded, pad_size=pad_size)
            print('validation generation end')

            # Store generated outputs
            output_ids = test_output_gen_batch.batch['responses']
            output_texts = [self.tokenizer.decode(ids, skip_special_tokens=True) for ids in output_ids]
            sample_outputs.extend(output_texts)
            
            test_batch =  dataprotoitem_to_dataproto(test_output_gen_batch) #test_batch.union(test_output_gen_batch)

            # evaluate using reward_function
            reward_tensor = self.val_reward_fn(test_batch)

            # Store scores
            scores = torch.clamp(reward_tensor.sum(-1), min=0.0,max=1.0).cpu().tolist()
            sample_scores.extend(scores)

            reward_tensor_lst.append(reward_tensor)
            data_source_lst.append(test_batch.non_tensor_batch.get('data_source', ['unknown'] * reward_tensor.shape[0]))

        self._maybe_log_val_generations(inputs=sample_inputs, outputs=sample_outputs, scores=sample_scores)

        reward_tensor = torch.clamp(torch.cat(reward_tensor_lst, dim=0).sum(-1), min=0.0, max=1.0).cpu()  # (batch_size,)
        data_sources = np.concatenate(data_source_lst, axis=0)

        # evaluate test_score based on data source
        data_source_reward = {}
        for i in range(reward_tensor.shape[0]):
            data_source = data_sources[i]
            if data_source not in data_source_reward:
                data_source_reward[data_source] = []
            data_source_reward[data_source].append(reward_tensor[i].item())

        metric_dict = {}
        for data_source, rewards in data_source_reward.items():
            metric_dict[f'val/test_score/{data_source}'] = np.mean(rewards)

        return metric_dict

    def init_workers(self):
        """Init resource pool and worker group"""
        self.resource_pool_manager.create_resource_pool()

        self.resource_pool_to_cls = {pool: {} for pool in self.resource_pool_manager.resource_pool_dict.values()}

        # create actor and rollout
        if self.hybrid_engine:
            resource_pool = self.resource_pool_manager.get_resource_pool(Role.ActorRollout)
            actor_rollout_cls = RayClassWithInitArgs(cls=self.role_worker_mapping[Role.ActorRollout],
                                                     config=self.config.actor_rollout_ref,
                                                     role='actor_rollout',
                                                     reward_config=self.config.reward_model)
            self.resource_pool_to_cls[resource_pool]['actor_rollout'] = actor_rollout_cls
        else:
            assert Role.Actor in self.role_worker_mapping and Role.Rollout in self.role_worker_mapping, "Actor and Rollout must be in role_worker_mapping"
            actor_resource_pool = self.resource_pool_manager.get_resource_pool(Role.Actor)
            # actor_gpu_ids = actor_resource_pool.gpu_assignments if isinstance(actor_resource_pool, RayResourcePool) else None
            actor_cls = RayClassWithInitArgs(
                cls=self.role_worker_mapping[Role.Actor],
                config=self.config.actor_rollout_ref,
                role='actor',
                reward_config=self.config.reward_model,
            )
            self.resource_pool_to_cls[actor_resource_pool]['actor'] = actor_cls

            # Get rollout resource pool
            rollout_resource_pool = self.resource_pool_manager.get_resource_pool(Role.Rollout)
            # rollout_gpu_ids = rollout_resource_pool.gpu_assignments if isinstance(rollout_resource_pool, RayResourcePool) else None
            rollout_cls = RayClassWithInitArgs(
                cls=self.role_worker_mapping[Role.Rollout],
                config=self.config.actor_rollout_ref,
                role='rollout',
                reward_config=self.config.reward_model,
            )
            self.resource_pool_to_cls[rollout_resource_pool]['rollout'] = rollout_cls

        # create critic
        if self.use_critic:
            resource_pool = self.resource_pool_manager.get_resource_pool(Role.Critic)
            critic_cls = RayClassWithInitArgs(cls=self.role_worker_mapping[Role.Critic], config=self.config.critic)
            self.resource_pool_to_cls[resource_pool]['critic'] = critic_cls

        # create reference policy if needed
        if self.use_reference_policy:
            resource_pool = self.resource_pool_manager.get_resource_pool(Role.RefPolicy)
            ref_policy_cls = RayClassWithInitArgs(self.role_worker_mapping[Role.RefPolicy],
                                                  config=self.config.actor_rollout_ref,
                                                  role='ref')
            self.resource_pool_to_cls[resource_pool]['ref'] = ref_policy_cls

        # create a reward model if reward_fn is None
        if self.use_rm:
            # we create a RM here
            resource_pool = self.resource_pool_manager.get_resource_pool(Role.RewardModel)
            rm_cls = RayClassWithInitArgs(self.role_worker_mapping[Role.RewardModel], config=self.config.reward_model)
            self.resource_pool_to_cls[resource_pool]['rm'] = rm_cls

        # initialize WorkerGroup
        # NOTE: if you want to use a different resource pool for each role, which can support different parallel size,
        # you should not use `create_colocated_worker_cls`. Instead, directly pass different resource pool to different worker groups.
        # See https://github.com/volcengine/verl/blob/master/examples/ray/tutorial.ipynb for more information.
        all_wg = {}
        self.wg_dicts = []
        for resource_pool, class_dict in self.resource_pool_to_cls.items():
            worker_dict_cls = create_colocated_worker_cls(class_dict=class_dict)
            wg_dict = self.ray_worker_group_cls(resource_pool=resource_pool, ray_cls_with_init=worker_dict_cls)
            spawn_wg = wg_dict.spawn(prefix_set=class_dict.keys())
            all_wg.update(spawn_wg)
            # keep the referece of WorkerDict to support ray >= 2.31. Ref: https://github.com/ray-project/ray/pull/45699
            self.wg_dicts.append(wg_dict)

        if self.use_critic:
            self.critic_wg = all_wg['critic']
            self.critic_wg.init_model()

        if self.use_reference_policy:
            self.ref_policy_wg = all_wg['ref']
            self.ref_policy_wg.init_model()

        if self.use_rm:
            self.rm_wg = all_wg['rm']
            self.rm_wg.init_model()

        # we should create rollout at the end so that vllm can have a better estimation of kv cache memory
        if self.hybrid_engine:
            self.actor_rollout_wg = all_wg['actor_rollout']
            self.actor_rollout_wg.init_model()
        else:
            self.actor_wg = all_wg['actor']
            self.actor_wg.init_model()
            self.rollout_wg = all_wg['rollout']
            self.rollout_wg.init_model()

    def _save_checkpoint(self):
        # path: given_path + `/global_step_{global_steps}` + `/actor`
        local_global_step_folder = os.path.join(self.config.trainer.default_local_dir,
                                                f'global_step_{self.global_steps}')
        # Make dirs from this absolute path
        os.makedirs(local_global_step_folder, exist_ok=True)
        actor_local_path = os.path.join(local_global_step_folder, 'actor')

        actor_remote_path = None if self.config.trainer.default_hdfs_dir is None else os.path.join(
            self.config.trainer.default_hdfs_dir, f'global_step_{self.global_steps}', 'actor')
        
        if self.hybrid_engine:
            save_actor_cls = self.actor_rollout_wg
        else:
            save_actor_cls = self.actor_wg
        
        save_actor_cls.save_checkpoint(actor_local_path,
                                              actor_remote_path,
                                              self.global_steps,
                                              remove_previous_ckpt=self.config.trainer.remove_previous_ckpt_in_save)

        if self.use_critic:
            critic_local_path = os.path.join(local_global_step_folder, 'critic')
            critic_remote_path = None if self.config.trainer.default_hdfs_dir is None else os.path.join(
                self.config.trainer.default_hdfs_dir, f'global_step_{self.global_steps}', 'critic')
            self.critic_wg.save_checkpoint(critic_local_path,
                                           critic_remote_path,
                                           self.global_steps,
                                           remove_previous_ckpt=self.config.trainer.remove_previous_ckpt_in_save)

        # save dataloader
        dataloader_local_path = os.path.join(local_global_step_folder, 'data.pt')
        dataloader_state_dict = self.train_dataloader.state_dict()
        torch.save(dataloader_state_dict, dataloader_local_path)

        # latest checkpointed iteration tracker (for atomic usage)
        local_latest_checkpointed_iteration = os.path.join(self.config.trainer.default_local_dir,
                                                           'latest_checkpointed_iteration.txt')
        with open(local_latest_checkpointed_iteration, 'w') as f:
            f.write(str(self.global_steps))

    def _load_checkpoint(self):
        if self.config.trainer.resume_mode == 'disable':
            return 0

        # load from hdfs
        if self.config.trainer.default_hdfs_dir is not None:
            raise NotImplementedError('load from hdfs is not implemented yet')
        else:
            checkpoint_folder = self.config.trainer.default_local_dir  # TODO: check path
            if not os.path.isabs(checkpoint_folder):
                working_dir = os.getcwd()
                checkpoint_folder = os.path.join(working_dir, checkpoint_folder)
            global_step_folder = find_latest_ckpt_path(checkpoint_folder)  # None if no latest

        # find global_step_folder
        if self.config.trainer.resume_mode == 'auto':
            if global_step_folder is None:
                print('Training from scratch')
                return 0
        else:
            if not (self.config.trainer.resume_from_path and global_step_folder is not None):
                assert isinstance(self.config.trainer.resume_mode, str), "resume ckpt must be str type"
                assert 'global_step_' in self.config.trainer.resume_mode, "resume ckpt must specify the global_steps"
                global_step_folder = self.config.trainer.resume_mode
                if not os.path.isabs(global_step_folder):
                    working_dir = os.getcwd()
                    global_step_folder = os.path.join(working_dir, global_step_folder)
        print(f'Load from checkpoint folder: {global_step_folder}')
        # set global step
        self.global_steps = int(global_step_folder.split('global_step_')[-1])

        print(f'Setting global step to {self.global_steps}')
        print(f'Resuming from {global_step_folder}')

        actor_path = os.path.join(global_step_folder, 'actor')
        critic_path = os.path.join(global_step_folder, 'critic')
        # load actor
        if self.hybrid_engine:
            load_actor_cls = self.actor_rollout_wg
        else:
            load_actor_cls = self.actor_wg
            
        load_actor_cls.load_checkpoint(actor_path,
                                              del_local_after_load=self.config.trainer.del_local_ckpt_after_load)

        if not self.hybrid_engine:
            # Broadcast actor to rollout workers if not using hybrid engine
            updated_actor_module_fsdp_ref = self.actor_wg.get_state_dict()
            if isinstance(updated_actor_module_fsdp_ref, list):
                updated_actor_module_fsdp_ref = updated_actor_module_fsdp_ref[0]
            self.rollout_wg.update_rollout_actor_module(updated_actor_module_fsdp_ref)
        # if not self.hybrid_engine:
        #     self.rollout_wg.load_checkpoint(actor_path,
        #                                           del_local_after_load=self.config.trainer.del_local_ckpt_after_load)
        
        # load critic
        if self.use_critic:
            self.critic_wg.load_checkpoint(critic_path,
                                           del_local_after_load=self.config.trainer.del_local_ckpt_after_load)

        # load dataloader,
        # TODO: from remote not implemented yet
        dataloader_local_path = os.path.join(global_step_folder, 'data.pt')
        if os.path.exists(dataloader_local_path):
            dataloader_state_dict = torch.load(dataloader_local_path)
            self.train_dataloader.load_state_dict(dataloader_state_dict)
        else:
            print(f"Warning: No dataloader state found at {dataloader_local_path}, will start from scratch")

    def _balance_batch(self, batch: DataProto, metrics, logging_prefix='global_seqlen'):
        """Reorder the data on single controller such that each dp rank gets similar total tokens"""
        attention_mask = batch.batch['attention_mask']
        batch_size = attention_mask.shape[0]
        global_seqlen_lst = batch.batch['attention_mask'].view(batch_size, -1).sum(-1).tolist()  # (train_batch_size,)
        if self.hybrid_engine:
            world_size = self.actor_rollout_wg.world_size
        else:
            world_size = self.actor_wg.world_size
        global_partition_lst = get_seqlen_balanced_partitions(global_seqlen_lst,
                                                              k_partitions=world_size,
                                                              equal_size=True)
        # reorder based on index. The data will be automatically equally partitioned by dispatch function
        global_idx = torch.tensor([j for partition in global_partition_lst for j in partition])
        batch.reorder(global_idx)
        global_balance_stats = log_seqlen_unbalance(seqlen_list=global_seqlen_lst,
                                                    partitions=global_partition_lst,
                                                    prefix=logging_prefix)
        metrics.update(global_balance_stats)

    def fit(self):
        """
        The training loop of PPO.
        The driver process only need to call the compute functions of the worker group through RPC to construct the PPO dataflow.
        The light-weight advantage computation is done on the driver process.
        """
        from verl.utils.tracking import Tracking
        from omegaconf import OmegaConf

        logger = Tracking(project_name=self.config.trainer.project_name,
                          experiment_name=self.config.trainer.experiment_name,
                          default_backend=self.config.trainer.logger,
                          config=OmegaConf.to_container(self.config, resolve=True))

        self.global_steps = 0

        # load checkpoint before doing anything
        self._load_checkpoint()

        # perform validation before training
        # currently, we only support validation using the reward_function.
        if self.val_reward_fn is not None and self.config.trainer.get('val_before_train', True):
            val_metrics = self._validate()
            pprint(f'Initial validation metrics: {val_metrics}')
            logger.log(data=val_metrics, step=self.global_steps)
            if self.config.trainer.get('val_only', False):
                return

        # we start from step 1
        self.global_steps += 1
        last_val_metrics = None

        for epoch in range(self.config.trainer.total_epochs):
            for batch_dict in self.train_dataloader:
                metrics = {}
                timing_raw = {}

                batch: DataProto = DataProto.from_single_dict(batch_dict)
                batch.non_tensor_batch['uid'] = np.array([str(uuid.uuid4()) for _ in range(len(batch.batch))], dtype=object)
                is_last_step = self.global_steps >= self.total_training_steps

                with _timer('step', timing_raw):
                    with _timer('gen', timing_raw):
                        if not self.config.actor_rollout_ref.rollout.async_engine:
                            batch = self.actor_rollout_wg.generate_sequences(batch)
                        else:
                            #Get the generator function which will yield results as they complete
                            gen_seq_generator = self.actor_rollout_wg.generate_sequences_async(prompts=batch)
                            # Collect outputs in a dict keyed by prompt_idx
                            outputs = []
                            for output in gen_seq_generator:
                                outputs.append(output)
                            # Combine all outputs
                            batch = DataProto.concat(outputs)

                    if self.config.algorithm.adv_estimator == AdvantageEstimator.REMAX:
                        with _timer('gen_max', timing_raw):
                            gen_baseline_batch = deepcopy(batch)
                            gen_baseline_batch.meta_info['do_sample'] = False
                            gen_baseline_output = self.actor_rollout_wg.generate_sequences(gen_baseline_batch)

                            batch = batch.union(gen_baseline_output)
                            reward_baseline_tensor = self.reward_fn(batch)
                            reward_baseline_tensor = reward_baseline_tensor.sum(dim=-1)

                            batch.pop(batch_keys=list(gen_baseline_output.batch.keys()))

                            batch.batch['reward_baselines'] = reward_baseline_tensor

                            del gen_baseline_batch, gen_baseline_output

                    with _timer('adv', timing_raw):
                        # compute scores using reward model and/or reward function
                        if self.use_rm:
                            reward_tensor = self.rm_wg.compute_rm_score(batch)
                            batch = batch.union(reward_tensor)
                        if not self.config.actor_rollout_ref.rollout.compute_reward:
                            reward_tensor = self.reward_fn(batch)
                            batch.batch['token_level_scores'] = reward_tensor
                        else:
                            reward_tensor = batch.batch['token_level_scores']

                        # Rejection sampling based on rewards
                        # Group rewards by uid
                        uids = batch.non_tensor_batch['uid']
                        unique_uids = np.unique(uids)
                        valid_mask = torch.ones(len(uids), dtype=torch.bool)
                        solve_none = 0
                        solve_all = 0
                        for uid in unique_uids:
                            uid_mask = uids == uid
                            uid_rewards = reward_tensor[uid_mask].sum(-1)  # Sum rewards for each sequence
                            
                            # Check if all rewards are 0 or all are 1 for this uid
                            if (uid_rewards == 0).all():
                                valid_mask[uid_mask] = False
                                solve_none += 1
                            elif (uid_rewards == 1).all():
                                valid_mask[uid_mask] = False
                                solve_all += 1
                        
                        # Log to metrics
                        metrics['batch/solve_none'] = solve_none
                        metrics['batch/solve_all'] = solve_all
                        metrics['batch/solve_partial'] = len(unique_uids) - solve_none - solve_all

                        if self.config.trainer.rejection_sample:
                            # If no valid samples remain, skip this batch and get a new one
                            if not valid_mask.any():
                                continue
                            # Keep track of valid samples and non-valid samples
                            valid_indices = torch.where(valid_mask)[0]
                            non_valid_indices = torch.where(~valid_mask)[0]
                            
                            num_valid_samples = len(valid_indices)
                            # Calculate how many samples we need to add for a full batch
                            total_batch_size = self.config.data.train_batch_size * self.config.actor_rollout_ref.rollout.n
                            padding_needed = total_batch_size - num_valid_samples
                            # If we need padding and have non-valid samples available, use them
                            combined_indices = valid_indices.tolist()
                            if padding_needed > 0 and len(non_valid_indices) > 0:
                                # Select padding_needed non-valid samples (or as many as available)
                                padding_samples = min(padding_needed, len(non_valid_indices))
                                # Randomly select from non-valid indices to use as padding
                                padding_indices = non_valid_indices[torch.randperm(len(non_valid_indices))[:padding_samples]]
                                combined_indices.extend(padding_indices.tolist())
                            
                            # Create a new mask for the combined set of samples
                            final_mask = torch.zeros(len(batch.batch['input_ids']), dtype=torch.bool)
                            final_mask[combined_indices] = True
                            
                            # Apply the mask to keep only selected samples
                            batch = batch[final_mask]
                            batch = dataprotoitem_to_dataproto(batch)
                        
                        if self.config.actor_rollout_ref.rollout.enable_log_prob:
                            # Avoid recompute log_prob bugs. Log probs from vLLM. (Could be buggy)
                            batch.meta_info['micro_batch_size'] = self.config.actor_rollout_ref.rollout.log_prob_micro_batch_size_per_gpu
                            batch.meta_info['max_token_len'] = self.config.actor_rollout_ref.rollout.log_prob_max_token_len_per_gpu
                            batch.meta_info['use_dynamic_bsz'] = self.config.actor_rollout_ref.rollout.log_prob_use_dynamic_bsz
                            batch.meta_info['temperature'] = self.config.actor_rollout_ref.rollout.temperature
                        else:
                            # Recompute old_log_probs using Pytorch FSDP.
                            with _timer('old_log_prob', timing_raw):
                                old_log_prob = self.actor_rollout_wg.compute_log_prob(batch)
                                batch = batch.union(old_log_prob)

                        if self.use_reference_policy:
                            # compute reference log_prob
                            with _timer('ref', timing_raw):
                                ref_log_prob = self.ref_policy_wg.compute_ref_log_prob(batch)
                                batch = batch.union(ref_log_prob)

                        # compute values
                        if self.use_critic:
                            with _timer('values', timing_raw):
                                values = self.critic_wg.compute_values(batch)
                                batch = batch.union(values)

                        batch.batch['token_level_rewards'] = batch.batch['token_level_scores']

                        # compute advantages, executed on the driver process
                        batch = compute_advantage(batch,
                                                  adv_estimator=self.config.algorithm.adv_estimator,
                                                  gamma=self.config.algorithm.gamma,
                                                  lam=self.config.algorithm.lam,
                                                  mask_truncated_samples=self.config.algorithm.mask_truncated_samples)

                    # balance the number of valid tokens on each dp rank.
                    # Note that this breaks the order of data inside the batch.
                    # Please take care when you implement group based adv computation such as GRPO and rloo
                    if self.config.trainer.balance_batch:
                        self._balance_batch(batch, metrics=metrics)

                    # compute global_valid tokens
                    batch.meta_info['global_token_num'] = torch.sum(batch.batch['attention_mask'], dim=-1).tolist()

                    # update critic
                    if self.use_critic:
                        with _timer('update_critic', timing_raw):
                            critic_output = self.critic_wg.update_critic(batch)
                        critic_output_metrics = reduce_metrics(critic_output.meta_info['metrics'])
                        metrics.update(critic_output_metrics)

                    # implement critic warmup
                    if self.config.trainer.critic_warmup <= self.global_steps:
                        # update actor
                        with _timer('update_actor', timing_raw):
                            actor_output = self.actor_rollout_wg.update_actor(batch)
                        actor_output_metrics = reduce_metrics(actor_output.meta_info['metrics'])
                        metrics.update(actor_output_metrics)

                    # validate
                    if self.val_reward_fn is not None and self.config.trainer.test_freq > 0 and \
                        (is_last_step or  self.global_steps % self.config.trainer.test_freq == 0):
                        with _timer('testing', timing_raw):
                            val_metrics: dict = self._validate()
                            if is_last_step:
                                last_val_metrics = val_metrics
                        metrics.update(val_metrics)

                    if self.config.trainer.save_freq > 0 and ( is_last_step or \
                            self.global_steps % self.config.trainer.save_freq == 0):
                        with _timer('save_checkpoint', timing_raw):
                            self._save_checkpoint()

                # collect metrics
                metrics.update(compute_data_metrics(batch=batch, use_critic=self.use_critic))
                metrics.update(compute_timing_metrics(batch=batch, timing_raw=timing_raw))
                # TODO: implement actual tflpo and theoretical tflpo
                n_gpus = self.resource_pool_manager.get_n_gpus()
                metrics.update(compute_throughout_metrics(batch=batch, timing_raw=timing_raw, n_gpus=n_gpus))

                # TODO: make a canonical logger that supports various backend
                logger.log(data=metrics, step=self.global_steps)

                if is_last_step:
                    pprint(f'Final validation metrics: {last_val_metrics}')
                    return

                self.global_steps += 1
