import isaacgym

import torch
import torch.nn as nn

# Import the skrl components to build the RL system
from skrl.models.torch import Model, GaussianMixin, DeterministicMixin
from skrl.memories.torch import RandomMemory
from skrl.agents.torch.ppo import PPO, PPO_DEFAULT_CONFIG
from skrl.resources.schedulers.torch import KLAdaptiveRL
from skrl.resources.preprocessors.torch import RunningStandardScaler
from skrl.trainers.torch import SequentialTrainer
from skrl.envs.torch import wrap_env
from skrl.utils import set_seed


# set the seed for reproducibility
set_seed(42)


# Define the models (stochastic and deterministic models) for the agent using helper mixin.
# - Policy: takes as input the environment's observation/state and returns an action
# - Value: takes the state as input and provides a value to guide the policy
class Policy(GaussianMixin, Model):
    def __init__(self, observation_space, action_space, device, clip_actions=False,
                 clip_log_std=True, min_log_std=-20, max_log_std=2):
        Model.__init__(self, observation_space, action_space, device)
        GaussianMixin.__init__(self, clip_actions, clip_log_std, min_log_std, max_log_std)

        self.net = nn.Sequential(nn.Linear(self.num_observations, 256),
                                 nn.ELU(),
                                 nn.Linear(256, 128),
                                 nn.ELU(),
                                 nn.Linear(128, 64),
                                 nn.ELU(),
                                 nn.Linear(64, self.num_actions))
        self.log_std_parameter = nn.Parameter(torch.zeros(self.num_actions))

    def compute(self, inputs, role):
        return self.net(inputs["states"]), self.log_std_parameter, {}

class Value(DeterministicMixin, Model):
    def __init__(self, observation_space, action_space, device, clip_actions=False):
        Model.__init__(self, observation_space, action_space, device)
        DeterministicMixin.__init__(self, clip_actions)

        self.net = nn.Sequential(nn.Linear(self.num_observations, 256),
                                 nn.ELU(),
                                 nn.Linear(256, 128),
                                 nn.ELU(),
                                 nn.Linear(128, 64),
                                 nn.ELU(),
                                 nn.Linear(64, 1))

    def compute(self, inputs, role):
        return self.net(inputs["states"]), {}


# instantiate and configure the task
headless = True  # set headless to False for rendering

from reaching_franka_isaacgym_env import ReachingFrankaTask, TASK_CFG

TASK_CFG["headless"] = headless
TASK_CFG["env"]["numEnvs"] = 1024
TASK_CFG["env"]["controlSpace"] = "joint"  # "joint" or "cartesian"

env = ReachingFrankaTask(cfg=TASK_CFG)

# wrap the environment
env = wrap_env(env, "isaacgym-preview4")

device = env.device


# Instantiate a RandomMemory as rollout buffer (any memory can be used for this)
memory = RandomMemory(memory_size=16, num_envs=env.num_envs, device=device)


# Instantiate the agent's models (function approximators).
# PPO requires 2 models, visit its documentation for more details
# https://skrl.readthedocs.io/en/latest/modules/skrl.agents.ppo.html#spaces-and-models
models_ppo = {}
models_ppo["policy"] = Policy(env.observation_space, env.action_space, device)
models_ppo["value"] = Value(env.observation_space, env.action_space, device)


# Configure and instantiate the agent.
# Only modify some of the default configuration, visit its documentation to see all the options
# https://skrl.readthedocs.io/en/latest/modules/skrl.agents.ppo.html#configuration-and-hyperparameters
cfg_ppo = PPO_DEFAULT_CONFIG.copy()
cfg_ppo["rollouts"] = 16
cfg_ppo["learning_epochs"] = 8
cfg_ppo["mini_batches"] = 8
cfg_ppo["discount_factor"] = 0.99
cfg_ppo["lambda"] = 0.95
cfg_ppo["learning_rate"] = 5e-4
cfg_ppo["learning_rate_scheduler"] = KLAdaptiveRL
cfg_ppo["learning_rate_scheduler_kwargs"] = {"kl_threshold": 0.008}
cfg_ppo["random_timesteps"] = 0
cfg_ppo["learning_starts"] = 0
cfg_ppo["grad_norm_clip"] = 1.0
cfg_ppo["ratio_clip"] = 0.2
cfg_ppo["value_clip"] = 0.2
cfg_ppo["clip_predicted_values"] = True
cfg_ppo["entropy_loss_scale"] = 0.0
cfg_ppo["value_loss_scale"] = 2.0
cfg_ppo["kl_threshold"] = 0
cfg_ppo["state_preprocessor"] = RunningStandardScaler
cfg_ppo["state_preprocessor_kwargs"] = {"size": env.observation_space, "device": device}
cfg_ppo["value_preprocessor"] = RunningStandardScaler
cfg_ppo["value_preprocessor_kwargs"] = {"size": 1, "device": device}
# logging to TensorBoard and write checkpoints each 32 and 250 timesteps respectively
cfg_ppo["experiment"]["write_interval"] = 5
cfg_ppo["experiment"]["checkpoint_interval"] = 250

agent = PPO(models=models_ppo,
            memory=memory,
            cfg=cfg_ppo,
            observation_space=env.observation_space,
            action_space=env.action_space,
            device=device)


# Configure and instantiate the RL trainer
cfg_trainer = {"timesteps": 5000, "headless": True}
trainer = SequentialTrainer(cfg=cfg_trainer, env=env, agents=agent)

# start training
trainer.train()