import isaacgym

import torch
import torch.nn as nn

# import the skrl components to build the RL system
from skrl.envs.loaders.torch import load_bidexhands_env
from skrl.envs.wrappers.torch import wrap_env
from skrl.memories.torch import RandomMemory
from skrl.models.torch import DeterministicMixin, GaussianMixin, Model
from skrl.multi_agents.torch.ippo import IPPO, IPPO_DEFAULT_CONFIG
from skrl.resources.preprocessors.torch import RunningStandardScaler
from skrl.resources.schedulers.torch import KLAdaptiveRL
from skrl.trainers.torch import SequentialTrainer
from skrl.utils import set_seed


# seed for reproducibility
set_seed()  # e.g. `set_seed(42)` for fixed seed


# define models (stochastic and deterministic models) using mixins
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, reduction="sum"):
        Model.__init__(self, observation_space, action_space, device)
        GaussianMixin.__init__(self, clip_actions, clip_log_std, min_log_std, max_log_std, reduction)

        self.net = nn.Sequential(nn.Linear(self.num_observations, 512),
                                 nn.ELU(),
                                 nn.Linear(512, 256),
                                 nn.ELU(),
                                 nn.Linear(256, 128),
                                 nn.ELU(),
                                 nn.Linear(128, 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, 512),
                                 nn.ELU(),
                                 nn.Linear(512, 256),
                                 nn.ELU(),
                                 nn.Linear(256, 128),
                                 nn.ELU(),
                                 nn.Linear(128, 1))

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


# load and wrap the environment
env = load_bidexhands_env(task_name="ShadowHandOver")
env = wrap_env(env, wrapper="bidexhands")

device = env.device


# instantiate memories as rollout buffer (any memory can be used for this)
memories = {}
for agent_name in env.possible_agents:
    memories[agent_name] = RandomMemory(memory_size=24, num_envs=env.num_envs, device=device)


# instantiate the agent's models (function approximators).
# IPPO requires 2 models, visit its documentation for more details
# https://skrl.readthedocs.io/en/latest/api/multi_agents/ippo.html#models
models = {}
for agent_name in env.possible_agents:
    models[agent_name] = {}
    models[agent_name]["policy"] = Policy(env.observation_space(agent_name), env.action_space(agent_name), device)
    models[agent_name]["value"] = Value(env.observation_space(agent_name), env.action_space(agent_name), device)


# configure and instantiate the agent (visit its documentation to see all the options)
# https://skrl.readthedocs.io/en/latest/api/multi_agents/ippo.html#configuration-and-hyperparameters
cfg = IPPO_DEFAULT_CONFIG.copy()
cfg["rollouts"] = 24  # memory_size
cfg["learning_epochs"] = 5
cfg["mini_batches"] = 6  # 24 * 4096 / 16384
cfg["discount_factor"] = 0.99
cfg["lambda"] = 0.95
cfg["learning_rate"] = 3e-4
cfg["learning_rate_scheduler"] = KLAdaptiveRL
cfg["learning_rate_scheduler_kwargs"] = {"kl_threshold": 0.008}
cfg["random_timesteps"] = 0
cfg["learning_starts"] = 0
cfg["grad_norm_clip"] = 1.0
cfg["ratio_clip"] = 0.2
cfg["value_clip"] = 0.2
cfg["clip_predicted_values"] = True
cfg["entropy_loss_scale"] = 0.001
cfg["value_loss_scale"] = 1.0
cfg["kl_threshold"] = 0
cfg["state_preprocessor"] = RunningStandardScaler
cfg["state_preprocessor_kwargs"] = {"size": next(iter(env.observation_spaces.values())), "device": device}
cfg["value_preprocessor"] = RunningStandardScaler
cfg["value_preprocessor_kwargs"] = {"size": 1, "device": device}
# logging to TensorBoard and write checkpoints (in timesteps)
cfg["experiment"]["write_interval"] = 180
cfg["experiment"]["checkpoint_interval"] = 1800
cfg["experiment"]["directory"] = "runs/torch/ShadowHandOver"

agent = IPPO(possible_agents=env.possible_agents,
             models=models,
             memories=memories,
             cfg=cfg,
             observation_spaces=env.observation_spaces,
             action_spaces=env.action_spaces,
             device=device)


# configure and instantiate the RL trainer
cfg_trainer = {"timesteps": 36000, "headless": True}
trainer = SequentialTrainer(cfg=cfg_trainer, env=env, agents=agent)

# start training
trainer.train()