#!/usr/bin/env python3

import argparse
import datetime
import os
import pprint

import gym
import numpy as np
import torch
from torch.utils.tensorboard import SummaryWriter

from examples.offline.utils import load_buffer_d4rl
from tianshou.data import Collector
from tianshou.env import SubprocVectorEnv
from tianshou.policy import ImitationPolicy
from tianshou.trainer import offline_trainer
from tianshou.utils import TensorboardLogger, WandbLogger
from tianshou.utils.net.common import Net
from tianshou.utils.net.continuous import Actor


def get_args():
    parser = argparse.ArgumentParser()
    parser.add_argument("--task", type=str, default="HalfCheetah-v2")
    parser.add_argument("--seed", type=int, default=0)
    parser.add_argument(
        "--expert-data-task", type=str, default="halfcheetah-expert-v2"
    )
    parser.add_argument("--hidden-sizes", type=int, nargs="*", default=[256, 256])
    parser.add_argument("--lr", type=float, default=1e-4)
    parser.add_argument("--epoch", type=int, default=200)
    parser.add_argument("--step-per-epoch", type=int, default=5000)
    parser.add_argument("--batch-size", type=int, default=256)
    parser.add_argument("--test-num", type=int, default=10)
    parser.add_argument("--logdir", type=str, default="log")
    parser.add_argument("--render", type=float, default=1 / 35)
    parser.add_argument("--gamma", default=0.99)
    parser.add_argument(
        "--device", type=str, default="cuda" if torch.cuda.is_available() else "cpu"
    )
    parser.add_argument("--resume-path", type=str, default=None)
    parser.add_argument("--resume-id", type=str, default=None)
    parser.add_argument(
        "--logger",
        type=str,
        default="tensorboard",
        choices=["tensorboard", "wandb"],
    )
    parser.add_argument("--wandb-project", type=str, default="offline_d4rl.benchmark")
    parser.add_argument(
        "--watch",
        default=False,
        action="store_true",
        help="watch the play of pre-trained policy only",
    )
    return parser.parse_args()


def test_il():
    args = get_args()
    env = gym.make(args.task)
    args.state_shape = env.observation_space.shape or env.observation_space.n
    args.action_shape = env.action_space.shape or env.action_space.n
    args.max_action = env.action_space.high[0]  # float
    print("device:", args.device)
    print("Observations shape:", args.state_shape)
    print("Actions shape:", args.action_shape)
    print("Action range:", np.min(env.action_space.low), np.max(env.action_space.high))

    args.state_dim = args.state_shape[0]
    args.action_dim = args.action_shape[0]
    print("Max_action", args.max_action)

    test_envs = SubprocVectorEnv(
        [lambda: gym.make(args.task) for _ in range(args.test_num)]
    )
    # seed
    np.random.seed(args.seed)
    torch.manual_seed(args.seed)
    test_envs.seed(args.seed)

    # model
    net = Net(
        args.state_shape,
        args.action_shape,
        hidden_sizes=args.hidden_sizes,
        device=args.device,
    )
    actor = Actor(
        net,
        action_shape=args.action_shape,
        max_action=args.max_action,
        device=args.device
    ).to(args.device)
    optim = torch.optim.Adam(actor.parameters(), lr=args.lr)

    policy = ImitationPolicy(
        actor,
        optim,
        action_space=env.action_space,
        action_scaling=True,
        action_bound_method="clip"
    )

    # load a previous policy
    if args.resume_path:
        policy.load_state_dict(torch.load(args.resume_path, map_location=args.device))
        print("Loaded agent from: ", args.resume_path)

    # collector
    test_collector = Collector(policy, test_envs)

    # log
    now = datetime.datetime.now().strftime("%y%m%d-%H%M%S")
    args.algo_name = "cql"
    log_name = os.path.join(args.task, args.algo_name, str(args.seed), now)
    log_path = os.path.join(args.logdir, log_name)

    # logger
    if args.logger == "wandb":
        logger = WandbLogger(
            save_interval=1,
            name=log_name.replace(os.path.sep, "__"),
            run_id=args.resume_id,
            config=args,
            project=args.wandb_project,
        )
    writer = SummaryWriter(log_path)
    writer.add_text("args", str(args))
    if args.logger == "tensorboard":
        logger = TensorboardLogger(writer)
    else:  # wandb
        logger.load(writer)

    def save_best_fn(policy):
        torch.save(policy.state_dict(), os.path.join(log_path, "policy.pth"))

    def watch():
        if args.resume_path is None:
            args.resume_path = os.path.join(log_path, "policy.pth")

        policy.load_state_dict(
            torch.load(args.resume_path, map_location=torch.device("cpu"))
        )
        policy.eval()
        collector = Collector(policy, env)
        collector.collect(n_episode=1, render=1 / 35)

    if not args.watch:
        replay_buffer = load_buffer_d4rl(args.expert_data_task)
        # trainer
        result = offline_trainer(
            policy,
            replay_buffer,
            test_collector,
            args.epoch,
            args.step_per_epoch,
            args.test_num,
            args.batch_size,
            save_best_fn=save_best_fn,
            logger=logger,
        )
        pprint.pprint(result)
    else:
        watch()

    # Let's watch its performance!
    policy.eval()
    test_envs.seed(args.seed)
    test_collector.reset()
    result = test_collector.collect(n_episode=args.test_num, render=args.render)
    print(f"Final reward: {result['rews'].mean()}, length: {result['lens'].mean()}")


if __name__ == "__main__":
    test_il()