##################################################
# Copyright (c) Xuanyi Dong [GitHub D-X-Y], 2021 #
##################################################
from __future__ import division
from __future__ import print_function

import os, math, random
from collections import OrderedDict
import numpy as np
import pandas as pd
import copy
from functools import partial
from typing import Optional, Text

from qlib.utils import (
    unpack_archive_with_buffer,
    save_multiple_parts_file,
    get_or_create_path,
    drop_nan_by_y_index,
)
from qlib.log import get_module_logger

import torch
import torch.nn.functional as F
import torch.optim as optim
import torch.utils.data as th_data

from log_utils import AverageMeter
from utils import count_parameters
from trade_models.transformers import DEFAULT_NET_CONFIG
from trade_models.transformers import get_transformer


from qlib.model.base import Model
from qlib.data.dataset import DatasetH
from qlib.data.dataset.handler import DataHandlerLP


DEFAULT_OPT_CONFIG = dict(
    epochs=200, lr=0.001, batch_size=2000, early_stop=20, loss="mse", optimizer="adam", num_workers=4
)


class QuantTransformer(Model):
    """Transformer-based Quant Model"""

    def __init__(self, net_config=None, opt_config=None, metric="", GPU=0, seed=None, **kwargs):
        # Set logger.
        self.logger = get_module_logger("QuantTransformer")
        self.logger.info("QuantTransformer PyTorch version...")

        # set hyper-parameters.
        self.net_config = net_config or DEFAULT_NET_CONFIG
        self.opt_config = opt_config or DEFAULT_OPT_CONFIG
        self.metric = metric
        self.device = torch.device("cuda:{:}".format(GPU) if torch.cuda.is_available() and GPU >= 0 else "cpu")
        self.seed = seed

        self.logger.info(
            "Transformer parameters setting:"
            "\nnet_config : {:}"
            "\nopt_config : {:}"
            "\nmetric     : {:}"
            "\ndevice     : {:}"
            "\nseed       : {:}".format(
                self.net_config,
                self.opt_config,
                self.metric,
                self.device,
                self.seed,
            )
        )

        if self.seed is not None:
            random.seed(self.seed)
            np.random.seed(self.seed)
            torch.manual_seed(self.seed)
            if self.use_gpu:
                torch.cuda.manual_seed(self.seed)
                torch.cuda.manual_seed_all(self.seed)

        self.model = get_transformer(self.net_config)
        self.logger.info("model: {:}".format(self.model))
        self.logger.info("model size: {:.3f} MB".format(count_parameters(self.model)))

        if self.opt_config["optimizer"] == "adam":
            self.train_optimizer = optim.Adam(self.model.parameters(), lr=self.opt_config["lr"])
        elif self.opt_config["optimizer"] == "adam":
            self.train_optimizer = optim.SGD(self.model.parameters(), lr=self.opt_config["lr"])
        else:
            raise NotImplementedError("optimizer {:} is not supported!".format(optimizer))

        self.fitted = False
        self.model.to(self.device)

    @property
    def use_gpu(self):
        return self.device != torch.device("cpu")

    def loss_fn(self, pred, label):
        mask = ~torch.isnan(label)
        if self.opt_config["loss"] == "mse":
            return F.mse_loss(pred[mask], label[mask])
        else:
            raise ValueError("unknown loss `{:}`".format(self.loss))

    def metric_fn(self, pred, label):
        # the metric score : higher is better
        if self.metric == "" or self.metric == "loss":
            return -self.loss_fn(pred, label)
        else:
            raise ValueError("unknown metric `{:}`".format(self.metric))

    def train_or_test_epoch(self, xloader, model, loss_fn, metric_fn, is_train, optimizer=None):
        if is_train:
            model.train()
        else:
            model.eval()
        score_meter, loss_meter = AverageMeter(), AverageMeter()
        for ibatch, (feats, labels) in enumerate(xloader):
            feats = feats.to(self.device, non_blocking=True)
            labels = labels.to(self.device, non_blocking=True)
            # forward the network
            preds = model(feats)
            loss = loss_fn(preds, labels)
            with torch.no_grad():
                score = self.metric_fn(preds, labels)
                loss_meter.update(loss.item(), feats.size(0))
                score_meter.update(score.item(), feats.size(0))
            # optimize the network
            if is_train and optimizer is not None:
                optimizer.zero_grad()
                loss.backward()
                torch.nn.utils.clip_grad_value_(model.parameters(), 3.0)
                optimizer.step()
        return loss_meter.avg, score_meter.avg

    def fit(
        self,
        dataset: DatasetH,
        save_path: Optional[Text] = None,
    ):
        def _prepare_dataset(df_data):
            return th_data.TensorDataset(
                torch.from_numpy(df_data["feature"].values).float(),
                torch.from_numpy(df_data["label"].values).squeeze().float(),
            )

        def _prepare_loader(dataset, shuffle):
            return th_data.DataLoader(
                dataset,
                batch_size=self.opt_config["batch_size"],
                drop_last=False,
                pin_memory=True,
                num_workers=self.opt_config["num_workers"],
                shuffle=shuffle,
            )

        df_train, df_valid, df_test = dataset.prepare(
            ["train", "valid", "test"],
            col_set=["feature", "label"],
            data_key=DataHandlerLP.DK_L,
        )
        train_dataset, valid_dataset, test_dataset = (
            _prepare_dataset(df_train),
            _prepare_dataset(df_valid),
            _prepare_dataset(df_test),
        )
        train_loader, valid_loader, test_loader = (
            _prepare_loader(train_dataset, True),
            _prepare_loader(valid_dataset, False),
            _prepare_loader(test_dataset, False),
        )

        save_path = get_or_create_path(save_path, return_dir=True)
        self.logger.info("Fit procedure for [{:}] with save path={:}".format(self.__class__.__name__, save_path))

        def _internal_test(ckp_epoch=None, results_dict=None):
            with torch.no_grad():
                train_loss, train_score = self.train_or_test_epoch(
                    train_loader, self.model, self.loss_fn, self.metric_fn, False, None
                )
                valid_loss, valid_score = self.train_or_test_epoch(
                    valid_loader, self.model, self.loss_fn, self.metric_fn, False, None
                )
                test_loss, test_score = self.train_or_test_epoch(
                    test_loader, self.model, self.loss_fn, self.metric_fn, False, None
                )
                xstr = "train-score={:.6f}, valid-score={:.6f}, test-score={:.6f}".format(
                    train_score, valid_score, test_score
                )
                if ckp_epoch is not None and isinstance(results_dict, dict):
                    results_dict["train"][ckp_epoch] = train_score
                    results_dict["valid"][ckp_epoch] = valid_score
                    results_dict["test"][ckp_epoch] = test_score
                return dict(train=train_score, valid=valid_score, test=test_score), xstr

        # Pre-fetch the potential checkpoints
        ckp_path = os.path.join(save_path, "{:}.pth".format(self.__class__.__name__))
        if os.path.exists(ckp_path):
            ckp_data = torch.load(ckp_path)
            import pdb

            pdb.set_trace()
        else:
            stop_steps, best_score, best_epoch = 0, -np.inf, -1
            start_epoch = 0
            results_dict = dict(train=OrderedDict(), valid=OrderedDict(), test=OrderedDict())
            _, eval_str = _internal_test(-1, results_dict)
            self.logger.info("Training from scratch, metrics@start: {:}".format(eval_str))

        for iepoch in range(start_epoch, self.opt_config["epochs"]):
            self.logger.info(
                "Epoch={:03d}/{:03d} ::==>> Best valid @{:03d} ({:.6f})".format(
                    iepoch, self.opt_config["epochs"], best_epoch, best_score
                )
            )

            train_loss, train_score = self.train_or_test_epoch(
                train_loader, self.model, self.loss_fn, self.metric_fn, True, self.train_optimizer
            )
            self.logger.info("Training :: loss={:.6f}, score={:.6f}".format(train_loss, train_score))

            current_eval_scores, eval_str = _internal_test(iepoch, results_dict)
            self.logger.info("Evaluating :: {:}".format(eval_str))

            if current_eval_scores["valid"] > best_score:
                stop_steps, best_epoch, best_score = 0, iepoch, current_eval_scores["valid"]
                best_param = copy.deepcopy(self.model.state_dict())
            else:
                stop_steps += 1
                if stop_steps >= self.opt_config["early_stop"]:
                    self.logger.info("early stop at {:}-th epoch, where the best is @{:}".format(iepoch, best_epoch))
                    break
            save_info = dict(
                net_config=self.net_config,
                opt_config=self.opt_config,
                net_state_dict=self.model.state_dict(),
                opt_state_dict=self.train_optimizer.state_dict(),
                best_param=best_param,
                stop_steps=stop_steps,
                best_score=best_score,
                best_epoch=best_epoch,
                start_epoch=iepoch + 1,
            )
            torch.save(save_info, ckp_path)
        self.logger.info("The best score: {:.6f} @ {:02d}-th epoch".format(best_score, best_epoch))
        self.model.load_state_dict(best_param)

        if self.use_gpu:
            torch.cuda.empty_cache()
        self.fitted = True

    def predict(self, dataset):
        if not self.fitted:
            raise ValueError("The model is not fitted yet!")
        x_test = dataset.prepare("test", col_set="feature")
        index = x_test.index

        self.model.eval()
        x_values = x_test.values
        sample_num, batch_size = x_values.shape[0], self.opt_config["batch_size"]
        preds = []

        for begin in range(sample_num)[::batch_size]:

            if sample_num - begin < batch_size:
                end = sample_num
            else:
                end = begin + batch_size

            x_batch = torch.from_numpy(x_values[begin:end]).float().to(self.device)

            with torch.no_grad():
                pred = self.model(x_batch).detach().cpu().numpy()
            preds.append(pred)

        return pd.Series(np.concatenate(preds), index=index)