import logging
import os
import pathlib as Path
import random

import click
import numpy as np
import polars as pl
import torch
from model import SASRecEncoder
from torch.utils.data import DataLoader

from data import Data, TrainDataset, collate_fn, preprocess


logging.basicConfig(
    level=logging.DEBUG, format='[%(asctime)s] [%(levelname)s]: %(message)s', datefmt='%Y-%m-%d %H:%M:%S'
)
logger = logging.getLogger(__name__)


def train(
    train_dataloader: DataLoader,
    model: SASRecEncoder,
    optimizer: torch.optim.Optimizer,
    device: str = 'cpu',
    num_epochs: int = 100,
):
    logger.debug('Start training...')

    model.train()

    for epoch_num in range(num_epochs):
        logger.debug(f'Start epoch {epoch_num + 1}')
        for batch in train_dataloader:
            for key in batch.keys():
                batch[key] = batch[key].to(device)

            loss = model(batch)

            optimizer.zero_grad()
            loss.backward()
            optimizer.step()

    logger.debug('Training procedure has been finished!')
    return model.state_dict()


@click.command()
@click.option('--exp_name', required=True, type=str)
@click.option('--data_dir', required=True, type=str, default='../../data/', show_default=True)
@click.option('--checkpoint_dir', required=True, type=str, default='./checkpoints/', show_default=True)
@click.option(
    '--size',
    required=True,
    type=click.Choice(['50m', '500m', '5b']),
    default='50m',
    show_default=True,
)
@click.option(
    '--interaction',
    required=True,
    type=click.Choice(['likes', 'listens']),
    default='likes',
    show_default=True,
)
@click.option('--batch_size', required=True, type=int, default=256, show_default=True)
@click.option('--max_seq_len', required=False, type=int, default=200, show_default=True)
@click.option('--embedding_dim', required=False, type=int, default=64, show_default=True)
@click.option('--num_heads', required=False, type=int, default=2, show_default=True)
@click.option('--num_layers', required=False, type=int, default=2, show_default=True)
@click.option('--learning_rate', required=False, type=float, default=1e-3, show_default=True)
@click.option('--dropout', required=False, type=float, default=0.0, show_default=True)
@click.option('--seed', required=False, type=int, default=42, show_default=True)
@click.option('--device', required=True, type=str, default='cuda:0', show_default=True)
@click.option('--num_epochs', required=True, type=int, default=100, show_default=True)
def main(
    exp_name: str,
    data_dir: str,
    checkpoint_dir: str,
    size: str,
    interaction: str,
    batch_size: int,
    max_seq_len: int,
    embedding_dim: int,
    num_heads: int,
    num_layers: int,
    learning_rate: float,
    dropout: float,
    seed: int,
    device: str,
    num_epochs: int,
):
    random.seed(seed)
    np.random.seed(seed)
    torch.manual_seed(seed)
    torch.cuda.manual_seed_all(seed)
    torch.set_float32_matmul_precision('high')

    data_path = Path.Path(data_dir) / 'sequential' / size / interaction
    df = pl.scan_parquet(data_path.with_suffix('.parquet'))

    checkpoint_path = Path.Path(checkpoint_dir) / f'{exp_name}_best_state.pth'
    os.makedirs(checkpoint_dir, exist_ok=True)

    logger.debug('Preprocessing data...')
    data: Data = preprocess(df, interaction, val_size=0, max_seq_len=max_seq_len)
    train_df = data.train.collect(engine="streaming")
    logger.debug('Preprocessing data has finished!')

    train_dataset = TrainDataset(dataset=train_df, num_items=data.num_items, max_seq_len=max_seq_len)

    train_dataloader = DataLoader(
        dataset=train_dataset,
        batch_size=batch_size,
        collate_fn=collate_fn,
        drop_last=True,
        shuffle=True,
        num_workers=3,
        prefetch_factor=10,
        pin_memory_device="cuda",
        pin_memory=True,
    )

    model = SASRecEncoder(
        num_items=data.num_items,
        max_sequence_length=max_seq_len,
        embedding_dim=embedding_dim,
        num_heads=num_heads,
        num_layers=num_layers,
        dropout=dropout,
    ).to(device)

    optimizer = torch.optim.Adam(model.parameters(), lr=learning_rate)

    best_checkpoint = train(
        train_dataloader=train_dataloader, model=model, optimizer=optimizer, device=device, num_epochs=num_epochs
    )

    logger.debug('Saving model...')

    os.makedirs(checkpoint_dir, exist_ok=True)

    model.load_state_dict(best_checkpoint)
    torch.save(model, checkpoint_path)
    logger.debug(f'Saved model as {checkpoint_path}')


if __name__ == '__main__':
    main()