import os
import re
from PIL import Image
from typing import Tuple
import torch
from torch.utils.data import DataLoader
from a3.annotation import read_groundtruth_file
from torchvision import transforms


class MMP_Dataset(torch.utils.data.Dataset):
    """Exercise 3.2"""

    def __init__(self, path_to_data: str, image_size: int):
        """
        @param path_to_data: Path to the folder that contains the images and annotation files, e.g. dataset_mmp/train
        @param image_size: Desired image size that this dataset should return
        """
        self.image_size = image_size
        img_pattern = re.compile(r'^(\d+)\.jpg$')
        files = set(os.listdir(path_to_data))
        self.images = []

        for fname in files:
            match = img_pattern.match(fname)
            if match:
                img_file = os.path.join(path_to_data, fname)
                annotations = read_groundtruth_file(os.path.join(
                    path_to_data, f"{match.group(1)}.gt_data.txt"))
                self.images.append((img_file, annotations))

        self.images.sort(key=lambda x: int(
            re.match(r"(.*/)(\d+)(\.jpg)", x[0]).group(2)))

    def __getitem__(self, idx: int) -> Tuple[torch.Tensor, int]:
        """
        @return: Tuple of image tensor and label. The label is 0 if there is one person and 1 if there a multiple people.
        """
        img = Image.open(self.images[idx][0]).convert("RGB")
        padding = self.__padding__(img)
        transform = transforms.Compose([
            transforms.Pad(padding, 0),
            transforms.Resize((self.image_size, self.image_size)),
            transforms.ToTensor(),
            transforms.Normalize(
                mean=[0.485, 0.456, 0.406],
                std=[0.229, 0.224, 0.225]
            )
        ])
        return (transform(img), 1 if len(self.images[idx][1]) > 1 else 0)

    def __padding__(self, img) -> Tuple[int, int, int, int]:
        w, h = img.size
        size = max(w, h)
        right_pad = size - w
        bottom_pad = size - h
        return (0, 0, right_pad, bottom_pad)

    def __len__(self) -> int:
        return len(self.images)


def get_dataloader(
        path_to_data: str, image_size: int, batch_size: int, num_workers: int, is_train: bool = True
) -> DataLoader:
    """Exercise 3.2d"""
    path = os.path.join(path_to_data, "train") if is_train else os.path.join(
        path_to_data, "val")
    dataset = MMP_Dataset(path_to_data=path, image_size=image_size)
    dataloader = DataLoader(
        dataset, batch_size=batch_size,
        shuffle=is_train,
        num_workers=num_workers,
        pin_memory=True
    )
    return dataloader