import enum
import functools
import io
import pathlib
from typing import Any, Callable, Dict, List, Optional, Tuple

import torch
from torchdata.datapipes.iter import IterDataPipe, Mapper, Filter, IterKeyZipper, Demultiplexer, CSVDictParser
from torchvision.prototype.datasets.utils import (
    Dataset,
    DatasetConfig,
    DatasetInfo,
    HttpResource,
    OnlineResource,
    DatasetType,
)
from torchvision.prototype.datasets.utils._internal import (
    INFINITE_BUFFER_SIZE,
    hint_sharding,
    hint_shuffling,
    getitem,
    path_accessor,
    path_comparator,
)
from torchvision.prototype.features import Label


class OxfordIITPetDemux(enum.IntEnum):
    SPLIT_AND_CLASSIFICATION = 0
    SEGMENTATIONS = 1


class OxfordIITPet(Dataset):
    def _make_info(self) -> DatasetInfo:
        return DatasetInfo(
            "oxford-iiit-pet",
            type=DatasetType.IMAGE,
            homepage="https://www.robots.ox.ac.uk/~vgg/data/pets/",
            valid_options=dict(
                # FIXME
                split=("trainval", "test", "train"),
            ),
        )

    def resources(self, config: DatasetConfig) -> List[OnlineResource]:
        images = HttpResource(
            "https://www.robots.ox.ac.uk/~vgg/data/pets/data/images.tar.gz",
            sha256="67195c5e1c01f1ab5f9b6a5d22b8c27a580d896ece458917e61d459337fa318d",
            decompress=True,
        )
        anns = HttpResource(
            "https://www.robots.ox.ac.uk/~vgg/data/pets/data/annotations.tar.gz",
            sha256="52425fb6de5c424942b7626b428656fcbd798db970a937df61750c0f1d358e91",
            decompress=True,
        )
        return [images, anns]

    def _classify_anns(self, data: Tuple[str, Any]) -> Optional[int]:
        return {
            "annotations": OxfordIITPetDemux.SPLIT_AND_CLASSIFICATION,
            "trimaps": OxfordIITPetDemux.SEGMENTATIONS,
        }.get(pathlib.Path(data[0]).parent.name)

    def _filter_images(self, data: Tuple[str, Any]) -> bool:
        return pathlib.Path(data[0]).suffix == ".jpg"

    def _filter_segmentations(self, data: Tuple[str, Any]) -> bool:
        return not pathlib.Path(data[0]).name.startswith(".")

    def _decode_classification_data(self, data: Dict[str, str]) -> Dict[str, Any]:
        label_idx = int(data["label"]) - 1
        return dict(
            label=Label(label_idx, category=self.info.categories[label_idx]),
            species="cat" if data["species"] == "1" else "dog",
        )

    def _collate_and_decode_sample(
        self,
        data: Tuple[Tuple[Dict[str, str], Tuple[str, io.IOBase]], Tuple[str, io.IOBase]],
        *,
        decoder: Optional[Callable[[io.IOBase], torch.Tensor]],
    ) -> Dict[str, Any]:
        ann_data, image_data = data
        classification_data, segmentation_data = ann_data
        segmentation_path, segmentation_buffer = segmentation_data
        image_path, image_buffer = image_data

        return dict(
            self._decode_classification_data(classification_data),
            segmentation_path=segmentation_path,
            segmentation=decoder(segmentation_buffer) if decoder else segmentation_buffer,
            image_path=image_path,
            image=decoder(image_buffer) if decoder else image_buffer,
        )

    def _make_datapipe(
        self,
        resource_dps: List[IterDataPipe],
        *,
        config: DatasetConfig,
        decoder: Optional[Callable[[io.IOBase], torch.Tensor]],
    ) -> IterDataPipe[Dict[str, Any]]:
        images_dp, anns_dp = resource_dps

        images_dp = Filter(images_dp, self._filter_images)

        split_and_classification_dp, segmentations_dp = Demultiplexer(
            anns_dp,
            2,
            self._classify_anns,
            drop_none=True,
            buffer_size=INFINITE_BUFFER_SIZE,
        )

        split_and_classification_dp = Filter(
            split_and_classification_dp, path_comparator("name", f"{config.split}.txt")
        )
        split_and_classification_dp = CSVDictParser(
            split_and_classification_dp, fieldnames=("image_id", "label", "species"), delimiter=" "
        )
        split_and_classification_dp = hint_sharding(split_and_classification_dp)
        split_and_classification_dp = hint_shuffling(split_and_classification_dp)

        segmentations_dp = Filter(segmentations_dp, self._filter_segmentations)

        anns_dp = IterKeyZipper(
            split_and_classification_dp,
            segmentations_dp,
            key_fn=getitem("image_id"),
            ref_key_fn=path_accessor("stem"),
            buffer_size=INFINITE_BUFFER_SIZE,
        )

        dp = IterKeyZipper(
            anns_dp,
            images_dp,
            key_fn=getitem(0, "image_id"),
            ref_key_fn=path_accessor("stem"),
            buffer_size=INFINITE_BUFFER_SIZE,
        )
        return Mapper(dp, functools.partial(self._collate_and_decode_sample, decoder=decoder))

    def _filter_split_and_classification_anns(self, data: Tuple[str, Any]) -> bool:
        return self._classify_anns(data) == OxfordIITPetDemux.SPLIT_AND_CLASSIFICATION

    def _generate_categories(self, root: pathlib.Path) -> List[str]:
        config = self.default_config
        resources = self.resources(config)

        dp = resources[1].load(root)
        dp = Filter(dp, self._filter_split_and_classification_anns)
        dp = Filter(dp, path_comparator("name", f"{config.split}.txt"))
        dp = CSVDictParser(dp, fieldnames=("image_id", "label"), delimiter=" ")

        raw_categories_and_labels = {(data["image_id"].rsplit("_", 1)[0], data["label"]) for data in dp}
        raw_categories, _ = zip(
            *sorted(raw_categories_and_labels, key=lambda raw_category_and_label: int(raw_category_and_label[1]))
        )
        return [" ".join(part.title() for part in raw_category.split("_")) for raw_category in raw_categories]
