import os
import json
import shutil
import tifffile
import datasets

import pandas as pd
import numpy as np

from PIL import Image

S2_MEAN = [414.02531376, 318.62204958, 245.42788408]

S2_STD = [106.80525378,  90.46894665,  96.68293436]

class FBPDataset(datasets.GeneratorBasedBuilder):
    VERSION = datasets.Version("1.0.0")
    
    DATA_URL = "https://huggingface.co/datasets/yuxuanw8/FBP/resolve/main/Five-Billion-Pixels.zip" 

    metadata = {
        "s2c": {
            "bands": ["B2", "B3", "B4"],
            "channel_wv": [492.4, 559.8, 664.6],
            "mean": S2_MEAN,
            "std": S2_STD,
        },
        "s1": {
            "bands": None,
            "channel_wv": None,
            "mean": None,
            "std": None   
        }
    }

    SIZE = HEIGHT = WIDTH = 96

    spatial_resolution = 4

    NUM_CLASSES = 25

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)


    def _info(self):
        metadata = self.metadata
        metadata['size'] = self.SIZE
        metadata['num_classes'] = self.NUM_CLASSES
        metadata['spatial_resolution'] = self.spatial_resolution
        return datasets.DatasetInfo(
            description=json.dumps(metadata),
            features=datasets.Features({
                "optical": datasets.Array3D(shape=(3, self.HEIGHT, self.WIDTH), dtype="float32"),
                "label": datasets.Array2D(shape=(self.HEIGHT, self.WIDTH), dtype="int32"),
                "optical_channel_wv": datasets.Sequence(datasets.Value("float32")),
                "spatial_resolution": datasets.Value("int32"),
            }),
        )
    
    def _split_generators(self, dl_manager):
        if isinstance(self.DATA_URL, list):
            downloaded_files = dl_manager.download(self.DATA_URL)
            combined_file = os.path.join(dl_manager.download_config.cache_dir, "combined.tar.gz")        
            with open(combined_file, 'wb') as outfile:
                for part_file in downloaded_files:
                    with open(part_file, 'rb') as infile:
                        shutil.copyfileobj(infile, outfile)
            data_dir = dl_manager.extract(combined_file)
            os.remove(combined_file)
        else:
            data_dir = dl_manager.download_and_extract(self.DATA_URL)

        return [
            datasets.SplitGenerator(
                name="train",
                gen_kwargs={
                    "split": 'train',
                    "data_dir": data_dir, 
                },
            ),
            datasets.SplitGenerator(
                name="val",
                gen_kwargs={
                    "split": 'val',
                    "data_dir": data_dir,
                },
            ),
            datasets.SplitGenerator(
                name="test",
                gen_kwargs={
                    "split": 'test',
                    "data_dir": data_dir,
                },
            )
        ]

    def _generate_examples(self, split, data_dir):
        optical_channel_wv = self.metadata["s2c"]["channel_wv"]
        spatial_resolution = self.spatial_resolution

        data_dir = os.path.join(data_dir, "Five-Billion-Pixels")
        metadata = pd.read_csv(os.path.join(data_dir, "metadata.csv"))
        metadata = metadata[metadata["split"] == split].reset_index(drop=True)

        for index, row in metadata.iterrows():
            optical_path = os.path.join(data_dir, row.img_path)
            optical = self._read_image(optical_path).astype(np.float32) # CxHxW

            label_path = os.path.join(data_dir, row.label_path)
            label = self._read_label(label_path).astype(np.int32)

            sample = {
                "optical": optical,
                "optical_channel_wv": optical_channel_wv,
                "label": label,
                "spatial_resolution": spatial_resolution,
            }

            yield f"{index}", sample

    def _read_image(self, image_path):
        """Read tiff image from image_path
        Args:
            image_path: 
                Image path to read from
        Return:
            image: 
                C, H, W numpy array image
        """
        image = tifffile.imread(image_path) # B, G, R, Nir
        image = image[:, :, :3] # B, G, R
        image = np.transpose(image, (2, 0, 1)) # C, H, W

        return image

    def _read_label(self, label_path):
        """Read label image from label_path
        Args:
            label_path: 
                Label path to read from
        Return:
            label: 
                H, W numpy array label
        """
        label = Image.open(label_path)
        label = np.array(label, dtype=np.int32)

        return label