import os
from io import BytesIO
import datasets
import pandas as pd
import numpy as np
import json
from astropy.io import fits

from utils.parallelzipfile import ParallelZipFile as ZipFile

_DESCRIPTION = (
    "AstroM3 is a time-series astronomy dataset containing photometry, spectra, "
    "and metadata features for variable stars. The dataset includes multiple "
    "subsets (full, sub10, sub25, sub50) and supports different random seeds (42, 66, 0, 12, 123). "
    "Each sample consists of:\n"
    "- **Photometry**: Light curve data of shape `(N, 3)` (time, flux, flux_error).\n"
    "- **Spectra**: Spectral observations of shape `(M, 3)` (wavelength, flux, flux_error).\n"
    "- **Metadata**: Auxiliary features of shape `(25,)`.\n"
    "- **Label**: The class name as a string."
)

_HOMEPAGE = "https://huggingface.co/datasets/AstroM3"
_LICENSE = "CC BY 4.0"
_URL = "https://huggingface.co/datasets/MeriDK/AstroM3Dataset/resolve/main"
_VERSION = datasets.Version("1.0.0")

_CITATION = """ 
@article{AstroM3,
  title={AstroM3: A Multi-Modal Astronomy Dataset},
  author={Your Name},
  year={2025},
  journal={AstroML Conference}
}
"""


class AstroM3Dataset(datasets.GeneratorBasedBuilder):
    """Hugging Face dataset for AstroM3 with configurable subsets and seeds."""

    DEFAULT_CONFIG_NAME = "full_42"
    BUILDER_CONFIGS = [
        datasets.BuilderConfig(name=f"{sub}_{seed}", version=_VERSION, data_dir=None)
        for sub in ["full", "sub10", "sub25", "sub50"]
        for seed in [42, 66, 0, 12, 123]
    ]

    def _info(self):
        return datasets.DatasetInfo(
            description=_DESCRIPTION,
            features=datasets.Features(
                {
                    "photometry": datasets.Sequence(datasets.Sequence(datasets.Value("float32"), length=3)),
                    "spectra": datasets.Sequence(datasets.Sequence(datasets.Value("float32"), length=3)),
                    "metadata": datasets.Sequence(datasets.Value("float32"), length=38),
                    "label": datasets.Value("string"),
                }
            ),
            homepage=_HOMEPAGE,
            license=_LICENSE,
            citation=_CITATION,
        )

    def _get_photometry(self, file_name):
        csv = BytesIO()
        file_name = file_name.replace(' ', '')
        data_path = f'vardb_files/{file_name}.dat'

        csv.write(self.reader_v.read(data_path))
        csv.seek(0)

        lc = pd.read_csv(csv, sep=r'\s+', skiprows=2, names=['HJD', 'MAG', 'MAG_ERR', 'FLUX', 'FLUX_ERR'],
                         dtype={'HJD': float, 'MAG': float, 'MAG_ERR': float, 'FLUX': float, 'FLUX_ERR': float})

        return lc[['HJD', 'FLUX', 'FLUX_ERR']].values

    @staticmethod
    def _get_spectra(file_name):
        hdulist = fits.open(file_name)
        len_list = len(hdulist)

        if len_list == 1:
            head = hdulist[0].header
            scidata = hdulist[0].data
            coeff0 = head['COEFF0']
            coeff1 = head['COEFF1']
            pixel_num = head['NAXIS1']
            specflux = scidata[0,]
            ivar = scidata[1,]
            wavelength = np.linspace(0, pixel_num - 1, pixel_num)
            wavelength = np.power(10, (coeff0 + wavelength * coeff1))
            hdulist.close()
        elif len_list == 2:
            head = hdulist[0].header
            scidata = hdulist[1].data
            wavelength = scidata[0][2]
            ivar = scidata[0][1]
            specflux = scidata[0][0]
        else:
            raise ValueError(f'Wrong number of fits files. {len_list} should be 1 or 2')

        return np.vstack((wavelength, specflux, ivar)).T

    def _split_generators(self, dl_manager):
        """Returns SplitGenerators for train, val, and test."""

        # Get subset and seed info from the name
        sub, seed = self.config.name.split("_")

        # Load the splits and info files
        urls = {
            "train": f"{_URL}/splits/{sub}/{seed}/train.csv",
            "val": f"{_URL}/splits/{sub}/{seed}/val.csv",
            "test": f"{_URL}/splits/{sub}/{seed}/test.csv",
            "info": f"{_URL}/splits/{sub}/{seed}/info.json",
        }
        extracted_path = dl_manager.download(urls)

        df1 = pd.read_csv(extracted_path["train"])
        df2 = pd.read_csv(extracted_path["val"])
        df3 = pd.read_csv(extracted_path["test"])
        df_combined = pd.concat([df1, df2, df3], ignore_index=True)

        # Load all spectra files
        spectra_urls = {}
        for _, row in df_combined.iterrows():
            spectra_urls[row["spec_filename"]] = f"{_URL}/spectra/{row['target']}/{row['spec_filename']}"
        spectra = dl_manager.download(spectra_urls)

        # Load photometry and init reader
        photometry_path = dl_manager.download(f"{_URL}/photometry.zip")
        self.reader_v = ZipFile(photometry_path)

        return [
            datasets.SplitGenerator(
                name=datasets.Split.TRAIN, gen_kwargs={"csv_path": extracted_path["train"],
                                                       "info_path": extracted_path["info"],
                                                       "spectra": spectra,
                                                       "split": "train"}
            ),
            datasets.SplitGenerator(
                name=datasets.Split.VALIDATION, gen_kwargs={"csv_path": extracted_path["val"],
                                                            "info_path": extracted_path["info"],
                                                            "spectra": spectra,
                                                            "split": "val"}
            ),
            datasets.SplitGenerator(
                name=datasets.Split.TEST, gen_kwargs={"csv_path": extracted_path["test"],
                                                      "info_path": extracted_path["info"],
                                                      "spectra": spectra,
                                                      "split": "test"}
            ),
        ]

    def _generate_examples(self, csv_path, info_path, spectra, split):
        """Yields examples from a CSV file containing photometry, spectra, metadata, and labels."""

        if not os.path.exists(csv_path):
            raise FileNotFoundError(f"Missing dataset file: {csv_path}")

        if not os.path.exists(info_path):
            raise FileNotFoundError(f"Missing info file: {info_path}")

        df = pd.read_csv(csv_path)

        with open(info_path) as f:
            info = json.loads(f.read())

        for idx, row in df.iterrows():
            photometry = self._get_photometry(row["name"])
            spectra = self._get_spectra(spectra[row["spec_filename"]])

            yield idx, {
                "photometry": photometry,
                "spectra": spectra,
                "metadata": row[info["all_cols"]],
                "label": row["target"],
            }