import os, h5py, numpy as np
from utils.io import from_npy
from split_dataset import split
from ..helpers.app_settings import get_app_settings

meta_dtype = np.dtype(
    [
        ("rec_id", "S256"),
        ("snippet_idx", np.int32),
        ("modulation", "S32"),
        ("snr", np.int32),
        ("beta", np.float32),
        ("sps", np.int32),
    ]
)

info_dtype = np.dtype(
    [
        ("num_records", np.int32),
        ("dataset_name", "S64"),  # up to 64‐byte UTF-8 strings
        ("creator", "S64"),
    ]
)


def write_hdf5_file(records, output_path, dataset_name="data"):
    """
    Writes a list of records to an HDF5 file.
    Parameters:
        records (list): List of records to be written to the file
        output_path (str): Path to the output HDF5 file
        dataset_name (str): Name of the dataset in the HDF5 file (default: "data")
    Returns:
        str: Path to the created HDF5 file
    """
    meta_arr = np.empty(len(records), dtype=meta_dtype)
    for i, (_, md) in enumerate(records):
        meta_arr[i] = (
            md["rec_id"].encode("utf-8"),
            md["snippet_idx"],
            md["modulation"].encode("utf-8"),
            int(md["snr"]),
            float(md["beta"]),
            int(md["sps"]),
        )

    first_rec, _ = records[0]  # records[0] is a tuple of (data, md)
    sample = first_rec
    shape, dtype = sample.shape, sample.dtype

    with h5py.File(output_path, "w") as hf:
        dset = hf.create_dataset(
            dataset_name, shape=(len(records),) + shape, dtype=dtype, compression="gzip"
        )

        for idx, (snip, md) in enumerate(records):
            dset[idx, ...] = snip

        mg = hf.create_group("metadata")
        mg.create_dataset("metadata", data=meta_arr, compression="gzip")

        print(dset.shape, f"snippets created in {dataset_name}")

        info_arr = np.array(
            [
                (
                    len(records),
                    dataset_name.encode("utf-8"),
                    b"generate_dataset.py",  # already bytes
                )
            ],
            dtype=info_dtype,
        )

        mg.create_dataset("dataset_info", data=info_arr)

    return output_path


def split_recording(recording_list, num_snippets):
    """
    Splits a list of recordings into smaller chunks.

    Parameters:
        recording_list (list): List of recordings to be split

    Returns: yeah yeah
        list: List of split recordings
    """
    snippet_list = []

    for data, md in recording_list:
        C, N = data.shape
        L = N // num_snippets
        for i in range(num_snippets):
            start = i * L
            end = (i + 1) * L
            snippet = data[:, start:end]
            # copy the metadata, adding a snippet index
            snippet_md = md.copy()
            snippet_md["snippet_idx"] = i
            snippet_list.append((snippet, snippet_md))
    return snippet_list


def generate_datasets(cfg):
    """
    Generates a dataset from a folder of .npy files and saves it to an HDF5 file

    Parameters:
        path_to_recordings (str): Path to the folder containing .npy files
        output_path (str): Path to the output HDF5 file
        dataset_name (str): Name of the dataset in the HDF5 file (default: "data")

    Returns:
        dset (h5py.Dataset): The created dataset object
    """

    parent = os.path.dirname(cfg.output_dir)
    if parent:
        os.makedirs(parent, exist_ok=True)

    # we assume the recordings are in .npy format
    files = os.listdir(cfg.input_dir)
    if not files:
        raise ValueError("No files found in the specified directory.")

    records = []
    for fname in files:
        rec = from_npy(os.path.join(cfg.input_dir, fname))

        data = rec.data

        md = rec.metadata  # pull metadata from the recordinh
        md.setdefault("recid", len(records))
        records.append((data, md))

    # split each recording into 8 snippets each
    records = split_recording(records, cfg.num_slices)

    train_records, val_records = split(records, cfg.train_split, cfg.seed)

    train_path = os.path.join(cfg.output_dir, "train.h5")
    val_path = os.path.join(cfg.output_dir, "val.h5")

    write_hdf5_file(train_records, train_path, "training_data")
    write_hdf5_file(val_records, val_path, "validation_data")

    return train_path, val_path

def main():
    settings = get_app_settings()
    dataset_cfg = settings.dataset
    train_path, val_path = generate_datasets(dataset_cfg)
    print(f"✅ Train: {train_path}\n✅ Val: {val_path}")

    
if __name__ == "__main__":
    main()