# Lint as: python3
"""Speech Segment dataset.
"""
import os
from pathlib import Path

import datasets
import torchaudio


class SpeechSegmentConfig(datasets.BuilderConfig):
    """BuilderConfig for Speech Segment.
    For long audio files, segment them into smaller segments of fixed length.
    For short audio files, return the whole audio file.
    """

    def __init__(self, segment_length, **kwargs):
        super(SpeechSegmentConfig, self).__init__(**kwargs)
        self.segment_length = segment_length


class SpeechSegment(datasets.GeneratorBasedBuilder):
    """Speech Segment dataset."""

    BUILDER_CONFIGS = [
        SpeechSegmentConfig(name="all", segment_length=60.0,),
    ]

    @property
    def manual_download_instructions(self):
        return (
            "Specify the data_dir as the path to the folder, will recursively search for .flac and .wav files. "
            "`datasets.load_dataset('subatomicseer/speech_segment', data_dir='path/to/folder/folder_name')`"
        )

    def _info(self):
        features = datasets.Features(
            {
                "id": datasets.Value("string"),
                "file": datasets.Value("string"),
                'sample_rate': datasets.Value('int64'),
                'offset': datasets.Value('int64'),
                'num_frames': datasets.Value('int64'),
            }
        )

        return datasets.DatasetInfo(
            features=features,
        )

    def _split_generators(self, dl_manager):
        base_data_dir = os.path.abspath(os.path.expanduser(dl_manager.manual_dir))
        if not os.path.exists(base_data_dir):
            raise FileNotFoundError(
                f"{base_data_dir} does not exist. Manual download instructions: {self.manual_download_instructions}"
            )

        data_dirs = [str(p) for p in Path(base_data_dir).rglob('*') if p.suffix in ['.flac', '.wav']]
        print(f"Found {len(data_dirs)} audio files in {base_data_dir}")
        return [
            datasets.SplitGenerator(
                name=datasets.Split.TRAIN,
                gen_kwargs={"data_dirs": data_dirs},
            ),
        ]

    def _generate_examples(self, data_dirs):
        for key, path in enumerate(data_dirs):
            path_split = path.split("/")
            id_ = '/'.join(path_split[-4:]).replace(".flac", "")

            audio_metadata = torchaudio.info(path)
            segment_length = int(self.config.segment_length * audio_metadata.sample_rate)
            total_length = audio_metadata.num_frames

            if total_length <= segment_length:
                yield id_, {
                    "id": id_,
                    "file": path,
                    'sample_rate': audio_metadata.sample_rate,
                    'offset': 0,
                    'num_frames': total_length,
                }
            else:
                # generate non-overlapping segments of segment_length
                offsets = list(range(0, total_length, segment_length))
                if total_length - offsets[-1] < 1 * audio_metadata.sample_rate:
                    # if the last segment is less than 2 seconds, discard it
                    offsets.pop()

                for segment_id, start in enumerate(offsets):
                    end = start + segment_length - 1
                    if end > total_length:
                        end = total_length
                    yield f'{id_}_{segment_id}', {
                        "id": f'{id_}_{segment_id}',
                        "file": path,
                        'sample_rate': audio_metadata.sample_rate,
                        'offset': start,
                        'num_frames': end-start+1,
                    }