import argparse
import logging
from typing import Optional

import torch
import torchaudio
from torchaudio.models.decoder import ctc_decoder, download_pretrained_files


logger = logging.getLogger(__name__)


def run_inference(args):
    # get pretrained wav2vec2.0 model
    bundle = getattr(torchaudio.pipelines, args.model)
    model = bundle.get_model()

    # get decoder files
    files = download_pretrained_files("librispeech-4-gram")

    decoder = ctc_decoder(
        lexicon=files.lexicon,
        tokens=files.tokens,
        lm=files.lm,
        nbest=args.nbest,
        beam_size=args.beam_size,
        beam_size_token=args.beam_size_token,
        beam_threshold=args.beam_threshold,
        lm_weight=args.lm_weight,
        word_score=args.word_score,
        unk_score=args.unk_score,
        sil_score=args.sil_score,
        log_add=False,
    )

    dataset = torchaudio.datasets.LIBRISPEECH(args.librispeech_path, url=args.split, download=False)

    total_edit_distance = 0
    total_length = 0
    for idx, sample in enumerate(dataset):
        waveform, _, transcript, _, _, _ = sample
        transcript = transcript.strip().lower().strip()

        with torch.inference_mode():
            emission, _ = model(waveform)
        results = decoder(emission)

        total_edit_distance += torchaudio.functional.edit_distance(transcript.split(), results[0][0].words)
        total_length += len(transcript.split())

        if idx % 100 == 0:
            logger.info(f"Processed elem {idx}; WER: {total_edit_distance / total_length}")
    logger.info(f"Final WER: {total_edit_distance / total_length}")


def _parse_args():
    parser = argparse.ArgumentParser(
        description=__doc__,
        formatter_class=argparse.RawTextHelpFormatter,
    )
    parser.add_argument(
        "--librispeech_path",
        type=str,
        help="folder where LibriSpeech is stored",
    )
    parser.add_argument(
        "--split",
        type=str,
        help="LibriSpeech dataset split",
        choices=["dev-clean", "dev-other", "test-clean", "test-other"],
        default="test-other",
    )
    parser.add_argument(
        "--model",
        type=str,
        default="WAV2VEC2_ASR_BASE_960H",
        help="pretrained Wav2Vec2 model from torchaudio.pipelines",
    )
    parser.add_argument("--nbest", type=int, default=1, help="number of best hypotheses to return")
    parser.add_argument(
        "--beam-size", type=int, default=500, help="beam size for determining number of hypotheses to store"
    )
    parser.add_argument(
        "--beam-size-token",
        type=Optional[int],
        default=None,
        help="number of tokens to consider at each beam search step",
    )
    parser.add_argument("--beam-threshold", type=int, default=50, help="beam threshold for pruning hypotheses")
    parser.add_argument(
        "--lm-weight",
        type=float,
        default=1.74,
        help="languge model weight",
    )
    parser.add_argument(
        "--word-score",
        type=float,
        default=0.52,
        help="word insertion score",
    )
    parser.add_argument("--unk_score", type=float, default=float("-inf"), help="unknown word insertion score")
    parser.add_argument("--sil_score", type=float, default=0, help="silence insertion score")
    parser.add_argument("--debug", action="store_true", help="whether to use debug level for logging")
    return parser.parse_args()


def _init_logger(debug):
    fmt = "%(asctime)s %(message)s" if debug else "%(message)s"
    level = logging.DEBUG if debug else logging.INFO
    logging.basicConfig(format=fmt, level=level, datefmt="%Y-%m-%d %H:%M:%S")


def _main():
    args = _parse_args()
    _init_logger(args.debug)
    run_inference(args)


if __name__ == "__main__":
    _main()