from pathlib import Path

import torch
from torch import nn
from einops import rearrange

import fairseq

from torchaudio.functional import resample

from audiolm_pytorch.utils import curtail_to_multiple

def exists(val):
    return val is not None

class FairseqVQWav2Vec(nn.Module):
    def __init__(
        self,
        checkpoint_path,
        target_sample_hz = 24000,
        seq_len_multiple_of = None
    ):
        super().__init__()
        self.target_sample_hz = target_sample_hz
        self.seq_len_multiple_of = seq_len_multiple_of

        path = Path(checkpoint_path)
        assert path.exists(), f'path {checkpoint_path} does not exist'

        checkpoint = torch.load(checkpoint_path)
        load_model_input = {checkpoint_path: checkpoint}
        model, *_ = fairseq.checkpoint_utils.load_model_ensemble_and_task(load_model_input)

        self.model = model[0]
        self.model.eval()

    @property
    def groups(self):
        return self.model.vector_quantizer.groups

    @property
    def codebook_size(self):
        return self.model.vector_quantizer.embedding.shape[0]

    @torch.no_grad()
    def forward(
        self,
        wav_input,
        flatten = True,
        input_sample_hz = None
    ):
        if exists(input_sample_hz):
            wav_input = resample(wav_input, input_sample_hz, self.target_sample_hz)

        if exists(self.seq_len_multiple_of):
            wav_input = curtail_to_multiple(wav_input, self.seq_len_multiple_of)

        embed = self.model.feature_extractor(wav_input)
        _, codebook_indices = self.model.vector_quantizer.forward_idx(embed)

        if not flatten:
            return codebook_indices

        return rearrange(codebook_indices, 'b ... -> b (...)')
