from transformers import Wav2Vec2Processor, Wav2Vec2ForCTC
from datasets import load_dataset
import torch

# load model and processor
processor = Wav2Vec2Processor.from_pretrained("GetmanY1/wav2vec2-large-sami-cont-pt-22k-finetuned")
model = Wav2Vec2ForCTC.from_pretrained("GetmanY1/wav2vec2-large-sami-cont-pt-22k-finetuned")

# tokenize
input_values = processor(ds[0]["audio"]["array"], return_tensors="pt", padding="longest").input_values  # Batch size 1

# retrieve logits
logits = model(input_values).logits

# take argmax and decode
predicted_ids = torch.argmax(logits, dim=-1)
transcription = processor.batch_decode(predicted_ids)

import re
import numpy as np

def prefix_beam_search(ctc, lm=None, k=25, alpha=0.30, beta=5, prune=0.001):
	"""
	Performs prefix beam search on the output of a CTC network.

	Args:
		ctc (np.ndarray): The CTC output. Should be a 2D array (timesteps x alphabet_size)
		lm (func): Language model function. Should take as input a string and output a probability.
		k (int): The beam width. Will keep the 'k' most likely candidates at each timestep.
		alpha (float): The language model weight. Should usually be between 0 and 1.
		beta (float): The language model compensation term. The higher the 'alpha', the higher the 'beta'.
		prune (float): Only extend prefixes with chars with an emission probability higher than 'prune'.

	Returns:
		string: The decoded CTC output.
	"""

	lm = (lambda l: 1) if lm is None else lm # if no LM is provided, just set to function returning 1
	W = lambda l: re.findall(r'\w+[\s|>]', l)
	alphabet = list({k: v for k, v in sorted(processor.tokenizer.vocab.items(), key=lambda item: item[1])})
	alphabet = list(map(lambda x: x.replace(processor.tokenizer.special_tokens_map['eos_token'], '>') \
						.replace(processor.tokenizer.special_tokens_map['pad_token'], '%') \
						.replace('|', ' '), alphabet))


	F = ctc.shape[1]
	ctc = np.vstack((np.zeros(F), ctc)) # just add an imaginative zero'th step (will make indexing more intuitive)
	T = ctc.shape[0]

	# STEP 1: Initiliazation
	O = ''
	Pb, Pnb = defaultdict(Counter), defaultdict(Counter)
	Pb[0][O] = 1
	Pnb[0][O] = 0
	A_prev = [O]
	# END: STEP 1

	# STEP 2: Iterations and pruning
	for t in range(1, T):
		pruned_alphabet = [alphabet[i] for i in np.where(ctc[t] > prune)[0]]
		for l in A_prev:
			if len(l) > 0 and l.endswith('>'):
				Pb[t][l] = Pb[t - 1][l]
				Pnb[t][l] = Pnb[t - 1][l]
				continue  
			for c in pruned_alphabet:
				c_ix = alphabet.index(c)
				# END: STEP 2
				
				# STEP 3: “Extending” with a blank
				if c == '%':
					Pb[t][l] += ctc[t][0] * (Pb[t - 1][l] + Pnb[t - 1][l]) 
				# END: STEP 3
				
				# STEP 4: Extending with the end character
				else:
					l_plus = l + c
					if len(l) > 0 and l.endswith(c):
						Pnb[t][l_plus] += ctc[t][c_ix] * Pb[t - 1][l]
						Pnb[t][l] += ctc[t][c_ix] * Pnb[t - 1][l]
				# END: STEP 4

					# STEP 5: Extending with any other non-blank character and LM constraints
					elif len(l.replace(' ', '')) > 0 and c in (' ', '>'):
						lm_prob = lm(l_plus.strip(' >')) ** alpha
						Pnb[t][l_plus] += lm_prob * ctc[t][c_ix] * (Pb[t - 1][l] + Pnb[t - 1][l])
					else:
						Pnb[t][l_plus] += ctc[t][c_ix] * (Pb[t - 1][l] + Pnb[t - 1][l])
					# END: STEP 5

					# STEP 6: Make use of discarded prefixes
					if l_plus not in A_prev:
						Pb[t][l_plus] += ctc[t][0] * (Pb[t - 1][l_plus] + Pnb[t - 1][l_plus])
						Pnb[t][l_plus] += ctc[t][c_ix] * Pnb[t - 1][l_plus]
					# END: STEP 6

		# STEP 7: Select most probable prefixes
		A_next = Pb[t] + Pnb[t]
		sorter = lambda l: A_next[l] * (len(W(l)) + 1) ** beta
		A_prev = sorted(A_next, key=sorter, reverse=True)[:k]
		# END: STEP 7

	return A_prev[0].strip('>')

def map_to_pred_prefix_beam_search(batch):
    device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
    input_values = processor(batch["speech"], sampling_rate=16000, return_tensors="pt", padding="longest").input_values
    with torch.no_grad():
        logits = model(input_values.to(device)).logits
    probs = torch.softmax(logits, dim=-1)
    transcription = [prefix_beam_search(probs[0].cpu().numpy(), lm=None)]
    batch["transcription"] = transcription
    return batch

result = ds.map(map_to_pred_prefix_beam_search, batched=True, batch_size=1, remove_columns=["speech"])