import re

# Clean and tokenize text

def clean_text(text):
    text = text or ""
    text = text.lower()
    text = re.sub(r"http\S+|www\S+|https\S+", "", text)
    text = re.sub(r"[@#]\w+", "", text)
    text = re.sub(r"[^a-z\s]", "", text)
    text = re.sub(r"\s+", " ", text).strip()
    return text

# Example: encode tokens to indices (implement your vocab)
def encode(text, vocab):
    tokens = text.split()
    return [vocab.get(t, vocab.get("<UNK>")) for t in tokens]

# Pad or truncate sequences to fixed length
def pad_sequence(seq, max_len, pad_value=0):
    if len(seq) >= max_len:
        return seq[:max_len]
    return seq + [pad_value] * (max_len - len(seq))