Similarity.py

import nltk
from sentence_transformers import util

class Similarity:
    def __init__(self, model):
        self.model = SentenceTransformer("lighteternal/stsb-xlm-r-greek-transfer")
        # Make sure nltk punkt tokenizer is downloaded
        nltk.download('punkt')

    def chunk_text(self, text, chunk_size=1400, overlap_size=200):
        sentences = nltk.sent_tokenize(text)
        chunks = []
        current_chunk = ""
        for sentence in sentences:
            if len(current_chunk) + len(sentence) <= chunk_size:
                current_chunk += " " + sentence if current_chunk else sentence
            else:
                chunks.append(current_chunk)
                # Start the next chunk with overlap
                current_chunk = sentence[:overlap_size] + sentence[overlap_size:]
        if current_chunk:
            chunks.append(current_chunk)
        return chunks

    def get_sim_text(self, text, claim_embedding, min_threshold=0.4, chunk_size=1500):
        if not text:
            return []

        filtered_results = []
        chunks = self.chunk_text(text, chunk_size)
        if not chunks:
            return []

        chunk_embeddings = self.model.encode(
            chunks, convert_to_tensor=True, show_progress_bar=False
        )
        chunk_similarities = util.cos_sim(claim_embedding, chunk_embeddings)

        for chunk, similarity in zip(chunks, chunk_similarities[0]):
            if similarity >= min_threshold:
                print(chunk)
                print()
                print(similarity)
                print("--------------------------------------------------")
                filtered_results.append(chunk)

        return filtered_results