metrics_v2.py

import nltk
from transformers import pipeline, AutoModelForSequenceClassification, AutoTokenizer, AutoModelForCausalLM
import torch
from sentence_transformers import SentenceTransformer, util
from bert_score import score
from nltk.translate.bleu_score import sentence_bleu, SmoothingFunction
from rouge import Rouge
from tqdm import tqdm
from datasets import load_metric

# Download necessary NLTK data
nltk.download('punkt')
nltk.download('stopwords')

# --- Model and Metric Loading ---
class ContentEvaluator:
    def __init__(self):
        self.semantic_similarity_model = SentenceTransformer('neuralmind/bert-large-portuguese-cased')
        self.perplexity_model_name = "unicamp-dl/ptt5-base-portuguese-vocab"
        self.perplexity_tokenizer = AutoTokenizer.from_pretrained(self.perplexity_model_name)

        # Load Hugging Face metrics
        self.bertscore_metric = load_metric("bertscore")
        self.bleu_metric = load_metric("bleu")
        self.rouge_metric = load_metric("rouge")
        self.meteor_metric = load_metric("meteor")
        self.sacrebleu_metric = load_metric("sacrebleu")  # More robust BLEU implementation

        # Load a powerful LLM for judging content and detecting hallucinations
        self.judge_model_name = "gpt-3.5-turbo"  # Gemini Or GPT-4 if available
        self.judge = pipeline("text-generation", model=self.judge_model_name)

    
    def calculate_perplexity(self, text):
        """
        Calculates the perplexity of a text using a Portuguese LLM model.

        Perplexity measures how well the language model understands the text. 
        Lower perplexity indicates that the text is more predictable and likely to be grammatically correct.
        Higher perplexity suggests the text is more surprising or unusual, potentially indicating errors or nonsensical content.
        """
        try:
            perplexity_model = AutoModelForCausalLM.from_pretrained(self.perplexity_model_name)
            with torch.no_grad():
                tokenize_input = self.perplexity_tokenizer.tokenize(text)
                tensor_input = self.perplexity_tokenizer.encode(text, return_tensors='pt')
                loss = perplexity_model(tensor_input, labels=tensor_input)[0]
                return torch.exp(loss).item()
        except Exception as e:
            print(f"Error calculating perplexity: {e}")
            return float('inf')


    def detect_hallucination_with_llm(self, text, window_size=200):
        """
        Detects potential hallucinations using an LLM with a refined prompt.
        """
        hallucinations = []
        text_chunks = nltk.word_tokenize(text)

        for i in range(0, len(text_chunks), window_size):
            chunk = " ".join(text_chunks[i:i + window_size])

            prompt = f"""
            You are an expert in identifying factual errors and inconsistencies in educational text.
            Your task is to meticulously analyze the provided text excerpt and pinpoint any potential hallucinations. 

            Focus on identifying claims or statements that exhibit the following characteristics:

            * **Factual Inaccuracy:**  Assertions that are demonstrably false or lack credible supporting evidence.
            * **Logical Fallacies:** Statements containing flawed reasoning or internal contradictions.
            * **Nonsensical Claims:**  Assertions that are absurd, meaningless, or defy common sense.
            * **Invented Information:**  Fabricated details or events that have no basis in reality.

            Text Excerpt:
            ```
            {chunk}
            ```

            For each potential hallucination, provide:
            - **Hallucination:** The specific text you believe is a hallucination.
            - **Explanation:**  A detailed and precise justification for why you classify it as a hallucination.

            Return your analysis as a JSON list of dictionaries, strictly adhering to the following format:

            ```json
            [
              {{"hallucination": "[The hallucinated text]", "explanation": "[Your detailed explanation]"}} 
            ]
            ```
            """
            response = self.judge(prompt, max_length=300)[0]['generated_text'].strip()

            try:
                chunk_hallucinations = eval(response)
                for hallucination in chunk_hallucinations:
                    hallucinations.append({
                        'chunk': chunk,
                        'hallucination': hallucination['hallucination'],
                        'explanation': hallucination['explanation']
                    })
            except Exception as e:
                print(f"Error parsing LLM response: {e}")
                print(f"LLM Response: {response}")

        return hallucinations

    def calculate_metrics(self, generated_text, reference_text):
        """Calculates BERTScore, BLEU, ROUGE, METEOR, and SacreBLEU metrics."""
        results = {}
        try:
            results['bertscore'] = self.bertscore_metric.compute(predictions=[generated_text], references=[reference_text], lang="pt")['f1'][0]
            bleu_results = self.bleu_metric.compute(predictions=[generated_text.split()], references=[[reference_text.split()]])
            results['bleu'] = bleu_results['bleu']
            rouge_results = self.rouge_metric.compute(predictions=[generated_text], references=[reference_text])
            results['rougeL'] = rouge_results['rougeL']
            meteor_results = self.meteor_metric.compute(predictions=[generated_text], references=[reference_text])
            results['meteor'] = meteor_results['meteor']

            # SacreBLEU (more robust BLEU implementation)
            sacrebleu_results = self.sacrebleu_metric.compute(predictions=[generated_text], references=[[reference_text]])
            results['sacrebleu'] = sacrebleu_results['score']

        except Exception as e:
            print(f"Error calculating metrics: {e}")
            results = {'bertscore': None, 'bleu': None, 'rougeL': None, 'meteor': None, 'sacrebleu': None}
        return results

    def analyze_text(self, text, perplexity_threshold=40):
        """
        Analyzes a text for perplexity and potential hallucinations.
        """
        results = []
        sentences = nltk.sent_tokenize(text)

        for i, sentence in enumerate(sentences):
            perplexity = self.calculate_perplexity(sentence)
            hallucinations = self.detect_hallucination_with_llm(sentence)

            issues = []
            if perplexity > perplexity_threshold:
                issues.append(f"- **High Perplexity:** ({perplexity:.2f}) The sentence might be grammatically incorrect or nonsensical.")
            if hallucinations:
                for hallucination in hallucinations:
                    issues.append(f"- **Potential Hallucination (LLM):** {hallucination['hallucination']} - {hallucination['explanation']}")

            review_flag = len(issues) > 0
            explanation = "\n".join(issues) if issues else "No potential issues detected."

            results.append({
                'sentence_index': i,
                'review_flag': review_flag,
                'explanation': explanation,
                'perplexity': perplexity,
                'hallucinations': hallucinations,
                'sentence': sentence
            })

        return results

    def analyze_content_for_review(self, generated_text, reference_text, 
                                 similarity_threshold, 
                                 bertscore_threshold,
                                 bleu_threshold,
                                 rouge_threshold,
                                 meteor_threshold):
        """Analyzes content and flags potential issues based on provided thresholds and LLM judgment."""
        similarity = self.estimate_semantic_similarity(generated_text, reference_text)
        metrics = self.calculate_metrics(generated_text, reference_text)
        llm_judgment = self.get_llm_judgment(generated_text, reference_text)

        issues = []
        if similarity < similarity_threshold:
            issues.append(f"- **Low Semantic Similarity:** ({similarity:.2f}) Content might be off-topic or not factually aligned.")
        if metrics['bertscore'] and metrics['bertscore'] < bertscore_threshold:
            issues.append(f"- **Low BERTScore:** ({metrics['bertscore']:.2f}) There might be factual inaccuracies or significant paraphrasing.")
        if metrics['bleu'] and metrics['bleu'] < bleu_threshold:
            issues.append(f"- **Low BLEU Score:** ({metrics['bleu']:.2f}) The generated text might not be fluent or use appropriate wording.")
        if metrics['rougeL'] and metrics['rougeL'] < rouge_threshold:
            issues.append(f"- **Low ROUGE-L Score:** ({metrics['rougeL']:.2f}) The generated text might not cover important information from the reference.")
        if metrics['meteor'] and metrics['meteor'] < meteor_threshold:
            issues.append(f"- **Low METEOR Score:** ({metrics['meteor']:.2f}) The generated text might have poor word alignment with the reference.")

        # Use LLM judgment as the primary decision-maker
        if llm_judgment == "major issues":
            review_flag = True
            explanation = f"LLM Judgment: **Major Issues**\n" + "\n".join(issues)
        elif llm_judgment == "minor issues":
            review_flag = True
            explanation = f"LLM Judgment: **Minor Issues**\n" + "\n".join(issues)
        else:
            review_flag = False
            explanation = "LLM Judgment: **No Issues**"

        return {
            'review_flag': review_flag,
            'explanation': explanation,
            'semantic_similarity': similarity,
            'metrics': metrics,
            'llm_judgment': llm_judgment,
            'generated_text': generated_text,
            'reference_text': reference_text
        }

# --- Example Usage ---
if __name__ == "__main__":
    evaluator = ContentEvaluator()

    # Example text (replace with your actual data)
    text = """
    A Terra é plana e o Sol gira em torno dela. 
    A gravidade é uma força fraca. 
    As plantas precisam de água para sobreviver.
    A Lua é feita de queijo. 
    Os dinossauros ainda vivem na Amazônia.
    """

    analysis_results = evaluator.analyze_text(text)

    for result in analysis_results:
        print(f"----- Sentence {result['sentence_index'] + 1} -----")
        print(f"Review Flag: {result['review_flag']}")
        print(f"Explanation: {result['explanation']}")
        print(f"Perplexity: {result['perplexity']:.2f}")
        print(f"Sentence: {result['sentence']}\n")

# 2. Content Evaluation Phase (using the best thresholds)
    new_generated_text = evaluator.generate_educational_content("Matemática")
    new_reference_text = "Content from your educational material..."

    evaluation_result = evaluator.analyze_content_for_review(
        new_generated_text, new_reference_text,
        best_thresholds['similarity_threshold'],
        best_thresholds['bertscore_threshold'],
        best_thresholds['bleu_threshold'],
        best_thresholds['rouge_threshold'],
        best_thresholds['meteor_threshold']
    )

    print("\n----- Evaluation Result -----")
    print(f"Review Flag: {evaluation_result['review_flag']}")
    print(f"Explanation: {evaluation_result['explanation']}")