app.py

import os
import re
import random
import requests
import gradio as gr
import numpy as np
import nltk 
import nltkmodule
from newspaper import Article
from nltk.tokenize import sent_tokenize
from sentence_transformers import SentenceTransformer, util
import spacy
import en_core_sci_lg
from transformers import AutoTokenizer, AutoModelForSequenceClassification, pipeline
import torch

# --- Models (load once, globally) ---
scispacy = en_core_sci_lg.load()
sbert_keybert = SentenceTransformer("pritamdeka/BioBERT-mnli-snli-scinli-scitail-mednli-stsb")  # for keybert query
sbert_rerank = SentenceTransformer("pritamdeka/S-PubMedBert-MS-MARCO")           # for abstract reranking
NLI_MODEL_NAME = "pritamdeka/PubMedBERT-MNLI-MedNLI"
nli_tokenizer = AutoTokenizer.from_pretrained(NLI_MODEL_NAME)
nli_model = AutoModelForSequenceClassification.from_pretrained(NLI_MODEL_NAME)
NLI_LABELS = ['CONTRADICTION', 'NEUTRAL', 'ENTAILMENT']

PUBMED_N = 100
TOP_ABSTRACTS = 10

# --- Summarizer model options ---
model_options = {
    "Llama-3.2-1B-Instruct (Meta, gated)": "meta-llama/Llama-3.2-1B-Instruct",
    "Gemma-3-1B-it (Google, gated)": "google/gemma-3-1b-it",
    "TinyLlama-1.1B-Chat (Open)": "TinyLlama/TinyLlama-1.1B-Chat-v1.0"
}
pipe_cache = {}

# --- Utility: get robust keybert-style query ---
def get_keybert_query(text, top_n=10):
    doc = scispacy(text)
    phrases = [ent.text for ent in doc.ents]
    if not phrases:
        phrases = [chunk.text for chunk in doc.noun_chunks]
    phrases = list(set([ph.strip() for ph in phrases if len(ph) > 2]))
    if not phrases:
        return ""
    doc_emb = sbert_keybert.encode([text])
    phrase_embs = sbert_keybert.encode(phrases)
    sims = np.array(util.pytorch_cos_sim(doc_emb, phrase_embs))[0]
    top_idxs = sims.argsort()[-top_n:]
    keywords = [phrases[i] for i in top_idxs]
    query = " OR ".join(f'"{kw}"' for kw in keywords)
    return query

# --- PubMed retrieval ---
def retrieve_pubmed_abstracts_simple(text, n=PUBMED_N, fallback_headline=None):
    query = get_keybert_query(text, top_n=10)
    ncbi_url = 'https://eutils.ncbi.nlm.nih.gov/entrez/eutils/'
    for q in [query, fallback_headline, text]:
        if not q:
            continue
        search_url = f"{ncbi_url}esearch.fcgi?db=pubmed&term={q}&retmax={n}&sort=relevance"
        r = requests.get(search_url)
        pmids = re.findall(r"<Id>(\d+)</Id>", r.text)
        if pmids:
            ids = ','.join(pmids)
            fetch_url = f"{ncbi_url}efetch.fcgi?db=pubmed&id={ids}&rettype=xml&retmax={n}"
            resp = requests.get(fetch_url)
            titles = re.findall(r"<ArticleTitle>(.*?)</ArticleTitle>", resp.text, flags=re.DOTALL)
            abstracts = re.findall(r"<AbstractText.*?>(.*?)</AbstractText>", resp.text, flags=re.DOTALL)
            if not abstracts:
                abstracts = [""] * len(titles)
            titles = [re.sub(r"\s+", " ", t).strip() for t in titles]
            abstracts = [re.sub(r"\s+", " ", a).strip() for a in abstracts]
            return titles, abstracts
    return [], []

# --- Claim extraction ---
indicator_phrases = [
    "found that", "findings suggest", "shows that", "showed that", "demonstrated", "demonstrates",
    "revealed", "reveals", "suggests", "suggested", "indicated", "indicates", "reported", "reports",
    "was reported", "concluded", "concludes", "conclusion", "authors state", "stated", "data suggest",
    "observed", "observes", "study suggests", "study shows", "study found", "researchers found",
    "results indicate", "results show", "confirmed", "confirm", "confirming", "point to",
    "documented", "document", "evidence of", "evidence suggests", "associated with", "correlated with",
    "link between", "linked to", "relationship between", "was linked", "connected to", "relationship with",
    "tied to", "association with", "increase", "increases", "increased", "decrease", "decreases", "decreased",
    "greater risk", "lower risk", "higher risk", "reduced risk", "raises the risk", "reduces the risk",
    "risk of", "risk for", "likelihood of", "probability of", "chance of", "rate of", "incidence of",
    "prevalence of", "mortality", "survival rate", "death rate", "odds of", "number of", "percentage of",
    "percent of", "caused by", "causes", "cause", "resulted in", "results in", "leads to", "led to",
    "contributed to", "responsible for", "due to", "as a result", "because of",
    "randomized controlled trial", "RCT", "clinical trial", "participants", "enrolled", "sample size",
    "statistically significant", "compared to", "compared with", "versus", "compared against",
    "more than", "less than", "greater than", "lower than", "higher than", "significantly higher",
    "significantly lower", "significantly increased", "significantly decreased", "significant difference",
    "effect of", "impact of", "influence of", "predictor of", "predicts", "predictive of", "factor for",
    "determinant of", "plays a role in", "contributes to", "related to", "affects", "influences",
    "difference between", "according to", "a recent study", "researchers from"
]

def extract_claims_pattern(article_text):
    sentences = sent_tokenize(article_text)
    claims = [
        s for s in sentences
        if any(phrase in s.lower() for phrase in indicator_phrases)
        or re.search(r"\b\d+(\.\d+)?%?\b", s)
    ]
    return list(dict.fromkeys(claims))

def match_claims_to_headline(claims, headline):
    emb_model = sbert_keybert  # (or any SBERT for matching)
    headline_emb = emb_model.encode([headline])
    claim_embs = emb_model.encode(claims)
    sims = util.pytorch_cos_sim(headline_emb, claim_embs)[0]
    matched_claims = [claim for claim, sim in zip(claims, sims) if sim >= 0.6]
    if not matched_claims and claims:
        idxs = np.argsort(-sims.cpu().numpy())[:min(3, len(claims))]
        matched_claims = [claims[i] for i in idxs]
    return matched_claims

# --- Semantic reranking of abstracts using s-pubmedbert-msmarco ---
def semantic_rerank_claim_abstracts(claim, titles, abstracts, top_k=TOP_ABSTRACTS):
    doc_texts = [f"{t}. {a}" for t, a in zip(titles, abstracts)]
    doc_embs = sbert_rerank.encode(doc_texts)
    claim_emb = sbert_rerank.encode([claim])
    sims = util.pytorch_cos_sim(claim_emb, doc_embs)[0]
    idxs = np.argsort(-sims.cpu().numpy())[:top_k]
    return [titles[i] for i in idxs], [abstracts[i] for i in idxs]

# --- NLI evidence extraction ---
def extract_evidence_nli(claim, title, abstract):
    sentences = sent_tokenize(abstract)
    evidence = []
    for sent in sentences:
        encoding = nli_tokenizer(
            sent, claim,
            return_tensors='pt',
            truncation=True,
            max_length=256,
            padding=True
        )
        with torch.no_grad():
            outputs = nli_model(**encoding)
            probs = torch.softmax(outputs.logits, dim=1).cpu().numpy().flatten()
            max_idx = probs.argmax()
            label = NLI_LABELS[max_idx]
            score = float(probs[max_idx])
        evidence.append({
            "sentence": sent,
            "label": label,
            "score": score
        })
    return evidence

# --- Summarizer model loading ---
def get_summarizer(model_choice):
    model_id = model_options[model_choice]
    if model_id in pipe_cache:
        return pipe_cache[model_id]
    kwargs = {
        "model": model_id,
        "torch_dtype": torch.float16 if torch.cuda.is_available() else torch.float32,
        "device_map": "auto",
        "max_new_tokens": 128
    }
    if any(gated in model_id for gated in ["meta-llama", "gemma"]):
        hf_token = os.environ.get("HF_TOKEN", None)
        if hf_token:
            kwargs["token"] = hf_token
        else:
            raise RuntimeError(f"Model '{model_choice}' requires a Hugging Face access token. Please set 'HF_TOKEN' as a Space secret or environment variable.")
    pipe_cache[model_id] = pipeline("text-generation", **kwargs)
    return pipe_cache[model_id]

def summarize_evidence_llm(claim, evidence_list, model_choice):
    support = [ev['sentence'] for ev in evidence_list if ev['label'] == 'ENTAILMENT']
    contradict = [ev['sentence'] for ev in evidence_list if ev['label'] == 'CONTRADICTION']
    messages = [
        {"role": "system", "content": "You are a helpful biomedical assistant. Summarize scientific evidence in plain English for the general public."},
        {"role": "user", "content":
            f"Claim: {claim}\n"
            f"Supporting evidence:\n" + ("\n".join(support) if support else "None") + "\n"
            f"Contradicting evidence:\n" + ("\n".join(contradict) if contradict else "None") + "\n"
            "Explain to a layperson: Is this claim likely true, false, or uncertain based on the evidence above? Give a brief and simple explanation in 2-3 sentences."
        }
    ]
    try:
        pipe = get_summarizer(model_choice)
        outputs = pipe(
            messages,
            max_new_tokens=96,
            do_sample=False,
            temperature=0.1,
        )
        out = outputs[0]["generated_text"]
        if isinstance(out, list) and "content" in out[-1]:
            return out[-1]["content"].strip()
        return out.strip()
    except Exception as e:
        return f"Summary could not be generated: {e}"

def format_evidence_html(evidence_list):
    color_map = {"ENTAILMENT":"#e6ffe6", "CONTRADICTION":"#ffe6e6", "NEUTRAL":"#f8f8f8"}
    html = ""
    for ev in evidence_list:
        color = color_map[ev["label"]]
        html += (
            f'<div style="background:{color};padding:6px;border-radius:6px;margin-bottom:3px">'
            f'<b>{ev["label"]}</b> (confidence {ev["score"]:.2f}): {ev["sentence"]}'
            '</div>'
        )
    return html

def factcheck_app(article_url, summarizer_choice):
    try:
        art = Article(article_url)
        art.download()
        art.parse()
        text = art.text
        headline = art.title
    except Exception as e:
        return f"<b>Error downloading or reading article:</b> {e}", None

    claims = extract_claims_pattern(text)
    matched_claims = match_claims_to_headline(claims, headline)
    if not matched_claims:
        return "<b>No check-worthy claims found that match the headline.</b>", None

    results_html = ""
    all_results = []
    for claim in matched_claims:
        titles, abstracts = retrieve_pubmed_abstracts_simple(claim, fallback_headline=headline)
        if not titles:
            results_html += f"<hr><b>Claim:</b> {claim}<br><i>No PubMed results found.</i><br>"
            all_results.append({"claim": claim, "summary": "No PubMed results found.", "evidence": []})
            continue
        top_titles, top_abstracts = semantic_rerank_claim_abstracts(claim, titles, abstracts)
        idx_non_top = random.choice([i for i in range(len(titles)) if i not in [titles.index(t) for t in top_titles]]) if len(titles) > len(top_titles) else None
        evidence_results = []
        for title, abstract in zip(top_titles, top_abstracts):
            evidence = extract_evidence_nli(claim, title, abstract)
            evidence_results.append({"title": title, "evidence": evidence})
        if idx_non_top is not None:
            control_ev = extract_evidence_nli(claim, titles[idx_non_top], abstracts[idx_non_top])
            evidence_results.append({"title": f"(Control) {titles[idx_non_top]}", "evidence": control_ev})
        all_evidence_sentences = [ev for abs_res in evidence_results for ev in abs_res["evidence"]]
        summary = summarize_evidence_llm(claim, all_evidence_sentences, summarizer_choice)
        results_html += f"<hr><b>Claim:</b> {claim}<br><b>Layman summary:</b> {summary}<br>"
        for abs_res in evidence_results:
            results_html += f"<br><b>Abstract:</b> {abs_res['title']}<br>{format_evidence_html(abs_res['evidence'])}"
        all_results.append({"claim": claim, "summary": summary, "evidence": evidence_results})
    return results_html, all_results

description = """
<b>What does this app do?</b><br>
This app extracts key scientific claims from a news article, finds the most relevant PubMed biomedical research papers using robust keyphrase extraction and semantic reranking, checks which sentences in those papers support or contradict each claim, and gives you a plain-English summary verdict.<br><br>
<b>How to use it:</b><br>
1. Paste the link to a biomedical news article.<br>
2. Choose an AI summarizer model below. If you have no special access, use 'TinyLlama' (works for everyone).<br>
3. Wait for the results.<br>
4. For each claim, you will see:<br>
- A plain summary of what research says.<br>
- Color-coded evidence sentences (green=support, red=contradict, gray=neutral).<br>
- The titles of the most relevant PubMed articles.<br><br>
<b>Everything is 100% open source and runs on this website—no personal info or cloud API needed.</b>
"""

iface = gr.Interface(
    fn=factcheck_app,
    inputs=[
        gr.Textbox(lines=2, label="Paste a news article URL"),
        gr.Dropdown(
            choices=list(model_options.keys()),
            value="TinyLlama-1.1B-Chat (Open)",
            label="Choose summarizer model"
        )
    ],
    outputs=[gr.HTML(label="Fact-Check Results (Summary & Evidence)"), gr.JSON(label="All Results (JSON)")],
    title="BioMedical News Fact-Checking & Research Evidence Finder",
    description=description,
    examples=[["https://www.medicalnewstoday.com/articles/omicron-what-do-we-know-about-the-stealth-variant", "TinyLlama-1.1B-Chat (Open)"]],
    allow_flagging="never"
)

iface.launch(share=False, server_name='0.0.0.0', show_error=True)